Quantized feedback control for nonlinear feedforward systems with unknown output functions and unknown control coefficients

This paper investigates the quantized feedback control for nonlinear feedforward systems with unknown output functions and unknown control coefficients. The unknown output function is Lipschitz continuous but may not be derivable, and the unknown control coefficients are assumed to be bounded. To deal with this challenging quantized control problem, a time-varying low-gain observer is designed and a delicate time-varying scaling transformation is introduced, which can avoid using the derivative information of the output function. Then, based on the well-known backstepping method and the sector bound approach, a time-varying quantized feedback controller is designed using the quantized output, which can achieve the boundedness of the closed-loop system states and the convergence of the original system states. Moreover, a guideline is provided for choosing the parameters of the input and output quantizers such that the closed-loop system is stable. Finally, two simulation examples are given to show the effectiveness of the control scheme.