The Research And Development Of The Speed Regulating System Of Automotive Air-condition Fan

With the development of the technology and the improvement of the people's life level, people have more requirement to the comfort of automobile. Therefore, many kinds of automotive air-conditions system come out rapidly. The speed regulating system of the air-condition fan influences the air-condition system's performance of adjusting the temperature in a large extent. The engineer all over the world are studying the better speed regulating system of air-condition fan.According to the change of the environment's temperature and people's different requirements to the automotive inner temperature, comfort and saving power, it is necessary for air-condition fan regulating the speed in all kinds of situations in order that it can adjust the exchange ratio of the inner air temperature and wind speed of the exit of air-condition fan, thereupon, the different requirements of passengers are satisfied, consequently, it is necessary for air-condition fan to regulate speed, and then it appears many varieties of the speed regulating system of air-condition fan.DC motor has the high running efficiency and benign performance of speed regulating, therefore, the early speed regulating systems of automotive air-condition fan mostly adopt DC motor to regulate the speed. DC motor adopt the brush to change direction, so the reliability and life-span of the system is being reduced, in the mean time, it can lead strong electromagnetic interference, as a result of that, the other electrical system of the automobile and environment can also be influenced.With the maturity of the technology of the AC frequency conversion, asynchronous motor speed regulating system has a extensive application in each industrial field. This kind of speed regulating system has the merits such as simple framework, credibility of working, without mechanical abrasion and less electromagnetic interference, thereby, it gradually replace the DC motor speed regulating system. On the other hand, the power factor of the asynchronous motor is low, so it faces the trend that it will be replaced by the brushless DC motor speed regulating system whose performance is much better than former system.At present, research personnel put more energy on the study on the permanent brushless DC motor speed regulating system of air-condition fan, in order that the speed regulating system of automotive air-condition whose performance is better than before face to the world as early as possible. Permanent brushless DC motor can be divided into two kinds. The one has position sensor, the other has not position sensor, it is called sensorless one. The research on the latter one is hotspot.The detecting system of position sensorless does not need mechanical position sensor. At the present time, the research core and key on position sensorless brushless DC motor controlling is detecting circuitry of the framework rotor position signal. The rotor position signal can be gained from software and hardware credibly, and then touch off the corresponding power apparatus, later, the motor run.Recent years, there appears a lot of the method of detecting rotor position worldwide. There are several kinds in general below: the method of inverted-electromotive force,the method of using inductance, the method of state observer,the method of vortex, the method of Kalman filter, the method of estimating magnetic chain.The aim of this dissertation is the study on the speed regulating system of automotive air-condition fan, the content and conclusion is below:1.Introduce the developing status quo of speed regulating system of automotive air-condition fan, analyze the merits and defects of three kings of speed regulating system of automotive air-condition fan, indicate the research significance and content of dissertation.2.Analyze the base framework and working theory of brushless DC motor, demonstrate the rotor position detecting and switch circuitry case of brushless DC motor. This article adopt a newly detecting method to achieve the rotor position detecting, it is called the method of G (θ) function. The result proves that this method is a effective one.3.Analyze the working theory and feature of the PID control system, introduce the theory and composing of the fuzzy control and double fuzzy control specially and feasibility and advantage of using former theory in the speed regulating system of air-condition fan. Finally, choose the method of fuzzy PID control to apply to the speed regulating system of air-condition fan control.4.Setup the mathematic model and simulating model of speed regulating, analyze by simulating, evaluate the control strategy. Through comparing with the double PI adjusting simulation, the advantage of the fuzzy PI control strategy is obvious. Fuzzy PI control strategy has benign steady precision , less steady error and strong ability of countering the interference. Thereby, with the development of modern control technology, fuzzy PI control will apply in variety of speed regulating in a large extent.5.Finish the software design of speed regulating system of automotive air-condition fan. As the limit of condition, this article does not finish the hardware design of the system, this is the main direction of next step work.Position sensorless permanent brushless DC motor speed regulating system of automotive air-condition fan will realize in the late future, produce in many batches and apply in the real car. The study on this system will promote the development of the motor controlling, and naissance more applied method of detecting.