A hybrid controller design for bi-axial inverted pendulum system

Abstract

This study presents the use of Tustin's friction model and a disturbance observer (DOB) to improve the steady-state error (SSE) of a bi-axial inverted pendulum-cart system (IPCS). Furthermore, a hybrid controller contains a feedback linearization control for pendulum angle in the region of 3-12 degrees to enlarge the angle of operation and an H(infinity) control using loop shaping design procedure (LSDP) for cart position and pendulum angle in the region of 0-3 degrees to stabilize the IPCS, respectively. Experimental results reveal that the pendulum maximum angle of operation is improved from 7 to 12; the SSE of the angle of the pendulum is reduced from 0.85 to 0.1 degrees, and the SSE of the position of the cart is reduced from 10 to 1.4 mm. Experimental results are illustrated and films are provided at the web site http://hinfinity.myweb.hinet.net to show the effectiveness and robustness of the hybrid controller with Tustin's friction model and DOB compensation. Copyright (c) 2008 John Wiley & Sons, Ltd.