CoppeliaSim forums

Good afternoon. How do I use sim.setJointTargetposition to control the joint of a robot arm on Coppelia Python script such that the joint bends to the location I desire?

I was able to figure out how to do it using angular positioning: 'sim.setJointTargetPosition(fulcrumJoint,300*math.pi/360)' but how do I do so linearly, setting specific x,y,z coordinates?

Hello,

if you want to control a joint or kinematic chain in 3D space instead of joint space, then you should use inverse kinematics (IK).

In your case, if you want a joint to follows a specific 3D point, try with this exercise:

• Make sure your joint (for now) is in kinematics mode
• attach it to an object that you then mark as model base
• Add a dummy to the scene, and attach it to your joint. Rename that dummy to tip
• Copy-paste that dummy and rename it to target. Attach it to the model base.
• Select the model base
• Go to [Menu bar > Modules > Kinematics > Inverse kinematics generator...]
• Uncheck Alpha+Beta and Gamma
• Set the Damping factor to e.g. 2
• Click Generate

Now move the target dummy around, and you will see the tip dummy follow (because the joint is now controlled in IK).

Cheers