Hello,
Currently I am facing an issue when the end-effector is in contact with a long surface, for example, a table, the end-effector 'jumps' suddenly and oscillates quite drastically. I also noted, that when the arm is more or less close to singularity, the shoulder elbow and wrist almost align, the end-effector starts also to oscillate
Scenario:
The robotic arm is on a table and has 7 joints. The end-effector is basically a long thin plate, with length of 0.90m, width of 0.40 and height of 0.01m. The end-effector is in contact with the surface of the table. I am using Mujoco physics engine.
I suppose the problem comes from the many contact points between end-effector surface with the table. Is it possible to solve this problem and continue to use position control, or do I have to implement force control where the controller receives as input position and velocity and transform to force input? If so, do you think the scenario "inverseDynamics" is a good starting point for this case?
Any recommendations to solve this problem I would be grateful.
Sliding end-effector on a table
Re: Sliding end-effector on a table
Hello,
being close to a singularity while using the IK functionality is never a good idea, since this will indeed result in an instable behaviour. You can somehow mitigate this by "pre-tensioning" the incriminated joint in the desired direction. Also adding damping and increasing the maximum number of iterations (simIK.setGroupCalculation) or reducing the max. step size (simIK.setJointMaxStepSize) can help.
Regarding the jumps/oscillations due to the end-effector contact with the table: this could be for various reasons: are your shapes primitive shapes? Or convex shapes at least? If they are very thin, try to make them thicker and play with the various Mujoco parameters available for both shapes.
Cheers
being close to a singularity while using the IK functionality is never a good idea, since this will indeed result in an instable behaviour. You can somehow mitigate this by "pre-tensioning" the incriminated joint in the desired direction. Also adding damping and increasing the maximum number of iterations (simIK.setGroupCalculation) or reducing the max. step size (simIK.setJointMaxStepSize) can help.
Regarding the jumps/oscillations due to the end-effector contact with the table: this could be for various reasons: are your shapes primitive shapes? Or convex shapes at least? If they are very thin, try to make them thicker and play with the various Mujoco parameters available for both shapes.
Cheers