For the strong nonlinear coupling between the level control and product density control loops of the forced-circulation evaporation system

a kind of linear time-invariant active disturbance rejection decoupling control based on particle swarm optimization is proposed.First

two virtual control variables are introduced to transform the system into two single-input-single-output subsystems

and a reduced-order extended state observer is designed for each loop of the system.Then two proportional controllers are employed to control the approximate integrators.At last

the time-invariant coupling matrix of the controller and the proportional gains are obtained by using particle swarm optimization in the possible operation envelope.Therefore

the dynamic coupling part is estimated and compensated by the observer

so the dependency of the controller on the refined mathematical model can be reduced considerably.The constant control gain matrix is optimized and there is no need to measure the temperature of the product.Therefore

the temperature sensor can be removed.These improvements can enhance reliability and the implementation is readily done by applying time-invariant control strategy.Simulation results show that the proposed method can not only decouple the loops effectively but also ensure performance robustness under external disturbances.