MobilizedBody Class Reference

This is the base class for all MobilizedBody classes, just a handle for the underlying hidden implementation. More...

#include <MobilizedBody.h>

Inheritance diagram for MobilizedBody:

List of all members.

Classes
class	Ball
	Three mobilities -- unrestricted orientation modeled with a quaternion which is never singular. More...
class	BendStretch
	Two mobilities: The z axis of the parent's F frame is used for rotation (and that is always aligned with the M frame z axis). More...
class	Custom
	The handle class MobilizedBody::Custom (dataless) and its companion class MobilizedBody::Custom::Implementation can be used together to define new MobilizedBody types with arbitrary properties. More...
class	Cylinder
	Two mobilities -- rotation and translation along the common z axis of the inboard and outboard mobilizer frames. More...
class	Ellipsoid
	Three mobilities -- coordinated rotation and translation along the surface of an ellipsoid fixed to the parent (inboard) body. More...
class	Free
	Unrestricted motion for a rigid body (six mobilities). More...
class	FreeLine
	Five mobilities, representing unrestricted motion for a body which is inertialess along its own z axis. More...
class	FunctionBased
	This is a subclass of MobilizedBody::Custom which uses a set of Function objects to define the behavior of the MobilizedBody. More...
class	Gimbal
	Three mobilities -- unrestricted orientation modeled as a 1-2-3 body-fixed Euler angle sequence. More...
class	Ground
	This is a special type of "mobilized" body used as a placeholder for Ground in the 0th slot for a MatterSubsystem's mobilized bodies. More...
class	LineOrientation
	Two mobilities, representing unrestricted orientation for a body which is inertialess along its own z axis. More...
class	Pin
	One mobility -- rotation about the common z axis of the inboard and outboard mobilizer frames. More...
class	Planar
	Three mobilities -- z rotation and x,y translation. More...
class	Screw
	One mobility -- coordinated rotation and translation along the common z axis of the inboard and outboard mobilizer frames. More...
class	Slider
	One mobility -- translation along the common x axis of the inboard and outboard mobilizer frames. More...
class	SphericalCoords
	Three mobilities -- body fixed 3-2 (z-y) rotation followed by translation along body z or body x. More...
class	Translation
	Three translational mobilities. More...
class	Universal
	Two mobilities -- rotation about the x axis, followed by a rotation about the new y axis. More...
class	Weld
	Zero mobilities. More...
Public Types
enum	Direction { Forward = 0, Reverse = 1 }
	Constructors can take an argument of this type to indicate that the mobilizer is being defined in the reverse direction, meaning from child to parent. More...
typedef Pin	Torsion
typedef Slider	Prismatic
typedef Translation2D	Cartesian2D
typedef Translation2D	CartesianCoords2D
typedef Translation	Cartesian
typedef Translation	CartesianCoords
typedef BendStretch	PolarCoords
typedef TorsionStretch	ConicalCoords2D
typedef Ball	Orientation
typedef Ball	Spherical
Public Member Functions
MobilizedBody &	setDefaultMotionType (Motion::Level, Motion::Method=Motion::Prescribed)
	The default behavior of this mobilizer will normally be determined by whether you provide a Motion object for it.
void	setMotionType (State &, Motion::Level, Motion::Method=Motion::Prescribed) const
	This is an Instance stage setting.
bool	isAccelerationAlwaysZero (const State &) const
bool	isVelocityAlwaysZero (const State &) const
	MobilizedBody ()
	The default constructor initializes the base class so that it contains a null implementation.
	MobilizedBody (MobilizedBodyImpl *r)
	Internal use only.
State Access - Bodies
These methods extract already-computed information from the State or State cache, or set values in the State.
const Transform &	getBodyTransform (const State &) const
	Extract from the state cache the already-calculated spatial configuration X_GB of body B's body frame, measured with respect to the Ground frame and expressed in the Ground frame.
const Rotation &	getBodyRotation (const State &s) const
	Extract from the state cache the already-calculated spatial orientation R_GB of body B's body frame x, y, and z axes expressed in the Ground frame, as the Rotation matrix R_GB.
const Vec3 &	getBodyOriginLocation (const State &s) const
	Extract from the state cache the already-calculated spatial location of body B's body frame origin OB, measured from the Ground origin OG and expressed in the Ground frame, as the position vector p_GB (== p_OG_OB).
const Transform &	getMobilizerTransform (const State &) const
	At stage Position or higher, return the cross-mobilizer transform X_FM, the body's inboard mobilizer frame M measured and expressed in the parent body's corresponding outboard frame F.
const SpatialVec &	getBodyVelocity (const State &) const
	Extract from the state cache the already-calculated spatial velocity V_GB of this body's reference frame B, measured with respect to the Ground frame and expressed in the Ground frame.
const Vec3 &	getBodyAngularVelocity (const State &s) const
	Extract from the state cache the already-calculated inertial angular velocity vector w_GB of this body B, measured with respect to the Ground frame and expressed in the Ground frame.
const Vec3 &	getBodyOriginVelocity (const State &s) const
	Extract from the state cache the already-calculated inertial linear velocity vector v_GB (more explicitly, v_G_OB) of this body B's origin point OB, measured with respect to the Ground frame and expressed in the Ground frame.
const SpatialVec &	getMobilizerVelocity (const State &) const
	At stage Velocity or higher, return the cross-mobilizer velocity V_FM, the relative velocity of this body's "moving" mobilizer frame M in the parent body's corresponding "fixed" frame F, measured and expressed in F.
const SpatialVec &	getBodyAcceleration (const State &s) const
	Extract from the state cache the already-calculated spatial acceleration A_GB of this body's reference frame B, measured with respect to the Ground frame and expressed in the Ground frame.
const Vec3 &	getBodyAngularAcceleration (const State &s) const
	Extract from the state cache the already-calculated inertial angular acceleration vector b_GB of this body B, measured with respect to the Ground frame and expressed in the Ground frame.
const Vec3 &	getBodyOriginAcceleration (const State &s) const
	Extract from the state cache the already-calculated inertial linear acceleration vector a_GB (more explicitly, a_G_OB) of this body B's origin point OB, measured with respect to the Ground frame and expressed in the Ground frame.
const SpatialVec &	getMobilizerAcceleration (const State &) const
	TODO: Not implemented yet -- any volunteers? At stage Acceleration, return the cross-mobilizer acceleration A_FM, the relative acceleration of body B's "moving" mobilizer frame M in the parent body's corresponding "fixed" frame F, measured and expressed in F.
const MassProperties &	getBodyMassProperties (const State &) const
	Return a reference to this body's mass properties in the State cache.
Real	getBodyMass (const State &s) const
	Return the mass of this body. The State must have been realized to Stage::Instance.
const Vec3 &	getBodyMassCenterStation (const State &s) const
	Return this body's center of mass station (i.e., the vector fixed in the body, going from body origin to body mass center, expressed in the body frame.
const Inertia &	getBodyInertiaAboutBodyOrigin (const State &s) const
	Return a reference to this body's inertia matrix in the State cache, taken about the body origin and expressed in the body frame.
const Transform &	getInboardFrame (const State &) const
	Return a reference to this mobilizer's frame F fixed on the parent body P, as the fixed Transform from P's body frame to the frame F fixed to P.
const Transform &	getOutboardFrame (const State &) const
	Return a reference to this MobilizedBody's mobilizer frame M, as the fixed Transform from this body B's frame to the frame M fixed on B.
void	setInboardFrame (State &, const Transform &X_PF) const
	TODO: not implemented yet.
void	setOutboardFrame (State &, const Transform &X_BM) const
	TODO: not implemented yet.
State Access - Mobilizer generalized coordinates q and speeds u
These methods extract q- or u-related information from the State or State cache, or set q or u values in the State.
int	getNumQ (const State &) const
	Return the number of generalized coordinates q currently in use by this mobilizer.
int	getNumU (const State &) const
	Return the number of generalized speeds u currently in use by this mobilizer.
QIndex	getFirstQIndex (const State &) const
	Return the global QIndex of the first q for this mobilizer; all the q's range from getFirstQIndex() to QIndex(getFirstQIndex()+getNumQ()-1).
UIndex	getFirstUIndex (const State &) const
	Return the global UIndex of the first u for this mobilizer; all the u's range from getFirstUIndex() to UIndex(getFirstUIndex()+getNumU()).
Real	getOneQ (const State &, int which) const
	Return one of the generalized coordinates q from this mobilizer's partition of the matter subsystem's full q vector in the State.
Real	getOneU (const State &, int which) const
	Return one of the generalized speeds u from this mobilizer's partition of the matter subsystem's full u vector in the State.
Vector	getQAsVector (const State &) const
	Return as a Vector of length getNumQ() all the generalized coordinates q currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full q vector in the State.
Vector	getUAsVector (const State &) const
	Return as a Vector of length getNumU() all the generalized speeds u currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full u vector in the State.
Real	getOneQDot (const State &, int which) const
	Return one of the generalized coordinate derivatives qdot from this mobilizer's partition of the matter subsystem's full qdot vector in the State cache.
Vector	getQDotAsVector (const State &) const
	Return as a Vector of length getNumQ() all the generalized coordinate derivatives qdot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full qdot vector in the State cache.
Real	getOneUDot (const State &, int which) const
	Return one of the generalized accelerations udot from this mobilizer's partition of the matter subsystem's full udot vector in the State cache.
Real	getOneQDotDot (const State &, int which) const
	Return one of the generalized coordinate second derivatives qdotdot from this mobilizer's partition of the matter subsystem's full qdotdot vector in the State cache.
Vector	getUDotAsVector (const State &) const
	Return as a Vector of length getNumU() all the generalized accelerations udot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full udot vector in the State cache.
Vector	getQDotDotAsVector (const State &) const
	Return as a Vector of length getNumQ() all the generalized coordinate second derivatives qdotdot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full qdotdot vector in the State cache.
Vector	getTauAsVector (const State &) const
	Return the tau forces resulting from known (prescribed) acceleration, corresponding to each of this mobilizer's mobilities, as a Vector of length getNumU().
Real	getOneTau (const State &, MobilizerUIndex which) const
	Return one of the tau forces resulting from known (prescribed) acceleration, corresponding to one of this mobilizer's mobilities as selected here using the which parameter, numbered from zero to getNumU()-1.
void	setOneQ (State &, int which, Real v) const
	Set one of the generalized coordinates q to value v, in this mobilizer's partition of the matter subsystem's full q vector in the State.
void	setOneU (State &, int which, Real v) const
	Set one of the generalized speeds u to value v, in this mobilizer's partition of the matter subsystem's full u vector in the State.
void	setQFromVector (State &s, const Vector &v) const
	Set all of the generalized coordinates q to value v (a Vector of length getNumQ()), in this mobilizer's partition of the matter subsystem's full q vector in the State.
void	setUFromVector (State &s, const Vector &v) const
	Set all of the generalized speeds u to value v (a Vector of length getNumU()), in this mobilizer's partition of the matter subsystem's full u vector in the State.
void	setQToFitTransform (State &, const Transform &X_FM) const
	Adjust this mobilizer's q's to best approximate the supplied Transform which requests a particular relative orientation and translation between the "fixed" and "moving" frames connected by this mobilizer.
void	setQToFitRotation (State &, const Rotation &R_FM) const
	Adjust this mobilizer's q's to best approximate the supplied Rotation matrix which requests a particular relative orientation between the "fixed" and "moving" frames connected by this mobilizer.
void	setQToFitTranslation (State &, const Vec3 &p_FM) const
	Adjust this mobilizer's q's to best approximate the supplied position vector which requests a particular offset between the origins of the "fixed" and "moving" frames connected by this mobilizer, with any q's (rotational or translational) being modified if doing so helps satisfy the request.
void	setUToFitVelocity (State &, const SpatialVec &V_FM) const
	Adjust this mobilizer's u's (generalized speeds) to best approximate the supplied spatial velocity V_FM which requests the relative angular and linear velocity between the "fixed" and "moving" frames connected by this mobilizer.
void	setUToFitAngularVelocity (State &, const Vec3 &w_FM) const
	Adjust this mobilizer's u's (generalized speeds) to best approximate the supplied angular velocity w_FM which requests a particular relative angular between the "fixed" and "moving" frames connected by this mobilizer.
void	setUToFitLinearVelocity (State &, const Vec3 &v_FM) const
	Adjust any of this mobilizer's u's (generalized speeds) to best approximate the supplied linear velocity v_FM which requests a particular velocity for the "moving" frame M origin in the "fixed" frame F on the parent where these are the frames connected by this mobilizer.
SpatialVec	getHCol (const State &s, UIndex ux) const
	Expert use only: obtain a column of the hinge matrix H corresponding to one of this mobilizer's mobilities.
Basic Operators
Transform	findBodyTransformInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	These methods use state variables and Response methods to compute basic quantities which cannot be precomputed, but which can be implemented with an inline combination of basic floating point operations which can be reliably determined at compile time.
Rotation	findBodyRotationInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return R_AB, the rotation matrix giving this body B's axes in body A's frame.
Vec3	findBodyOriginLocationInAnotherBody (const State &s, const MobilizedBody &toBodyA) const
	Return the station on another body A (that is, a point measured and expressed in A) that is currently coincident in space with the origin OB of this body B.
SpatialVec	findBodyVelocityInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the angular and linear velocity of body B's frame in body A's frame, expressed in body A, and arranged as a SpatialVec.
Vec3	findBodyAngularVelocityInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the angular velocity w_AB of body B's frame in body A's frame, expressed in body A.
Vec3	findBodyOriginVelocityInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the velocity of body B's origin point in body A's frame, expressed in body A.
