(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2002/0100649 A1
`(43) Pub. Date: Aug. 1, 2002
`
`Agrotis et al.
`
`US 20020100649A1
`
`(54) VEHICLE SUSPENSION DAMPER WITH
`INTEGRAL LINEAR POSITION SENSOR
`
`(75)
`
`Inventors: Demetris A. Agrotis, El Paso, TX
`(US); Bradley S. Farrenkopf,
`Campinas (BR); Kari A. Roth, London,
`OH (US); George A. Spaeth, Mason,
`OH (US)
`
`Correspondence Address:
`DELPHI TECHNOLOGIES, INC.
`PO. BOX 5052
`
`1450 W. Long Lake
`Mail Code: 482-204-450
`
`Troy, MI 48098 (US)
`
`(73) Assignee: DELPHI AUTOMOTIVE SYSTEMS
`
`(21) Appl. No.:
`
`09/774,135
`
`(22)
`
`Filed:
`
`Jan. 30, 2001
`
`Publication Classification
`
`
`................... F16F 9/00
`Int. Cl.7 ..
`(51)
`(52) U.S.Cl.
`......................................... 188/266.1; 188/284
`
`(57)
`
`ABSTRACT
`
`A vehicle suspension damper configured to be arranged
`between a Wheel assembly and a body of a vehicle is
`provided that includes a cylindrical reservoir tube with a
`piston mounted for reciprocating movement Within the res-
`ervoir tube. A piston rod is connected to the piston and
`extending axially therefrom and through one end of the
`reservoir tube. An annular rod guide assembly surrounds the
`piston rod and includes a magnetic portion. Anon-magnetic
`dust tube is disposed around the reservoir tube, the dust tube
`being operatively connected to the piston rod. A generally
`longitudinal sensor housing is formed in the dust
`tube
`adjacent the magnetic portion and a linear sensor is disposed
`in the sensor housing adapted to detect the position of the
`magnetic portion.
`
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`Page 1 of 9
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`CATERPILLAR EXHIBIT 1 1 1 8
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`CATERPILLAR EXHIBIT 1118
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`Patent Application Publication
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`Aug. 1, 2002 Sheet 1 0f 4
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`US 2002/0100649 A1
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`Patent Application Publication
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`Aug. 1, 2002 Sheet 2 0f 4
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`US 2002/0100649 A1
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`Patent Application Publication
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`Aug. 1, 2002 Sheet 3 0f 4
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`US 2002/0100649 A1
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`Patent Application Publication
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`Aug. 1, 2002 Sheet 4 0f 4
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`US 2002/0100649 A1
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`US 2002/0100649 A1
`
`Aug. 1, 2002
`
`VEHICLE SUSPENSION DAMPER WITH
`INTEGRAL LINEAR POSITION SENSOR
`
`TECHNICAL FIELD
`
`[0001] The technical field of this disclosure is vehicle
`suspension dampers for use in active vehicle suspension
`systems. Such systems include struts, shocks or damper
`devices capable of varying the damping characteristics,
`preload and other characteristics of the vehicle suspension in
`response to position and velocity information of the damper
`device. An integral linear position sensor located on the
`damper device generates the position and velocity informa-
`tion.
`
`BACKGROUND OF THE INVENTION
`
`[0002] Current vehicle suspensions frequently incorporate
`shock or strut devices capable of varying their damping
`characteristics in response to input from a control system.
`This input is typically generated by a control system in
`response to one or more suspension related input signals.
`One important input signal indicates the velocity of move-
`ment between the vehicle sprung mass, i.e., the main body
`of the vehicle, and the vehicle unsprung mass, i.e., the wheel
`assembly. This input signal is used in controlling the per-
`formance of the damper.
`
`[0003] Another important relationship of a vehicle to
`driving surfaces is the vehicle ride height. When a vehicle
`weight changes, as when an additional load is added to the
`vehicle,
`the vehicle suspension is compressed and the
`vehicle ride height changes accordingly. If the position of
`the vehicle body can be sensed relative to the wheel assem-
`bly, the ride height of the vehicle can be corrected by various
`methods. For example, compressed air can be introduced or
`vented from one or more of the damper units to adjust the
`vehicle ride height.
