Identification And Sliding Mode Variable Structure Control Of Double Tank System

In the modern industrial production, the process of automatic control plays a very important role, liquid level control technology is widely used in the process industry. In actual production, the performance of liquid level control is directly related to the safety, efficiency and cost of the whole equipment. It is very important to develop advanced level control technology and strategy to ensure the safety and stability of process control. Multi-tank system is a prototype of many complex control systems in industrial production. It is a typical object of process control research and a platform for controlling algorithm.The multi-tank system is a typical nonlinear system. In this paper, the mathematical model of the system is deduced according to the mechanism modeling. The nonlinear model parameters are obtained by the system identification method and the nonlinear identification method, which are the foundation of the controller design.Sliding mode variable structure control (SMC) is an effective method to deal with uncertain systems. It has the advantages of fast response, no change to system parameters and external disturbances, simple controller structure and so on. It has an extensive application in the liquid level control system. However, it has the disadvantage of chattering. In order to improve the performance of the system, the concept of "quasi-sliding mode" is introduced,that is, the sliding mode variable structure control based with the boundary layer is introduced.The sliding mode variable structure controller of the single tank system and the double tank system is designed and the Lyapunov function is used to prove the stability of the designed controller. The simulation and experimental results verify that the effectiveness of the method.The sliding mode variable structure control with the boundary layer can effectively reduce the buffeting, but at the expense of increasing the tracking error, the control precision can be improved by introducing the integral effect in the sliding mode surface, but lead to the transient response overshoot, the shortcomings of a long time. A nonlinear integral sliding mode variable structure controller is designed by using the smooth nonlinear function with the function of "small error amplification and large error saturation". The controller design takes into account the influence of input restriction and can guarantee the input in a certain range.The stability of the designed controller is proved by Lyapunov function. The controller improves the transient performance compared with the conventional SMC ,and also maintains the desired properties of the traditional SMC, stabilizes the adjustment, effectively attenuates the buffering. The nonlinear integral SMC has shorter adjustment time and smaller stability error compared with the conditional integrator SMC, which has better performance. The dynamic performance of the system is not reduced when the input is limited.Finally, an identification and control method based on NN-SANARX model is proposed.The advantage of this method is that the mathematical model of the object is not needed. Only need to use the input and output data of the actual object to identify the object model by using the neural network model, output feedback linearization method is designed based on the neural network identification model of the controller. The experimental results show the effectiveness of the method. This method is an effective method for the unknown model of the object.