Calculating Torque required at a robot joint

[antoronson]

Hello all
I require a small suggestion from V-Rep Users. Right now my task for my academic is to find the torque required to operate a robot at a particular path. I followed the following method.
1. I created an IK simulation where the path position is absorbed from the path following robot.
2. I took this output file as input to a similar model in Force/Torque mode
3. I set target position for various joints from this input file and user set velocity.
4. I was able to calculate the torque required and the total time of operation

I know there could be a better and easier way. Could some one please help me to sort it out

[coppelia]

If I understood you correctly, you have two identical robots, one in IK mode (static robot), the other one in force/torque mode (dynamic robot). Then you apply the calculated joint positions of the IK robot to the dynamic robot.

If your robot joints operate in IK mode, with the hybrid operation flag on, then the calculated IK values will be applied to the various joints as target positions for the joint controllers. In that case you are also able to read the exerted force/torque in each joint.

Best would be to read the force/torque inside of a joint controll callback script: this way you will be able to read more values (i.e. by default, the physics engine runs 10 times in one simulation step, thus also producing 10 times more values).

Cheers

[antoronson]

Thank You for your reply

I tried to do the same in Hybrid mode. But the joints started dismantling when I try to simulate. I switched off the respondable oprion and switched off collision detection, but the joints keep dismantling. May I know the reason why this is happening

[antoronson]

I have an update to this. I tried playing with the respondable mask and able to hold the joint. I modified the Moment of Inertia too. Now the shapes stick to each other. But when I try to simulate, they do not follow IK Path, rather starts decelerating with oscillation towards ground

[coppelia]

Not sure about your scene. But try to adjust the PID parameters of the various joints. Also the other dynamic joint parameters.
Otherwise, it is much easier to check what is wrong if you can post the scene.

Cheers

[antoronson]

I dont have access to any online drive to post it. Please give me your email id, I will send it via online

[antoronson]

Can you provide a tutorial of a sample model with joint call back script as it would help me to understand it better

[coppelia]

Simply add a revolute joint to your scene. Make sure it is dynamically enabled. It should already be in force/torque mode.
Then enable its motor and the control loop in the joint dynamic properties, then click on Custom control, finally click Edit custom control loop: a default joint control callback script will be displayed. It performs a simply PID control.

Cheers