SpatialVec	findBodyAccelerationInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the angular and linear acceleration of body B's frame in body A's frame, expressed in body A, and arranged as a SpatialVec.
Vec3	findBodyAngularAccelerationInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the angular acceleration of body B's frame in body A's frame, expressed in body A.
Vec3	findBodyOriginAccelerationInAnotherBody (const State &s, const MobilizedBody &inBodyA) const
	Return the acceleration of body B's origin point in body A's frame, expressed in body A.
Vec3	findStationLocationInGround (const State &s, const Vec3 &stationOnB) const
	Return the Cartesian (ground) location that is currently coincident with a station (point) S fixed on body B.
Vec3	findStationLocationInAnotherBody (const State &s, const Vec3 &stationOnB, const MobilizedBody &toBodyA) const
	Given a station S on this body B, return the location on another body A which is at the same location in space.
Vec3	findStationVelocityInGround (const State &s, const Vec3 &stationOnB) const
	Given a station fixed on body B, return its inertial (Cartesian) velocity, that is, its velocity relative to the Ground frame, expressed in the Ground frame.
Vec3	findStationVelocityInAnotherBody (const State &s, const Vec3 &stationOnBodyB, const MobilizedBody &inBodyA) const
	Return the velocity of a station S fixed on body B, in body A's frame, expressed in body A.
Vec3	findStationAccelerationInGround (const State &s, const Vec3 &stationOnB) const
	Given a station fixed on body B, return its inertial (Cartesian) acceleration, that is, its acceleration relative to the ground frame, expressed in the ground frame.
Vec3	findStationAccelerationInAnotherBody (const State &s, const Vec3 &stationOnBodyB, const MobilizedBody &inBodyA) const
	Return the acceleration of a station S fixed on body B, in another body A's frame, expressed in body A.
void	findStationLocationAndVelocityInGround (const State &s, const Vec3 &locationOnB, Vec3 &locationOnGround, Vec3 &velocityInGround) const
	It is cheaper to calculate a station's ground location and velocity together than to do them separately.
void	findStationLocationVelocityAndAccelerationInGround (const State &s, const Vec3 &locationOnB, Vec3 &locationOnGround, Vec3 &velocityInGround, Vec3 &accelerationInGround) const
	It is cheaper to calculate a station's ground location, velocity, and acceleration together than to do them separately.
Vec3	findMassCenterLocationInGround (const State &s) const
	Return the Cartesian (ground) location of this body B's mass center.
Vec3	findMassCenterLocationInAnotherBody (const State &s, const MobilizedBody &toBodyA) const
	Return the point of another body A that is currently coincident in space with the mass center CB of this body B.
Vec3	findStationAtGroundPoint (const State &s, const Vec3 &locationInG) const
	Return the station (point) S of this body B that is coincident with the given Ground location.
Vec3	findStationAtAnotherBodyStation (const State &s, const MobilizedBody &fromBodyA, const Vec3 &stationOnA) const
	Return the station (point) on this body B that is coincident with the given station on another body A.
Vec3	findStationAtAnotherBodyOrigin (const State &s, const MobilizedBody &fromBodyA) const
	Return the station S of this body that is currently coincident in space with the origin OA of another body A.
Vec3	findStationAtAnotherBodyMassCenter (const State &s, const MobilizedBody &fromBodyA) const
	Return the station S of this body that is currently coincident in space with the mass center CA of another body B.
Transform	findFrameTransformInGround (const State &s, const Transform &frameOnB) const
	Return the current Ground-frame pose (position and orientation) of a frame F that is fixed to body B.
SpatialVec	findFrameVelocityInGround (const State &s, const Transform &frameOnB) const
	Return the current Ground-frame spatial velocity V_GF (that is, angular and linear velocity) of a frame F that is fixed to body B.
SpatialVec	findFrameAccelerationInGround (const State &s, const Transform &frameOnB) const
	Return the current Ground-frame spatial acceleration A_GF (that is, angular and linear acceleration) of a frame F that is fixed to body B.
Vec3	expressVectorInGroundFrame (const State &s, const Vec3 &vectorInB) const
	Re-express a vector expressed in this body B's frame into the same vector in G, by applying only a rotation.
Vec3	expressGroundVectorInBodyFrame (const State &s, const Vec3 &vectorInG) const
	Re-express a vector expressed in Ground into the same vector expressed in this body B, by applying only rotation.
Vec3	expressVectorInAnotherBodyFrame (const State &s, const Vec3 &vectorInB, const MobilizedBody &inBodyA) const
	Re-express a vector expressed in this body B into the same vector expressed in body A, by applying only a rotation.
MassProperties	expressMassPropertiesInGroundFrame (const State &s) const
	Re-express this body B's mass properties in Ground by applying only a rotation, not a shift of reference point.
MassProperties	expressMassPropertiesInAnotherBodyFrame (const State &s, const MobilizedBody &inBodyA) const
	Re-express this body B's mass properties in another body A's frame by applying only a rotation, not a shift of reference point.
High-Level Operators
High level operators combine State Access and Basic Operators with run-time tests to calculate more complex MoblizedBody-specific quantities, with more complicated implementations that can exploit special cases at run time.
SpatialMat	calcBodySpatialInertiaMatrixInGround (const State &s) const
	Return the mass properties of body B, measured from and about the B frame origin, but expressed in Ground and then returned as a Spatial Inertia Matrix.
Inertia	calcBodyCentralInertia (const State &s, MobilizedBodyIndex objectBodyB) const
	Return the central inertia for body B, that is, the inertia taken about body B's mass center CB, and expressed in B.
Inertia	calcBodyInertiaAboutAnotherBodyStation (const State &s, const MobilizedBody &inBodyA, const Vec3 &aboutLocationOnBodyA) const
	Return the inertia of this body B, taken about an arbitrary point PA of body A, and expressed in body A.
SpatialVec	calcBodyMomentumAboutBodyOriginInGround (const State &s)
	Calculate body B's momentum (angular, linear) measured and expressed in ground, but taken about the body origin OB.
SpatialVec	calcBodyMomentumAboutBodyMassCenterInGround (const State &s) const
	Calculate body B's momentum (angular, linear) measured and expressed in ground, but taken about the body mass center CB.
Real	calcStationToStationDistance (const State &s, const Vec3 &locationOnBodyB, const MobilizedBody &bodyA, const Vec3 &locationOnBodyA) const
	Calculate the distance from a station PB on body B to a station PA on body A.
Real	calcStationToStationDistanceTimeDerivative (const State &s, const Vec3 &locationOnBodyB, const MobilizedBody &bodyA, const Vec3 &locationOnBodyA) const
	Calculate the time rate of change of distance from a fixed point PB on body B to a fixed point PA on body A.
Real	calcStationToStationDistance2ndTimeDerivative (const State &s, const Vec3 &locationOnBodyB, const MobilizedBody &bodyA, const Vec3 &locationOnBodyA) const
	Calculate the second time derivative of distance from a fixed point PB on body B to a fixed point PA on body A.
Vec3	calcBodyMovingPointVelocityInBody (const State &s, const Vec3 &locationOnBodyB, const Vec3 &velocityOnBodyB, const MobilizedBody &inBodyA) const
	TODO: not implemented yet -- any volunteers? Return the velocity of a point P moving on body B, in body A's frame, expressed in body A.
Vec3	calcBodyMovingPointAccelerationInBody (const State &s, const Vec3 &locationOnBodyB, const Vec3 &velocityOnBodyB, const Vec3 &accelerationOnBodyB, const MobilizedBody &inBodyA) const
	TODO: not implemented yet -- any volunteers? Return the velocity of a point P moving (and possibly accelerating) on body B, in body A's frame, expressed in body A.
Real	calcMovingPointToPointDistanceTimeDerivative (const State &s, const Vec3 &locationOnBodyB, const Vec3 &velocityOnBodyB, const MobilizedBody &bodyA, const Vec3 &locationOnBodyA, const Vec3 &velocityOnBodyA) const
	TODO: not implemented yet -- any volunteers? Calculate the time rate of change of distance from a moving point PB on body B to a moving point PA on body A.
Real	calcMovingPointToPointDistance2ndTimeDerivative (const State &s, const Vec3 &locationOnBodyB, const Vec3 &velocityOnBodyB, const Vec3 &accelerationOnBodyB, const MobilizedBody &bodyA, const Vec3 &locationOnBodyA, const Vec3 &velocityOnBodyA, const Vec3 &accelerationOnBodyA) const
	TODO: not implemented yet -- any volunteers? Calculate the second time derivative of distance from a moving point PB on body B to a moving point PA on body A.
Construction and Misc Methods
These methods are the base class services which are used while building a concrete MobilizedBody, or to query a MobilizedBody to find out how it was built. These are unlikely to be used by end users of MobilizedBodies.
MobilizedBody &	addBodyDecoration (const Transform &X_BD, const DecorativeGeometry &g)
	Add decorative geometry specified relative to the new (outboard) body's reference frame B, or to the outboard mobilizer frame M attached to body B, or to the inboard mobilizer frame F attached to the parent body P.
MobilizedBody &	addOutboardDecoration (const Transform &X_MD, const DecorativeGeometry &)
	Add decorative geometry specified relative to the outboard mobilizer frame M attached to body B.
MobilizedBody &	addInboardDecoration (const Transform &X_FD, const DecorativeGeometry &)
	Add decorative geometry specified relative to the inboard mobilizer frame F attached to the parent body P.
const Body &	getBody () const
	Return a reference to the Body contained within this MobilizedBody.
Body &	updBody ()
	Return a writable reference to the Body contained within this MobilizedBody.
MobilizedBody &	setBody (const Body &)
	Replace the Body contained within this MobilizedBody with a new one.
MobilizedBody &	setDefaultMassProperties (const MassProperties &m)
	If the contained Body can have its mass properties set to the supplied value m its mass properties are changed, otherwise the method fails.
const MassProperties &	getDefaultMassProperties () const
	Return the mass properties of the Body stored within this MobilizedBody.
void	adoptMotion (Motion &ownerHandle)
	Provide a unique Motion object for this MobilizedBody.
void	clearMotion ()
	If there is a Motion object associated with this MobilizedBody it is removed; otherwise, nothing happens.
bool	hasMotion () const
	Check whether this MobilizedBody has an associated Motion object.
const Motion &	getMotion () const
	If there is a Motion object assocated with this MobilizedBody, this returns a const reference to it.
MobilizedBody &	setDefaultInboardFrame (const Transform &X_PF)
	Change this mobilizer's frame F on the parent body P.
MobilizedBody &	setDefaultOutboardFrame (const Transform &X_BM)
	Change this mobilizer's frame M fixed on this (the outboard) body B.
const Transform &	getDefaultInboardFrame () const
	Return a reference to this mobilizer's default for the frame F fixed on the parent body P, as the fixed Transform from P's body frame to the frame F fixed to P.
const Transform &	getDefaultOutboardFrame () const
	Return a reference to this MobilizedBody's default for mobilizer frame M, as the fixed Transform from this body B's frame to the frame M fixed on B.
	operator MobilizedBodyIndex () const
	This is an implicit conversion from MobilizedBody to MobilizedBodyIndex when needed.
MobilizedBodyIndex	getMobilizedBodyIndex () const
	Return the MobilizedBodyIndex of this MobilizedBody within the owning SimbodyMatterSubsystem.
const MobilizedBody &	getParentMobilizedBody () const
	Return a reference to the MobilizedBody serving as the parent body of the current MobilizedBody.
const MobilizedBody &	getBaseMobilizedBody () const
	Return a reference to this MobilizedBody's oldest ancestor other than Ground, or return Ground if this MobilizedBody is Ground.
const SimbodyMatterSubsystem &	getMatterSubsystem () const
	Obtain a reference to the SimbodyMatterSubsystem which contains this MobilizedBody.
SimbodyMatterSubsystem &	updMatterSubsystem ()
	Obtain a writable reference to the SimbodyMatterSubsystem which contains this MobilizedBody.
bool	isInSubsystem () const
	Determine whether the current MobilizedBody object is owned by a matter subsystem.
bool	isInSameSubsystem (const MobilizedBody &) const
	Determine whether a given MobilizedBody mBody is in the same matter subsystem as the current body.
bool	isSameMobilizedBody (const MobilizedBody &mBody) const
	Determine whether a given MobilizedBody mBody is the same MobilizedBody as this one.
bool	isGround () const
	Determine whether this body is Ground, meaning that it is actually body 0 of some matter subsytem, not just that its body type is Ground.
int	getLevelInMultibodyTree () const
	Return this body's level in the tree of bodies, starting with ground at 0, bodies directly connected to ground at 1, bodies directly connected to those at 2, etc.
MobilizedBody &	cloneForNewParent (MobilizedBody &parent) const
	Create a new MobilizedBody which is identical to this one, except that it has a different parent (and consequently might belong to a different MultibodySystem).
Real	getOneFromQPartition (const State &, int which, const Vector &qlike) const
	This utility selects one of the q's (generalized coordinates) associated with this mobilizer from a supplied "q-like" Vector, meaning a Vector which is the same length as the Vector of q's for the containing matter subsystem.
Real &	updOneFromQPartition (const State &, int which, Vector &qlike) const
	This utility returns a writable reference to one of the q's (generalized coordinates) associated with this mobilizer from a supplied "q-like" Vector, meaning a Vector which is the same length as the Vector of q's for the containing matter subsystem.
Real	getOneFromUPartition (const State &, int which, const Vector &ulike) const
	This utility selects one of the u's (generalized speeds) associated with this mobilizer from a supplied "u-like" Vector, meaning a Vector which is the same length as the Vector of u's for the containing matter subsystem.
Real &	updOneFromUPartition (const State &, int which, Vector &ulike) const
	This utility returns a writable reference to one of the u's (generalized speeds) associated with this mobilizer from a supplied "u-like" Vector, meaning a Vector which is the same length as the Vector of u's for the containing matter subsystem.
void	applyOneMobilityForce (const State &s, int which, Real f, Vector &mobilityForces) const
	This utility adds in the supplied generalized force force (a scalar) to the appropriate slot of the supplied mobilityForces Vector, which is a "u-like" Vector.
void	applyBodyForce (const State &s, const SpatialVec &spatialForceInG, Vector_< SpatialVec > &bodyForcesInG) const
	This utility adds in the supplied spatial force spatialForceInG (consisting of a torque vector, and a force vector to be applied at the current body's origin) to the appropriate slot of the supplied bodyForcesInG Vector.
void	applyBodyTorque (const State &s, const Vec3 &torqueInG, Vector_< SpatialVec > &bodyForcesInG) const
	This utility adds in the supplied pure torque torqueInG to the appropriate slot of the supplied bodyForcesInG Vector.
void	applyForceToBodyPoint (const State &s, const Vec3 &pointInB, const Vec3 &forceInG, Vector_< SpatialVec > &bodyForcesInG) const
	This utility adds in the supplied force forceInG applied at a point pointInB to the appropriate slot of the supplied bodyForcesInG Vector.

