US3705337A
Expired / Lapsed
US
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Motor control system with bridge sensing emf
Assignee: Unisys Corp
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Filing: 1970-10-12
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Granted: 1972-12-05
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Expires: 1990-10-12
Abstract
Abstract The rotational speed of a motor armature is controlled by sensing the counter EMF of the motor. The motor is excited responsive to the difference between a motor command signal and a feedback signal representative of the motor counter EMF. A temperature sensor changes the feedback signal responsive to changes in the armature temperature. A stream of fluid is directed from the armature to the temperature sensor so as to couple thermally the armature thereof. The feedback signal is generated across the output terminals of a bridge network to the input terminals of which the motor excitation signal is applied. The motor armature comprises one arm of the bridge and the other arms of the bridge are resistive elements of predetermined value. The change in the feedback signal responsive to temperature is effected by a thermistor that has a negative temperature coefficient substantially larger than that of the armature resistance. The thermistor forms part of one of the resistive elements of the bridge. The thermistor is also employed to sense overheating of the motor and discontinuance of the fluid stream. A low-pass filter connected across one output terminal of the bridge compensates for the inductance of the motor.
Inventors
- 👤 Sebastian E Grabl
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:24
CPC Classifications
H; H02; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/2855; Y; Y10; Y10S; Y10S388/00; Y10S388/923; Y10S388/934
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
337 words
Apparatus for sensing the counter EMF of a motor having an armature that rotates responsive to an excitation signal, the speed of rotation of the armature being proportional to the counter EMF of the motor and the counter EMF of the motor being equal to the armature terminal voltage minus the armature current times the armature resistance, the apparatus comprising: first means for sensing the armature current, the first sensing means comprising a first resistor connected in series with the armature of the motor and means for sensing the voltage across the first resistor; second means for sensing the armature terminal voltage, the second sensing means comprising a voltage divider having second and third resistors in series, the second resistor being connected to the armature and the third resistor being connected to the first resistor, and means for sensing the voltage across the third resistor; third means for sensing the armature temperature, the third sensing means comprising a first resistive element located in close proximity to the armature of the motor, the first resistive element having a larger temperature coefficient than the resistance of the armature and connected in circuit with one of the resistors so as to compensate for changes in resistance of the armature; a source of fluid; means for directing the fluid in a stream from the armature to the third means to couple the armature thermally to the third means; means responsive to the first, second, and third means for generating a signal representative of the counter EMF of the motor, the generating means comprising means for subtracting the voltage across the third resistor from the voltage across the first resistor; and a second resistive element having a termperature coefficient identical to the first resistive element, the second resistive element being disposed in the fluid stream between the source and the armature and being connected in circuit with one of the resistors to offset changes in the resistance of the first resistive element due to changes in temperature of the source of fluid.
Claim 2
Dependent Claim
337 words
Apparatus for sensing the counter EMF of a motor having an armature that rotates responsive to an excitation signal, the speed of rotation of the armature being proportional to the counter EMF of the motor and the counter EMF of the motor being equal to the armature terminal voltage minus the armature current times the armature resistance, the apparatus comprising: first means for sensing the armature current, the first sensing means comprising a first resistor connected in series with the armature of the motor and means for sensing the voltage across the first resistor; second means for sensing the armature terminal voltage, the second sensing means comprising a voltage divider having second and third resistors in series, the second resistor being connected to the armature and the third resistor being connected to the first resistor, and means for sensing the voltage across the third resistor; third means for sensing the armature temperature, the third sensing means comprising a first resistive element located in close proximity to the armature of the motor, the first resistive element having a larger temperature coefficient than the resistance of the armature and connected in circuit with one of the resistors so as to compensate for changes in resistance of the armature; a source of fluid; means for directing the fluid in a stream from the armature to the third means to couple the armature thermally to the third means; means responsive to the first, second, and third means for generating a signal representative of the counter EMF of the motor, the generating means comprising means for subtracting the voltage across the third resistor from the voltage across the first resistor; and a second resistive element having a termperature coefficient identical to the first resistive element, the second resistive element being disposed in the fluid stream between the source and the armature and being connected in circuit with one of the resistors to offset changes in the resistance of the first resistive element due to changes in temperature of the source of fluid.
Claim 3
Dependent Claim
40 words
The apparatus of claim 1, in which the first and second resistive elements are connected in series across the first resistor to form a voltage divider and the generating means is responsive to the voltage across the first resistive element.
Claim 4
Dependent Claim
124 words
The apparatus of claim 1, in which a fourth resistor, a fifth resistor, and a potentiometer are provided, the first resistor element, the fourth resistor, the fifth resistor and the second resistive element are connected in series across one of the resistors recited in claim 1 to form a voltage dIvider, the first resistive element and the fourth resistor lie on one side of a common node, the fifth resistor and the second resistive element lie on the other side of the common node, the fourth and fifth resistors are connected to the node, the potentiometer is connected in parallel with the fourth and fifth resistors, and the generating means is responsive to the voltage across the fifth resistor and the second resistive element.
