Controller Design For Several Types Of Nonlinear Systems With Constraint

In the theoretical research and practical application of automatic control systems,nonlinear systems have always been an important research field.Due to the physical limitations and safety specifications,almost all engineering systems are restricted by constraint requirements,including state constraints,output constraints,input saturation and so on.Therefore,it is of great significance to study the control methods of nonlinear systems with constraint requirements.In this paper,for several types of nonlinear systems with constraint requirements,research is carried out around three aspects of closed-loop system stability,constraint control,and operation performance.The main tasks completed are as follows:1.The practical prescribed time tracking problem based on event-triggered control is studied for a class of uncertain nonlinear systems subject to asymmetric state constraints.A settling time regulator is designed to get a performance function.Using this function,an event-triggered adaptive control method is put forward for acquiring specified tracking precision in the prescribed time.Then,the asymmetric state constraints are handled by introducing a novel nonlinear statedependent function.In combination with the backstepping technique,a coordinate transformation is constructed to convert the original state-constrained space into free space.Besides,a dynamic surface control is proposed to eliminate the demanding feasibility conditions on virtual controllers.The communication between controller and actuator is reduced by adopting the appropriate eventtriggered strategy.Moreover,it is indicated that without altering the control structure,not only the settling time and tracking precision can be selected,but also asymmetric state constraints are satisfied.Simulation examples confirm the effectiveness of the presented control scheme.2.An adaptive output feedback controller is considered for a class of nonlinear systems with integral input-to-state stable inverse dynamics,external disturbance and asymmetric output constraints.A tan-type barrier Lyapunov function is introduced to solve output constraints.Under the general framework,the designed scheme can be applied to systems with symmetric/asymmetric constraints or without constraint requirements.An extended state observer is proposed to estimate external disturbance by defining the disturbance as the generalized system state.Moreover,a reduced-order extended state observer is designed to establish the error dynamic system.In combination with the backstepping technique and linear matrix inequality,it is indicated that the adaptive output feedback controller not only guarantees the global asymptotic stability of the closed-loop system,but also does not violate asymmetric output constraints.Simulation results demonstrate the effectiveness of the proposed control scheme.3.The performance-guaranteed tracking control is investigated for Euler–Lagrange systems subject to input saturation and output constraints.The prescribed performance and output constraints are first considered for Euler–Lagrange systems with input saturation.Time-varying barrier Lyapunov function is employed to ensure constraint satisfaction.An adaptive control method for Euler–Lagrange systems with saturation is put forward by adding a speed transformation into the barrier Lyapunov function and designing auxiliary variables to the system.Subsequently,neural network is introduced to compensate for uncertainties of systems.In combination with the backstepping technique,it is demonstrated that the controller not only guarantees that the tracking error converges to a preset compact set near zero at a specified decay rate,but also ensures that the output always stays within a given boundary.Simulation results further demonstrate the effectiveness of the proposed control scheme.