These are great questions, thanks Amit. I'll answer one per post: I want to provide Initial angular velocity to the whole body , not one body. is function "setUToFitAngularVelocity" (https://simbody.github.io/3.5.0/classSi ... de27544411), but this function only provide the angular velocity between ...

I think you wanted: so that you are working with the actual MobilizedBody in your system rather than a copy.

I'm not familiar with OpenSim's IK interface so this is just Thanksgiving speculation in case no one else is available: - assuming there is a way to loosen the tolerance, you may find you can solve the problem using joints and constraints with a little more slop allowed - you may have a problem with...

This diagram may help (scroll down to "Mobilizer Terminology and Notation") -- notice that a mobilizer is a relationship between two frames. One (F) is on the parent (inboard) body and the other (M) is on the child (outboard) body. A Pin mobilizer aligns the Z axes of those two frames. Each frame c...

You are correct that kinematics doesn't consider forces so the force elements don't affect IK. IK always respects joints and should satisfy constraints also. "To a tolerance" means that (unlike joints) constraints won't be satisfied perfectly (that is, to machine precision). Instead there will be so...

Tom beat me to answering and gave a better answer than I would have! (Hi, Tom) To elaborate a little -- in your example of a Weld joint vs. Weld constraint: Say we weld body A to body B. With a weld joint, A and B essentially become the same body, with B attached exactly as specified by the joint. T...

Hi, Harshal. An important thing to know is that Simbody expects inertias to be provided taken about the body origin, NOT the body mass center. I suspect your specification of the motor inertia was intended to be about the COM (0,0,.4) but Simbody interpreted it about (0,0,0) which, when shifted to (...

Of course there is a limit to how big a system can run in real time, but I don't think you're close to it yet. Take a look at "ChainExample". That's an interactive 3d example with 100 bodies connected by ball joints so 300 dofs. Depending how stiff your springs are, you might find an explicit integr...

The rule to follow is this: Imagine the system with just the bodies and joints (constraints removed). That tree-structured system defines the mass matrix and must be non-singular. So you can weld massless bodies together if they are part of the tree system (i.e. using a weld joint rather than a weld...

No, sorry Nicos. Angular velocity is not the derivative of Euler angles (except in one special case: when all three Euler angles are zero). Otherwise you have to use Euler angle derivatives for u to get N=identity. Angular velocity is in fact not the derivative of any set of q's -- there is always a...