Novel adaptive control scheme for plant with separable nonlinearity

In many practical systems containing separable nonlinearity, an undesirable sustained oscillation is observed at the plant output. This is due to the existence of stable limit cycles. A general approach to eliminate the occurence of limit cycle, an inverse characteristic of the nonlinearity is implemented in closed loop. In this paper, a method is proposed to eliminate the effects of unknown nonlinearity by incorporating an adaptive inverse nonlinearity as a compensator. This unknown nonlinearity is identified through the general nonlinearity structure. A Recursive Least Square identification algorithm is used to identify the parameters of the unknown nonlinearity. The identified parameters are used to implement an adaptive inverse nonlinearity through general inverse nonlinearity which reduces the limit cycle oscillation considerably. The numerical simulation is carried out to validate the proposed method for a plant with backlash nonlinearity.