Brushless d.c. motor acceleration system

Claim 2

An improved brushless d.c. motor of the type employing a permanently magnetized rotor rotatably mounted in operative relationship with respect to a plurality of stator winding coils, said improvement comprising, resolver means for providing signals indicative of the sine and cosine of the instantaneous rotor displacement angle, power bridge means for sequentially energizing said stator winding coils so as to cause rotation of said rotor in response to output signals from said resolver means, a source of sinusoidal alternating current signals having a fixed frequency corresponding to the desired running speed of said motor, detection means coupled to receive signals from said source and from said resolver means, coincidence means in said detection means for providing a coincidence signal whenever the input signals to said detection means become synchronized, means in said detection means for providing a first mode signal until the occurrence of a coincidence signal and a second mode signal thereafter, and switching means for actuating said power bridge means from said resolver means in response to a first mode signal and only from said source in response to a second mode signal.

Claim 3

The apparatus of claim 1 wherein the stator winding coils include first and second coils arranged in space quadrature and wherein said power bridge means includes first and second power bridges for energizing said first and second coils respectively, said first power bridge being coupled through said switching means to respond to sine output signals from said resolver, said second power bridge being coupled through said switching means to respond to cosine output signals from said resolver.

Claim 4

The apparatus of claim 2 wherein each of said power bridges includes means for supplying a feedback signal indicative of the corresponding stator winding coil current being supplied by said power bridge, said apparatus further including first and second summer means for combining the feedback signal from said first power bridge with said sine signal and the feedback signal from said second power bridge with said cosine signal respectively, said power bridges being actuated in response to signals through said summer means.

Claim 5

The apparatus of claim 3 wherein the signals from said summers are coupled to the respective power bridges through individual pulse width modulators, said pulse width modulators being constructed to provide rectangular output pulses having a polarity and pulse duration determined by the polarity and amplitude of the signal from the corresponding summer circuit.

Claim 6

The apparatus of claim 4 wherein said resolver is excited by a resolver excitation circuit at a frequency that is high with respect to the product of the running speed and number of motor pole pairs and wherein said pulse width modulator includes means to convert a signal from said resolver excitation circuit into triangular waves and means to combine signals from the respective summer with said triangular wave, each of said pulse width modulators further including first and second comparator means to provide output signals whenever said combined signal exceeds a positive and negative threshold, respectively.

Claim 7

An improved brushless d.c. motor of the type employing a permanently magnetized rotor constructed to rotate in response to magnetic fields established sequentially by first and second stator windings arranged in space quadrature, said improvement including first and second switching means for selectively passing current in either direction through said first and second windings respectively, resolver means for producing sine and cosine waves having relative magnitudes uniquely defining the position of said rotor, first and second feedback means coupled to said first and second stator windings respectively for providing feedback signals indicative of the instantaneous magnitude of the current flowing in the associated stator winding, first summing means for adding the signal in said first feedback means to said cosine wave, second summing means for adding a signal in said second feedback means to said sine wave, means to couple the output of the first summing means through said first switching means to said first stator winding, means to couple the output of said second summing means through said second switching means to said second stator winding, a two-phase oscillator, means to couple one phase of said oscillator to said first switching means and the other phase of said oscillator to said second switching means, coincidence means coupled to receive signals from one of said oscillator phases and one of the waves from said resolving means, said coincidence means being constructed to provide an output signal when the signals applied to the coincidence means become synchronized, means coupled to the output of said coincidence means for providing a first mode signal until said coincidence means detects synchronism and for providing a second mode signal thereafter, means in said switching means for coupling the output from said summing means to said motor in response to a first mode signal, and means in said switching means for coupling the output of said oscillator to said motor in response to a second mode signal.

Claim 8

An improved brushless d.c. motor of the type employing a permanently magnetized rotor constructed to rotate in response to magnetic fields established sequentially by first and second stator windings arranged in space quadrature, said improvement including first and second switching means for selectively passing current in either direction through said first and second windings respectively, resolver means for producing sine and cosine waves having relative magnitudes uniquely defining the position of said rotor, first and second feedback means coupled to said first and second stator windings respectively for providing feedback signals indicative of the instantaneous magnitude of the current flowing in the associated stator winding, first summing means for adding the signal in said first feedback means to said cosine wave, second summing means for adding a signal in said second feedback means to said sine wave, means to couple the output of the first summing means through said first switching means to said first stator winding, means to couple the output of said second summing means through said second switching means to said second stator winding, a two-phase oscillator, means to couple one phase of said oscillator to said first switching means and the other phase of said oscillator to said second switching means, coincidence means coupled to receive signals from one of said oscillator phases and one of the waves from said resolving means, said coincidence means being constructed to provide an output signal when the signals applied to the coincidence means become synchronized, means coupled to the output of said coincidence means for providing a first mode signal until said coincidence means detects synchronism and for providing a second mode signal thereafter, means in said switching means for coupling the output from said summing means to said motor in response to a first mode signal, and means in said switching means for coupling the output of said oscillator to said motor in response to a second mode signal.