---

Detailed Description

This is the base class for all MobilizedBody classes, just a handle for the underlying hidden implementation.

Each built-in MobilizedBody type is a local subclass within MobilizedBody, so the built-ins have names like MobilizedBody::Pin. All concrete MobilizedBodies, including the built-ins, are derived from MobilizedBody.

There are three sets of methods used for obtaining MobilizedBody-specific data from the containing System's State. These are:

• State Access
• Basic Operators
• High Level Operators

State Access methods simply extract already-calculated data from the State or State Cache, or set State values. They involve no additional computation, have names beginning with "get" and "upd" (update) and return references to the requested quantities rather than calculated values. We divide these into routines which deal with bodies and routines which deal with mobilizers and mobilities.

Basic Operators use State Access methods to compute basic quantities which cannot be precomputed, such as the velocity of an arbitrary point, using an inline combination of basic floating point operations which can be reliably determined at compile time. These have names beginning with "find" or a more specific verb, as a reminder that they do not require a great deal of computation.

High Level Operators combine responses and basic operators with run-time tests to calculate more complex quantities, with more complicated implementations that can exploit special cases at run time. These begin with "calc" (calculate) as a reminder that they may involve substantial run time computation.

There is also a set of methods used for construction, and miscellaneous utilities. These methods are primarly intended for use by concrete MobilizedBody classes and are not generally used by end users.

In the API below, we'll refer to the current ("this") MobilizedBody as "body B". It is the "object" or "main" body with which we are concerned. Often there will be another body mentioned in the argument list as a target for some conversion. That "another" body will be called "body A". The Ground body is abbreviated "G".

We use OF to mean "the origin of frame F", CB is "the mass center of body B". R_AF is the rotation matrix giving frame F's orientation in frame A, such that a vector v expressed in F is reexpressed in A by v_A = R_AF * v_F. X_AF is the spatial transform giving frame F's origin location and orientation in frame A, such that a point P whose location is measured from F's origin OF and expressed in F by position vector p_FP (or more explicitly p_OF_P) is remeasured from frame A's origin OA and reexpressed in A via p_AP = X_AF * p_FP, where p_AP==p_OA_P.

---

Member Typedef Documentation

typedef Translation Cartesian

typedef Translation2D Cartesian2D

typedef Translation CartesianCoords

typedef Translation2D CartesianCoords2D

typedef TorsionStretch ConicalCoords2D

typedef Ball Orientation

typedef BendStretch PolarCoords

typedef Slider Prismatic

typedef Ball Spherical

typedef Pin Torsion

---

Member Enumeration Documentation

enum Direction

Constructors can take an argument of this type to indicate that the mobilizer is being defined in the reverse direction, meaning from child to parent.

That means that the mobilizer coordinates and speeds will be defined as though the tree had been built in the opposite direction. This is a topological setting and can't be changed dynamically.

