Adaptive Constrained Control For Uncertain Strict Feedback Nonlinear Systems

With the rapid development of modern industry,the objects of industrial control have become increasingly complex.In practical engineering applications,there are often many uncertainties such as unknown control directions,actuator failures,and system delays due to changes in the surrounding environment,aging of actuators,and communication delays between devices.These complex systems often operate under certain constraints,such as unmanned vehicles driving in tunnels,or the furnace temperature of a rolling system.Therefore,ensuring the safe operation of uncertain nonlinear systems under constraints has become one of the hot and difficult problems in the current control field.This article focuses on the research of two aspects of strict feedback nonlinear system constraint control: full-state constraint and output predesign performance constraint.For a class of strict feedback nonlinear system controller design problems,this article discusses the lemmas involved in the design of controllers for stochastic nonlinear systems and the design of dynamic gain observers,as well as stability criteria for nonlinear systems under different conditions.The basic methods of restricted controller design are introduced,and the advantages of the selected method in this article are compared.For a class of strict feedback stochastic nonlinear systems with actuator failures and unknown control coefficients,the problem of designing a full-state constraint state feedback controller is studied.First,a new type of delay constraint function and coordinate transformation is introduced to eliminate the feasibility conditions in the obstacle Lyapunov function method.Second,to solve the problem of time-varying unknown control directions,a Nussbaum-type function is introduced.Then,a new adaptive full-state constraint control scheme is designed based on the recursive design method,and the stability analysis of the closed-loop system is given.Compared with previous work,the delay constraint function proposed in this article allows the initial values of each state to be arbitrarily selected and can enter the constraint boundary within a given time T,thereby improving the convergence speed of tracking errors.For a class of strict feedback nonlinear systems with actuator saturation and state delay,the problem of designing an adaptive predesign performance constraint output feedback controller is studied.First,a dynamic gain extended state observer is constructed to estimate the unmeasurable states and input deviations in the system and relax the assumption of nonlinear terms.Second,a new auxiliary system driven by the difference between the actual output of the saturated actuator and the designed output of the controller is designed to solve the problem of input saturation,and the boundary of the performance function is dynamically adjusted when input saturation occurs.Compared with previous work,the state transformation adopted in this article can make the initial value of the predesign performance function tend to infinity,allowing the error initial value to be arbitrarily selected.Finally,stability analysis is provided,and the effectiveness of the control scheme is demonstrated through simulation.