Adaptive Fuzzy Command Filtered Control For Cascaded Continuous Stirred Tank Reactors

The cascaded continuous stirred tank reactors(CSTRs)are simple in operation and sufficient in reaction,it can continuously add reactants and take out products(ie,products),thus so it is widely used in many chemical production processes.However,due to the complex internal reaction mechanism of CSTRs,the dynamic characteristics are susceptible.The mathematical model has high nonlinearity,time-varying,strong coupling and uncertainty.When there is external disturbance and noise,the system operation may deviate from the intermediate steady state very quickly,thus affecting production efficiency and product quality.Therefore,designing a stable,efficient,and practical CSTRs system controller has important research significance,which helps to improve production efficiency and reactant conversion rate,thereby maximizing economic benefits.Based on the basic principle of backstepping,this paper realized fuzzy adaptive command filtering control of cascaded continuous stirred reactor tank through fuzzy logic system and command filtering technology,and it is extended by the Barrier Lyapunov function(BLF)to BLF-based fuzzy adaptive command filtering control considering input and output constraints(ie.reaction temperature,reactant concentration,and the limitations of the reactor's own performance).The main research results of this paper are as follows:(1)For a class of nonlinear systems with feedback form is given based on the steps of the fuzzy adaptive control command filter,and its extended by the Barrier Lyapunov function(BLF)to BLF-based fuzzy adaptive command filtering control considering input and output constraints.Backstepping combines Barrier Lyapunov function to constrain the output of the system,and a novel method is used to process the input signal to achieve the purpose of input constraints.Finally,the stability is analysed by Lyapunov function analysis.(2)Taking a cascaded CSTRs system consisting of two reactors as the control object,the fuzzy adaptive control based on command filtering technology is studied.The fuzzy logic system is used to approximate the nonlinear part of the CSTRs system,and the command filtering technique is used to introduce the error compensation signal,which avoids the “computation explosion” and eliminates the influence of the filtering error.The control strategy can ensure the internal stability of the closed-loop system while tracking the reference signal asymptotically.Finally,the stability and effectiveness of the scheme are ensured by stability analysis and simulation.This paper also designs classical backstepping control method and fuzzy adaptive DSC control for CSTRs system.The result shows that this controller has better control effect than the other two control methods.(3)For the cascaded CSTRs system subject to input and output constraints,a fuzzy adaptive command filtering control based on BLF is proposed.The Barrier Lyapunov function is used to constrain the state variables such as temperature and reactant concentration into a given interval.A novel method is used to process the input signal to achieve input constraints.The simulation results show that the scheme meets the control requirements.At the same time,the constraints on the input and output of the CSTRs system are realized.