Does SimMechanics 2nd Gen compute inverse dynamic ?

I made a model on which I give all the motion as input with some gimbal joints of the the simmechanics 2 gen. The motion is reproduced quite fine but the motion doesn't seems have any impact one the forces and torques in the joint. However, when I gives some external forces on the feet, I get the signal on the hip joint... So from here my question : does SimMechanics 2nd generation compute inverse dynamic or it is only to do some forward dynamic simulation ?

Answer 1

[Sebastian Castro]

Yes, SimMechanics allows you to prescribe motion and automatically computes forces and torques -- both along the axis of motion and any reaction forces due to constraints in other directions.

http://www.mathworks.com/help/physmod/sm/ug/sense-internal-forces-in-double-pendulum-link.html

http://www.mathworks.com/help/physmod/sm/ug/prescribe-joint-motion-in-planar-manipulator-model.html

Which version of MATLAB are you using? I ask because SimMechanics 2nd Generation is fairly new and the features have been catching up over the last 6 releases.

- Sebastian

[Pierrick Bersier]

I use the 2014a... I saw this both example already, but none of them provide the motion as input. It is both forward dynamic if I make no mistake ?

[Sebastian Castro]

Ah yes, R2014a has the motion input. That second example (the Planar Manipulator) uses motion inputs. You can tell because the input ports in that 6-DOF joint say "px" and "py" for position instead of "fx" and "fy" for force.

[Pierrick Bersier]

OK thank you for your answer ! I think I found the problem. It come from my computation of the second derivatives...

[Pierrick Bersier]

Can you tell me where I can find how does simulink exactly compute inverse dynamic? I'm looking for these informations in the user manual but didn't found anything yet.

Thank you for your help.