Search found 809 matches
- Fri Dec 13, 2024 6:25 pm
- Forum: Simbody: SimTK multibody dynamics API
- Topic: MobilizedBody::Custom to off-the-shelf solution?
- Replies: 1
- Views: 49
Re: MobilizedBody::Custom to off-the-shelf solution?
Hi, Simone. Congratulations on getting a custom mobilizer to work -- very nice! I think you are correct that that's the only way to implement the singularity-free behavior you want. The fact that MobilizedBody::FunctionBased assumes 3 angles for rotation dooms it. (BTW that is itself a custom mobili...
- Sun Dec 08, 2024 2:57 pm
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Understanding Linear Velocities in a Rotational System Simulation Using Simbody
- Replies: 2
- Views: 146
Re: Understanding Linear Velocities in a Rotational System Simulation Using Simbody
Sorry for the delay in responding to this. I ran your program to see what's happening. My guess is you didn't realize that when you apply a mobility force it is applied equal and opposite to the two connected bodies. So a torque is being applied both to the actuated wheel and the free-floating chass...
- Wed Sep 04, 2024 11:40 am
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Integrate over short transients
- Replies: 4
- Views: 6171
Re: Integrate over short transients
Hi, Simone. Simbody's integrators interpolate when a reporting time doesn't coincide with a step completion.
That's on by default but can be controlled by Integrator methods like setAllowInterpolation().
Regards,
Sherm
That's on by default but can be controlled by Integrator methods like setAllowInterpolation().
Regards,
Sherm
- Wed Aug 07, 2024 2:20 pm
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Integrate over short transients
- Replies: 4
- Views: 6171
Re: Integrate over short transients
Hi Simone. If you use one of SImbody's variable step integrators, it should be able to figure out to take small steps over the rapid transition automatically.
Regards,
Sherm
Regards,
Sherm
- Tue Jul 23, 2024 9:15 am
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Leaf spring substitute system
- Replies: 5
- Views: 6466
Re: Leaf spring substitute system
Awesome! Thanks, Walter.
- Wed Jul 17, 2024 1:44 pm
- Forum: Simbody: SimTK multibody dynamics API
- Topic: SimTK Initial Velocity Analysis:
- Replies: 2
- Views: 2588
Re: SimTK Initial Velocity Analysis:
Sadly, no. There is a nice Assembly analysis in Simbody but no InitialVelocity analysis (there should be!) You can work around that by adding a velocity constraint (or Motion object) to one of the dofs (assuming a net-1-dof system). Then constraint projection will figure out all the other velocities...
- Wed Jul 17, 2024 7:40 am
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Leaf spring substitute system
- Replies: 5
- Views: 6466
Re: Leaf spring substitute system
You could try:
- CPodes limited to Order 1 (that makes it implicit Euler)
- SemiExplicitEulerIntegrator
- Use fixed step or very loose accuracy requirement, like 10%
- Use less damping or large masses to avoid extreme stiffness
Optimization is still probably the most direct approach.
- CPodes limited to Order 1 (that makes it implicit Euler)
- SemiExplicitEulerIntegrator
- Use fixed step or very loose accuracy requirement, like 10%
- Use less damping or large masses to avoid extreme stiffness
Optimization is still probably the most direct approach.
- Tue Jul 16, 2024 8:40 am
- Forum: Simbody: SimTK multibody dynamics API
- Topic: Leaf spring substitute system
- Replies: 5
- Views: 6466
Re: Leaf spring substitute system
Assembly analysis is for satisfying position constraints. In this case it sounds like you would like the spring to minimize its stored potential energy, that is have the system relax so that it is in a steady state. That's a "static" or "equilibrium" analysis, if I understand your question. Simbody ...
- Thu Jul 11, 2024 10:20 am
- Forum: OpenSim
- Topic: Using SimTK Assemblar object to assemble Closed-Chain systems
- Replies: 2
- Views: 2930
Re: Using SimTK Assemblar object to assemble Closed-Chain systems
I think all you need is a C-style cast like
SimTK::MobilizerQIndex(int)
SimTK::MobilizerQIndex(int)
- Mon Jun 24, 2024 6:15 pm
- Forum: Simbody: SimTK multibody dynamics API
- Topic: GeneralContactSubsystem
- Replies: 2
- Views: 3092
Re: GeneralContactSubsystem
Hi, Andrea. The entire System (including all its Subsystems) needs to be built before any computations are done. It looks like you are adding a Subsystem later, would be good to get that sorted out (might not be the problem but could cause trouble). Also, the GeneralContactSubsystem is old and super...