The Research On Variable Air Volume Control System Based On ADRC

Variable air volume (VAV) air-conditioning system change the air volume transferred into the air-conditioning region as to adjust the contemporary change of corresponding region heat loads. Due to its flexible, energy saving and comfortable advantages, VAV air-conditioning system is becoming the most popular among the large air conditioning systems at home and abroad nowadays. However, the features of VAV air-conditioning system (such as multi-loop, nonlinear and strong coupling) make the design and operation of the VAV system much complicated and difficult. Therefore, investigation of VAV system control techniques is of important and practical significance.This paper mainly studies PID control methods and Active Disturbance Rejection Control (ADRC) Techniques of VAV air-conditioning system, and completes software and hardware designs. The context is organized as follows:1. Model investigation of VAV air-conditioning system. Starting from the object principles, we study the coupling relationships between each variable of the system and set up mathematical models of the equipments in the VAV system, including: room, VAV terminal unit, inverter, blower, cooler, valve and others. Then we obtain the corresponding transferring function via the Taylor series expansion around the predetermined working condition together with the approximately linear treatment. The obtained transferring function provides a valuable tool for further studying system control techniques of the VAV system.2. Combined with the principles and characteristics of ADRC techniques, we here present a discrete algorithm of the ADRC controllers. Furthermore, we performed simulations of the ADRC controllers by making use of the S-function in the MATLAB Simulink module.3. For the VAV terminal equipment, we design an ADRC controller to control the temperatures inside the room. The simulation results show that, compared with PID control methods, ADRC techniques are easily to adjust the change of the room heat loads and influence from the surrounding disturbance, while maintaining the room temperature around the predetermined one with very small fluctuation range.4. We use the ADRC methods to realize multivariable decoupling control, while considering the strong coupling among control loops of VAV system based on the room temperature and static pressure and temperature of supply air. Our study reveals that the couplings of the system are all dynamic thus can be compensated by total disturbance inside each separate loop. MATLAB simulation results show that the ADRC methods can effectively compensate interaction among the individual loops of the system, and make the operation of the system more stable.5. Based on the project background, design the hardware of the VAV control System. The controller uses the AT91SAM9261 processor as the core, with a sound structure and strong processing power. We can run PID, ADRC and other complex control algorithms on it.