`
`[0004] The prior art includes sensors that sense the relative
`position between the sprung and unsprung masses (body and
`wheel assembly) of a vehicle. One example discloses a
`standalone non-integral-to-damper sensor positioned in the
`wheel well of a vehicle or body of a vehicle and having a
`link attaching the body mounted sensor to the unsprung
`mass. The sensor measures wheel to body motion as well as
`compliance, due to rubber bushings incorporated in the
`suspension. Due to the bushings and normal manufacturing
`tolerances, and non-linear mounting linkage ratios, the sen-
`sor also measures motion that is not related directly to the
`damper motion. Over time, due to normal wear, the toler-
`ances can increase and the rubber can deteriorate such that
`
`accuracy the accuracy of the sensor is reduced. Control
`algorithms must necessarily be complicated to account for
`these extraneous motions and wear. Further, the location of
`the sensor in the wheel well makes it vulnerable to damage
`in harsh driving conditions.
`
`[0005] The prior art includes publications describing sys-
`tems in which the vehicle suspension at a wheel includes a
`suspension relative position sensor such as a Linear Variable
`Differential Transformer (LVDT). The position signal from
`such a sensor may be differentiated to provide a relative
`velocity signal. The prior art also includes relative velocity
`sensors incorporated in suspension components such as
`dampers. For example, one such system discloses a sensor
`incorporated in a vehicle shock absorber of the type having
`
`Page 6 0f 9
`
`a cylinder attached to one of the sprung and unsprung
`masses and a piston in the cylinder attached through a rod
`extending out of the cylinder to the other of the sprung and
`unsprung masses. The rod further carries a dust tube that
`extends over a substantial portion of the cylinder. An axially
`polarized annular magnet is attached to but magnetically
`spaced from the top of the cylinder and is further magneti-
`cally spaced from the piston rod; and a sensor winding is
`distributed axially along the inside of the dust tube, which is
`made of a non-magnetic material. Vertical motion between
`the sprung and unsprung masses causes similar axial motion
`between the dust tube and cylinder and moves the magnet
`axially along the sensor winding. Avariation of flux linkage
`with respect to the position of the magnet generates an
`output voltage. The voltage generated is used to calculate the
`relative position of the unit and over time, can be used to
`calculate velocity information. Electrical
`components
`extending into the rod control the magnetic flux in the
`damper to effect changes in a MR fluid and thus, effects
`damping characteristics of the damper unit.
`
`require
`typically
`systems
`these
`[0006] However,
`extremely small air gaps, which limits design options, and
`can affect the accuracy of the information generated if not
`properly maintained. In addition, the coils, made of a very
`fine wire, are easily damaged if an attempt is made to mold
`them into a plastic element of a damper such as a dust tube.
`The coils can be damaged due to thermal stress, contact with
`a harsh environment or misalignment of the damper and so
`on.
`
`It would be advantageous to provide a robust, high
`[0007]
`resolution, fast response time linear position sensor to gen-
`erate detailed position and velocity information for a vehicle
`control system.
`
`SUMMARY OF THE INVENTION
`
`[0008] One aspect of the present invention provides a
`vehicle suspension damper configured to be arranged
`between a wheel assembly and a body of a vehicle including
`a cylindrical reservoir tube with a piston mounted for
`reciprocating movement within the reservoir tube. A piston
`rod is connected to the piston and extends axially therefrom
`and through one end of the reservoir tube. An annular rod
`guide assembly surrounds the piston rod and includes a
`magnetic portion. A non-magnetic dust tube is disposed
`around the reservoir tube, the dust tube being operatively
`connected to the piston rod. A generally longitudinal sensor
`housing is formed in the dust tube adjacent the magnetic
`portion and a linear sensor is disposed in the sensor housing
`adapted to detect the position of the magnetic portion.
