The Development Of Duty Ratio Fuzzy Controller And The Experimental Research For Fan-coil Unit

Fan-coil unit is an important kind of central HVAC system terminal device in our country, where its controllers are widely used. The traditional control of fan-coil unit is to detect the indoor temperature by sensors and then to control the relay of the fan or the electric valve independently, which leads a lag and makes indoor temperature fluctuate greatly. Also it influences control accuracy and comfort. At the same time, it could not modify controller's working parameter in time according to the changing temperature, why wastes much power.Basing on domestic and abroad achievements, independently develop an efficient fan-coil unit fuzzy controller, which could replace some related products. MC9S08QE128, a kind of 8-bit microcontroller from Freescale company, is chosen as the master chip. Present a new type of energy efficiency control method, which employs the conception of duty ratio on electric valve in order to fully utilize the cooling capacity of the fan-coil unit. By means of Mamdani type fuzzy rule and method of functioning fuzzy subsets inference, duty ratio of electric valve and fan speed signal are decided according to deviation and deviation change of indoor temperature. The new method could solve the existing problems.The exploitation of the fuzzy controller on hardware and software is introduced in the paper. Hardware designing mainly includes forward channel circuit, single-chip interface circuit and backward channel circuit. While temperature sampling program, fuzzy control method's realization and output control are included in software designing. Emphases are the realization of the fuzzy control method and optimization method applied to microcontrollers' programming.Experiments indicate that it is practical to use the newly exploited fan-coil unit fuzzy controller and its method. Results show that presented method could achieve at least 30% energy saving than traditional control method as well as a preferable room temperature control effect. On the background of people's hankering to comfortable surroundings but lacking of enough energy resources, there ia a very important theoretical value and practical significance to develop such efficient controllers.