Claim 5
Dependent Claim
30 words
The apparatus of claim 6, in which means are provided for delaying the voltage appearing across the third resistor to compensate for the inductance of the armature of the motor.
Claim 6
Dependent Claim
47 words
The apparatus of claim 7, additionally comprising a threshold detector coupled to the first resistive element to sense a sharp change in its resistance and an alarm actuated responsive to the threshold detector when a sharp change takes place in the resistance of the first resistive element.
Claim 7
Dependent Claim
91 words
The apparatus of claim 1, in which the first sensing means generates an electrical signal representative of the armature current, the second sensing means generates an electrical signal representative of the armature terminal voltage, the apparatus additionally comprising means for delaying the electrical signal generated by the second sensing means to compensate for the inductance of the armature, the means for generating a signal representative of the counter EMF of the motor being responsive to the signal generated by the first means and the delayed signal generated by the second means.
Claim 8
Dependent Claim
207 words
Apparatus for sensing the counter EMF of a motor, the apparatus comprising: first and second input nodes; first and second output nodes; a motor connected between the first input node and the first output node, the motor having a rotating armature, the counter EMF generated by the motor being proportional to the speed of rotation of the armature; a first impedance connected between the second input node and the first output node in series with the armature of the motor; a second impedance and a third impedance connected in series respectively between the first input node and the second output node and between the second output node and the second input node to form a bridge network; and a fourth impedance and a fifth impedance connected in series between one of the output nodes and the second input node, the value of the fourth impedance changing in response to temperature changes of the armature to compensate for such armature temperature changes, the temperature coefficient of the fourth impedance being larger than the temperature coefficient of the resistance of the armature, the value of the remaining impedances including the fifth impedance connected between the one output node and the second input node being unaffected by armature temperature changes.
Claim 9
Dependent Claim
207 words
Apparatus for sensing the counter EMF of a motor, the apparatus comprising: first and second input nodes; first and second output nodes; a motor connected between the first input node and the first output node, the motor having a rotating armature, the counter EMF generated by the motor being proportional to the speed of rotation of the armature; a first impedance connected between the second input node and the first output node in series with the armature of the motor; a second impedance and a third impedance connected in series respectively between the first input node and the second output node and between the second output node and the second input node to form a bridge network; and a fourth impedance and a fifth impedance connected in series between one of the output nodes and the second input node, the value of the fourth impedance changing in response to temperature changes of the armature to compensate for such armature temperature changes, the temperature coefficient of the fourth impedance being larger than the temperature coefficient of the resistance of the armature, the value of the remaining impedances including the fifth impedance connected between the one output node and the second input node being unaffected by armature temperature changes.
Claim 10
Dependent Claim
40 words
The apparatus of claim 7, additionally comprising means for directing a stream of air from the armature to the fourth impedance so as to couple thermally the armature to the fourth impedance so its value responds to armature temperature changes.
Claim 11
Dependent Claim
55 words
The apparatus of claim 7, in which one end of the fourth impedance is connected to the first output node, one end of the fifth impedance is connected to the second input node, the fourth impedance has a negative temperature coefficient, and the voltage across the fifth impedance is utilized to indicate the counter EMF.
Claim 12
Dependent Claim
51 words
The apparatus of claim 8, in which the fifth impedance has a temperature coefficient identical to that of the fourth impedance and is disposed in the stream of air upstream of the armature to compensate for the effect of changes in temperature of the stream of air on the fourth impedance.
Claim 13
Dependent Claim
194 words
A motor control system comprising: a motor having an armature that rotates response to an excitation signal, the motor generating a counter EMF proportional to the rotational speed of its armature, the counter EMF of the motor being equal to the armature terminal voltage minus the product of the Armature current and the armature resistance; means for producing an electrical feedback signal representative of the counter EMF of the motor; first means in proximity to one side of the armature responsive to temperature changes for changing the feedback signal; second means in proximity to the other side of the armature responsive to temperature changes for changing the feedback signal; a source of fluid directed in a fluid stream that passes the first feedback signal changing means, the armature, and the second feedback signal changing means such that the first feedback signal changing means lies between the source and the armature and the armature lies between the first and second feedback signal changing means in the path of the fluid stream; and means responsive to the difference between a motor command signal and the feedback signal for applying an excitation signal to the motor armature.
Claim 14
Dependent Claim
194 words
A motor control system comprising: a motor having an armature that rotates response to an excitation signal, the motor generating a counter EMF proportional to the rotational speed of its armature, the counter EMF of the motor being equal to the armature terminal voltage minus the product of the Armature current and the armature resistance; means for producing an electrical feedback signal representative of the counter EMF of the motor; first means in proximity to one side of the armature responsive to temperature changes for changing the feedback signal; second means in proximity to the other side of the armature responsive to temperature changes for changing the feedback signal; a source of fluid directed in a fluid stream that passes the first feedback signal changing means, the armature, and the second feedback signal changing means such that the first feedback signal changing means lies between the source and the armature and the armature lies between the first and second feedback signal changing means in the path of the fluid stream; and means responsive to the difference between a motor command signal and the feedback signal for applying an excitation signal to the motor armature.
