Research On Adaptive Output Feedback Control For Nonlinear Systems With Input Quantization

In recent years,with more researches on nonlinear control,network control has been diffusely applied in the different nonlinear system control.Because of bandwidth constraints,the network can only transmit a limited amount of data in a certain period of time.For the popurse of improving the transmission property of the network and prevent congestion and data loss during transmission,data has to be quantized and encoded before transmission.So the control signal is necessary to be quantified before being sent to the controlled systems.The subsequent quantization error greatly affects the stability of the system.Therefore,when we design nonlinear systems,it is important to consider how to eliminate the impact of signal quantization on the stability of the system.In addition,there is often unmodeled dynamics in actual nonlinear systems,which makes the system more unstable.How to guareent the stability of the system under unmodeled dynamic conditions is very significant to ensure system performance.Moreover,in order to achieve effective control of nonlinear systems,the state or output of the system also requires certain constraints during operation.So investigate how to guarantee the system is stable and the system output meets the output constraints when the system contains unmodeled dynamics and the control signals are quantified has great theoretical and practical meaning.Some control schemes for different categories of uncertain nonlinear systems with input quantization,state unmodeled dynamics,and output constraints are proposed in this paper.The main research contents are summarized as follows:(1)We consider the issue of adaptive output-feedback tracking control for nonlinear systems with input quantization,unmodeled dynamics,and output constraints.A novel quantizer with the advantages of hysteresis and uniform quantizer is introduced to handle input signals.A barrier Lyapunov function is applied to handle the output constraints.The state unmodeled dynamics is solved by using a Lyapunov description,and RBFNNs are adopted to approximate the unknown functions which are produced in the adaptive control design procedure.The controller design is simplified by combining the new quantizer with dynamic surface control method.The mathematical derivation shows the stability of the closed-loop system and the effectiveness of output constraints.Simulation illustrates and clarifies the theoretical findings.(2)An observer-based decentralized adaptive control strategy is put forward for a class of uncertain nonlinear interconnected systems with input quantization and time-varying output restrictions.Decentralized hysteresis quantizer is employed to handle input signal.The unmeasured states are estimated by designing K-filters.A Lyapunov description is used to dispose of state unmodeled dynamics.The constrained interconnected nonlinear systems are transformed into novel interconnected nonlinear systems without output constraints by constructing invertible nonlinear mappings.By combining dynamic surface control(DSC)with a hyperbolic tangent function,decentralized controller which has a simpler structure is designed.Stability analysis indicates that all the closed-loop system signals are semi-globally uniformly ultimately bounded(SGUUB)and system outputs satisfy the constraints.A triple inverted pendulum is used as a practical example to certificate the effectiveness of the theoretical findings.(3)We propose a new adaptive output feedback control strategy for a class of strict feedback nonlinear systems with input quantization,unmodeled dynamics and time-varying output constraints.A hysteresis quantizer is employed to quantify input signal.Dynamic signal is used to deal with state unmodeled dynamics.The constrained nonlinear system is transformed into novel nonlinear system without output constraints by constructing invertible nonlinear mapping.High-gain observer is designed to estimate the unmeasured states.By combining dynamic surface control(DSC)with,a hyperbolic tangent function a controller which has a simpler structure is designed.All the closed-loop system signals are SGUUB and system outputs satisfy the constraints.The utility of the developed control scheme is certificated by the numerical simulation results.