Enumerator:

Forward
Reverse

---

Constructor & Destructor Documentation

MobilizedBody

(

)

The default constructor initializes the base class so that it contains a null implementation.

This should be called only from concrete MobilizedBody constructors.

MobilizedBody

(

MobilizedBodyImpl *

r

)

[explicit]

Internal use only.

---

Member Function Documentation

MobilizedBody& addBodyDecoration	(	const Transform &	X_BD,
		const DecorativeGeometry &	g
	)			[inline]

Add decorative geometry specified relative to the new (outboard) body's reference frame B, or to the outboard mobilizer frame M attached to body B, or to the inboard mobilizer frame F attached to the parent body P.

Note that the body itself may already have had some decorative geometry on it when it was first put into this MobilizedBody; in that case this just adds more.

Reimplemented in Pin, Slider, Screw, Universal, Cylinder, BendStretch, Planar, SphericalCoords, Gimbal, Ball, Ellipsoid, Translation, Free, LineOrientation, FreeLine, Weld, and Ground.

Referenced by Ellipsoid::addBodyDecoration(), Ground::addBodyDecoration(), Weld::addBodyDecoration(), Pin::addBodyDecoration(), Free::addBodyDecoration(), LineOrientation::addBodyDecoration(), Screw::addBodyDecoration(), Universal::addBodyDecoration(), Cylinder::addBodyDecoration(), SphericalCoords::addBodyDecoration(), Translation::addBodyDecoration(), FreeLine::addBodyDecoration(), BendStretch::addBodyDecoration(), Ball::addBodyDecoration(), Planar::addBodyDecoration(), Gimbal::addBodyDecoration(), and Slider::addBodyDecoration().

MobilizedBody& addInboardDecoration	(	const Transform &	X_FD,
		const DecorativeGeometry &
	)

Add decorative geometry specified relative to the inboard mobilizer frame F attached to the parent body P.

If body P already has decorative geometry on it, this just adds some more.

Reimplemented in Pin, Slider, Screw, Universal, Cylinder, BendStretch, Planar, SphericalCoords, Gimbal, Ball, Ellipsoid, Translation, Free, LineOrientation, FreeLine, and Weld.

Referenced by Ball::addInboardDecoration(), Screw::addInboardDecoration(), LineOrientation::addInboardDecoration(), Planar::addInboardDecoration(), BendStretch::addInboardDecoration(), Free::addInboardDecoration(), Slider::addInboardDecoration(), FreeLine::addInboardDecoration(), Ellipsoid::addInboardDecoration(), Universal::addInboardDecoration(), Weld::addInboardDecoration(), SphericalCoords::addInboardDecoration(), Pin::addInboardDecoration(), Gimbal::addInboardDecoration(), Translation::addInboardDecoration(), and Cylinder::addInboardDecoration().

MobilizedBody& addOutboardDecoration	(	const Transform &	X_MD,
		const DecorativeGeometry &
	)

Add decorative geometry specified relative to the outboard mobilizer frame M attached to body B.

If body B already has decorative geometry on it, this just adds some more.

Reimplemented in Pin, Slider, Screw, Universal, Cylinder, BendStretch, Planar, SphericalCoords, Gimbal, Ball, Ellipsoid, Translation, Free, LineOrientation, FreeLine, and Weld.

Referenced by Weld::addOutboardDecoration(), Pin::addOutboardDecoration(), SphericalCoords::addOutboardDecoration(), Slider::addOutboardDecoration(), Ellipsoid::addOutboardDecoration(), Free::addOutboardDecoration(), Cylinder::addOutboardDecoration(), Planar::addOutboardDecoration(), BendStretch::addOutboardDecoration(), FreeLine::addOutboardDecoration(), LineOrientation::addOutboardDecoration(), Screw::addOutboardDecoration(), Translation::addOutboardDecoration(), Universal::addOutboardDecoration(), Ball::addOutboardDecoration(), and Gimbal::addOutboardDecoration().

void adoptMotion

(

Motion &

ownerHandle

)

Provide a unique Motion object for this MobilizedBody.

The MobilizedBody takes over ownership of the Motion object and is responsible for cleaning up its heap space when the time comes. This is a Topology-changing operation and consequently requires write access to the MobilizedBody which will propagate to invalidate the containing Subsystem and System's topology. There can only be one Motion object per mobilizer; this method will throw an exception if there is already one here.

void applyBodyForce	(	const State &	s,
		const SpatialVec &	spatialForceInG,
		Vector_< SpatialVec > &	bodyForcesInG
	)			const

This utility adds in the supplied spatial force spatialForceInG (consisting of a torque vector, and a force vector to be applied at the current body's origin) to the appropriate slot of the supplied bodyForcesInG Vector.

Note that we are adding this not setting it so it important that mobilityForces be initialized to zero before making a set of calls to applyBodyForce().

void applyBodyTorque	(	const State &	s,
		const Vec3 &	torqueInG,
		Vector_< SpatialVec > &	bodyForcesInG
	)			const

This utility adds in the supplied pure torque torqueInG to the appropriate slot of the supplied bodyForcesInG Vector.

Note that we are adding this not setting it so it important that bodyForcesInG be initialized to zero before making a set of calls to applyBodyTorque().

void applyForceToBodyPoint	(	const State &	s,
		const Vec3 &	pointInB,
		const Vec3 &	forceInG,
		Vector_< SpatialVec > &	bodyForcesInG
	)			const

This utility adds in the supplied force forceInG applied at a point pointInB to the appropriate slot of the supplied bodyForcesInG Vector.

Notes:

• we are adding this not setting it so it important that bodyForcesInG be initialized to zero before making a set of calls to applyForceToBodyPoint().
• pointInB represents a fixed station of B and is provided by giving the vector from body B's origin to the point, expressed in the B frame, while the applied force (and resulting body forces and torques) are expressed in the ground frame.

void applyOneMobilityForce	(	const State &	s,
		int	which,
		Real	f,
		Vector &	mobilityForces
	)			const [inline]

This utility adds in the supplied generalized force force (a scalar) to the appropriate slot of the supplied mobilityForces Vector, which is a "u-like" Vector.

Note that we are adding this not setting it so it important that mobilityForces be initialized to zero before making a set of calls to applyOneMobilityForce().

Inertia calcBodyCentralInertia	(	const State &	s,
		MobilizedBodyIndex	objectBodyB
	)			const [inline]

Return the central inertia for body B, that is, the inertia taken about body B's mass center CB, and expressed in B.

Required stage

Stage::Instance

Inertia calcBodyInertiaAboutAnotherBodyStation	(	const State &	s,
		const MobilizedBody &	inBodyA,
		const Vec3 &	aboutLocationOnBodyA
	)			const [inline]

Return the inertia of this body B, taken about an arbitrary point PA of body A, and expressed in body A.

TODO: this needs testing!

References MassProperties::calcShiftedInertia(), MobilizedBody::findBodyRotationInAnotherBody(), and Inertia_< P >::reexpress().

SpatialVec calcBodyMomentumAboutBodyMassCenterInGround

(

const State &

s

)

const [inline]

Calculate body B's momentum (angular, linear) measured and expressed in ground, but taken about the body mass center CB.

References MassProperties::calcCentralInertia(), MassProperties::getMass(), MassProperties::getMassCenter(), and Inertia_< P >::reexpress().

SpatialVec calcBodyMomentumAboutBodyOriginInGround

(

const State &

s

)

[inline]

Calculate body B's momentum (angular, linear) measured and expressed in ground, but taken about the body origin OB.

References MassProperties::toSpatialMat().

Vec3 calcBodyMovingPointAccelerationInBody	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const Vec3 &	velocityOnBodyB,
		const Vec3 &	accelerationOnBodyB,
		const MobilizedBody &	inBodyA
	)			const [inline]

TODO: not implemented yet -- any volunteers? Return the velocity of a point P moving (and possibly accelerating) on body B, in body A's frame, expressed in body A.

References Vec< 3 >::getNaN(), and SimTK_ASSERT_ALWAYS.

Vec3 calcBodyMovingPointVelocityInBody	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const Vec3 &	velocityOnBodyB,
		const MobilizedBody &	inBodyA
	)			const [inline]

TODO: not implemented yet -- any volunteers? Return the velocity of a point P moving on body B, in body A's frame, expressed in body A.

References Vec< 3 >::getNaN(), and SimTK_ASSERT_ALWAYS.

SpatialMat calcBodySpatialInertiaMatrixInGround

(

const State &

s

)

const [inline]

Return the mass properties of body B, measured from and about the B frame origin, but expressed in Ground and then returned as a Spatial Inertia Matrix.

The mass properties are arranged in the SpatialMat like this:

       M=[      I_OB      crossMat(m*CB) ]
         [ ~crossMat(m*CB)   diag(m)     ]
 

where I_OB is the inertia taken about the B frame origin OB, and CB is the vector r_OB_CB from B's origin to its mass center.

The Spatial Inertia Matrix for Ground has infinite mass and inertia, with the cross terms set to zero. That is, it looks like a 6x6 diagonal matrix with Infinity on the diagonals.

Required stage

Stage::Position, unless objectBodyB == GroundIndex

References MassProperties::reexpress(), and MassProperties::toSpatialMat().

Real calcMovingPointToPointDistance2ndTimeDerivative	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const Vec3 &	velocityOnBodyB,
		const Vec3 &	accelerationOnBodyB,
		const MobilizedBody &	bodyA,
		const Vec3 &	locationOnBodyA,
		const Vec3 &	velocityOnBodyA,
		const Vec3 &	accelerationOnBodyA
	)			const [inline]

TODO: not implemented yet -- any volunteers? Calculate the second time derivative of distance from a moving point PB on body B to a moving point PA on body A.

We are given the location vectors r_OB_PB and r_OA_PA, and the velocities and accelerations of PB in B and PA in A, all expressed in their respective frames. We return d^2/dt^2 |r_OA_OB|, taking into account the time derivatives of the locations in their local frames, as well as the relative velocities and accelerations of the bodies.

References SimTK_ASSERT_ALWAYS.

Real calcMovingPointToPointDistanceTimeDerivative	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const Vec3 &	velocityOnBodyB,
		const MobilizedBody &	bodyA,
		const Vec3 &	locationOnBodyA,
		const Vec3 &	velocityOnBodyA
	)			const [inline]

TODO: not implemented yet -- any volunteers? Calculate the time rate of change of distance from a moving point PB on body B to a moving point PA on body A.