`
`In other aspects of the present invention the sensor
`[0009]
`housing can include a electronics housing portion and a
`waveguide housing portion extending from the electronics
`housing portion. The linear sensor can include a waveguide
`portion disposed in the waveguide housing portion. The
`linear sensor can include an associated electronics portion
`operatively connected to the waveguide portion, the elec-
`tronics portion disposed in the electronics housing portion.
`The linear sensor can include a magneto-restrictive sensor.
`The dust tube can be formed of a plastic material. The sensor
`can include a magnetostrictive waveguide portion. The
`waveguide portion can be spaced apart from the magnetic
`portion a distance less than about 13 millimeters. The sensor
`
`Page 6 of 9
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`

`US 2002/0100649 A1
`
`Aug. 1, 2002
`
`can be adapted to determine a relative velocity between the
`vehicle wheel assembly and body.
`
`[0010] Another aspect of the present invention provides a
`dust tube for a vehicle damper including a non-magnetic
`cylindrical portion having an annular, disc-shaped upper
`end. A sensor housing is formed in the cylindrical portion,
`the sensor housing including an electronics housing portion
`and a waveguide housing portion.
`
`In other aspects of the present invention the elec-
`[0011]
`tronics housing portion can be formed adjacent the upper
`end of the cylindrical portion. The waveguide housing can
`extend from the electronics housing portion toward a lower
`end of the cylindrical portion. The dust tube can be made of
`a non-magnetic material such as a plastic material. The dust
`tube can further include a linear sensor disposed in the
`sensor housing adapted to detect the position of the magnetic
`portion. The linear sensor can include a waveguide portion
`operatively connected to
`an
`electronic portion. The
`waveguide portion can be disposed in the waveguide hous-
`ing portion and the electronic portion can be disposed in the
`electronic housing portion. The linear sensor can be a
`magneto-restrictive sensor. The linear sensor can include a
`magnetostrictive waveguide portion.
`
`[0012] The foregoing and other features and advantages of
`the invention will become further apparent from the follow-
`ing detailed description of the presently preferred embodi-
`ments, read in conjunction with the accompanying drawings.
`The detailed description and drawings are merely illustrative
`of the invention rather than limiting,
`the scope of the
`invention being defined by the appended claims and equiva-
`lents thereof.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0013] FIG. 1 is a side view of one embodiment of the
`damper of the present invention.
`
`[0014] FIG. 2 is a cross-sectional view of FIG. 1 along
`lines 2-2.
`
`[0015] FIG. 3 is a side view of the dust tube of the damper
`of FIG. 1.
`
`[0016] FIG. 4 is a cross-sectional view of FIG. 3 along
`lines 4-4.
`
`[0017] FIG. 5 is a perspective view of a portion of the
`damper of and embodiment of the present invention showing
`a terminal portion of the sensor.
`
`[0018] FIG. 6 is a perspective view of a top portion of the
`damper of an embodiment of the present invention.
`
`[0019] FIG. 7 is a perspective view of an embodiment of
`the sensor of the present invention.
`
`[0020] FIG. 8 is an alternate perspective view of the
`sensor of FIG. 7.
`
`DETAILED DESCRIPTION OF THE
`PRESENTLY PREFERRED EMBODIMENTS
`
`[0021] Referring to FIG. 1, one embodiment of a vehicle
`damper of the present invention is shown in a side view
`generally at 10. Shock absorber or monotube damper 10
`includes a reservoir tube 12, a lower end of which is shown
`
`Page 7 0f 9
`
`at 14. The lower end 14 of reservoir tube 12 includes a
`
`standard fitting 18 for connection to an associated vehicle
`wheel assembly (not shown).
`
`[0022] The damper 10 includes a dust tube 20 with a radial
`disc portion 22 adjacent an upper fitting 24. The dust tube 20
`includes a cylindrical sidewall portion 26 that extends from
`disc portion 22. The reservoir tube 12 movably fits within
`cylindrical sidewall portion 26 of dust tube 20. A rubber bag
`28 is connected to the bottom 30 of the sidewall 26 and
`connects to the reservoir tube 12 in a manner that will be
`
`described more fully hereinafter. Along the outside of cylin-
`drical sidewall 26 and extending axially from a position
`adjacent the periphery of the disc portion 22 to a point
`adjacent the rubber bag 28 a hollow longitudinal sensor
`housing 31 is provided. The sensor housing 31 includes a
`wide, generally rectangular electronic housing portion 32,
`which narrows to a narrow, waveguide housing portion 34.
