The Research Of Sliding Mode Control And Its Application In Wastewater Treatment

The uncertainties, external disturbances and time-delays are widely existed in realengineering, such as the control of the dissolved oxygen concentration in the process ofsewage treatment. The existence of various uncertainties, external disturbances andtime-delays is important factors that lead to system instability. Therefore, when thecontrolled object using the intelligent control, the impact of these factors on the controleffort should be taken into considered. The sliding mode variable structure control whichhas strong robustness to the external disturbance and the parameter stands out among themany intelligent control methods. At present, the sliding mode variable structure controlhas been successfully applied in many fields, for example, the control of the invertedpendulum, the control of3DOF planar robot manipulators, the control of power systemand so on. The paper deeply studies the sliding mode variable structure control foruncertain nonlinear systems with time-delay and external disturbances. To solve thedefects of the single sliding mode control, it is combined with other intelligent controlmethods. This paper research content is as follows:First, aiming at the existing problem of sliding mode variable structure control, on thebasis of traditional sliding mode controller design method, this study proposes a novelsliding mode control with self-turning law for uncertain nonlinear systems with time-delayand external disturbances. The adaptive gain and sigmoid function instead of the signfunction of the traditional sliding mode controller. The design method of the controller inthis paper not only solves the chattering problem in the conventional sliding mode control,but also improves the tracking accuracy of the system on basis of the guarantee gooddynamic performance and steady-state performance of the control system.Secondly, for the control problems of a class of uncertain nonlinear switch systemswith the time delay and the external disturbances, this paper considers the design of thesliding mode control through consulting relevant literature both at home and abroad.Based on Lyapunov function, a sufficient condition for the control of such uncertainswitch systems is derived by means of sliding mode control and the appropriate switchinglaw. It is showed that the designed sliding mode controller can guarantee the state of theswitched systems to converge to the single sliding surface and remained on it thereafter.The simulation experiments further demonstrate the feasibility and effectiveness of thecontroller through the application of LMI and MATLAB. Finally, the part of the research results for the uncertain nonlinear system withtime-delay is applied to the control of the dissolved oxygen concentration in the process ofsewage treatment. The PID control algorithm and the Sliding-mode control algorithm inthe paper are compared through the experiment platform. Through the computersimulation and the results of experiment platform, using the proposed control algorithm inthis paper t is better than PID control algorithm for the control of the dissolved oxygenconcentration in the process of sewage treatment.