Real time position control to induce artificial braking

[antoronson]

Hello All
When we look into V-Rep while simulating a joint in torque mode, the max torque is applied and the body id moved. mean time, we see a negative torque applied to adjust the position with max velocity. When the body is nearing the target position, a max negative torque is applied and the body is brought to rest. I felt, if I can trap this torque, I can induce artificial braking, with the brake power required would be slightly more than this torque. I am not sure how to bring it into my model for example, where the target position is changed, then my model fails as the brake needs to be applied when the body arrives at the new position. Could anyone suggest me a suitable procedure with example.

[coppelia]

Hello,

not sure I understood your question. I suppose you have a mobile robot and are acting on the wheels? So the wheel joints are in force/torque mode, the motor is enabled but the control loop is disabled. In that situation, if you set a zero velocity, then the motor will kind of brake: the specified torque will act as friction in the motor. So if you set that torque very high, friction will be higher too. Also, there is an option where you can specify that if velocity is zero, the joint will act as a rigid link.

Cheers

[antoronson]

Thank You for your reply.
I would also like to induce the brake based on the position control. For eg. I set a target position. Then I track the position and when it reaches near the target position, I would like to bring in this loop into control, to induce artificial braking. I am not using a mobile robot. But when I measure the joint parameters of a manipulator model, When the joint approach the target position, the torque is higher and velocity is lower. But when I measure the power, the graph shoots abnormally at the end. I want a smooth curve.

[coppelia]

First, make sure that you have the same behaviour with all 4 physics engines. Some engines perform better than others, and overshoots might be linked to that. Overshoots might also be linked to the PID controller (if in position control). So you can try to adjust the PID values, or write your own controller via a joint control callback script, which gives you most flexibility and control on the joint.

Cheers

[antoronson]

Is there an API function to put a check on how near to the target position is our joint?

[coppelia]

Sorry, I don't understand what you mean with your question.

Cheers