We are given the location vectors r_OB_PB and r_OA_PA, and the velocities of PB in B and PA in A, all expressed in their respective frames. We return d/dt |r_OB_OA|, taking into account the (given) time derivatives of the locations in their local frames, as well as the relative velocities of the bodies.

References SimTK_ASSERT_ALWAYS.

Real calcStationToStationDistance	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const MobilizedBody &	bodyA,
		const Vec3 &	locationOnBodyA
	)			const [inline]

Calculate the distance from a station PB on body B to a station PA on body A.

We are given the location vectors (stations) p_OB_PB and p_OA_PA, expressed in their respective frames. We return |p_PB_PA|.

References MobilizedBody::findStationLocationInGround(), and Vec< M, ELT, STRIDE >::norm().

Real calcStationToStationDistance2ndTimeDerivative	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const MobilizedBody &	bodyA,
		const Vec3 &	locationOnBodyA
	)			const [inline]

Calculate the second time derivative of distance from a fixed point PB on body B to a fixed point PA on body A.

We are given the location vectors (stations) r_OB_PB and r_OA_PA, expressed in their respective frames. We return d^2/dt^2 |p_PB_PA|, under the assumption that the time derivatives of the two given vectors in their own frames is zero.

References SimTK::dot(), MobilizedBody::findStationLocationVelocityAndAccelerationInGround(), and Vec< M, ELT, STRIDE >::norm().

Real calcStationToStationDistanceTimeDerivative	(	const State &	s,
		const Vec3 &	locationOnBodyB,
		const MobilizedBody &	bodyA,
		const Vec3 &	locationOnBodyA
	)			const [inline]

Calculate the time rate of change of distance from a fixed point PB on body B to a fixed point PA on body A.

We are given the location vectors r_OB_PB and r_OA_PA, expressed in their respective frames. We return d/dt |r_OB_OA|, under the assumption that the time derivatives of the two given vectors in their own frames is zero.

References SimTK::dot(), MobilizedBody::findStationLocationAndVelocityInGround(), and Vec< M, ELT, STRIDE >::norm().

void clearMotion

(

)

If there is a Motion object associated with this MobilizedBody it is removed; otherwise, nothing happens.

If a Motion is deleted, the containing System's topology is invalidated.

MobilizedBody& cloneForNewParent

(

MobilizedBody &

parent

)

const

Create a new MobilizedBody which is identical to this one, except that it has a different parent (and consequently might belong to a different MultibodySystem).

Vec3 expressGroundVectorInBodyFrame	(	const State &	s,
		const Vec3 &	vectorInG
	)			const [inline]

Re-express a vector expressed in Ground into the same vector expressed in this body B, by applying only rotation.

That is, we return vectorInB = R_BG * vectorInG. Cost is 15 flops. This operator is available at Position stage.

Referenced by MobilizedBody::expressVectorInAnotherBodyFrame(), and MobilizedBody::findBodyAngularVelocityInAnotherBody().

MassProperties expressMassPropertiesInAnotherBodyFrame	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Re-express this body B's mass properties in another body A's frame by applying only a rotation, not a shift of reference point.

The mass properties remain measured in the body B frame, taken about the body B origin OB, but are reexpressed in A.

References MassProperties::reexpress().

MassProperties expressMassPropertiesInGroundFrame

(

const State &

s

)

const [inline]

Re-express this body B's mass properties in Ground by applying only a rotation, not a shift of reference point.

The mass properties remain measured in the body B frame, taken about the body B origin OB, but are reexpressed in Ground.

References MassProperties::reexpress().

Vec3 expressVectorInAnotherBodyFrame	(	const State &	s,
		const Vec3 &	vectorInB,
		const MobilizedBody &	inBodyA
	)			const [inline]

Re-express a vector expressed in this body B into the same vector expressed in body A, by applying only a rotation.

That is, we return vectorInA = R_AB * vectorInB. Cost is 30 flops. This operator is available at Position stage. Note: if you know one of the bodies is Ground, call one of the specialized methods above to save 15 flops.

References MobilizedBody::expressGroundVectorInBodyFrame().

Vec3 expressVectorInGroundFrame	(	const State &	s,
		const Vec3 &	vectorInB
	)			const [inline]

Re-express a vector expressed in this body B's frame into the same vector in G, by applying only a rotation.

That is, we return vectorInG = R_GB * vectorInB. Cost is 15 flops. This operator is available at Position stage.

SpatialVec findBodyAccelerationInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the angular and linear acceleration of body B's frame in body A's frame, expressed in body A, and arranged as a SpatialVec.

Cost is 105 flops. If you know that inBodyA is Ground, don't use this operator; instead, use the response method getBodyAcceleration() which is free. This operator is available in Acceleration stage.

See also:

getBodyAcceleration()

References MobilizedBody::getBodyAcceleration(), MobilizedBody::getBodyTransform(), MobilizedBody::getBodyVelocity(), Transform_< P >::p(), and Transform_< P >::R().

Vec3 findBodyAngularAccelerationInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the angular acceleration of body B's frame in body A's frame, expressed in body A.

Cost is 33 flops. If you know inBodyA is Ground, don't use this operator; instead use the response method getBodyAngularAccleration() which is free. This operator is available at AccelerationStage.

See also:

getBodyAngularAcceleration()

References MobilizedBody::getBodyAngularAcceleration(), MobilizedBody::getBodyAngularVelocity(), and MobilizedBody::getBodyRotation().

Vec3 findBodyAngularVelocityInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the angular velocity w_AB of body B's frame in body A's frame, expressed in body A.

Cost is 18 flops. If you know inBodyA is Ground, don't use this routine; use the response method getBodyAngularVelocity() which is free. This operator is available in Velocity stage.

See also:

getBodyAngularVelocity()

References MobilizedBody::expressGroundVectorInBodyFrame(), and MobilizedBody::getBodyAngularVelocity().

Vec3 findBodyOriginAccelerationInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the acceleration of body B's origin point in body A's frame, expressed in body A.

Cost is 105 flops. If you know that inBodyA is Ground, don't use this operator; instead, use the response method getBodyOriginAcceleration() which is free. This operator is available in Acceleration stage.

See also:

getBodyOriginAcceleration()

Vec3 findBodyOriginLocationInAnotherBody	(	const State &	s,
		const MobilizedBody &	toBodyA
	)			const [inline]

Return the station on another body A (that is, a point measured and expressed in A) that is currently coincident in space with the origin OB of this body B.

Cost is 18 flops. This operator is available at Position stage. Note: "findBodyOriginLocationInGround" doesn't exist because it would be the same as the response getBodyOriginLocation().

See also:

getBodyOriginLocation()

References MobilizedBody::findStationAtGroundPoint().

Vec3 findBodyOriginVelocityInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the velocity of body B's origin point in body A's frame, expressed in body A.

Cost is 51 flops. If you know inBodyA is Ground, don't use this routine; use the response method getBodyOriginVelocity() which is free. This operator is available in Velocity stage.

See also:

getBodyOriginVelocity()

Rotation findBodyRotationInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return R_AB, the rotation matrix giving this body B's axes in body A's frame.

Cost is 45 flops. If you know that one of the bodies is Ground, use the 0-cost response getBodyRotation() instead of this operators. This operator is available in Position stage.

See also:

getBodyRotation()

References MobilizedBody::getBodyRotation().

Referenced by MobilizedBody::calcBodyInertiaAboutAnotherBodyStation().

Transform findBodyTransformInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

These methods use state variables and Response methods to compute basic quantities which cannot be precomputed, but which can be implemented with an inline combination of basic floating point operations which can be reliably determined at compile time.

The method names and descriptions use the following terms:

• Body or ThisBody: the Body B associated with the current MobilizedBody. ThisBody is implied when no other Body is mentioned.
• Ground: the "MobilizedBody" G representing the Ground reference frame which never moves.
• AnotherBody: the Body A being referenced, which in general is neither ThisBody nor Ground.
• Station: a point S fixed on ThisBody B, located by a position vector p_BS (or more explicitly, p_OB_S) from the B-frame origin OB to the point S, expressed in the B-frame coordinate system.
• Vector: a vector v fixed on ThisBody B, given by a vector v_B expressed in the B-frame coordinate system.
• Direction: a unit vector u fixed on ThisBody B, given by a unit vector u_B expressed in the B-frame coordinate system.
• Frame: an origin and coordinate axes F fixed on ThisBody B, given by a transform X_BF that locates F's origin (a Station) in B and expresses each of F's axes (Directions) in B.
• Origin: the Station located at (0,0,0) in ThisBody frame B, that is, body B's origin point.
• MassCenter: the Station on ThisBody B which is the center of mass for B.
• GroundPoint, GroundVector: a Point P or Vector v on the Ground "Body" G. These are measured and expressed in the Ground frame, as p_GP or v_G.
• AnotherBodyStation, AnotherBodyVector, etc.: a Station S or Vector v on AnotherBody A. These are measured and expressed in the A frame, as p_AS or v_A. Return X_AB, the spatial transform giving this body B's frame in body A's frame. Cost is 63 flops. If you know that one of the bodies is Ground, use the 0-cost response getBodyTransform() instead of this operators. This operator is available in Position stage.

  See also:

  getBodyTransform()

References MobilizedBody::getBodyTransform().

SpatialVec findBodyVelocityInAnotherBody	(	const State &	s,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the angular and linear velocity of body B's frame in body A's frame, expressed in body A, and arranged as a SpatialVec.

Cost is 51 flops. If you know inBodyA is Ground, don't use this routine; use the response method getBodyVelocity() which is free. This operator is available in Velocity stage.

See also:

getBodyVelocity()

References MobilizedBody::getBodyTransform(), MobilizedBody::getBodyVelocity(), Transform_< P >::p(), and Transform_< P >::R().

SpatialVec findFrameAccelerationInGround	(	const State &	s,
		const Transform &	frameOnB
	)			const [inline]

Return the current Ground-frame spatial acceleration A_GF (that is, angular and linear acceleration) of a frame F that is fixed to body B.

The angular acceleration of F is the same as that of B, but the linear acceleration is the acceleration of F's origin OF rather than B's origin OB. This operator is available at Acceleration stage. Cost is 48 flops.

References Transform_< P >::p().

Transform findFrameTransformInGround	(	const State &	s,
		const Transform &	frameOnB
	)			const [inline]

Return the current Ground-frame pose (position and orientation) of a frame F that is fixed to body B.

That is, we return X_GF=X_GB*X_BF. Cost is 63 flops. This operator is available at Position stage.

