Struggling to set up Newton/MuJoCo manipulator
Posted: 08 Dec 2023, 13:40
I am still struggling to set up a complete 8DoF manipulator arm with a force sensor in its base. The general setup is working, but the numbers I receive for the base force/torques seem to be wrong. I use a fully dynamic manipulator with position controllers. With the exception of the MuJoCo armature parameter, I use the default engine parameters, as it is used by the demo model robots.
For the Newton physics engine: The robot seems to behave well, however, I get an offset value of 20-100N for the forces at the base, even if there is no motion commanded and the gravity is switched off. It is quite a stable, reproducible offset error, but I have no idea where it is originating.
For the MuJoCo physics engine: The offset value does not appear when using this engine. However, when I try to move the manipulator, there is a lot of oscillation in the commanded torque values for the joints, with quite substantial Nm values reached. With higher speeds, this leads to a 'trembling' of the whole robot, and the target position (set by sim.setJointTargetPosition) is never exactly reached, leaving the manipulator in its oscillating behaviour. This behaviour remains even if the force-torque sensor is removed, the joint masses are equally distributed, and the armature value of all joints is increased (up to 20).
Does any of this sound like a known issue ? Do I make some fundamental mistakes ?
For the Newton physics engine: The robot seems to behave well, however, I get an offset value of 20-100N for the forces at the base, even if there is no motion commanded and the gravity is switched off. It is quite a stable, reproducible offset error, but I have no idea where it is originating.
For the MuJoCo physics engine: The offset value does not appear when using this engine. However, when I try to move the manipulator, there is a lot of oscillation in the commanded torque values for the joints, with quite substantial Nm values reached. With higher speeds, this leads to a 'trembling' of the whole robot, and the target position (set by sim.setJointTargetPosition) is never exactly reached, leaving the manipulator in its oscillating behaviour. This behaviour remains even if the force-torque sensor is removed, the joint masses are equally distributed, and the armature value of all joints is increased (up to 20).
Does any of this sound like a known issue ? Do I make some fundamental mistakes ?