Research & Design On MCU Of Frequency-Variable Air-Condition With Brushless DC Motor

Temperature control system of traditional air-condition depends on its sensors to monitor indoor temperature's changes and to control the compressor to run at a specified speed. The compressor can't adjust its running situation at an appropriate speed according to indoor temperature changes, which will result in dweller's comfortableness and energy waste. In recent years, frequency-variable air-condition has the intelligence character that temperature is adjusted automatically, continuously, according to temperature's change indoors. All this will avoid frequent switches of the compressor and economize energy.Brushless DC motor (BLDC) with permanent magnet excitation, in which electrical commutation is used instead of mechanical, has the same good characteristics of speed control as traditional DC motor. Brushless DC motors have found wide application due to their high power density and ease of control. Moreover, the machines have high efficiency over wide speed range. Attachment of sensorless control not only overcomes a lot of disadvantages generated by the sensor, but also expands the application range of brushless DC motor further. At present, the research on Frequency-Variable Air-condition with sensorless brushless DC motors has become a development trend of control technique for frequency-variable air-condition.Depending on the Research and development of all DC frequency-variable air-condition, this dissertation researches and discusses the design of the microcomputer controller of DC frequency-variable air-condition's outdoor machine. The specific work needed to do is as follows:(1) Give the introduction in detail for isolation between light current area and heavy current area, and bring forward a hardware design of power supply.(2) Application and improvement of the zero back EMF sensing and commutation point sensing respectively are advanced for sensorless brushless DC motors control in frequency-variable air-condition, while the control method of sensorless brushless DC motors based on MCU ST7MC1 is discussed in this dissertation.(3) Utilize fuzzy algorithm to optimize control air- conditioner's compressor and electronic expansion valve.Now, the design and test of project have been completed. It has good capability of temperatures modulation, energy conseration, protect function and run security.