SpatialVec findFrameVelocityInGround	(	const State &	s,
		const Transform &	frameOnB
	)			const [inline]

Return the current Ground-frame spatial velocity V_GF (that is, angular and linear velocity) of a frame F that is fixed to body B.

The angular velocity of F is the same as that of B, but the linear velocity is the velocity of F's origin OF rather than B's origin OB. This operator is available at Velocity stage. Cost is 27 flops.

References Transform_< P >::p().

Vec3 findMassCenterLocationInAnotherBody	(	const State &	s,
		const MobilizedBody &	toBodyA
	)			const [inline]

Return the point of another body A that is currently coincident in space with the mass center CB of this body B.

Cost is 36 flops. This operator is available at Position stage.

Vec3 findMassCenterLocationInGround

(

const State &

s

)

const [inline]

Return the Cartesian (ground) location of this body B's mass center.

Cost is 18 flops. This operator is available at Position stage.

Vec3 findStationAccelerationInAnotherBody	(	const State &	s,
		const Vec3 &	stationOnBodyB,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the acceleration of a station S fixed on body B, in another body A's frame, expressed in body A.

Cost is 186 flops. If you know that inBodyA is Ground, don't use this operator; instead, use the operator findStationAccelerationInGround() which is much cheaper. This operator is available in Acceleration stage.

Vec3 findStationAccelerationInGround	(	const State &	s,
		const Vec3 &	stationOnB
	)			const [inline]

Given a station fixed on body B, return its inertial (Cartesian) acceleration, that is, its acceleration relative to the ground frame, expressed in the ground frame.

Cost is 48 flops. If you know the station is the body origin (0,0,0) don't use this routine; use the response getBodyOriginAcceleration() which is free. This operator is available at Acceleration stage.

See also:

getBodyOriginAcceleration()

Vec3 findStationAtAnotherBodyMassCenter	(	const State &	s,
		const MobilizedBody &	fromBodyA
	)			const [inline]

Return the station S of this body that is currently coincident in space with the mass center CA of another body B.

Cost is 36 flops. This operator is available at Position stage.

References MobilizedBody::findStationLocationInAnotherBody().

Vec3 findStationAtAnotherBodyOrigin	(	const State &	s,
		const MobilizedBody &	fromBodyA
	)			const [inline]

Return the station S of this body that is currently coincident in space with the origin OA of another body A.

Cost is 18 flops. This operator is available at Position stage.

References MobilizedBody::getBodyOriginLocation().

Vec3 findStationAtAnotherBodyStation	(	const State &	s,
		const MobilizedBody &	fromBodyA,
		const Vec3 &	stationOnA
	)			const [inline]

Return the station (point) on this body B that is coincident with the given station on another body A.

That is we return stationOnB = X_BA * stationOnA, which means the result is measured from the body origin OB and expressed in the body frame. Cost is 36 flops. This operator is available at Position stage.

See also:

findStationLocationInAnotherBody()

References MobilizedBody::findStationLocationInAnotherBody().

Vec3 findStationAtGroundPoint	(	const State &	s,
		const Vec3 &	locationInG
	)			const [inline]

Return the station (point) S of this body B that is coincident with the given Ground location.

That is we return locationOnB = X_BG*locationInG, which means the result is measured from the body origin OB and expressed in the body frame. In more precise notation, we're calculating p_BS = X_BG*p_GS. Cost is 18 flops. This operator is available at Position stage.

Referenced by MobilizedBody::findBodyOriginLocationInAnotherBody(), and MobilizedBody::findStationLocationInAnotherBody().

void findStationLocationAndVelocityInGround	(	const State &	s,
		const Vec3 &	locationOnB,
		Vec3 &	locationOnGround,
		Vec3 &	velocityInGround
	)			const [inline]

It is cheaper to calculate a station's ground location and velocity together than to do them separately.

Here we can return them both in 30 flops, vs. 45 to do them in two calls. This operator is available at Velocity stage.

Referenced by MobilizedBody::calcStationToStationDistanceTimeDerivative().

Vec3 findStationLocationInAnotherBody	(	const State &	s,
		const Vec3 &	stationOnB,
		const MobilizedBody &	toBodyA
	)			const [inline]

Given a station S on this body B, return the location on another body A which is at the same location in space.

That is, we return locationOnA= X_AB*locationOnB, which means the result is measured from the body A origin and expressed in body A. In more precise notation, we're calculating p_AS = X_AB * p_BS, which we actually calculate as p_AS = X_AG*(X_GB*p_BS). Cost is 36 flops. Note: if you know that one of the bodies is Ground, use one of the routines above which is specialized for Ground to avoid half the work. This operator is available at Position stage or higher.

References MobilizedBody::findStationAtGroundPoint().

Referenced by MobilizedBody::findStationAtAnotherBodyMassCenter(), and MobilizedBody::findStationAtAnotherBodyStation().

Vec3 findStationLocationInGround	(	const State &	s,
		const Vec3 &	stationOnB
	)			const [inline]

Return the Cartesian (ground) location that is currently coincident with a station (point) S fixed on body B.

That is, we return locationInG= X_GB*stationOnB which means the result is measured from the Ground origin and expressed in Ground. In more precise notation, we're calculating p_GS = X_GB * p_BS for position vectors p_GS and p_BS. Cost is 18 flops. This operator is available at Position stage.

Referenced by MobilizedBody::calcStationToStationDistance().

void findStationLocationVelocityAndAccelerationInGround	(	const State &	s,
		const Vec3 &	locationOnB,
		Vec3 &	locationOnGround,
		Vec3 &	velocityInGround,
		Vec3 &	accelerationInGround
	)			const [inline]

It is cheaper to calculate a station's ground location, velocity, and acceleration together than to do them separately.

Here we can return them all in 54 flops, vs. 93 to do them in three calls. This operator is available at Acceleration stage.

Referenced by MobilizedBody::calcStationToStationDistance2ndTimeDerivative().

Vec3 findStationVelocityInAnotherBody	(	const State &	s,
		const Vec3 &	stationOnBodyB,
		const MobilizedBody &	inBodyA
	)			const [inline]

Return the velocity of a station S fixed on body B, in body A's frame, expressed in body A.

Cost is 93 flops. If you know inBodyA is Ground, don't use this operator; instead use the operator findStationVelocityInGround() which is much cheaper. This operator is available in Velocity stage.

See also:

findStationVelocityInGround()

Vec3 findStationVelocityInGround	(	const State &	s,
		const Vec3 &	stationOnB
	)			const [inline]

Given a station fixed on body B, return its inertial (Cartesian) velocity, that is, its velocity relative to the Ground frame, expressed in the Ground frame.

Cost is 27 flops. If you know the station is the body origin (0,0,0) don't use this routine; use the response getBodyOriginVelocity() which is free. This operator is available at Velocity stage.

See also:

getBodyOriginVelocity()

const MobilizedBody& getBaseMobilizedBody

(

)

const

Return a reference to this MobilizedBody's oldest ancestor other than Ground, or return Ground if this MobilizedBody is Ground.

That is, we return the "base" MobilizedBody for this MobilizedBody, meaning the one which connects this branch of the multibody tree directly to Ground.

const Body& getBody

(

)

const

Return a reference to the Body contained within this MobilizedBody.

const SpatialVec& getBodyAcceleration

(

const State &

s

)

const

Extract from the state cache the already-calculated spatial acceleration A_GB of this body's reference frame B, measured with respect to the Ground frame and expressed in the Ground frame.

That is, we return the linear acceleration a_GB of the body frame's origin in G, and the body's angular acceleration b_GB as the spatial acceleration vector A_GB = {b_GB, a_GB}. This response is available at Acceleration stage.

Referenced by MobilizedBody::findBodyAccelerationInAnotherBody().

const Vec3& getBodyAngularAcceleration

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated inertial angular acceleration vector b_GB of this body B, measured with respect to the Ground frame and expressed in the Ground frame.

This response is available at Acceleration stage.

Referenced by MobilizedBody::findBodyAngularAccelerationInAnotherBody().

const Vec3& getBodyAngularVelocity

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated inertial angular velocity vector w_GB of this body B, measured with respect to the Ground frame and expressed in the Ground frame.

This response is available at Velocity stage.

Referenced by MobilizedBody::findBodyAngularAccelerationInAnotherBody(), and MobilizedBody::findBodyAngularVelocityInAnotherBody().

const Inertia& getBodyInertiaAboutBodyOrigin

(

const State &

s

)

const [inline]

Return a reference to this body's inertia matrix in the State cache, taken about the body origin and expressed in the body frame.

The State must have been realized to Stage::Instance or higher.

Real getBodyMass

(

const State &

s

)

const [inline]

Return the mass of this body. The State must have been realized to Stage::Instance.

const Vec3& getBodyMassCenterStation

(

const State &

s

)

const [inline]

Return this body's center of mass station (i.e., the vector fixed in the body, going from body origin to body mass center, expressed in the body frame.

) The State must have been realized to Stage::Instance or higher.

const MassProperties& getBodyMassProperties

(

const State &

)

const

Return a reference to this body's mass properties in the State cache.

The State must have been realized to Stage::Instance or higher.

const Vec3& getBodyOriginAcceleration

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated inertial linear acceleration vector a_GB (more explicitly, a_G_OB) of this body B's origin point OB, measured with respect to the Ground frame and expressed in the Ground frame.

This response is available at Acceleration stage.

const Vec3& getBodyOriginLocation

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated spatial location of body B's body frame origin OB, measured from the Ground origin OG and expressed in the Ground frame, as the position vector p_GB (== p_OG_OB).

This response is available at Position stage.

Referenced by MobilizedBody::findStationAtAnotherBodyOrigin().

const Vec3& getBodyOriginVelocity

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated inertial linear velocity vector v_GB (more explicitly, v_G_OB) of this body B's origin point OB, measured with respect to the Ground frame and expressed in the Ground frame.

This response is available at Velocity stage.

const Rotation& getBodyRotation

(

const State &

s

)

const [inline]

Extract from the state cache the already-calculated spatial orientation R_GB of body B's body frame x, y, and z axes expressed in the Ground frame, as the Rotation matrix R_GB.

The sense of this rotation matrix is such that if you have a vector v fixed on body B, represented by the vector v_B expressed in the B frame, then v_G=R_GB*v_B where v_G is the same vector but re-expressed in the Ground frame. The inverse transformation is obtained using the "~" operator where ~R_GB=R_BG, so that v_B = ~R_GB*v_G. This response is available at Position stage.

