US3659631A - Controller for a pulsed servovalve - Google Patents

Controller for a pulsed servovalve Download PDF

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Publication number
US3659631A
US3659631A US3659631DA US3659631A US 3659631 A US3659631 A US 3659631A US 3659631D A US3659631D A US 3659631DA US 3659631 A US3659631 A US 3659631A
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Prior art keywords
signal
circuit
repetitive
fluid
reference signal
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Expired - Lifetime
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English (en)
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John Peter Rakoske
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Moore Business Forms Inc
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Moore Business Forms Inc
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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D7/00—Control of flow
    • G05D7/06—Control of flow characterised by the use of electric means
    • G05D7/0617—Control of flow characterised by the use of electric means specially adapted for fluid materials
    • G05D7/0629—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means
    • G05D7/0635—Control of flow characterised by the use of electric means specially adapted for fluid materials characterised by the type of regulator means by action on throttling means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/87169—Supply and exhaust
    • Y10T137/87217—Motor

Definitions

  • Patented May 2, 1972 5X D v zaak, Q M flaw v 1 ATTO/FA/EYS This invention relates to control systems and, in particular, to a circuitry for generating signals to control the effective orifice size of a solenoid servovalve wherein the valve member is duty cycle modulated or oscillated.
  • the control circuitry of this invention actuates servovalves for controlling the ingress and egress of a hydraulic ora pneumatic fluid by digital techniques without the need for converting digital signals into analog control signals.
  • a mechanical member is moved from one position to another position to effect a change of the orifice size.
  • a primary advantage of such a digitally controlled servovalve is the elimination of the need for digital-to-analog conversion a paratus so that such a valve may be directly controlled by digital signals emitted from a control device.
  • the control system enables simple on/off valve elements to be used, thereby enhancing reliability because the failure of one element results only in degraded over-all servovalve performance.
  • a feature of the control system is that duty cycle modulation is used to obtain infinite resolution of the effective orifice size from zero to its maximum opening. That is, an orifice of I one thirty-secondth sq. in. which is closed 75 percent of the time and open 25 percent of the time has an effective average orifice size of one one hundred-twenty-eighth sq. in. Therefore, since the on/off element may be fully closed or fully opened, or o erated at any ratio of closed time to open time, it can be operated at any effective average orifice size from zero to the maximum opening, for example, one thirty-secondth sq. in.
  • the infinitely variable regulation of the duty cycle advantageously provides a very high resolution of the effective orifice size, and therefore the control in accordance withthis.
  • inventions may be used in a proportional closed loop or servo system.
  • the duty cycle modulated servovalve may provide system performance equal to a conventional servovalve with respect to frequency response, deadband, friction, drift, and resolution.
  • a generator provides a sawtooth waveform output at a fixed frequency.
  • the frequency of the sawtooth waveform may be modulated by a sweep frequency.
  • the sawtooth wavefonn is combined with a control signal which maybe analog, digital, a.c., d.c., or a hybrid signal.
  • the control signal varies the reference level of the sawtooth waveform and the combined signal is split and fed to each of two similarly constructed channels.
  • the signal in each channel is compared with a reference threshold signal which is of different amplitude in each channel.
  • the reference level difference is preferably selected so that one reference level forms an upper limit and the other reference level forms a lower limit for the combined signal.
  • the signal in each channel is compared with its respective reference threshold level and if the signal level exceeds the reference threshold level, the resultant output is used to excite the control coil of a servovalve in each channel.
  • This operation produces a pulsing or dithering of the valve in each channel and appropriate control of each valve by duty cycle modulation.
  • FIGS. -2z'z-2c' illustrate the relationship between the combined sawtooth waveform'and input control signal and the reference level in each of two channels of the circuit illustrated in FIG. 1;
  • FIG. 3 shows a sweep'generator circuit which may be used to drive the circuit of FIG. 1 in a modified embodiment of the invention.
  • FIG. 4 is a cross-sectional view of a servovalve which is controlled by the circuit illustrated in FIG. 1.
  • transistors 10, 12 With' reference to FIG. 1, the conduction of transistors 10, 12 produces a rising potential at 14 through resistor 16 to ground.
  • the collector current of transistor 12 charges capacitor 18 to produce a ramp voltage input to the base 20 of driver transistor 22.
  • capacitor 18 charges to the firing potential of unijunction transistor 24, it produces a positive spike on resistor 26, thereby discharging capacitor 18.
  • Transistors 10 and 12 remain conductive.
  • Transistor 10 is a temperature compensating transistor for the current source provided by transistor 12. Capacitor 18 discharges through resistor 26 and the aforementioned cycle is repeated as the potential at 14 becomes sufficiently negative to render transistors l0, 12 conductive.
  • the ramp or staircase signal across capacitor 18 is amplified by transistor 22 and provided to voltage divider 28 from the emitter 30 of transistor 22 via emitter resistor 32 and divider resistor 34.
  • the components of the sawtooth generator circuit are selected to provide thedesired sawtooth waveform output signal to divider28in' accordance with characteristics of the system. For example, the frequency of the sawtooth wavefon-n may be in the range consistent with the characteristics of the servovalve.
  • a signal input for example, from a controller, is applied at terminals 36, 38.
  • Terminal '38 is grounded and the input signal at 36 is superimposed with the-aforedescribed sawtooth signal at junction 40of voltage divider 28 through resistor 42.
  • the combined singal is split into two channels and fed respectively to high gain operational amplifiers 44, 46 through resistors 48, 50.
  • the networkof resistors 52, 54, 56, 58, 60, 62 establishes different thresholdoperating potentials 49,51 for each of high gain amplifiers 44, '46, respectively.
