Online motion adjustment using compliance control for a multi-axis robot manipulator

The demand for more human-robot interactions is increasing rapidly. Safety of these interactions is a crucial concern and is closely related to the design of the control system. When the robot is affected by an external force, in order to have a safe interaction, it is necessary to regulate the speed and position changes that may occur due to this expected or unexpected force. This work focuses on robot compliance control that can online adjust the motion of the robot manipulator according to the external force applied to the end effector. The proposed control law calculates the Jacobian matrix and modifies the task-space velocities of the end-effector with respect to the prescribed force/velocity relationship, i.e. the admittance law; then the desired position is achieved by the computed-torque control in the joint space. Simulations of the proposed algorithm show that the trajectory of the end effector can be modified online based on the magnitude and direction of the external force. These results can be further applied to lead-through teaching applications where we want the robot to comply with the force to achieve the specified task.