Dual-model Economic Predictive Control Strategies Of Affine Input Systems

Modern industrial process systems have the characteristics of non-linear,various soft and hard constraints,and are restricted by system safety and environmental protection.Model predictive control(MPC)has been widely concerned due to its ability to deal with constraints,nonlinearities,etc.Dual-mode strategy is one of the main solutions to ensure the closed-loop stability of non-linear MPC(NMPC).Although the existing dual-mode NMPC strategy solves the problem of conservative terminal domain,it is still urgent to expand the initial feasible region for dual-mode economic MPC.In addition,research on dual-mode EMPC for variable economic performance and safe operation is still insufficient.Therefore,it is of great significance to study the predictive control strategy of economic model for affine input system.Based on the review of the related literature at home and abroad,the dual-mode EMPC strategy of affine input system with state and control constraints for continuous time affine input nonlinear system is studied in this paper,by using the tools of balance surface,control Lyapunov function(CLF)and control barrier function(CBF).The main research work of this paper is as follows:(1)To solve the problem of the large-scale economic performance optimization control of constrained systems,a multi-balance point dual-mode EMPC strategy for affine input systems is proposed.A group of transition equilibrium points are obtained by using the concept of nonlinear system equilibrium surface,and the union set of terminal regions is obtained.Compared with the conventional terminal domain,the union expands the area on the basis of achieving the same function,thereby the pressure of calculation during system operation is reduced and initially feasible region is expanded,that is,the scope of economic performance optimization is expanded.The isothermal CSTR is taken as an example to verify the superiority of the scheme.(2)Aiming at the problem that the economic performance of the nonlinear constraint system changes,a dual-mode EMPC strategy with variable economic performance for affine input systems is proposed.Through the schedule of steady state points,the above multi-equilibrium point dual-mode empc strategy is applied to meet the time-varying economic performance,and the calculation burden is relieved to a certain extent.The feasibility of the algorithm in the case of changes in economic performance is also reflected by the chemical process example of isothermal CSTR.(3)Considering the disastrous consequences of unsafe operation on life and property,a dual-mode EMPC strategy is proposed to ensure safety and stability.The control method based on the control Lyapunov-Barrier Function is used in the dual-mode EMPC strategy to obtain closed-loop stability performance,process operational security,and optimal economic performance.Finally,the effectiveness of the controller is verified by simulation.