Global Adaptive Output Feedback Control For Nonlinear Systems Based On Event-triggered And Quantized Input

In practical engineering,most systems have varying degrees of nonlinearities and uncertainties.Adaptive control has been proved to be one of the effective methods for dealing with uncertain information in nonlinear systems.In addition,with the rapid development of networked control systems,quantitative control and event-triggered control,as effective means to reduce the efficiency of signal transmission,have important theoretical and practical significance.Based on the existing works,this dissertation explores the output feedback control problem of uncertain nonlinear systems in some triangular growth cases based on event-triggered control or quantization control.The main contents of this dissertation are as follows:1.For a class of nonlinear systems with lower-triangular growth,the global adaptive output feedback practical tracking control problem is discussed,where the unknown time-varying control coefficients are constrained by known constants.Firstly,the input and output of the original systems are used to reconstruct the system states and the dynamic gain is ingeniously embedded in it.Then an adaptive controller based on event triggering mechanism is designed by combining dynamic scaling transform technology and backstepping control algorithm.The stability analysis shows that all closed-loop system states are bounded,and the system output can track the reference signal under any given allowable tracking error.2.The adaptive output feedback control problem is studied for a class of nonlinear systems with unknown control coefficient,where the upper and lower bounds of the control coefficient do not need to be known prior.For the relaxed control coefficient assumption,an improved backstepping control algorithm is used,and a continuous time controller based on high gain observer is obtained.On this basis,firstly,for the single-input single-output nonlinear systems under the framework of event triggering mechanism,the event triggering controllers based on the time-varying threshold strategy and the dynamic threshold strategy are designed respectively;Secondly,an adaptive controller based on hysteresis quantizer is designed for nonlinear systems with quantization input and output polynomial growth rates.All the proposed control schemes ensure that the control target of global practical tracking can be realized.3.For a class of uncertain nonlinear large-scale systems with strong interconnection,the practical tracking control problem is considered again.First of all,in order to better balance the system performance and communication constraints,the event triggering mechanism based on switching threshold strategy is adopted.Furthermore,combined with the Lyapunov-like inequality with time-varying parameter,a non-backstepping control scheme based on adaptive output feedback is proposed.By using the dynamic gain scaling technique,it is proved that under any initial conditions,the output tracking error of each subsystem can eventually converge to a given compact set and the states of all closed-loop systems are bounded.4.The problem of adaptive state asymptotic regulation is investigated for a class of triangular structure nonlinear large-scale systems with quantized inputs.Firstly,in order to balance system performance and the transmission cost of the signal,a new combined quantizer combining logarithmic quantizer and universal quantizer is quoted.Then based on dynamic scaling technique and dual-gain control method,a pair of high gain observers and controllers are designed for the lower-triangle case;for large-scale nonlinear systems with upper-triangular structure,a dynamic low-gain output feedback control scheme is proposed.Finally,using Barbǎlat lemma to prove that the states of systems converge to zero asymptotically.