`Laterally displaced from the rectangular electronic housing
`portion 32 is an extending terminal housing portion 36. A
`sensor housing cap 37, which connects to sensor housing
`portions 32 and 36, permits insertion and inspection of the
`internal sensor parts and associated circuitry.
`
`[0023] With reference to FIG. 2, a cross-sectional view of
`the damper of FIG. 1,
`is shown generally at 10. Shock
`absorber 10 includes a reservoir tube 12 having an upper rod
`guide 40 and is closed at the lower end 14 to define a
`gas-filled cylindrical cavity 42 with seal 44 and a fluid
`chamber 46 with upper rod guide 40. The upper rod guide 40
`can include one or more seals 50 and a cap 52. The cap 52
`includes a magnetic portion or magnet 54. The fluid chamber
`46 is divided into upper and lower chambers by a piston 56
`that is slidably disposed for axial movement therein.
`
`[0024] The axial movement of piston 56 pumps fluid
`between the chambers in fluid chamber 46 with orifices and
`
`valves providing damping in the conventional manner nor-
`mal for shock absorbers. Since the sensor of this invention
`
`would normally be used with dampers having variable
`damping, one or more of the valves or orifices may be
`controllable in response to a control signal.
`
`[0025] Damper piston 56 is attached to the lower end of
`rod 58, which extends upward through an opening 60 in rod
`guide 40 and sealed thereto by a standard sliding seal
`arrangement that retains the fluid in fluid chamber 46. Rod
`58 extends upward and ends in a standard fitting 24 for
`attachment to the sprung mass or body of a motor vehicle at
`one comer thereof. A fitting 18 is attached to the lower end
`of reservoir tube 14 to provide attachment to a member of
`the unsprung mass or wheel assembly of the vehicle such as
`a control arm thereof.
`
`[0026] A dust tube 20 includes a radial disc portion 22
`attached to rod 58 at the end thereof adjacent fitting 24. A
`cylindrical portion 26 extends downwardly from disk por-
`tion 22, covering over a substantial length of the reservoir
`tube 12. Dust tube 20 can prevent dirt from entering and
`harming the seals. Rubber bag 28 can be a cylindrical sheath
`having one end 62 attached and sealed to a portion of the
`reservoir tube 12 adjacent the cap 52. The other end 63 of
`rubber bag 28 can be attached and sealed to a lower end of
`the dust tube 20 defining an air chamber 64 between the dust
`tube 20 and the reservoir tube 12. The air chamber 64 can be
`
`attached to a source of compressed air (not shown) by a
`fitting (not shown) for introducing or venting air from the air
`
`Page 7 of 9
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`

`

`US 2002/0100649 A1
`
`Aug. 1, 2002
`
`chamber 64, changing the overall length of the damper 10
`and thus, the ride height of the vehicle. Relative movement
`of the sprung and unsprung masses of the vehicle can
`produce relative axial movement between reservoir tube 12,
`which is attached to and moves with the unsprung mass, and
`the assembly of rod 58, dust tube 20 and the piston 56, which
`is attached to and moves with the spring mass of the vehicle.
`Dust tube 20 can be made of a non-magnetic material such
`as plastic.
`
`[0027] The linear sensor 72 includes a waveguide portion
`70, which can be a sensor known as a magneto-restrictive,
`or magnetostrictive sensor, is positioned in the waveguide
`housing portion 34. It will be understood that the waveguide
`portion 70 can be considered the sensor, which typically has
`associated therewith electronic components that operatively
`permit the sensor to provide position data and so on. The
`electronics can be attached to the waveguide or located at a
`remote location. However, in regards to the present inven-
`tion, it should be understood that the term sensor can refer
`to the waveguide sensor portion or a combination of ele-
`ments including a waveguide sensor portion and an elec-
`tronic portion. The waveguide portion 70 can be a rod-
`shaped member of the sensor 72 oriented in an axial
`direction with respect to the longitudinal axis of the damper
`10. The waveguide portion 70 can be held in the dust tube
`housing portion 34 such that it is maintained a predeter-
`mined distance with respect to the magnet 54 on the cap 52.
