Controlled-velocity drive control

Claim 2

A control for a controlled-velocity drive having a driven member and an electromagnetic coupling having a winding the energization of which controls the angular velocity of the driven member, the control comprising: a triggerable semiconductor current switching device adapted to be connected between a source of AC power and the winding for controlling the energization thereof; a first feedback circuit for producing a first degenerative feedback signal having an amplitude which varies as a function of the instantaneous angular velocity of the driven member; a second feedback circuit for producing a second degenerative feedback signal having an amplitude which varies as a function of the current in the winding; a third feedback circuit for producing a third degenerative feedback signal having an amplitude which varies as a function of the rate of change of the current in the winding; means for producing a reference voltage proportional to a preselected angular velocity of the driven member; and means responsive to the reference voltage and to the three feedback signals for causing triggering of the current switching device at varying phase angles of the AC power to drive the driven member substantially at said preselected angular velocity and for also causing triggering of the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power voltage and the voltage across the winding are inverted whereby current in the winding rapidly decays when energization thereof is rapidly reduced.

Claim 3

A control as set forth in claim 1 further comprising means, interconnected with the first feedback circuit and with the means for causing triggering of the switching device, for limiting the varying phase angle of triggering of the switching device when the winding current incipiently exceeds a preset value thereby to substantially prevent the winding current from exceeding said preset value.

Claim 4

A control as set forth in claim 1 wherein the means for causing triggering of the switching device includes mEans for algebraically summing the reference voltage and the three feedback signals and for producing a triggering control signal varying as a proportional function of the algebraic sum.

Claim 5

A control as set forth in claim 3 further comprising feedback means, adapted to be interconnected with the summing means, for causing the triggering control signal to vary also as a function of the time integral of the algebraic sum whereby the angular velocity of the drive member is maintained substantially equal to said preselected angular velocity with a high order of accuracy.

Claim 6

A control as set forth in claim 4 wherein the summing means is constituted by a differential operational amplifier and the feedback means includes a capacitive circuit adapted to be interconnected between the output terminal and one of the input terminals of the differential amplifier.

Claim 7

A control as set forth in claim 1 further comprising circuit means, adapted to be interconnected with the means for producing a reference voltage, for causing the reference voltage to increase as a logarithmic function of time upon startup of the driven member.

Claim 8

A control as set forth in claim 1 further comprising circuit means, adapted to be interconnected with the means for producing a reference voltage, for causing the reference voltage to increase as a linear function of time upon startup of the driven member.

Claim 9

A control as set forth in claim 1 wherein the means for producing a reference voltage comprises tachometer follower circuitry adapted to be connected with the means for causing triggering and with an external tachometer generator thereby to produce a signal which varies as a reference voltage proportional to the instantaneous angular velocity of the external tachometer generator whereby the angular velocity of the driven member follows the angular velocity of the driven member.

Claim 10

A control as set forth in claim 1 wherein said third feedback circuit includes a band-pass filtering circuit for AC coupling a voltage proportional to the current in said winding to provide said third feedback signal, said filtering circuit having a passband substantially encompassing the dynamic range of frequency response of the control.

Claim 11

A control as set forth in claim 9 wherein the upper end of said passband is substantially below any AC power ripple frequency and the lower end of said passband is substantially above 0 frequency.

Claim 12

A control as set forth in claim 1 wherein said first feedback circuit comprises an AC tachometer generator driven by said driven member and means for rectifying the AC output of the tachometer generator thereby to provide said first feedback signal.

Claim 13

A control as set forth in claim 1 wherein said means responsive to the reference voltage and to the three feedback signals comprises an operational amplifier providing a triggering control signal varying according to the algebraic sum of the reference voltage and the three feedback signals, a pulse generator circuit providing pulses at said varying phase angles in response to the triggering control signal, said pulse generator also providing pulses at said constant phase angle, and means, including a pulse amplifier, for supplying said pulses of varying and constant phase angles to said switching device.

Claim 14

A control as set forth in claim 12 further comprising a switching circuit interconnected with said operational amplifier and said first feedback circuit and operative to limit the value of said triggering control signal and thereby to limit the varying phase angle of triggering of the switching device, when the winding current incipiently exceeds a preset value thereby to prevent the winding current from substantially exceeding said preset value.

Claim 15

A control as set forth in claim 12 wherein said pulse generator circuit comprises a first voltage comparator operative to supply a pulse each time the AC power voltage if 0-valued, a ramp generator including a capacitor, means for chargiNg the capacitor, means controlled by pulses from the first voltage comparator for periodically discharging the capacitor to provide a periodic ramp voltage characteristic in synchronism with the AC power, a second voltage comparator for summing the voltage of said triggering control signal with the voltage across said capacitor and operative to supply an output pulse at a preset sum thereby to provide pulses at said variable phase angle, and circuit means interconnected with the ramp generator and responsive to discharge of the capacitor to provide a pulse upon said discharge which discharge pulse is thereby at said constant phase angle.

Claim 16

A control as set forth in claim 14 wherein said pulse generator circuit includes means for inhibiting delivery of said discharge pulse when less than a predetermined duration, thereby to prevent delivery of any discharge pulse caused by AC power source noise.

Claim 17

A control as set forth in claim 15 wherein the inhibiting means comprises a logic gate for controlling delivery of said discharge pulse, and a further switching circuit interconnected with the first voltage comparator for controlling said gate to inhibit delivery of the discharge pulse for said predetermined duration, whereby the discharge pulse is delivered only when greater than said predetermined duration.

