| 摘要 |
A process for starting-up in a desired forward sense of rotation a multiphase, brushless, sensorless, DC motor, while limiting then extent of a possible backward rotation, consists in exciting a predefined phase for accelerating the rotor toward a relative equilibrium position for a fraction of the time necessary to the accelerated rotor to travel through a nearest angular position which would determine a "zero-crossing" in the waveform of any one of the back electromotive forces (BEMFs) which are induced by the rotor on the windings of the motor. After the elapsing of this brief impulse of excitation, the sign of the BEMFs induced in the windings of the motor are digitally read thus producing a first reading. The occurrence of a first "zero-crossing" event if monitored and if this happens within a preset interval of time subsequent to the instant of interruption of the first excitation impulse, the optimal phase to be excited first for accelerating the motor in the desired direction is confirmatively decoded through a "look-up table" and the start-up process may proceed. If such a "zero-crossing" occurrence is not detected within said period of time, the routine is repeated by exciting a different phase which is functionally shifted of two phase positions from said predefined phase. The maximum backward rotation that may occur in the worst of cases is sensibly less than the angular distance which separates two adjacent equilibrium positions of the rotor and in practice may be of just few degrees. <IMAGE> |
