Non-smooth observer for sandwich systems with backlash

Industrial systems involving backlash,such as mechanical transmission systems and hydraulic systems,can be described by so-called sandwich systems with backlash.A novel non-smooth observer is proposed to handle the state estimation for sandwich systems with backlash.Based on the characteristics of the system,a non-smooth state-space equation is constructed by using the sepa-ration principle.A non-smooth observer is developed based on the obtained state-space equation.The observer switches automatically among different operating zones according to the changes of operation conditions.The convergence of the non-smooth observer is discussed.The application of this observer to a practical hydraulic servo system is realized.The comparison of tracking performances of the hydraulic servo system is made between the proposed non-smooth scheme and the conventional method.It is shown that the proposed non-smooth approach is with much better estimated performance.