  • high gain amplifiers 44, 46 function as comparator circuits in an on/off mode.
  • the positive input to comparator 44 is connected to threshold potential 49 as is the negative input to comparator 46 connected to threshold potentialSl.
  • the combined input signal is then respectively applied to thenegative and positive inputs of these same comparators.
  • signals more positive than threshold potential 49 are compared by comparator 44 and signals more negative than threshold potential 51 are compared by comparator 46.
  • the output from comparator 44 is supplied to transistor 64 via resistor 66 and diode 68.
  • Transistors 64 and 70 are connected in a well-known Darlington circuit to provide current amplification of the output from comparator 44 to drive coil 72 of solenoid 74.
  • Resistor 76 and diode 78 are connected in parallel across coil 72 to dampen fly-back voltages across coil 72.
  • the output from comparator 46 is fed to transistor 80 through resistor 82 and diode 84.
  • Transistors 80 and 86 also are connected in a Darlington circuit to provide current amplification of the output of comparator 46 to drive coil 88 of solenoid 90.
  • Resistor 7 same function as described above for resistor 76 and diode 78.
  • Solenoid 74 represents an exhaust solenoid and solenoid 90 may represent a pressure solenoid whereby pneumatic or hydraulic fluid may be exhausted from, or applied to, a desired system such as a brake for a controller in accordance with the signal input from the controller, at 36.
  • FIG. 2a represents the sawtooth waveform in the case where the input at 36 is zero and, as illustrated, the waveform lies between threshold potentials 49, 51.
  • the reference threshold potentials may be raised or lowered to obtain different operating conditions of the controlled servovalve mechanisms. For example, lowering each of the threshold potentials increases the duty cycle operation of the servovalves, whereas increasing the threshold potentials causesthe duty cycle to decrease.
  • the sensitivity and deadband are also afcycle modulation of solenoid 90.
  • the input signal at point 36 of FIG. 1 will vary in accordance with a desired control condition of the system operated by actuation of solenoids 74, 90.
  • Thesignal input at 36 may be analog, or an a.c. or d.c. signal, or a hybrid signal representing a combination of signal types.
  • FIG. 3 illustrates a sweep generator circuit which may be used to modify the sawtooth waveform at 40 in the following manner.
  • Beating may be reduced or eliminated by sweeping the sawtooth output from, for example, to Hz at a l Hz rate.
  • the sawtooth generator of FIG. 1 will produce such an output if a ramp input of 1 Hz repetition rate is applied to control the conduction of transistors 10 and 12.
  • the 1 Hz repetitive sawtooth waveform may be produced by the circuit illustrated in FIG. 3.
  • This circuit functions essentially in the same manner as the previously described sawtooth generator wherein transistors 100 and 102 charge capacitor 104 to provide a ramp input to the base 106 of driver transistor 108.
  • Unijunction transistor 110 fires when the potential at capacitor 104 reaches its firing potential and discharges capacitor 104, with the resultant positive spike on resistor 107.
  • Transistors 100, 102 remain conductive; transistor 100 provides temperature compensation, and transistor 102 is a constant current source. The aforementioned cycle is repeated and the components may obviously be selected to provide the necessary 1 Hz repetition rate.
  • the output from the emitter of transistor 108 is applied as the sweep generatorinput to the sweep generator circuit of FIG. 1 at point 114..
  • FIG. 4 shows, a typical solenoid or servovalve which is represented by solenoid 74, 90 in FIG. 1.
  • a pneumatic or hydraulic input is provided at port 120 of solenoid 122 and an exhaust is obtained at port 124.
  • Magnetically inductive slug 126 includes valve seat 128 which is spring biased by spring 130 to seat against opening 132. Slug 126 is withdrawn from seat 128 by the application of a current to coil 134. Application of a pulsating current to coil 134 will cause slug 126 and valve seat 128 to oscillate or be duty cycle modulated, thereby effectively controlling the orifice opening at 132.
  • Resistor 42 18K Ohms Resistor 48 100K Ohms Resistor 50 100K Ohms Resistor 52 100K Ohms Resistor $4 387 Ohms 1% Resistor 56 13K Ohms 1% Resistor 58 10K Ohms 1% Resistor 60 332K Ohms 1% Resistor 62 100K Ohms Resistor 64 4.7K Ohms Resistor 67 2.2K Ohms Resistor 69 560 Ohms Resistor 76 100 Ohms Resistor 82 4.7K Ohms Resistor 83 560 Ohms Resistor 85 2.2K Ohms Resistor 92 100 Ohms Transistor l0, l2 2N49l7 Transistor 22 2N5306 Transistor 24 2N 2646 Transistor 64, 80 2N656 Transistor 70, 86 2N3055 Amplifier 44, 46 2Pl5A output/input 50K Capacitor 18 .47 uf,
  • solenoids 74, 90 respectively are connected to the exhaust and pressure ports of a brake mechanism which is controlling the tension of a paper feed roller for a printing press.
  • the brake mechanism is controlled by the aforedescribed operationof solenoids 74, 90 to regulate the egress and ingress of air to the brake mechanism in accordance with input signals at 36 (FIG. 1) from a tension controller associated with the paper feed roll.
  • Such apparatus is well known to those skilled in the art and requires no further description to enable the control circuit of this invention to be used.
  • Other applications of the control circuit, as well as modifications of the circuit described herein, will be apparent to those having familiarity with control system techniques.
  • a circuit for controlling the application of fluid to a device operated thereby in response to input signals compris- 8;
  • said means for comparing includes two channels each responsive to said combined signal and'each having different threshold reference levels so that each channel operates on a different polarity of said combined signal, one of said channels controls the egress of fluid and the other channel controlling the ingress of fluid, and
  • a circuit as in claim 1 wherein said means for generating includes means for modifying the repetition rate of said reference signal at a predetermined sweep frequency.
  • said means for generating includes a cyclic current generator, means for integrating the current from said current generator, and means responsive to said integrated current for determining the repetitive operareference signal from an open to a closed position in ac- 5 cordance with said input signal thereby varying the effective orifice size of said valve members.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Automation & Control Theory (AREA)
  • Magnetically Actuated Valves (AREA)
  • Servomotors (AREA)
  • Feedback Control In General (AREA)
  • Control Of Position Or Direction (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Control Of Fluid Pressure (AREA)
US3659631D 1970-08-05 1970-08-05 Controller for a pulsed servovalve Expired - Lifetime US3659631A (en)

