High-Precision Tracking of Cubic Stewart Platform Using Active Disturbance Rejection Control

The paper presents the high-precision tracking of the cubic Stewart platform using active disturbance rejection control (ADRC). For a given Cartesian pose of the platform, the required leg lengths are calculated by utilizing inverse kinematics. From the information of actuators output, the actual position of the platform is computed by applying the Newton-Raphson method for forward kinematics. Comprehensive dynamic model of cubic Stewart platform is constructed. As a highlight, the intrinsic rate-dependent hysteretic nonlinear characteristic of piezoelectric actuator (PEA) which is used to drive the legs is taken into account in the process of modeling. The hysteresis is regarded as disturbance and estimated by employing an linear extended state observer (LESO). Control law is designed to compensate the hysteresis. The availability of the proposed control method is validated by numerical simulations and results manifest that the ADRC technique has better tracking precision than pure propertional-integral (PI) control method.