Study On Matching And Control Strategy Of Electric Bus Air-condition System

This paper is based on the momentous item——"Research and Development of Faw-EV Bus's Control System and Specimen"(serial number: 20076025)which is developed by the Jilin Province Science and Technology Office, research the electric control system of air-condition and its strategy which is matching with the EV bus. To considering that this new generation EV bus protect environment, since its power is much less than the traditional vehicle, the power it can supply to the air-condition system is limited. For the sake of making the product competitive in market, decreasing source consuming, processing a suit of air-condition system which is saving resource, high efficiency and reliable has much practical meaning.Compressor, expansive valve,evaporator and condensator are four most important parts of air-condition system. Reasonable matching of each parts can well improve the whole system's economy and reliability. Quality of auto air-condition's parts directly affects the performance of whole system, but unequal to say parts'quality is good, then the auto air-condition system is good. Only basing on reasonable matching of each parts can make the whole system to perform well. In this paper, compressor part of air-condition system chose the method of assembling DC non-brushing motor and oblique tray type compressor which is broadly application, storage battery supply electricity, compressor's rotate speed was controlled by controller. When compressor's speed is smallest, calculated the biggest displacement that the compressor needed. Expansive valve chose EX7-U21 electronic expansive valve whose temperature control is accurate operation scope is abroad. Evaporator and condensator's diathermanous area can satisfy air-condition system's need when system's refrigeration capacity is biggest. The whole system can satisfy EV bus'request for refrigeration.Vehicle compartment temperature's affect factors are very much, compartment environment are very bad and sudden change is much, so traditional controller sometimes can't reaction in time, and can't betimes follow body's feeling, it is very hard to establish accurate mathematical model of this complex system. The paper requires the air-condition system to reach the follow targets: (1) Adjust time is less than 60 seconds; (2) Stable state error is less than 0.5℃; (3) Over-regulation temperature is less than 0.8℃. For the sake of reaching these targets, first of all, the paper adopted the method of fuzzy control. Compartment temperature margin and its change rate is as fuzzy controller's input parameters, then carried on fuzzy processing to the input parameters. Then we established fuzzy subjection degree of the inputs according to their fuzzy membership functions. Second, we established fuzzy control rule according to people's experience, ensured output fuzzy parameter corresponding to the input parameter. Finally, we translated the fuzzy outputs to precise value—the control signal of compressor control—according to output fuzzy membership functions.The paper established module of vehicle air-condition system, and simulated it in software——Matlab/Simulink: First of all, we proceeded a thermodynamic analysis to the compartment temperature and established a simple mathematical model. Second used fuzzy control tool box in Matlab/Simulink and established fuzzy control module of the vehicle air conditioner. Finally, combinated the two module one fuzzy control system with real time temperature. We used this module to check out the effect of this new type air-condition system with electronic compressor and fuzzy control. In three different kinds of work situation, we simulated the system module, analyzed the simulate results which indicated that the temperature curve didn't have obvious overshoot, Overshoot temperature is less than 0.5℃; Adjust time is less than 60 seconds; Stable state error is less than 0.2℃. These results absolutely satisfied the control target. Comparing and analyzing the electronic air-condition system and other traditional systems'simulate curve, the results indicated that the electronic air-condition system this paper used is saving resource, high efficiency and its control effect is best.Last but not least, this paper presented a plan for air-condition system's design (including software and hardware). Using singlechip PIC16F87 as core of hardware in system electronic control unit. The plan described each part of the hardware's functions and control methods, then on the base of hardware design, designed fuzzy controller's procedure flow. At last, the paper briefly illuminated each part of the procedure's function.