Regenerative motor control system

Claim 2

In an electrical system comprising a motor, a cyclic power source, and means for conducting current between said power source and said motor, control apparatus comprising means for providing a motor speed signal, means for providing a signal of rate of change of motor armature voltage, means for combining said motor speed signal and said rate of change of motor armature voltage signal to provide an error signal, first means for supplying current to said motor from said source in response to said error signal when said motor is to operate in a motoring mode, second means for conducting current between said motor and said power source when said motor is operating in a regenerative mode, third means for selectively enabling said first means and disenabling said second means when said motor is to operate in a motoring mode and for disenabling said first means and enabling said second means when said motor is to operate in a regenerative mode comprising comparing means for comparing an input signal dependent on said error signal with a first feedback signal from said motor to said third means, said first feedback signal indicating the value of the counter-electromotive force of the motor to allow said comparing means to determine when said first means is not capable of conducting current flow to said motor in response to the error signal, said third means utilizing a second feedback signal from said motor to said third means indicating armature current in said motor to allow said third means to determine when armature current is substantially zero, said third means including means responsive to said comparing means and said second feedback signal to switch said motor being said motoring mode and said regenerative mode when concurrently said first means is incapable of conductive current flow to said motor in response to said error signal and the armature current in said motor is zero by disenabling said first means and enabling said second means.

Claim 3

Control apparatus as defined in claim 1 wherein said first and second means each comprises a conductive element periodically biased in a forward conductive direction by a forward voltage lobe of a respective polarity from said source and perIodically reverse-biased by a respective voltage lobe of opposite polarity, and said conductive element is rendered conductive in response to a triggering pulse when biased in a forward direction and non-conductive by a reverse bias applied periodically to said element, said first means comprising means for changing the phase of a triggering pulse from the trailing end of the forward voltage lobe to an earlier phase in dependency on the value of said error signal and said second means comprising means for changing the phase of its triggering pulse from the leading end of its reverse voltage lobe to a later phase in dependency on the value of said error signal.

Claim 4

Control apparatus as defined in claim 1 wherein said first means comprises a conductive element which may be started into conduction at a trigger phase angle in response to a triggering signal when the voltage drop thereacross as a result of the forward bias by the power wave and the reverse bias by the armature voltage of the motor produces a forward bias across the conductive element.

Claim 5

An electrical system as defined in claim 3 wherein said power source provides a cyclic power wave whose voltage magnitude periodically reduces to zero and said first means is started into conduction at a trigger phase angle in response to said control signal and ceases to conduct each cycle, said first means being incapable of being started into conduction when the armature voltage of the motor is greater than the instantaneous value of the power wave, said third means comprises means for determining when the value of said power wave at the trigger phase angle becomes less than the value of the armature voltage of the motor.

Claim 6

Control apparatus as defined in claim 3 wherein said means for comparing comprises means for adding said signal indicative of the armature voltage of the motor in opposition to said input signal to provide an output signal which changes in polarity when the value of the forward bias from said power source at said trigger phase angle becomes less than the armature voltage and logic means responsive to one polarity of the signal to enable said first means and responsive to the second polarity of said signal to condition said third means to enable said second means and disable said first means upon detection by said third means of the armature current in the motor becoming zero.

