Command Filtered Discrete Control For Cascade Continuous Stirred Tank Reactors Considering Input Saturation

Cascade continuous stirred tank reactors(CCSTRs)are widely applied in numerous chemical production processes.It is advantaged by simple operation,low cost,and strong heat transfer capacity.However,the CCSTRs system is a nonlinear object with characteristics of complex such as large delay,time variability and uncertainty.When the external disturbance occurs during the operation of the CCSTRs system,the oscillation amplitude of the reaction temperature and concentration of the system is too large or the stability range is too small,which the stability of the CCSTRs control system will be reduced,and there is a risk that the system will run out of control.But the traditional control technology such as PID(or improved PID)technology is difficult to achieve good dynamic and static control performance.Therefore,it is necessary to design a new practical and efficient controller for CCSTRs system such as to provide technical support for enterprises to improve production efficiency and economic benefits.In addition,with the gradual improvement of science and technology,the digital computer industry has also experienced rapid development,and the discrete control has been widely used in the field of digital computers due to its good stability,strong realization and other advantages,because compared with continuous control method,the discrete control can help it describe practical issues more easily and make it easier to apply the results to practical engineering by introducing the sampling method.Therefore,fuzzy adaptive backstepping command filtered control technology is introduced for CCSTRs system considering the input saturation constraint,and the discrete controller of CCSTRs based on the actual different application scenarios was designed respectively,so that the tracking control of the concentration and temperature of the reactant in CCSTRs system was realized.The main research achievements are as follows:(1)In this paper,the CCSTRs as the control object,a command filtered discrete controller is designed for CCSTRs with input saturation.The input saturation function is used to limit the input signal in a certain range,which the control performance of the system is improved,the realizable cost is reduced and make its closer to the practical application.The nonlinear terms are solved by introducing the fuzzy adaptive control and the backstepping method in the system,which the design process of the controller is simplified,the amount of calculation in the operation process of the system is reduced.Combined with the command filtered technology and the error compensation mechanism,the complex difference process of virtual control function is avoided,the problem of "causality contradiction" is overcome,the filtered error is reduced and eliminated,and the control precision of the system is improved.The simulation results show that the proposed control strategy has better control performance.(2)In this paper,further considers that the sensor performance is reduced due to various environmental factors in the reaction process of system,such as external noise interference or humidity,and the temperature and concentration sensors cannot be installed normally due to cost constraints.The command filtered discrete controller for CCSTRs considering input saturation based on observer is designed.The dynamic and static processes of temperature and concentration of products and reactants can be estimated by introducing the adaptive observer in real time,which the cost is saved and make it easier to apply the results to practical engineering.The superiority of the proposed controller is verified by simulation results.(3)Considers the phenomenon of the actual control law and frequent updating of adaptive law in CCSTRs discrete system,a new command filtered event-triggered control strategy considering input saturation is proposed in this paper.The eventtriggered mechanism is introduced between the sensor and the controller,and the trigger conditions is set to judge whether the control signal needs to be updated,so that the trigger times are reduced,the transmission of redundant signals is avoided,the update frequency of the controller and the calculation amount is reduced,and the utilization rate of resources is improved.Through further simulation,the control strategy is proved to be effective and feasible,and has certain practical value.