| 摘要 |
A low noise, high bandwidth, sensorless vector control for a brushless DC motor includes a phase locked loop control having a digital counter and ROM look-up table which is responsive to a VCO to generate digital signals representing the sine and cosine of the instantaneous phase angle of the VCO. These signals are modulated by a current command and applied to a two-phase to three-phase converter. A flux sensor senses the air gap flux in the three motor coils and converts this signal to quadrature components which are compared with the output of the look-up table to derive a phase error signal that drives the VCO. Another feature of the invention is a timed self-starting network that cause the VCO frequency to ramp upwards then automatically switch to loop control without any abrupt change in the frequency of the VCO.
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