LINEAR ACTIVE DISTURBANCE REJECTION CONTROLWITH A HIGHER ORDER SLIDING MODE OBSERVER APPLIED TO A CART INVERTED PENDULUM

Suhail A. Suhail, Mohammad A. Bazaz, and Shoeb Hussain

Keywords

Inverted pendulum, LADRC, PID, ESO, sliding mode observer (SMO)

Abstract

Numerous practical applications like robot balancing, Segway/hover board riding and operation of a rocket propeller are inherently based on inverted pendulum (IP). The control of an IP is a sophisticated problem due to various real-world phenomena that make it unstable, non-linear and an under-actuated system. Active Disturbance Rejection Control (ADRC) is a model independent controller and has a high disturbance rejection profile. The main idea behind ADRC is to decouple the original system from the actual perturbation acting on it by estimating the total disturbances (external as well as internal) using an extended state observer (ESO). This estimate is then used to generate the required control law without knowing the precise analytical description of the system. In this manuscript, a novel control strategy for position and angle control of a cart IP based on linear active disturbance rejection control is proposed. The control signal for position and angle of the system is obtained without the need to first linearize and decouple the system as is usually done in most of the control techniques. Furthermore, we propose a Higher Order Sliding Mode Observer against a conventional ESO so as to cope with different types of disturbances and to obtain a finite-time convergence. Simulation results show that the proposed scheme provides a better disturbance/noise rejection and robustness against parameter uncertainties as compared to two-loop PID and LQR.

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