LAB 4: TASK SPACE IMPEDANCE CONTROL

In this lab, we had to implement an impedance control algorithm which was to be used for the final main project. The main motivation for applying this control algorithm is to have both position and force control. The requirement is to make the end effector follow the desired trajectory, however, in directions perpendicular to the trajectory, we want the arm to compliant, i.e, forces exerted should be really small. The above video shows an implementation of impedance control in the global frame coordinates. As one can clearly see, the end effector is very stiff in one direction where as in all other directions it is compliant. The direction which has a higher gains will be more stiff and hence, the position control algorithm will work well in that direction.

ROTATING AXIS OF CONTROL GAINS

This case is just a special case of the above one. Instead of having stiffness and compliant directions being defined with respect to the global coordinate frame, we define it with respect to a rotated coordinate frame attached at the end effector. As seen in the video, we are able to successfully make the robot arm move along an axis which is at an angle to the global coordinate frame (the axis direction, does not align with the x,y and z axis of global coordinate frame). The directions perpendicular to it are stiff.