Physical Human-Robot Interaction under Joint and Cartesian Constraints

This paper handles the problem of including Cartesian and joint constraints in the stack of tasks for torque-controlled robots. A novel approach is proposed to handle Cartesian constraints and joint constraints on three different levels: position, velocity and acceleration. These constraints are included in the stack of tasks ensuring the maximum possible fulfillment of the tasks despite of the constraints. The algorithm proceeds by creating two tasks with the highest priority in a stack of tasks scheme. The highest priority task saturates the acceleration of the joints that would exceed their motion limits. The second highest priority task saturates the acceleration of the Cartesian directions that would exceed their motion limits. Experiments to test the performance of the algorithm are performed on the KUKA LBR iiwa.