A novel passive path following controller for a rehabilitation robot

In this paper, we present a path generation and control strategy for a robotic manipulator to mimic the dynamics of a continuously reconfigurable anisotropic impedance. Motivated by a nonholonomic kinematic constraint, a dynamic path generator is designed to trace a desired contour in the robot´s workspace when an interaction force is applied at the robot´s end-effector. The proposed continuous control strategy achieves semi-global asymptotically stable path following for the robot manipulator in the presence of uncertainty in the robot dynamics. Additionally, the path generator also ensures safety by maintaining the desired net flow of energy during the human robot interaction from the user toward the manipulator. In addition to providing asymptotic path following, the control algorithm also ensures sufficiently rapid error convergence at the end-effector such that the actual energy transfer profile follows the desired energy transfer profile - thus rigorously ensuring user safety.