Development of Cascaded Disturbance Rejection Control Strategy for 6-DOF Stewart Platform

Abstract

Achieving accurate attitude regulation of a 6-DOF Stewart platform becomes difficult when nonlinear coupling and external disturbances simultaneously affect the system. To address this issue, this paper develops a cascaded compensation and disturbance-rejection scheme based on active disturbance rejection control (ADRC). The proposed framework combines feedforward compensation and feedback disturbance rejection. Specifically, future roll and pitch estimates of the lower platform are first incorporated into the inverse kinematic mapping, from which the corresponding displacement commands of the six actuators are generated. This mechanism enables the controller to compensate for part of the disturbance effect before it propagates to the platform. An ADRC-based position controller is then established for each actuator, where disturbance estimation and nonlinear feedback regulation are employed to improve tracking performance. In addition, velocity feedback compensation is introduced to enhance damping characteristics and suppress residual oscillations. The proposed method is implemented in MATLAB/Simulink and Simscape Multibody environments, and comparative simulations with conventional PID control are conducted under different disturbance conditions. The results demonstrate that the proposed cascaded controller achieves improved attitude compensation accuracy and stronger disturbance rejection capability.