Cascade control of underactuated manipulator based on reinforcement learning framework

In this article, we propose a cascade control framework to attenuate the residual vibration of the underactuated manipulator. The control framework is divided into two phases. In the first phase, a path generator trained by the reinforcement learning produces the leading signal for the tracking controller. In the second phase, the leading signal stabilizes the underactuated manipulator, and the adaptive proportional derivative controller is implemented to reduce the vibration. In the process, a novel path planning method is proposed to improve exploration efficiency, and a negative reward is introduced to avoid unsafe strategies and simulation instability. The effectiveness of the proposed control scheme is verified in the simulations of the double pendulum crane and the two-link flexible manipulator.