Referenced by MobilizedBody::findBodyAngularAccelerationInAnotherBody(), and MobilizedBody::findBodyRotationInAnotherBody().

const Transform& getBodyTransform

(

const State &

)

const

Extract from the state cache the already-calculated spatial configuration X_GB of body B's body frame, measured with respect to the Ground frame and expressed in the Ground frame.

That is, we return the location of the body frame's origin, and the orientation of its x, y, and z axes, as the Transform X_GB. This notation is intended to convey unambiguously the sense of this transform, which is as follows: if you have a station (body fixed point) S on body B, represented by position vector p_BS (a.k.a. p_OB_S) from the origin OB of B to the point S and expressed in the B frame, then p_GS=X_GB*p_BS where p_GS (== p_OG_S) is the position vector from the Ground origin OG to the point in space currently coincident with S and expressed in the Ground frame. The inverse transformation is obtained using the "~" operator where ~X_GB=X_BG, so that p_BS = ~X_GB*p_GS. This response is available at Position stage.

Referenced by RNA::calcRNABaseNormal(), MobilizedBody::findBodyAccelerationInAnotherBody(), MobilizedBody::findBodyTransformInAnotherBody(), and MobilizedBody::findBodyVelocityInAnotherBody().

const SpatialVec& getBodyVelocity

(

const State &

)

const

Extract from the state cache the already-calculated spatial velocity V_GB of this body's reference frame B, measured with respect to the Ground frame and expressed in the Ground frame.

That is, we return the linear velocity v_GB of the body frame's origin in G, and the body's angular velocity w_GB as the spatial velocity vector V_GB = {w_GB, v_GB}. This response is available at Velocity stage.

Referenced by MobilizedBody::findBodyAccelerationInAnotherBody(), and MobilizedBody::findBodyVelocityInAnotherBody().

const Transform& getDefaultInboardFrame

(

)

const

Return a reference to this mobilizer's default for the frame F fixed on the parent body P, as the fixed Transform from P's body frame to the frame F fixed to P.

This default Transform is stored with the MobilizedBody object, not the State.

const MassProperties& getDefaultMassProperties

(

)

const [inline]

Return the mass properties of the Body stored within this MobilizedBody.

const Transform& getDefaultOutboardFrame

(

)

const

Return a reference to this MobilizedBody's default for mobilizer frame M, as the fixed Transform from this body B's frame to the frame M fixed on B.

This default Transform is stored with the MobilizedBody object, not the State.

QIndex getFirstQIndex

(

const State &

)

const

Return the global QIndex of the first q for this mobilizer; all the q's range from getFirstQIndex() to QIndex(getFirstQIndex()+getNumQ()-1).

Referenced by QValue::calcErrorJacobian(), and QValue::calcGoalGradient().

UIndex getFirstUIndex

(

const State &

)

const

Return the global UIndex of the first u for this mobilizer; all the u's range from getFirstUIndex() to UIndex(getFirstUIndex()+getNumU()).

SpatialVec getHCol	(	const State &	s,
		UIndex	ux
	)			const

Expert use only: obtain a column of the hinge matrix H corresponding to one of this mobilizer's mobilities.

const Transform& getInboardFrame

(

const State &

)

const

Return a reference to this mobilizer's frame F fixed on the parent body P, as the fixed Transform from P's body frame to the frame F fixed to P.

If this frame is changeable, the result comes from the State cache, otherwise it is from the MobilizedBody object itself. The State must have been realized to Stage::Instance or higher.

int getLevelInMultibodyTree

(

)

const

Return this body's level in the tree of bodies, starting with ground at 0, bodies directly connected to ground at 1, bodies directly connected to those at 2, etc.

This is callable after realizeTopology(). This is the graph distance of the body from Ground.

const SimbodyMatterSubsystem& getMatterSubsystem

(

)

const

Obtain a reference to the SimbodyMatterSubsystem which contains this MobilizedBody.

This will fail unless this MobilizedBody is owned by some SimbodyMatterSubsystem.

MobilizedBodyIndex getMobilizedBodyIndex

(

)

const

Return the MobilizedBodyIndex of this MobilizedBody within the owning SimbodyMatterSubsystem.

This will fail unless this MobilizedBody is owned by some SimbodyMatterSubsystem. We guarantee that the MobilizedBodyIndex of a mobilized body is numerically larger than the MobilizedBodyIndex of its parent.

Referenced by VanDerWaalsForce::decorateBoundingSpheres().

const SpatialVec& getMobilizerAcceleration

(

const State &

)

const [inline]

TODO: Not implemented yet -- any volunteers? At stage Acceleration, return the cross-mobilizer acceleration A_FM, the relative acceleration of body B's "moving" mobilizer frame M in the parent body's corresponding "fixed" frame F, measured and expressed in F.

Note that this isn't the usual spatial acceleration since it isn't expressed in G.

Reimplemented in Translation.

References SimTK_ASSERT_ALWAYS.

const Transform& getMobilizerTransform

(

const State &

)

const

At stage Position or higher, return the cross-mobilizer transform X_FM, the body's inboard mobilizer frame M measured and expressed in the parent body's corresponding outboard frame F.

const SpatialVec& getMobilizerVelocity

(

const State &

)

const

At stage Velocity or higher, return the cross-mobilizer velocity V_FM, the relative velocity of this body's "moving" mobilizer frame M in the parent body's corresponding "fixed" frame F, measured and expressed in F.

Note that this isn't the usual spatial velocity since it isn't expressed in G.

Reimplemented in Translation.

const Motion& getMotion

(

)

const

If there is a Motion object assocated with this MobilizedBody, this returns a const reference to it.

Otherwise it will throw an exception. You can check first using hasMotion(). Note that there is no provision to obtain a writable reference to the contained Motion object; if you want to change it clear the existing object instead and replace it with a new one.

See also:

hasMotion()

int getNumQ

(

const State &

)

const

Return the number of generalized coordinates q currently in use by this mobilizer.

State must have been realized to Stage::Model.

int getNumU

(

const State &

)

const

Return the number of generalized speeds u currently in use by this mobilizer.

State must have been realized to Stage::Model.

Real getOneFromQPartition	(	const State &	,
		int	which,
		const Vector &	qlike
	)			const

This utility selects one of the q's (generalized coordinates) associated with this mobilizer from a supplied "q-like" Vector, meaning a Vector which is the same length as the Vector of q's for the containing matter subsystem.

Real getOneFromUPartition	(	const State &	,
		int	which,
		const Vector &	ulike
	)			const

This utility selects one of the u's (generalized speeds) associated with this mobilizer from a supplied "u-like" Vector, meaning a Vector which is the same length as the Vector of u's for the containing matter subsystem.

Real getOneQ	(	const State &	,
		int	which
	)			const

Return one of the generalized coordinates q from this mobilizer's partition of the matter subsystem's full q vector in the State.

The particular coordinate is selected using the which parameter, numbering from zero to getNumQ()-1.

Referenced by QValue::calcErrors(), QValue::calcGoal(), and QValue::calcGoalGradient().

Real getOneQDot	(	const State &	,
		int	which
	)			const

Return one of the generalized coordinate derivatives qdot from this mobilizer's partition of the matter subsystem's full qdot vector in the State cache.

The particular coordinate is selected using the which parameter, numbering from zero to getNumQ()-1.

Real getOneQDotDot	(	const State &	,
		int	which
	)			const

Return one of the generalized coordinate second derivatives qdotdot from this mobilizer's partition of the matter subsystem's full qdotdot vector in the State cache.

The particular coordinate is selected using the which parameter, numbering from zero to getNumQ()-1.

Real getOneTau	(	const State &	,
		MobilizerUIndex	which
	)			const

Return one of the tau forces resulting from known (prescribed) acceleration, corresponding to one of this mobilizer's mobilities as selected here using the which parameter, numbered from zero to getNumU()-1.

See also:

getTauAsVector() for more information

Real getOneU	(	const State &	,
		int	which
	)			const

Return one of the generalized speeds u from this mobilizer's partition of the matter subsystem's full u vector in the State.

The particular coordinate is selected using the which parameter, numbering from zero to getNumU()-1.

Real getOneUDot	(	const State &	,
		int	which
	)			const

Return one of the generalized accelerations udot from this mobilizer's partition of the matter subsystem's full udot vector in the State cache.

The particular coordinate is selected using the which parameter, numbering from zero to getNumU()-1.

const Transform& getOutboardFrame

(

const State &

)

const

Return a reference to this MobilizedBody's mobilizer frame M, as the fixed Transform from this body B's frame to the frame M fixed on B.

If this frame is changeable, the result comes from the State cache, otherwise it is from the MobilizedBody object itself. The State must have been realized to Stage::Instance or higher.

const MobilizedBody& getParentMobilizedBody

(

)

const

Return a reference to the MobilizedBody serving as the parent body of the current MobilizedBody.

This call will fail if the current MobilizedBody is Ground, since Ground has no parent.

Vector getQAsVector

(

const State &

)

const

Return as a Vector of length getNumQ() all the generalized coordinates q currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full q vector in the State.

Vector getQDotAsVector

(

const State &

)

const

Return as a Vector of length getNumQ() all the generalized coordinate derivatives qdot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full qdot vector in the State cache.

Vector getQDotDotAsVector

(

const State &

)

const

Return as a Vector of length getNumQ() all the generalized coordinate second derivatives qdotdot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full qdotdot vector in the State cache.

Vector getTauAsVector

(

const State &

)

const

Return the tau forces resulting from known (prescribed) acceleration, corresponding to each of this mobilizer's mobilities, as a Vector of length getNumU().

If this mobilizer has known accelerations (UDots) due to an active Motion object, the set of generalized forces tau that must be added in order to produce those accelerations is calculated at Acceleration stage. There is one scalar tau per mobility and they can be returned individually or as a Vector. The return value is zero if the accelerations are free.

Vector getUAsVector

(

const State &

)

const

Return as a Vector of length getNumU() all the generalized speeds u currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full u vector in the State.

Vector getUDotAsVector

(

const State &

)

const

Return as a Vector of length getNumU() all the generalized accelerations udot currently in use by this mobilizer, from this mobilizer's partion in the matter subsystem's full udot vector in the State cache.

bool hasMotion

(

)

const

Check whether this MobilizedBody has an associated Motion object.

This does not tell you whether the Motion object is currently enabled or in use; just whether it is available.

bool isAccelerationAlwaysZero

(

const State &

)

const

bool isGround

(

)

const

Determine whether this body is Ground, meaning that it is actually body 0 of some matter subsytem, not just that its body type is Ground.

bool isInSameSubsystem

(

const MobilizedBody &

)

const

Determine whether a given MobilizedBody mBody is in the same matter subsystem as the current body.

