Robust Adaptive Control of Valve Mechanism with Unknown Backlash Nonlinearity

In this paper, two robust adaptive backstepping control algorithms are developed for valve control mechanism of a liquid tank. Unlike some existing control schemes for systems with backlash, the developed backstepping controllers do not require the uncertain parameters within known intervals. Also no knowledge is assumed on the bound of the ´disturbancelike´ term, a combination of the external disturbances and a term separated from the hysteresis model. It is shown that the proposed controllers not only can guarantee global stability, but also transient performance.