| In this paper, we study a 48V, 250W, 3-phase 6-pole Brushless DC Motor (BLDCM). And establish the digital control system of sensorless BLDCM based on microcontroller. Then the research is concentrated on three key point——rotor position detection, starting method and the control of speed-adjusting. Finally, we give the experimental verification.At the beginning, we illustrate various method of rotor position detection, and give a solution by checking the zero-crossing of the back electromotive force (Back-EMF) during PWM"ON" period. Based on the analyses of the"lagging 30°commutation"and the phase delay caused by filter in Back-EMF method, we adopt the delay process by means of a timer. This way, the phase delay caused by filter can be corrected immediately. Finally, we give a practical implementation of this solution in both software and hardware.Aiming at the starting method when BLDCM run in sensorless mode, we propose a solution named"3-step starting method"in consideration of effect and costs. In preposition phase, the chapter dissertate method of commutation order and the driving current. In forced synchronous mode, the starting direction, starting ramp table and the factor changed to self-synchronous mode are also discussed. After determining the executive plan, we carry out the software of it.In order to improve the dynamic and static performance as well as the stability and robustness of the BLDC speed-adjusting system, we bring forward a cascade speed control system with two control loop——current loop and velocity loop. As an inner-loop, current loop will greatly improve the anti-jamming capability of system by suppressing the disturbance of load current and voltage. The velocity loop will make better robust speed control with no static error.This paper gives a design of motor control system based on PSoCTM manufactured by Cypress in US. The experimental result proved that this BLDCM control system have broad prospects for application with its simplicity and suitability. |
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