A novel event based motion planning method, together with nonlinear feedback algorithm is applied to the controlled transition between unconstrained and constrained motion of a rigid robotic manipulator. The motion planner is driven by a task related scalar motion reference. This reference is a function of the actual manipulator position in the unconstrained directions and a function of the interaction force in the constrained directions. Impact is considered a discrete event, separating different operation modes. The dynamics of the arm is decoupled with respect to a path-relative representation of manipulator outputs. The feedback control law directly servos these outputs. The event based planning and control scheme was experimentally implemented for impact control and compared with impedance control and explicit force control.>

The trajectory tracking performance of the nonlinear feedback controller based on differential geometric control theory was experimentally studied. The performance is compared to three other methods: independent joint proportional-derivative (PD) control, independent joint PD control with feedforward torque computations, and the computed torque method. In the nonlinear feedback controller, servo is in the task space. In the other three methods servo is in the joint space. Path planning is in the task space. Circular and straight line paths are considered. A sampling frequency of 200 Hz is used. The effect of sampling frequency on tracking error is studied for the nonlinear feedback control scheme. The performance of these methods was tested on a PUMA 560 arm. The trajectory tracking performance of the robot arm under the nonlinear feedback controller is comparable to that of the computed torque control schemes.>