Claim 7

An electrical system having a motor to be controlled in response to a control signal comprising means for producing a rate of change of motor armature voltage signal, means for providing a reference signal, summing means for combining said rate of change of motor armature signal with said reference signal to provide said control signal, first means responsive to said control signal for conducting a portion of a forward biasing power wave to said motor, the portion of said wave being conducted dependent upon the magnitude of a characteristic of said control signal, second means for conducting current from said motor to said power source, and third means for selectively enabling one of said first and second means and disabling another comprising first circuit means responsive to a feedback signal to said third means of the armature current in said motor being zero and second circuit means responsive to signals indicative of the relative magnitudes of said control signal and a feedback signal at said third means of the counter-electromotive force of said motor for enabling said second means and disabling said first means when the armature voltage of the motor becomes greater than the magnitude of the forward biasing power wave at which said first means would become conductive in response to said control signal, said first circuit means comprising a current indicating circuit having first and second outputs which indicate the direction of current flow in the motor, a comparing circuit having first and second outputs when the error signal commands conduction of the forward biasing portion of said power wave beginning at a phase anglE where the magnitude is less than and greater than said armature voltage respectively, first logic means having set and reset conditions, second logic means having set and reset conditions, means connecting said first outputs to said first logic means to maintain said first logic means in a set condition in the presence of either of said outputs and otherwise in a reset condition, means connecting said second outputs to said second logic means to maintain the second logic means in a set condition in the presence of either of said second outputs and otherwise in a reset condition, and means responsive to the set condition of said first logic means and the reset condition of said second logic means to enable said first means and disenable said second means, and responsive to the set condition of said second logic means and the reset condition of said first logic means for enabling said second means.

Claim 8

An electrical system having a motor to be controlled in response to a control signal comprising means for producing a rate of change of motor armature voltage signal, means for providing a reference signal, summing means for combining said rate of change of motor armature signal with said reference signal to provide said control signal, first means responsive to said control signal for conducting a portion of a forward biasing power wave to said motor, the portion of said wave being conducted dependent upon the magnitude of a characteristic of said control signal, second means for conducting current from said motor to said power source, and third means for selectively enabling one of said first and second means and disabling another comprising first circuit means responsive to a feedback signal to said third means of the armature current in said motor being zero and second circuit means responsive to signals indicative of the relative magnitudes of said control signal and a feedback signal at said third means of the counter-electromotive force of said motor for enabling said second means and disabling said first means when the armature voltage of the motor becomes greater than the magnitude of the forward biasing power wave at which said first means would become conductive in response to said control signal, said first circuit means comprising a current indicating circuit having first and second outputs which indicate the direction of current flow in the motor, a comparing circuit having first and second outputs when the error signal commands conduction of the forward biasing portion of said power wave beginning at a phase anglE where the magnitude is less than and greater than said armature voltage respectively, first logic means having set and reset conditions, second logic means having set and reset conditions, means connecting said first outputs to said first logic means to maintain said first logic means in a set condition in the presence of either of said outputs and otherwise in a reset condition, means connecting said second outputs to said second logic means to maintain the second logic means in a set condition in the presence of either of said second outputs and otherwise in a reset condition, and means responsive to the set condition of said first logic means and the reset condition of said second logic means to enable said first means and disenable said second means, and responsive to the set condition of said second logic means and the reset condition of said first logic means for enabling said second means.

Claim 9

Control apparatus as defined in claim 1 wherein said means responsive to said comparing means includes a first diode assembly connected to said third means and between said combining means and said first current supplying means and a second diode assembly connected to said third means and between said combining means and said second current supplying means to bypass said characteristic of an error signal from said first current supplying means to said third means in response to a ''''low'''' output signal from said comparing means to disenable said first current supplying means thereby.

Claim 10

Control apparatus as defined in claim 7 wherein said comparing means of said third means includes a first operational amplifier having one input connected to said first feedback signal of motor counter-electromotive force, another input connected to said error signal, and an output connected to a bistable hysteresis circuit, a second operational amplifier having one input connected to said second motor armature current feedback signal and an output connected to a logic circuit, said logic circuit being also connected to the output of said bistable hysteresis circuit to produce enabling and disenabling control signals to said first and second diode assemblies in response to said first feedback signal being greater than said error signal and said second feedback signal being substantially zero.

Claim 11

Control apparatus as defined in claim 8 including means for producing a signal of the rate of change of motor armature current, and wherein said combining means combines said rate of change of motor armature current signal with said motor speed signal and said rate of change of motor armature voltage signal to provide said error signal.