If the bodies are not in a subsystem, this routine will return false.

bool isInSubsystem

(

)

const

Determine whether the current MobilizedBody object is owned by a matter subsystem.

bool isSameMobilizedBody

(

const MobilizedBody &

mBody

)

const

Determine whether a given MobilizedBody mBody is the same MobilizedBody as this one.

For this to be true the handles must not be empty, and the implementation objects must be the same object not separate objects with identical contents.

bool isVelocityAlwaysZero

(

const State &

)

const

operator MobilizedBodyIndex

(

)

const [inline]

This is an implicit conversion from MobilizedBody to MobilizedBodyIndex when needed.

This will fail unless this MobilizedBody is owned by some SimbodyMatterSubsystem. We guarantee that the MobilizedBodyIndex of a mobilized body is numerically larger than the MobilizedBodyIndex of its parent.

MobilizedBody& setBody

(

const Body &

)

Replace the Body contained within this MobilizedBody with a new one.

Calling this method invalidates the MobilizedBody's topology, so the containing matter subsystem's realizeTopology() method must be called again. A reference to this MobilizedBody is returned so that this can be chained like an assignment operator.

MobilizedBody& setDefaultInboardFrame

(

const Transform &

X_PF

)

Change this mobilizer's frame F on the parent body P.

Calling this method invalidates the MobilizedBody's topology, so the containing matter subsystem's realizeTopology() method must be called again. A reference to this MobilizedBody is returned so that this can be chained like an assignment operator.

Reimplemented in Pin, Slider, Screw, Universal, Cylinder, BendStretch, Planar, SphericalCoords, Gimbal, Ball, Ellipsoid, Translation, Free, LineOrientation, FreeLine, and Weld.

Referenced by Pin::setDefaultInboardFrame(), Cylinder::setDefaultInboardFrame(), Free::setDefaultInboardFrame(), Weld::setDefaultInboardFrame(), Ball::setDefaultInboardFrame(), LineOrientation::setDefaultInboardFrame(), BendStretch::setDefaultInboardFrame(), Gimbal::setDefaultInboardFrame(), SphericalCoords::setDefaultInboardFrame(), Screw::setDefaultInboardFrame(), Universal::setDefaultInboardFrame(), Ellipsoid::setDefaultInboardFrame(), Planar::setDefaultInboardFrame(), Translation::setDefaultInboardFrame(), Slider::setDefaultInboardFrame(), and FreeLine::setDefaultInboardFrame().

MobilizedBody& setDefaultMassProperties

(

const MassProperties &

m

)

[inline]

If the contained Body can have its mass properties set to the supplied value m its mass properties are changed, otherwise the method fails.

Calling this method invalidates the MobilizedBody's topology, so the containing matter subsystem's realizeTopology() method must be called again. A reference to this MobilizedBody is returned so that this can be chained like an assignment operator.

MobilizedBody& setDefaultMotionType	(	Motion::Level	,
		Motion::Method	= Motion::Prescribed
	)

The default behavior of this mobilizer will normally be determined by whether you provide a Motion object for it.

However, you can override that afterwards.

MobilizedBody& setDefaultOutboardFrame

(

const Transform &

X_BM

)

Change this mobilizer's frame M fixed on this (the outboard) body B.

Calling this method invalidates the MobilizedBody's topology, so the containing matter subsystem's realizeTopology() method must be called again. A reference to this MobilizedBody is returned so that this can be chained like an assignment operator.

Reimplemented in Pin, Slider, Screw, Universal, Cylinder, BendStretch, Planar, SphericalCoords, Gimbal, Ball, Ellipsoid, Translation, Free, LineOrientation, FreeLine, and Weld.

Referenced by Slider::setDefaultOutboardFrame(), Free::setDefaultOutboardFrame(), Screw::setDefaultOutboardFrame(), Gimbal::setDefaultOutboardFrame(), Planar::setDefaultOutboardFrame(), Cylinder::setDefaultOutboardFrame(), BendStretch::setDefaultOutboardFrame(), Ball::setDefaultOutboardFrame(), FreeLine::setDefaultOutboardFrame(), SphericalCoords::setDefaultOutboardFrame(), Ellipsoid::setDefaultOutboardFrame(), Pin::setDefaultOutboardFrame(), Universal::setDefaultOutboardFrame(), Translation::setDefaultOutboardFrame(), LineOrientation::setDefaultOutboardFrame(), and Weld::setDefaultOutboardFrame().

void setInboardFrame	(	State &	,
		const Transform &	X_PF
	)			const

TODO: not implemented yet.

Set the location and orientation of the inboard (parent) mobilizer frame F, fixed to this mobilizer's parent body P.

void setMotionType	(	State &	,
		Motion::Level	,
		Motion::Method	= Motion::Prescribed
	)			const

This is an Instance stage setting.

void setOneQ	(	State &	,
		int	which,
		Real	v
	)			const

Set one of the generalized coordinates q to value v, in this mobilizer's partition of the matter subsystem's full q vector in the State.

The particular coordinate is selected using the which parameter, numbering from zero to getNumQ()-1.

void setOneU	(	State &	,
		int	which,
		Real	v
	)			const

Set one of the generalized speeds u to value v, in this mobilizer's partition of the matter subsystem's full u vector in the State.

The particular coordinate is selected using the which parameter, numbering from zero to getNumU()-1.

void setOutboardFrame	(	State &	,
		const Transform &	X_BM
	)			const

TODO: not implemented yet.

Set the location and orientation of the outboard mobilizer frame M, fixed to this body B.

void setQFromVector	(	State &	s,
		const Vector &	v
	)			const

Set all of the generalized coordinates q to value v (a Vector of length getNumQ()), in this mobilizer's partition of the matter subsystem's full q vector in the State.

void setQToFitRotation	(	State &	,
		const Rotation &	R_FM
	)			const

Adjust this mobilizer's q's to best approximate the supplied Rotation matrix which requests a particular relative orientation between the "fixed" and "moving" frames connected by this mobilizer.

See also:

setQToFitTransform()

void setQToFitTransform	(	State &	,
		const Transform &	X_FM
	)			const

Adjust this mobilizer's q's to best approximate the supplied Transform which requests a particular relative orientation and translation between the "fixed" and "moving" frames connected by this mobilizer.

This set of methods sets the generalized coordinates, or speeds (state variables) for just the mobilizer associated with this MobilizedBody (ignoring all other mobilizers and constraints), without requiring knowledge of the meanings of the individual state variables. The idea here is to provide a physically-meaningful quantity relating the mobilizer's inboard and outboard frames, and then ask the mobilizer to set its state variables to reproduce that quantity to the extent it can.

These routines can be called in Stage::Model, however the routines may consult the current values of the state variables in some cases, so you must make sure they have been set to reasonable, or at least innocuous values (zero will work). In no circumstance will any of these routines look at any state variables which belong to another mobilizer; they are limited to working locally with one mobilizer.

Routines which specify only translation (linear velocity) may use rotational coordinates to help satisfy the translation requirement. An alternate "Only" method is available to forbid modification of purely rotational coordinates in that case. When a mobilizer uses state variables which have combined rotational and translational character (e.g. a screw joint) consult the documentation for the mobilizer to find out how it responds to these routines.

There is no guarantee that the desired physical quantity will be achieved by these routines; you can check on return if you're worried. Individual mobilizers make specific promises about what they will do; consult the documentation. These routines do not throw exceptions even for absurd requests like specifying a rotation for a sliding mobilizer. Nothing happens if there are no mobilities here, i.e. Ground or a Weld mobilizer.

void setQToFitTranslation	(	State &	,
		const Vec3 &	p_FM
	)			const

Adjust this mobilizer's q's to best approximate the supplied position vector which requests a particular offset between the origins of the "fixed" and "moving" frames connected by this mobilizer, with any q's (rotational or translational) being modified if doing so helps satisfy the request.

See also:

setQToFitTransform()

void setUFromVector	(	State &	s,
		const Vector &	v
	)			const

Set all of the generalized speeds u to value v (a Vector of length getNumU()), in this mobilizer's partition of the matter subsystem's full u vector in the State.

void setUToFitAngularVelocity	(	State &	,
		const Vec3 &	w_FM
	)			const

Adjust this mobilizer's u's (generalized speeds) to best approximate the supplied angular velocity w_FM which requests a particular relative angular between the "fixed" and "moving" frames connected by this mobilizer.

See also:

setQToFitTransform()

setUToFitVelocity()

void setUToFitLinearVelocity	(	State &	,
		const Vec3 &	v_FM
	)			const

Adjust any of this mobilizer's u's (generalized speeds) to best approximate the supplied linear velocity v_FM which requests a particular velocity for the "moving" frame M origin in the "fixed" frame F on the parent where these are the frames connected by this mobilizer.

See also:

setQToFitTransform()

setUToFitVelocity()

void setUToFitVelocity	(	State &	,
		const SpatialVec &	V_FM
	)			const

Adjust this mobilizer's u's (generalized speeds) to best approximate the supplied spatial velocity V_FM which requests the relative angular and linear velocity between the "fixed" and "moving" frames connected by this mobilizer.

Routines which affect generalized speeds u depend on the generalized coordinates q already having been set; they never change these coordinates.

See also:

setQToFitTransform()

Body& updBody

(

)

Return a writable reference to the Body contained within this MobilizedBody.

Calling this method invalidates the MobilizedBody's topology, so the containing matter subsystem's realizeTopology() method must be called again.

SimbodyMatterSubsystem& updMatterSubsystem

(

)

Obtain a writable reference to the SimbodyMatterSubsystem which contains this MobilizedBody.

This will fail unless this MobilizedBody is owned by some SimbodyMatterSubsystem.

Real& updOneFromQPartition	(	const State &	,
		int	which,
		Vector &	qlike
	)			const

This utility returns a writable reference to one of the q's (generalized coordinates) associated with this mobilizer from a supplied "q-like" Vector, meaning a Vector which is the same length as the Vector of q's for the containing matter subsystem.

Real& updOneFromUPartition	(	const State &	,
		int	which,
		Vector &	ulike
	)			const

This utility returns a writable reference to one of the u's (generalized speeds) associated with this mobilizer from a supplied "u-like" Vector, meaning a Vector which is the same length as the Vector of u's for the containing matter subsystem.

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The documentation for this class was generated from the following file:

• MobilizedBody.h