Control system for electric motor
First Claim
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1. A system for controlling energization of an electric motor from an electric power source, comprising;
- a switching circuit including switching devices for selectively connecting windings of the motor to the power source in accordance with the rotor position of the motor;
an error signal generating circuit for providing an error signal according to the difference between a control command an an actual motor condition; and
a pulse-width modultion control circuit responsive to said error signal and operatively connected to control said switching devices in said switching circuitto provide increased duty cycle pulse-width modulation control of said switching devices as said error signal approaches zero when operating the motor in a regenerative mode, andto provide decreased duty cycle pulse-width modulation control of said switching devices as said error signal approaches zero when operating the motor in a motoring mode.
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Abstract
A four quadrant control system for a brushless D.C. motor wherein the windings are energized via a drive switching circuit in a bridge configuration and the switching circuit is in turn controlled by a read-only memory. Pulse-width modulation control signals and position signals are supplied to the read-only memory as addresses together with other control signals. The system operates in a regenerative mode when changing direction and automatically makes a smooth transition into a motoring mode when the back EMF of the motor is no longer large enough to satisfy the requirements of the current loop.
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Citations
15 Claims
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1. A system for controlling energization of an electric motor from an electric power source, comprising;
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a switching circuit including switching devices for selectively connecting windings of the motor to the power source in accordance with the rotor position of the motor; an error signal generating circuit for providing an error signal according to the difference between a control command an an actual motor condition; and a pulse-width modultion control circuit responsive to said error signal and operatively connected to control said switching devices in said switching circuit to provide increased duty cycle pulse-width modulation control of said switching devices as said error signal approaches zero when operating the motor in a regenerative mode, and to provide decreased duty cycle pulse-width modulation control of said switching devices as said error signal approaches zero when operating the motor in a motoring mode. - View Dependent Claims (2, 3, 4, 5)
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6. A system for controlling energization of an electric motor from an electric power source, comprising:
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an error signal generating circuit for providing an error signal proportional to the difference between a control command and an actual motor condition; a positive sawtooth signal generator and a negative sawtooth signal generator; a pair of comparators each responsive to said error signal and operative to provide a pulse-width modulated control signal, one of said comparators being operatively connected to compare said error signal with the signal from said positive sawtooth signal generator, the other of said comparators being operatively connected to compare said error signal with the signal from said negative sawtooth signal generator;
a solid state switching circuit for selectively connecting windings of the motor to the power source wherein, for each current path from the source through the windings current flows through a pair of switching devices;said switching devices being so connected to said comparators that for one polarity of said error signal one of said switching devices of each pair is "off" and the other switching device of the pair is pulse-width modulated with an increased duty cycle as said error signal approaches zero to control regenerative current through the motor windings, and for the other polarity of said error signal at least one of said switching device of each pair is pulse-width modulated with a decreased duty cycle as said error signal approaches zero to control current from the source through the motor windings. - View Dependent Claims (7, 8, 9, 10)
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11. A motor control system for controlling energization from a D.C. power source comprising:
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a brushless D.C. motor including stator windings a permanent magnet rotating field and a position sensor for detecting the relative orientation between the stator and rotor of the motor; a plurality of solid state switching devices connected to control energization of selected ones of said stator windings from the power source; a memory device having data output lines connected to control the states of said switching devices to commutate said windings and control the energization level thereof; a pulse-width modulator for producing a pulse-width signal for controlling energization of said motor; said memory device being connected to receive signals from said position sensor and said pulse-width modulator to control said switching devices to provide commutated energization of said motor at a level indicated by said pulse-width signal. - View Dependent Claims (12, 13, 14, 15)
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Specification