Simscape revolute joint torque actuation issue

Hello,

I have a simscape model with two revolute joints. Firstly, I have generated angular postions for both of those joints in order for the end effector to follow straight line. I record the torque needed to move each joit in workspace. Then I set joints to be actuated by torques. As input torque I specify torques that I have previously recorded but then I do not get wanted motion. What can I be doing wrong?

Before first run of slx file "test_1_1.m" needs to be run. nce the first simulation ends I create two variables that reprenet torque. Those are variables a1 and b1. They are made from out variable that comes from Simulink (%a1=out.torque_J1; %b1=out.torque_21;)

Best regards

[Yifeng Tang]

I have only a hypothesis here.

If I comment out the 2nd joint and arm, so it's a simple arm around the base, the recorded torque will be able to drive the single arm to very high precision and follow the original position. I suspect the two-joint system is a bit too sensitive to any integration tolerance/error and a recorded torque will cause the motion to "drift" from the original trace. Maybe similar to how a double-pendulum can be chaotic?

[Ahmet]

Hi Yifeng Tang and thank you for taking look. I was hoping I might be doing something wrong.