Claim 18

A control as set forth in claim 12 wherein said pulse generator further comprises means for supplying a string of pulses for causing rapid repetitive triggering of said switching device following each of said pulses of varying phase angle thereby to ensure latching of said switching device.

Claim 19

A control as set forth in claim 17 wherein said means for supplying a string of pulses comprises an oscillator whose frequency is substantially greater than the frequency of the AC power source.

Claim 20

A control for a controlled-velocity drive having a driven member and an electromagnetic coupling having a winding, the energization of which controls the angular velocity of the driven member, the control comprising: a triggerable semiconductor current switching device adapted to be connected between a source of AC power and the winding for controlling the energization thereof; a first feedback circuit including a tachometer generator for producing a first degenerative feedback signal having an amplitude which varies as a function of the instantaneous angular velocity of the driven member; a second feedback circuit for producing a second degenerative feedback signal having an amplitude which varies as a function of the current in the winding; a third feedback circuit for producing a third degenerative feedback signal having an amplitude which varies as a function of the rate of change of the current in the winding; means for producing a reference voltage proportional to a preselected angular velocity of the driven member; means for algebraically summing the reference voltage and the three feedback signals and for producing a triggering control signal varying as a proportional function of the algebraic sum, including internal feedback circuitry adapted to be connected for causing the triggering control signal to vary also as a function of the time integral of the algebraic sum whereby the angular velocity of the driven member is maintained substantially equal to said preselected angular velocity with a high order of accuracy; and triggering means responsive to the triggering control signal for triggering the switching device at phase angles of the AC power varying in accordance with the triggering control signal to drive the driven member substantially at said preselected angular velocity, the triggering means being also operative for triggering the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power and the voltage across the winding are inverted whereby current in the winding rapidly decays upon rapid reduction of energization thereof.

Claim 21

A control for a controlled-velocity drive having a driven member and an electromagnetic coupling having a winding, the energization of which controls the angular velocity of the driven member, the control comprising: a triggerable semiconductor current switching device adapted to be connected between a source of AC power and the winding for controlling the energization thereof; a first feedback circuit including a tachometer generator for producing a first degenerative feedback signal having an amplitude which varies as a function of the instantaneous angular velocity of the driven member; a second feedback circuit for producing a second degenerative feedback signal having an amplitude which varies as a function of the current in the winding; a third feedback circuit for producing a third degenerative feedback signal having an amplitude which varies as a function of the rate of change of the current in the winding; means for producing a reference voltage proportional to a preselected angular velocity of the driven member; means for algebraically summing the reference voltage and the three feedback signals and for producing a triggering control signal varying as a proportional function of the algebraic sum, including internal feedback circuitry adapted to be connected for causing the triggering control signal to vary also as a function of the time integral of the algebraic sum whereby the angular velocity of the driven member is maintained substantially equal to said preselected angular velocity with a high order of accuracy; and triggering means responsive to the triggering control signal for triggering the switching device at phase angles of the AC power varying in accordance with the triggering control signal to drive the driven member substantially at said preselected angular velocity, the triggering means being also operative for triggering the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power and the voltage across the winding are inverted whereby current in the winding rapidly decays upon rapid reduction of energization thereof.

Claim 22

A control for a controlled-velocity drive having a between which controls the tension in a moving length of material, an electromagnetic coupling having a winding the energization of which controls the angular velocity of the drive member, said material including a tension loop the length of which changes in response to change in the tension of said material, the control comprising: a triggerable semiconductor current switching device adapted to be connected between a source of AC power and the winding for controlling the energization thereof; a first feedback circuit, including means responsive to the loop length, for producing a loop length signal having an amplitude which varies as a function of said loop length, and means for differentiating said loop length signal to provide a first degenerative feedback signal which varies as a function of the rate of change of said loop length; a second feedback circuit for producing a second degenerative feedback signal having an amplitude which varies as a function of the current in the winding; a third feedback circuit for producing a third degenerative feedback signal having an amplitude which varies as a function of the rate of change of the current in the winding; means for producing a reference voltage proportional to a preselected loop length; and means responsive to the reference voltage and to the three feedback signals for causing triggering of the current switching device at varying phase angles of the AC power to drive the drive member for maintaining the loop substantially at said preselected length thereby to maintain substantially constant tension in said moving material and for also causing triggering of the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power voltage and the voltage across the winding are inverted whereby current in the winding rapidly decays when energization thereof is rapidly reduced.

Claim 23

A control for a controlled-velocity drive having a between which controls the tension in a moving length of material, an electromagnetic coupling having a winding the energization of which controls the angular velocity of the drive member, said material including a tension loop the length of which changes in response to change in the tension of said material, the control comprising: a triggerable semiconductor current switching device adapted to be connected between a source of AC power and the winding for controlling the energization thereof; a first feedback circuit, including means responsive to the loop length, for producing a loop length signal having an amplitude which varies as a function of said loop length, and means for differentiating said loop length signal to provide a first degenerative feedback signal which varies as a function of the rate of change of said loop length; a second feedback circuit for producing a second degenerative feedback signal having an amplitude which varies as a function of the current in the winding; a third feedback circuit for producing a third degenerative feedback signal having an amplitude which varies as a function of the rate of change of the current in the winding; means for producing a reference voltage proportional to a preselected loop length; and means responsive to the reference voltage and to the three feedback signals for causing triggering of the current switching device at varying phase angles of the AC power to drive the drive member for maintaining the loop substantially at said preselected length thereby to maintain substantially constant tension in said moving material and for also causing triggering of the switching device at a substantially constant phase angle of the AC power to cause conduction of the switching device when the AC power voltage and the voltage across the winding are inverted whereby current in the winding rapidly decays when energization thereof is rapidly reduced.