Coordinated Adaptive Impedance Control of Redundantly Actuated Parallel Manipulators

Redundantly actuated parallel mechanisms (RAPMs) have been widely adopted in advanced robotic systems and precision machine tools. It has been demonstrated that redundant actuation can improve the performance of mechatronic systems but introduce challenges with respect to control. One main difficulty is in establishing an accurate dynamic model of the RAPM system. With an inaccurate dynamic model, the torque applied by the actuators will be incorrect, leading to increased antagonistic forces in the system. To solve this problem, a novel coordinated adaptive impedance control approach based on a new adaptive impedance control law is presented here, along with proof of the stability of the closed-loop system. The control algorithm has been validated experimentally by a prototype cable-driven parallel manipulator. It can be seen from the experimental results that the proposed control method is an effective way to correct the antagonistic forces of the system, thus facilitating the improvement of its dynamic performance and its efficacy in different applications.