Sensorless commutation position detection for brushless motors

摘要

A method and apparatus for the sensorless determination of commutation position in a brushless motor. The electric current flowing within the active, or energized, stator coil during energization is differentiated to produce a current rate of change waveform. The current rate of change waveform is compared to a predetermined voltage threshold which is set to approximate the point at which the rotor is in direct positional alignment with the active stator. From this comparison, it is determined when the current rate of change waveform fails to intersect the predetermined voltage threshold. This information may be used to commutate the application of a driving signal to the next stator coil in succession to maintain continuous torque on the rotor. This information may also be indicative of a stalled condition, in which case a stall indicator is triggered to alert the user of the stalled condition.