Precise Control And Disturbance Suppression Of Liquid Level In Multi-capacity Water Tank Systems

Multi-tank system has the characteristics of multivariable,strong coupling,high nonlinearity and high complexity,and it is one of the important fields in the application of nonlinear control theory.These characteristics will affect the stability of the control system,and the multi-tank system is greatly affected by the unknown disturbance and parameter uncertainty,which makes the control task more complex,and the accurate control of multi variables is also very difficult.Therefore,it is of great significance for industrial production to resolve the problems of disturbance suppression and multivariable control in multi-tank system.(1)An integral backstepping control strategy based on disturbance observer is adopted for the two-tank system with disturbance.Firstly,in order to ensure the position control performance of liquid level,an integral backstepping controller is designed.In addition,the disturbance observer is used resolve the external disturbance problem of the two-tank system.(2)For the quadruple-tank system,a state error feedback linearization control strategy based on disturbance observer and L₂-gain disturbance suppression is adopted.Firstly,the controller is choosen by using the feedback linearization technology to realize the position control and tracking control of liquid level.Secondly,the problems of uncertain external disturbance and disturbance compensation control for quadruple-tank system are disposed by disturbance observer.Moreover,a L₂-gain disturbance suppression controller is designed for a class of uncertain parameter disturbance in quadruple-tank system.(3)Based on the study of the feedback control method of the quadruple-tank system considering the existence of disturbance,the active disturbance rejection control strategy is adopted to suppress the influence of disturbance on the system.An active disturbance rejection technique and the dynamic model of quadruple-tank system are used to consider two forms of active disturbance rejection control with nonlinear function and linearization.Among them,the linearized active disturbance rejection control can still play a role in the process of arranging the reference input,the observation state of system and the disturbance compensation.(4)A port-controlled Hamiltonian(PCH)strategy based on sliding model disturbance observer is proposed for a quadruple-tank system with disturbance.Firstly,a PCH model of the quadruple-tank system is established based on the PCH principle.Secondly,a basic feedback controller is derived by configturing the interconnection structure and damping injection mode.Then,a terminal sliding model disturbance observer is used to suppress the disturbance effect in the quadruple-tank system.Several control strategies used in this study have been verified by simulation and experiment,which not only realize the precise control,tracking control and disturbance compensation control of liquid level,but also show better robustness,dynamic and steady-state performances compared with proportional-integral-differential control,sliding mode control and some research results of domestic and foreign research groups.Also,these proposed strategies have good effect in the suppression of uncertain exogenous interference,uncertain parameter disturbance and measurement noise and so on.Moreover,a large number of experimental results further confirm that the proposed strategies have great application value in the actual industrial production.