Claim 15
Dependent Claim
100 words
The control system of claim 11, in which the means for producing the feedback signal comprises: a first resistor connected in series with the armature; second and third resistors connected in series; means for connecting the second and third resistors in parallel with the armature and the first resistor to form a bridge network, the resistance ratio of the armature divided by the first impedance substantially equalling resistance ratio of the second impedance divided by the third impedance; and means for subtracting the voltage across the first impedance from the voltage across the third impedance to form the feedback signal.
Claim 16
Dependent Claim
44 words
The control system of claim 12, in which the second means for changing the feedback signal comprises a thermistor connected in circuit with one of the resistors, the armature being disposed in the path of the fluid stream between the source and the thermistor.
Claim 17
Dependent Claim
71 words
The control system of claim 13, in which the first means for changing the feedback signal additionally comprises a second thermistor connected in circuit with the first thermistor and the one resistor, the second thermistor being disposed in the path of the fluid stream between the source and the armature to offset the effect of changes in the fluid temperature prior to the armature on the resistance of the first thermistor.
Claim 18
Dependent Claim
163 words
Apparatus for sensing the counter EMF of a motor having an armature that rotates responsive to an excitation signal, the speed of rotation of the armature being proportional to the counter EMF of the motor, and the counter EMF of the motor being equal to the armature terminal voltage minus the armature current times the armature resistance, the apparatus comprising: a first impedance connected in series with the armature of the motor; a second impedance and a third impedance connected in series; means for connecting the motor armature and the first impedance in parallel with the second and third impedances to form a bridge network; first and second output terminals; means for means one of the junctions to the first output terminal; and a phase shifting network connecting the other junction to the second output terminal, the phase shifting network introducing a phase shift that brings the signal at the second output terminal into phase with the signal at the first output terminal.
Claim 19
Dependent Claim
163 words
Apparatus for sensing the counter EMF of a motor having an armature that rotates responsive to an excitation signal, the speed of rotation of the armature being proportional to the counter EMF of the motor, and the counter EMF of the motor being equal to the armature terminal voltage minus the armature current times the armature resistance, the apparatus comprising: a first impedance connected in series with the armature of the motor; a second impedance and a third impedance connected in series; means for connecting the motor armature and the first impedance in parallel with the second and third impedances to form a bridge network; first and second output terminals; means for means one of the junctions to the first output terminal; and a phase shifting network connecting the other junction to the second output terminal, the phase shifting network introducing a phase shift that brings the signal at the second output terminal into phase with the signal at the first output terminal.
Claim 20
Dependent Claim
30 words
The apparatus of claim 15, in which the phase shifting network is a low pass filter connecting the junction of the second and third impedances to the second output terminal.
Claim 21
Dependent Claim
266 words
Apparatus for sensing the counter EMF of a motor, the apparatus comprising: a motor having a rotating armature, the counter EMF generated by the motor being proportional to the speed of rotation of the armature; a first impedance connected in series with the armature of the motor; a second impedance and a third impedance connected in series; means for connecting the motor armature and the first impedance in parallel with the second and third impedances to form a bridge network; first and second output terminals connected respectively to the junction of the armature and the first impedance and the junction of the second and third impedances, the voltage at the second output terminal leading the voltage at the first output terminal due to the inductance of the motor; means responsive to temperature changes of the armature for changing the effective value of one of the impedances to maintain the ratio of the value of the impedance of the armature divided by the value of the first impedance substantially equal to the ratio of the value of the second impedance divided by the value of the third impedance; a voltage combining circuit having first and second inputs; means for coupling the first output terminal of the bridge network to the first input of the combining circuit; and means for coupling the second output terminal of the bridge network to the second input of the combining circuit, one of the coupling means introducing a phase shift that brings the voltages at the first and second inputs into phase so as to compensate for the inductance of the motor.
Claim 22
Dependent Claim
266 words
Apparatus for sensing the counter EMF of a motor, the apparatus comprising: a motor having a rotating armature, the counter EMF generated by the motor being proportional to the speed of rotation of the armature; a first impedance connected in series with the armature of the motor; a second impedance and a third impedance connected in series; means for connecting the motor armature and the first impedance in parallel with the second and third impedances to form a bridge network; first and second output terminals connected respectively to the junction of the armature and the first impedance and the junction of the second and third impedances, the voltage at the second output terminal leading the voltage at the first output terminal due to the inductance of the motor; means responsive to temperature changes of the armature for changing the effective value of one of the impedances to maintain the ratio of the value of the impedance of the armature divided by the value of the first impedance substantially equal to the ratio of the value of the second impedance divided by the value of the third impedance; a voltage combining circuit having first and second inputs; means for coupling the first output terminal of the bridge network to the first input of the combining circuit; and means for coupling the second output terminal of the bridge network to the second input of the combining circuit, one of the coupling means introducing a phase shift that brings the voltages at the first and second inputs into phase so as to compensate for the inductance of the motor.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-12-05 | 1976-06-05 | 1976-12-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-12-05 | 1980-06-05 | 1980-12-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-12-05 | 1984-06-05 | 1984-12-05 | $7700.00 | Window Closed / Lapsed |