Robust nonlinear nominal-model following control to overcome deadzone nonlinearities

A robust nonlinear nominal-model following control is proposed to overcome deadzone nonlinearities which are unavoidable in many physical systems due to the imperfections of system components. First, an ideal linear nominal model of the plant and a model controller are employed to generate an ideal reference output. Then, a nonlinear robust loop controller is added to force the actual output to follow the ideal reference output. The robust loop controller contains an ordinary proportional-integral-derivative controller combined with a deadband relay. The added deadband relay has the capability of reducing nonlinear effects of the plant. A systematic design methodology is established and it is linked to the conventional control system design. The proposed scheme is practically applied to the control of a DC motor position servo system containing a severe deadzone nonlinearity. Both simulation and experimental results have illustrated the effectiveness and robustness of the proposed technique.