Research On Sensorless Control Technology Of DC Brushless Fan For FFU

FFU has the meaning of "fan filter unit",which is an indoor air purification device composed of a centrifugal fan,a silent device and a filter net.It is mainly used in food,medicine,precision electronics and other factories with high cleanliness requirements to achieve the purpose of real-time air purification.However,the current FFU is generally driven by a single-phase asynchronous fan,which has the problems of large energy consumption and difficult to control the speed in real time.Therefore,a DC brushless fan is considered to replace the traditional driving method.At the same time,because the position detection transposition in the DC brushless fan has the risk of failure,after comprehensive consideration,this paper presents a control scheme of brushless DC fan based on sensorless sensor.The paper first analyzes the current status of domestic and foreign research on FFU and positionless sensor detection technology through literature review,and proposes a rotor position detection scheme using a three-stage start-up method and a back-EMF zero-crossing detection method.Secondly,according to the basic structure and operation principle of the DC brushless fan,the working principle of the fan is briefly described.Then mathematical modeling was performed on the brushless DC fan,and expressions including voltage,back-EMF,torque,armature current,and speed were obtained.Then,the article analyzes the three stages of rotor pre-positioning,acceleration,and state switching in the three-stage starting method used in the system.And the basic principle,algorithm implementation and data extraction of the back-EMF zero-crossing detection method are described theoretically.Because the control parameters of the system can only be obtained after a lot of actual debugging,in practice,it is necessary to design and test the control system model on the MATLAB / Simulink simulation platform based on the above theoretical knowledge to verify the effectiveness of the detection algorithm.Finally,use the TMS320F28335 DSP development board and the test fan to build a hardware control system.After experimental debugging,the hardware system can complete the normal startup and speed regulation process,which further verifies the feasibility of the proposed control scheme in practical applications.