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US6138670A 1970-08-05 1970-08-05

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3750693A (en) * 1971-10-13 1973-08-07 Xar Ind Inc Solenoid operated valve
US3823621A (en) * 1970-12-27 1974-07-16 Toyota Motor Co Ltd Vehicle automatic transmission control system
US3874407A (en) * 1974-01-02 1975-04-01 Ray F Griswold Pulse width modulation control for valves
US4103695A (en) * 1974-11-06 1978-08-01 Nissan Motor Company, Limited Method of and device for controlling solenoid operated flow control means
FR2420158A1 (fr) * 1978-03-16 1979-10-12 Knorr Bremse Gmbh Regulateur de pression pour des pressions pneumatiques notamment pour des vehicules
US4228880A (en) * 1978-09-25 1980-10-21 Eaton Corporation Pulse control of an electro magnetically actuated viscous fluid coupling
US4262784A (en) * 1973-06-18 1981-04-21 Sibeud Jean Paul Device with a jack for controlling a gear box synchromesh, and method for using same
FR2484106A1 (fr) * 1980-06-10 1981-12-11 Guettmann Pierre Convertisseur courant-debit a reponse rapide, notamment pour l'asservissement de dispositifs de manoeuvre de charges, ou autres, ou de dispositifs de distribution
US4366524A (en) * 1977-03-31 1982-12-28 Hitachi, Ltd. Electromechanical transducer controlling device
WO1983002935A1 (en) * 1982-02-26 1983-09-01 Signet Scient Co Fluid dispensing system
US4459819A (en) * 1982-03-05 1984-07-17 Emerson Electric Co. Pulse controlled expansion valve and method
US4546795A (en) * 1980-12-26 1985-10-15 Hitachi, Ltd. Solenoid valve
US4782860A (en) * 1984-06-15 1988-11-08 Bridgestion Corporation Magnetic flow control valve
US4813443A (en) * 1988-04-06 1989-03-21 Signet Scientific Company Method for controllably positioning a solenoid plunger
US4819693A (en) * 1983-06-28 1989-04-11 Rodder Jerome A Fast operating bistable valve
US20040084475A1 (en) * 2002-05-17 2004-05-06 Pepsico, Inc. Beverage forming and dispensing system
US20100187319A1 (en) * 2007-05-29 2010-07-29 Utc Power Corporation Rankine cycle power plant heat source control
US20130320250A1 (en) * 2012-05-29 2013-12-05 Daniel Graham Electronic flow control method for a spring diaphragm irrigation control valve using a pulsed signal

