U-Model-Based Adaptive Sliding Mode Control Using a Deep Deterministic Policy Gradient

Abstract

This paper presents a U-model-based adaptive sliding mode control (SMC) using a deep deterministic policy gradient (DDPG) for uncertain nonlinear systems. The configuration of the proposed methodology consisted of a U-model framework and an SMC with a variable boundary layer. The U-model framework forms the outer feedback loop that adjusts the overall performance of the nonlinear system, while SMC serves as a robust dynamic inverter that cancels the nonlinearity of the original plant. Besides, to alleviate the chattering problem while maintaining the intrinsic advantages of SMC, a DDPG network is designed to adaptively tune the boundary and switching gain. From the control perspective, this controller combines the interpretability of the U-model and the robustness of the SMC. From the deep reinforcement learning (DRL) point of view, the DDPG calculates nearly optimal parameters for SMC based on current states and maximizes its favourable features while minimizing the unfavourable ones. The simulation results of the single-pendulum system are compared with those of a U-model-based SMC optimized by the particle swarm optimization (PSO) algorithm. The comparison, as well as model visualization, demonstrates the superiority of the proposed methodology.

Adaptive nonsingular terminal sliding mode control of robot manipulator based on contour error compensation

“…SMC is a particular and powerful class of variable structure control essentially which can dynamically adjust based on the current state of the system 13 – 16 . Thus, the system is forced to track a pre-determined trajectory of sliding mode states.…”

DDPG-Based Adaptive Sliding Mode Control with Extended State Observer for Multibody Robot Systems

“…However, it is worth noting that the systems under consideration in these studies were relatively smaller than the industrial robot in our current research. Furthermore, a model-free reinforcement learning algorithm known as deep deterministic policy gradient (DDPG) has been observed to provide optimal SMC parameters, enhancing performance through learning and adapting to different sliding patterns [17][18][19].…”