Cooperative Optimal Control Of A Dual-Volume Liquid Level System Considering Unmodeled Dynamics And External Disturbance

The two tank liquid level system is one of the typical research objects in the field of process control,with control accuracy greatly affected by the unmodeled dynamics and external disturbances.Moreover,the system needs both of dynamic and steady-state performance,resulting in complex control.To address these challenges,this paper proposes a cooperative optimization control algorithm that combines two controllers designed from the perspectives of signal and energy.The main research contributions are as follows:（1）Aiming at the problems of external disturbance and model parameter uncertainty of two tank liquid level system,a neural network Sliding mode control method based on nonlinear disturbance observer is designed from the signal point of view.Based on the integral sliding mode controller,considering the unmodeled dynamics of the system,the nonlinear function of the system is approximated by the radial basis function neural network,and a nonlinear disturbance observer is designed to estimate the external disturbance.The simulation results show that the steady-state error of the designed method is reduced by 75%compared with the traditional integral sliding mode control,and the performance of the designed method is improved compared with the traditional integral Sliding mode control under various conditions.（2）An adaptive neural network backstepping sliding mode controller based on signal is designed to meet the demand of fast response of the system and effectively solve the influence of unmodeled dynamics and external disturbances of the system.A Port-controlled Hamiltonian controller was designed from the perspective of energy,which has good steady-state performance and can effectively eliminate the inherent chattering problem of backstepping sliding mode.Then,design a collaborative optimization control method that takes into account the advantages of both controllers.The simulation results show that this control method reduces the liquid level change amplitude of the cooperative optimal control by about 25%compared with the Port-controlled Hamiltonian control when the valve expands in the system,and there is no overshoot compared with the neural network backstepping Sliding mode control;The collaborative optimization control of external disturbances in the system reduces the amplitude of liquid level changes by 20%compared to the Port-controlled Hamiltonian control,and the recovery time to steady-state is shortened by 5s.（3）A model free adaptive Sliding mode control and improved Port-controlled Hamiltonian control cooperative optimization control method for two tank liquid level system is designed.Model free adaptive sliding mode controller is designed based on signal and super local model of the system;Using an extended observer to estimate disturbances and unmodeled dynamics in the system and perform feedforward compensation.Introducing Port-controlled Hamiltonian control from an energy perspective and utilizing L₂ gain to further suppress external disturbances.oombining signals with energy controllers through collaborative optimization control algorithms.The simulation results show that the time to reach the desired liquid level of the cooperative optimal control is 5s faster than that of the Port-controlled Hamiltonian control,the steady-state error is 0.1cm less than that of the modeless adaptive Sliding mode control,and the controllability of the single controller is improved under various conditions such as unmodeled dynamics and external disturbances.In summary,the paper proposes three different control methods,taking into account the advantages of signal control and energy control,and achieves the coordinated optimization control of signal and energy for the two tank liquid level system.In response to unmodeled dynamics and external disturbances in the system,collaborative optimization control enables the system to have faster response time,better robustness,and higher control accuracy.The viewpoint of optimizing control through signal and energy synergy provides new implementation schemes and scientific basis for high-performance control of two tank liquid level systems,which has important theoretical and practical significance.