`Due to the properties of the linear sensor, the predetermined
`distance may be as much as 13 millimeters. Thus the sensor
`72 may be advantageously located in a protected housing 34
`portion of the dust tube 20.
`
`[0028] The electronic circuitry or elements (not shown)
`necessary for the operation of the sensor 72 can be located
`in the electronic housing portion 32 of the dust tube 20. The
`electronic housing portion 32 can be located at a portion of
`the dust tube 20 adjacent disc portion 22. A terminal portion
`36, which contains electrical connecting leads and terminal
`elements (not shown) can be located adjacent the electronic
`housing portion 32 to allow connection thereto. Acap 37 can
`be connected to the terminal portion 36 to allow access to the
`housing, sensor, electrical components and so on.
`
`In operation, a current pulse is generated in the
`[0029]
`sensor 72. The current pulse is directed through the
`waveguide portion 70. The pulse
`travels
`along the
`waveguide 70 until the pulse arrives at a portion of the
`waveguide that is positioned adjacent the magnet 54. The
`magnetic field of the magnet 54 has the effect of creating
`strain in the waveguide. The pulse is, at
`least
`in part,
`reflected by the strain in the waveguide 70. The sensor 72
`measures the time elapsed between generating the pulse and
`receiving the reflection thereof. The sensor can calculate the
`distance the pulse traveled and thus, determine the position
`of the magnet. In addition, the position information, over
`time, can be used to calculate a velocity of the magnet, and
`thus, the relative changes in position and velocity between
`the vehicle body and respective wheel assemblies with a fast
`response time and high resolution. Thus, the damper 10 of
`the present invention can provide detailed information for a
`control system of a MR damper with no loss of accuracy of
`the measurements due to wear of the sensor elements.
`
`[0030] Referring to FIGS. 3-6, an embodiment of the dust
`tube 20 of the present invention is shown. The dust tube 20
`
`Page 8 0f 9
`
`can be made out of a non-magnetic material, which in a
`preferred embodiment, is formed of a thermoplastic mate-
`rial. Dust tube 20 can include disc portion 22 at an upper
`portion of the dust tube. A cylindrical sidewall portion 26
`extends from the disc portion 22 to a bottom portion 30. The
`sidewall 26 includes a hollow electronics housing portion 32
`located adjacent the side portion 22. The electronics housing
`32 narrows to a longitudinal waveguide housing portion 34,
`which terminates adjacent the bottom end 30 of the dust tube
`20. The electronics housing portion 32 is closed by cap 37
`in which a terminal portion 36 is formed for allowing
`connection to an exterior electric connection (not shown)
`thereto. The sensor 72 can include a rod-shaped waveguide
`portion 70 inserted into the waveguide housing portion 34.
`
`[0031] Referring to FIGS. 7 and 8, an embodiment of the
`linear sensor, which forms a portion of an embodiment of the
`present invention, is shown. In a preferred embodiment, the
`sensor 72 is a mangetostrictive linear sensor manufactured
`by NTS Instrumentation Corporation. The sensor 72
`includes a rod-shaped waveguide portion 70. The waveguide
`portion 70 is connected to base portion 84 and is in electrical
`communication with electrical circuitry 80. A terminal por-
`tion 36 includes connection socket 82. Terminal portion 36
`connects to base portion 84 adjacent the circuitry 80. Cap 37
`covers the base portion 84 to seal internal wiring to the
`terminal portion 36 from contamination and provides access
`to the sensor 72.
`
`[0032] While the embodiments of the invention disclosed
`herein are presently considered to be preferred, various
`changes and modifications can be made without departing
`from the spirit and scope of the invention. The scope of the
`invention is indicated in the appended claims, and all
`changes that come within the meaning and range of equiva-
`lents are intended to be embraced therein.
