Research On Sensorless Control Of Brushless DC Motor Based On ARM-cortex Controller

Since position sensors can bring in many problems, such as increasing the difficulty ofinstallation, easily getting disturbed, becoming restricted on some special occasions, technology ofsensorless control will further widen the application of brushless DC motor (BLDCM) in servosystems, electric vehicles, aerospace and so on. The paper focuses on sensorless control of BLDCMbased on an ARM-Cortex controller.The paper studies sensorless control on middle-high speed based on coordinate transformation,which realizes real-time compensation of phase lag of RC filter via adjusting the rotating angle of thecoordinate. On the basis, the paper continues to study the speed estimation method by calculating thedifference of angle to time, which improves the real-time performance but needs massive computation.In order to simplify calculating process, an optimization is made by reckoning the difference of sinewave. Both the two methods have the problem of inaccuracy of estimation value among low speed, sothe paper studies a new speed estimation method without doing differential operations by figuring upthe amplitude of sine wave, which effectively improves the real-time performance and accuracy ofspeed estimation at a low speed.In open-loop start of BLDCM without position sensors, pulsations of torque and speed are largeand motor often fail to start. In order to solve those problems, the paper analyzes Space Vector PulseWidth Modulation (SVPWM) control schema of three-phase inverter employing180°switch-on modeand derives the relationship between composed stator magnetomotive force (SMF) and currentmaximum phase’s magnetomotive force (PMF) with windings in Y connection. On the basis, thepaper proposes a new starting control strategy combing SMF regulation and SVPWM and thensimplifies the calculation of SMF. The proposed starting algorithm is independent of saliency or initialposition of rotor and also can effectively suppress ripples of speed and torque, so its startingperformance is greatly improved compared with conventional I/f variable-frequency open-loop start.The simulation model is established in Matlab/Simulink software to study sensorless control andclosed-loop control of speed and current.In the end, the software and hardware realization and debugging methods of the whole systemare introduced. The experimental results verify the validity and feasibility of the proposed theory.