State Estimation of Rotary Inverted Pendulum: A Comparative Study of Observers Performance

This paper conducts a performance comparison study among four different observers for state estimation of rotary inverted pendulum (RIP) system. The observation techniques, invoked in estimation, are the high gain observer (HGO), Extended State Observer (ESO), Linear Extended State Observer (LESO), and nonlinear extended state observer (NESO). The effectiveness of the proposed observer is assessed in terms of its tracking speed and its robustness characteristic, which is evaluated based on variance index of estimation error in the presence of disturbance and parametric uncertainties. The performances of proposed observers are evaluated via numerical simulation. As compared to other observers, the NESO showed better performance in terms of robust characteristics.

I. INTRODUCTION

The state observers have found their efficacy in different control applications like regulation, monitoring, fault diagnosis, detecting, and identifying failures. However, the need of system mathematical model is the main drawback, which has been accounted for when using state observers. As such, due to disturbances, nonlinearities and inherited dynamic uncertainties, the design of state observers encounter critical challenges in practical applications. Therefore, reaching to high-performance and robust observer was the aim of most researchers. Advances in design techniques of state observation have appeared in the last two decades, which produced efficient observers like disturbance observers (DO), sliding mode observers (SMO), high gain observers (HGOs), linear extended state observer (LESO), nonlinear extended state observer (NLESO) and extended state observer (ESO) [1]-[3].