Unified Adaptive Performance Control of MIMO Input-Quantized Nonlinear Systems

In this paper, a robust adaptive control scheme, capable of guaranteeing unified prescribed performances on the output tracking error and virtual errors, is developed for a class of multiple-input multiple-output (MIMO) strict-feedback nonlinear systems in presence of input quantization, which exhibits some features. Firstly, by constructing a series of function transformations multiple performance behaviors can be ensured under a fixed control framework by properly selecting the performance parameters, without the need for control redesign. Secondly, by constructing a novel performance function for the virtual errors, the demanding constraint on the initial values of virtual errors is completely circumvented. Consequently, there is no need for the tedious offline computations for the initial verification, making the control algorithm more user-friendly in design and implementation. Thirdly, due to the considerations of prescribed performance and quantization simultaneously, some additional product terms and drift terms occur in Lyapunov function differential inequality, further complicating the control design and stability analysis. To address this issue, useful Lemmas introduced, which ensure that under the normally used assumptions the closed-loop system is stable. The numerical simulations show the advantages and effectiveness of the proposed control.