United States Patent (19)
`Gebelein, Jr.
`
`3,857,081
`[11]
`(45) Dec. 24, 1974
`
`54)
`(75)
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`73
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`22
`21
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`52
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`51
`58)
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`56)
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`2,780,101
`
`PROPORTIONAL SOLENOID ACTUATOR
`Inventor: Edward F. Gebelein, Jr., Harwinton,
`Conn.
`Assignee: Chandler Evans Inc., West
`Hartford, Conn.
`June 25, 1973
`Filed:
`Appl. No.: 373,001
`
`U.S. Cl.................. 318/687,318/676, 31811 18,
`317/43, 335/25
`Int. Cl............................................ G05b 11/00
`Field of Search........... 318/676, 653, 687, 118;
`332/38 R; 324/45; 317/123, 143; 335/215
`
`.
`References Cited .
`UNITED STATES PATENTS
`Kinkel............................. 3 181676 X
`2, 1957
`
`
`
`2,814,768
`3,080,507
`3,660,695
`3,752, 189
`
`Kinkel................................. 3 181676
`fl957
`3, 1963 Wickerham et al................ 317|123
`5/1972 Schmitt............................. 338/32 R
`8, 1973 Marr et al.,.................. 3 81676 UX
`
`Primary Examiner-B. Dobeck
`
`ABSTRACT
`57
`A solenoid device which provides an output force pro
`portional to input signal amplitude regardless of the
`position of the solenoid plunger is disclosed. A flux
`measuring device is located in the magnetic circuit of
`the solenoid and provides a signal proportional to flux
`density. This flux density proportional signal is em
`ployed for control purposes to vary the solenoid coil
`excitation as a function of the input signal and the de
`sired output force.
`3 Claims, 1 Drawing Figure
`
`INPUT SIGNAL
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`Sleep Number Corp.
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`PATENTED DEC24 1974
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`3,857, O81
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`|NPUT SIGNAL
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`Sleep Number Corp.
`EXHIBIT 2025
`IPR2019-00514
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`15
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`35
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`5
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`O
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`3,857,081
`1.
`2
`PROPORTIONAL SOLENOD ACTUATOR
`pled to a movable load; the load typically being con
`stant and biasing the plunger toward the position of
`BACKGROUND OF THE INVENTION
`maximum air gap.
`1. Field of the Invention
`A transducer 16 responsive to the magnetic flux den
`The present invention relates to controlling the force
`sity is positioned in the magnetic circuit of solenoid 10.
`produced by an electro-magnetic actuator. More spe
`As depicted in the drawing, the transducer 16 is located
`cifically, the present invention is directed to a propor
`in the active air gap of the solenoid. Transducer 16 will
`tional solenoid system wherein the solenoid coil excita
`be a non-contacting type sensor device which exhibits
`tion is varied in such a manner as to provide a control
`a resistance which is a function of local magnetic flux
`lable flux density regardless of the position of the mov
`density B. The class of field responsive devices known
`ing member of the solenoid. Accordingly, the general
`in the art as magnetoresistors (MRs) are particularly
`objects of the present invention are to provide novel
`well suited for use in the present invention. A magneto
`and improved methods and apparatus of such charac
`resistor is a solid-state device comprised of indium anti
`ter.
`monide which does not have to be biased for proper op
`2. Description of the Prior Art
`eration.
