Robust cascade control system design for central airconditioning system

In the central air-conditioning system, the control system uses traditionally single loop PID controller. The control structure is simple, but the performance is usually not satisfactory. In this paper, the thermodynamic model of the heat exchanger and air-conditioning space in the central air-conditioning system are modeled in mathematic. Based on the models, we propose a robust cascade control strategy for temperature control of air-conditioning system. The robust cascade control system aims at eliminating the disadvantages of traditional design via complete decoupling of the design and performance of two cascaded control loops. Finally, the three controllers, the designed cascade control, traditional cascade PID control and single PID control are simulated in central air-conditioning system. It is found that the setpoint response, the robust and the performance of the designed robust cascade control system are better than the traditional cascade PID control system and single PID control system.