Brushless dc motor

Claim 2

Apparatus for controlling the speed of a brushless DC motor having a permanent magnetic field that rotates with respect to at least one armature winding, the flux in said winding varying with the location thereof within the field, comprising: sensor means responsive to the magnetic flux of said permanent magnetic field for providing a sensor signal substantially corresponding to the magnetic flux in said winding; a high gain amplifier means responsive to said sensor signal for amplifying and clipping said sensor signal to provide a rectangular voltage in phase with said sensor voltage; an analog switch having a control input and having a voltage input connected to the output of said high gain amplifier and having an output connected to said armature winding, said switch providing the voltage output of said high gain amplifier to said armature winding when said switch is actuated by a signal at its control input; a voltage integrator means having its input connected to the output of said high gain amplifier and providing at its output a triangular voltage which lags said rectangular voltage by a quarter cycle; a reference voltage; and a window comparator means connected to the output of said integrator and to said reference voltage source and providing an output signal during periods of time when said triangular voltage is of the same polarity as and lower in magnitude than said reference voltage, the output of said comparator being connected to the control input of said analog switch, whereby said armature is driven only when it is in a region of maximum flux.

Claim 3

Apparatus according to claim 1 further comprising: a peak detector connected to the output of said integrator; speed reference means for providing a signal voltage representative of a desired speed; speed comparison means for comparing the output of said peak detector with the voltage signal of said reference means and providing a low speed output signal in response to the relatiOnship between its inputs indicating that the speed of the motor is below the desired speed represented by said reference means; and means responsive to the output of said speed comparison means to block the output signal of said window comparator from actuating the control input of said analog switch in response to the absence of the output of said low speed signal from said speed comparison means.

Claim 4

Apparatus according to claim 1 further comprising: a peak detector connected to the output of said integrator; stall reference means for providing a voltage signal representative of a stall speed below which operation of said motor is not desired; a stall comparator having its inputs connected to the outputs of said stall reference means and said peak detector and providing an above-speed output signal in response to said peak detector indicating a speed in excess of said stall speed; and means responsive to the output of said stall comparator for blocking the output of said window comparator from actuating the control input of said analog switch in response to the absence of said above-speed signal.

Claim 5

Apparatus for controlling the speed of a two phase brushless DC motor having a permanent magnetic field that rotates with respect to at least a pair of armature windings, the flux in said windings varying with the location thereof within the field, the flux in a first winding leading the flux in a second winding by one quarter cycle; comprising: a pair of sensor means, each responsive to the magnetic flux of said permanent magnetic field for providing a sensor signal substantially corresponding to but lagging by an eighth of a cycle the magnetic flux in a related one of said armature windings; a pair of high gain amplifier means, each responsive to the sensor signal provided by a related one of said sensor means for amplifying and clipping said sensor signal to provide a corresponding rectangular voltage in phase with the related sensor voltage; a pair of analog switches, each having a control input and having a voltage input connected to the output of the related one of said high gain amplifiers and having an output connected to the related one of said armature windings, each of said switches providing the voltage output of said related high gain amplifier to said related armature winding when said switch is actuated by a signal at its control input; an exclusive OR circuit responsive to the outputs of both of said high gain amplifiers, said exclusive OR circuit providing an output signal in response to the outputs of said high gain amplifiers being of opposite polarity; and means responsive to the presence of an output from said exclusive OR circuit for providing a signal to the control input of a first one of said analog switches relating to said first armature winding, thereby to provide the output of the related high gain amplifier to drive said first armature winding, and responsive to the absence of an output signal from said exclusive OR circuit for providing a signal to the control input of a second one of said analog switches relating to said second armature winding, thereby providing the output of the related high gain amplifier to drive said second armature winding.

Claim 6

Apparatus for controlling the speed of a two phase brushless DC motor having a permanent magnetic field that rotates with respect to at least a pair of armature windings, the flux in said windings varying with the location thereof within the field, the flux in a first winding leading the flux in a second winding by one quarter cycle; comprising: a pair of sensor means, each responsive to the magnetic flux of said permanent magnetic field for providing a sensor signal substantially corresponding to but lagging by an eighth of a cycle the magnetic flux in a related one of said armature windings; a pair of high gain amplifier means, each responsive to the sensor signal provided by a related one of said sensor means for amplifying and clipping said sensor signal to provide a corresponding rectangular voltage in phase with the related sensor voltage; a pair of analog switches, each having a control input and having a voltage input connected to the output of the related one of said high gain amplifiers and having an output connected to the related one of said armature windings, each of said switches providing the voltage output of said related high gain amplifier to said related armature winding when said switch is actuated by a signal at its control input; an exclusive OR circuit responsive to the outputs of both of said high gain amplifiers, said exclusive OR circuit providing an output signal in response to the outputs of said high gain amplifiers being of opposite polarity; and means responsive to the presence of an output from said exclusive OR circuit for providing a signal to the control input of a first one of said analog switches relating to said first armature winding, thereby to provide the output of the related high gain amplifier to drive said first armature winding, and responsive to the absence of an output signal from said exclusive OR circuit for providing a signal to the control input of a second one of said analog switches relating to said second armature winding, thereby providing the output of the related high gain amplifier to drive said second armature winding.

Claim 7

Apparatus according to claim 4 further comprising: speed means responsive to the output of one of said high gain amplifiers for providing a voltage signal representative of the speed of said motor; reference means for providing a voltage signal representative of a desired speed; speed comparison means for comparing the output of said speed means with the voltage signal of said reference means and providing a low speed output signal in response to the relationship between its inputs indicating that the speed of the motor is below the desired speed represented by said reference means; and means responsive to the output of said speed comparison means to block the output signal of said exclusive OR circuit from actuating tHe control inputs of said analog switches in response to the absence of the output of said low speed signal from said speed comparison means.

Claim 8

Apparatus according to claim 1 further comprising: means responsive to the output of one of said high gain amplifiers for providing a voltage signal representative of the speed of said motor; stall reference means for providing a voltage signal representative of a stall speed below which operation of said motor is not desired; a stall comparator having its inputs connected to said stall reference means and to the output of said speed means and providing an above-speed output signal in response to said speed means indicating a speed in excess of said stall speed; and means responsive to the output of said stall comparator for blocking the output of said exclusive OR circuit from actuating the control inputs of said analog switches in response to the absence of said above-speed signal.