`As is well known, magnetic devices such as solenoids
`in the disclosed embodiment of the invention the
`are inherently unstable due to their characteristically
`transducer 16 is connected in a voltage divider circuit
`predominant negative 'spring rate'. This negative
`with a suitable constant voltage source, indicated sche
`"spring rate" results from a lowering of the reluctance
`matically as battery 18, and a resistor R1. The voltage
`of the magnetic path of the solenoid as the gap between
`at the junction of resistor R1 and the transducer 16
`the solenoid plunger and the position commensurate
`will, of course, vary with the resistance of the magneto
`with its innermost limit of movement closes. The nega
`resistor. This voltage is applied as an input to a com
`tive "spring rate' problem may be reduced, by conven
`pensation circuit 20. The resistance of a magnetore
`tional methods which sacrifice stroke and/or sensitiv
`sistor increases when a perpendicular magnetic field is
`ity, by making the air gap large with respect to the
`applied and MRs have a square-law response to fields
`stroke of the plunger. However, it has previously been
`up to 3-kG. Magnetoresistors can be obtained commer
`impossible to generate a force proportional to excita
`cially which exhibit a substantially linear ratio of resis
`tion current by means of a solenoid mechanism.
`tance to zero-field resistance in the range of 3-kG to
`In view of the problem briefly described in the imme
`100-kG. Thus, with the MR transducer 16 mounted in
`diately preceding paragraph, when it has in the prior art
`30
`the air gap of solenoid 10 as shown, the input to com
`been desired to position a load or generate a force pro
`pensation circuit 20 will be a signal which varies in
`portional to excitation current, resort has been had to
`versely with the local flux density. In accordance with
`the use of devices such as torque motors. While torque
`the invention it is possible to operate only in the linear
`motors have provided generally acceptable results,
`response region of the magnetoresistor. Operation in
`these results, when compared to the potential utiliza
`the square-law response region of the transducer is,
`tion of solenoid type mechanisms, have been obtained
`however, also possible through use of suitable circuitry
`at the sacrifice of size, weight and expense.
`in compensation circuit 20 to adjust for the non
`linearity of the transducer.
`SUMMARY OF THE INVENTION
`It is well known that the force generated by a sole
`40
`The present invention overcomes the above briefly
`noid is proportional to the square of the flux density for
`discussed and other deficiencies and disadvantages of
`a given gap area. Accordingly, in the case of a constant
`the prior art by providing means whereby the excitation
`load, should it be desired to have the solenoid output
`of a solenoid coil may be varied in such a manner as to
`force follow an input command signal, the compensa
`provide a controllable flux density. The present inven
`tion circuit 20 will serve primarily as again adjustment.
`tion comprises means for generating a feedback signal
`45
`Compensation circuit 20 may comprise a lead circuit
`proportional to solenoid flux density; the feedback sig
`and, if necessary or desirable, a non-linear function
`nal thus being a function of force. This feedback signal,
`generator which provides both dynamic and linearity
`after gain compensation, is summed with an input force
`compensation. Such compensation networks are well
`command. The results of the comparison are employed
`known in the art. In the embodiment being described
`50
`to adjust the solenoid excitation current so as to cause
`compensation circuit 20 will provide an output signal
`the generation or maintenance of the desired output
`commensurate with measured flux which, as noted,
`force.
`bears a square root relationship to force.
`While the output signal from the compensation cir
`BRIEF DESCRIPTION OF THE DRAWING
`cuit 20 may be operated upon to provide an output di
`55
`The present invention may be better understood and
`rectly proportional to force, in the disclosed embodi
`its numerous objects and advantages will become ap
`ment the input force command signal is applied to a
`parent by reference to the accompanying drawing
`squaring circuit 22 to produce an input signal propor
`which is an electrical block diagram of a preferred em
`tional to the flux density commensurate with the de
`bodiment of the invention.
`sired force. The output of squaring circuit 22 and the
`60
`output of the compensation circuit 20 are summed in
`DESCRIPTION OF THE PREFERRED
`operational amplifier 24. Amplifier 24 will thus func
`EMBODEMENT
`tion as a comparator to provide an output signal com
`With reference to the drawing, a solenoid assembly
`mensurate with any deviations between commanded
`is indicated generally at 10. The solenoid assembly in
`and actual flux density; the output of amplifier 24 thus
`65
`cludes a coil 12 and, disposed in the air gap, a movable
`varying in accordance with the square of any force er
`plunger 14 comprised of magnetic material. Plunger 14
`ror. The output of amplifier 24 is employed to control
`includes an extension which will be mechanically cou
`the gain of a solenoid driver amplifier 26 which pro
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`10
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`3,857,081
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`vides excitation current to coil 12. The current source
`for amplifier 26 has been omitted from the drawing in
`the interest of clarity.