`
`1. Avehicle suspension damper configured to be arranged
`between a wheel assembly and a body of a vehicle com-
`prising:
`
`a cylindrical reservoir tube;
`
`a piston mounted for reciprocating movement within the
`reservoir tube;
`
`a piston rod connected to the piston and extending axially
`therefrom and through one end of the reservoir tube;
`
`an annular rod guide assembly surrounding the piston rod
`and including a magnetic portion;
`
`a non-magnetic dust tube disposed around the reservoir
`tube, the dust tube being operatively connected to the
`piston rod;
`
`a generally longitudinal sensor housing formed in the dust
`tube adjacent the magnetic portion; and
`
`a linear sensor disposed in the sensor housing adapted to
`detect the position of the magnetic portion.
`2. The vehicle suspension damper of claim 1 wherein the
`sensor housing includes an electronics housing portion and
`a waveguide housing portion, the waveguide housing por-
`tion extending from the electronics housing portion.
`3. The vehicle suspension damper of claim 2 wherein the
`linear sensor includes a waveguide portion disposed in the
`waveguide housing portion.
`
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`

`US 2002/0100649 A1
`
`Aug. 1, 2002
`
`4. The vehicle suspension damper of claim 2 wherein the
`linear sensor includes an electronics portion operatively
`connected to the waveguide portion, the electronics portion
`being disposed in the electronics housing portion.
`5. The vehicle suspension damper of claim 1 wherein the
`linear sensor includes a magneto-restrictive sensor.
`6. The vehicle suspension damper of claim 1 wherein the
`dust tube is formed of a plastic material.
`7. The vehicle suspension damper of claim 1 wherein the
`sensor includes a magnetostrictive waveguide portion.
`8. The vehicle suspension damper of claim 7 wherein the
`waveguide portion is spaced apart from the magnetic portion
`a distance less than about 13 millimeters.
`
`9. The vehicle suspension damper of claim 1 wherein the
`sensor is adapted to determine a relative velocity between
`the vehicle wheel assembly and body.
`10. A dust tube for a vehicle damper comprising:
`
`a non-magnetic cylindrical portion having a closed upper
`end;
`
`a sensor housing formed in the cylindrical portion, the
`sensor housing including an electronics housing por-
`tion and a waveguide housing portion.
`11. The dust tube of claim 10 wherein the electronics
`
`housing portion is formed adjacent the upper end of the
`cylindrical portion.
`12. The dust tube of claim 11 wherein the waveguide
`housing extends from the electronics housing portion toward
`a lower end of the cylindrical portion.
`13. The dust tube of claim 10 wherein the dust tube is
`
`made of a non-magnetic material.
`14. The dust tube of claim 13 wherein the dust tube is
`
`made of a plastic material.
`
`15. The dust tube of claim 10 further comprising:
`
`a linear sensor disposed in the sensor housing adapted to
`detect the position of the magnetic portion.
`16. The dust tube of claim 15 wherein the linear sensor
`
`includes a waveguide portion operatively connected to an
`electronic portion.
`17. The dust tube of claim 16 wherein the waveguide
`portion is disposed in the waveguide housing portion.
`18. The dust tube of claim 17 wherein the electronic
`
`portion is disposed in the electronic housing portion.
`19. The dust tube of claim 15 wherein the linear sensor
`
`includes a magneto-restrictive sensor.
`20. The dust tube of claim 16 wherein the linear sensor
`
`includes a magnetostrictive waveguide portion.
`21. A suspension damper for a wheel assembly in a
`vehicle comprising:
`
`means for housing a linear sensor in a dust tube of the
`damper;
`
`means for magnetically creating a strain in the linear
`sensor positioned on a reservoir tube of the damper,
`wherein the dust tube and reservoir are adapted to
`reciprocate with respect to each other;
`
`means for detecting the position of the strain in the linear
`sensor; and
`
`means for calculating a relative position of the wheel
`assembly with respect
`to the vehicle based on the
`detected position of the strain.
`
`Page 9 0f 9
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`Page 9 of 9
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