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2741088A (en) * 1950-09-29 1956-04-10 Rolls Royce Flow control means for internal-combustion engine fuel systems

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2741088A (en) * 1950-09-29 1956-04-10 Rolls Royce Flow control means for internal-combustion engine fuel systems

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3823621A (en) * 1970-12-27 1974-07-16 Toyota Motor Co Ltd Vehicle automatic transmission control system
US3750693A (en) * 1971-10-13 1973-08-07 Xar Ind Inc Solenoid operated valve
US4262784A (en) * 1973-06-18 1981-04-21 Sibeud Jean Paul Device with a jack for controlling a gear box synchromesh, and method for using same
US3874407A (en) * 1974-01-02 1975-04-01 Ray F Griswold Pulse width modulation control for valves
US4103695A (en) * 1974-11-06 1978-08-01 Nissan Motor Company, Limited Method of and device for controlling solenoid operated flow control means
US4366524A (en) * 1977-03-31 1982-12-28 Hitachi, Ltd. Electromechanical transducer controlling device
USRE32035E (en) * 1977-03-31 1985-11-19 Hitachi, Ltd. Electromechanical transducer controlling device
FR2420158A1 (fr) * 1978-03-16 1979-10-12 Knorr Bremse Gmbh Regulateur de pression pour des pressions pneumatiques notamment pour des vehicules
US4228880A (en) * 1978-09-25 1980-10-21 Eaton Corporation Pulse control of an electro magnetically actuated viscous fluid coupling
FR2484106A1 (fr) * 1980-06-10 1981-12-11 Guettmann Pierre Convertisseur courant-debit a reponse rapide, notamment pour l'asservissement de dispositifs de manoeuvre de charges, ou autres, ou de dispositifs de distribution
EP0044263A1 (de) * 1980-06-10 1982-01-20 Pierre Guettmann Durchfluss-Strom-Umwandler mit schneller Reaktion, insbesondere zum Steuern von Betätigungs- oder Verteilvorrichtungen
US4546795A (en) * 1980-12-26 1985-10-15 Hitachi, Ltd. Solenoid valve
US4487333A (en) * 1982-02-26 1984-12-11 Signet Scientific Co. Fluid dispensing system
WO1983002935A1 (en) * 1982-02-26 1983-09-01 Signet Scient Co Fluid dispensing system
US4459819A (en) * 1982-03-05 1984-07-17 Emerson Electric Co. Pulse controlled expansion valve and method
US4819693A (en) * 1983-06-28 1989-04-11 Rodder Jerome A Fast operating bistable valve
US4782860A (en) * 1984-06-15 1988-11-08 Bridgestion Corporation Magnetic flow control valve
US4813443A (en) * 1988-04-06 1989-03-21 Signet Scientific Company Method for controllably positioning a solenoid plunger
US20040084475A1 (en) * 2002-05-17 2004-05-06 Pepsico, Inc. Beverage forming and dispensing system
US20050035152A1 (en) * 2002-05-17 2005-02-17 Bethuy Timothy W. Beverage forming and dispensing system
US7077290B2 (en) 2002-05-17 2006-07-18 Pepsico, Inc. Beverage forming and dispensing system
US7156259B2 (en) 2002-05-17 2007-01-02 Pepsico, Inc. Beverage forming and dispensing system
US20100187319A1 (en) * 2007-05-29 2010-07-29 Utc Power Corporation Rankine cycle power plant heat source control
US20130320250A1 (en) * 2012-05-29 2013-12-05 Daniel Graham Electronic flow control method for a spring diaphragm irrigation control valve using a pulsed signal

Also Published As

Publication number Publication date
GB1322818A (en) 1973-07-11
DE2139287B2 (de) 1974-05-02
IT938650B (it) 1973-02-10
DE2139287A1 (de) 1972-03-02
DE2139287C3 (de) 1974-12-12

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