`As discussed above, should it be desired to generate
`an input signal to driver amplifier 26 which varies lin
`early with any force error, the squaring circuit 22 will
`be omitted and the compensation circuit 22 will be em
`ployed to adjust for any non-linear characteristics of
`the transducer, 16.
`The above described embodiment of the invention
`will inherently compensate for the effects of the load
`on plunger 14. Should it be deemed necessary or desir
`able to control solenoid plunger position as a function
`of an input position command signal and without re
`gard to load, or should a non-uniform load be applied
`to the plunger, a signal commensurate with excitation
`current may be fed back to compensation circuit 20 as
`indicated by the dashed line on the drawing. With the
`flux density and excitation current known, and with a
`fixed known geometry of the solenoid, the air gap may
`20
`be computed. Such compensation may be performed in
`circuit 20 and may be based upon experimental results.
`By means of the computation of air gap the device may
`be caused to function as a servo loop on the gap.
`While a preferred embodiment has been shown and
`described, various modifications and substitutions may
`be made thereto without departing from the spirit and
`scope of the invention. Accordingly, it is to be under
`stood that the present invention has been described by
`way of illustration and not limitation.
`What is claimed is:
`1. A solenoid actuator system comprising:
`a solenoid, said solenoid having a coil defining an air
`gap and a plunger movable in said air gap in re
`sponse to the magnetic field generated as a result
`35
`of the passage of excitation current through said
`coil, said plunger being coupled to a load and gen
`erating a system output force;
`non-contacting transducer means positioned in said
`solenoid air gap, said transducer means including
`a magnetoresistor for generating an output signal
`which is a function of solenoid flux density;
`comparator means connected to said transducer
`means and responsive to the flux density signal pro
`vided thereby, said comparator means also being
`45
`
`4
`responsive to an input signal commensurate with a
`desired system output force, said comparator
`means generating an output signal commensurate
`with the differences between actual solenoid air
`gap flux density and the flux density which corre
`sponds to the desired plunger output force; and
`means responsive to the output signal generated by
`said comparator means for varying the excitation
`current delivered to said solenoid coil in accor
`dance with the difference between the actual and
`desired system output force.
`2. The apparatus of claim 1 wherein said comparator
`means comprises:
`means connected to said magnetoresistor for provid
`ing an output signal commensurate with changes in
`resistance;
`compensation circuit means responsive to said signal
`commensurate with changes in resistance for pro
`viding an output signal commensurate with flux
`density as sensed by said magnetoresistor;
`means responsive to an input signal commensurate
`with desired plunger output force for generating a
`signal commensurate with solenoid flux density
`corresponding to said desired force; and
`amplifier means for receiving and comparing said ac
`tual and desired flux density signals and for provid
`ing an output signal commensurate with differ
`ences therebetween.
`3. The apparatus of claim 1 wherein said comparator
`means comprises:
`30
`means connected to said magnetoresistor for provid
`ing an output signal commensurate with changes in
`resistance;
`compensation circuit means responsive to said signal
`commensurate with changes in resistance for pro
`viding an output signal commensurate with the
`force being generated by said solenoid plunger; and
`amplifier means responsive to an input signal com
`mensurate with desired plunger output force and to
`the signal generated by said compensation circuit
`means for generating an output signal commensu
`rate with differences between actual and desired
`solenoid output force.
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`>k
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`ck
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`ck
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`-k
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`xk
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`Sleep Number Corp.
`EXHIBIT 2025
`IPR2019-00514
`Page 4
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