Patent Publication Number: US-2022221307-A1

Title: Sensor system and a method of temperature-compensation thereof

Description:
FIELD 
     The presently disclosed subject matter relates to a sensor system, and more particularly to a sensor system and a method of temperature-compensation thereof. 
     BACKGROUND 
     An electrical differential locker (EDL) is an actuator which controls operation of a differential. The differential improves traction of a vehicle by providing equal torque to each wheel disposed at ends of an axle assembly thereof. It is known to position the EDL in an engaged state using an electromagnetic solenoid. The electromagnetic solenoid actuates a plunger, which in turn, moves a locking gear disposed within the differential. A sensor may be used to measure an engagement and a disengagement of the locking gear with the differential. Oftentimes, the sensor measures the engagement and disengagement of the locking gear by sensing an axial position of the locking gear. 
     One such type of sensor is an eddy current sensor. The eddy current ‘Sensor uses an inductive wire coil to generate a high-frequency alternating magnetic field. If a conductive material (e.g. the locking gear) is in close proximity to the eddy current sensor, eddy currents will form within the conductive material. These eddy currents create an opposing magnetic field to the magnetic field of the wire coil. An amplitude of the opposing magnetic field is proportional to a distance of the locking gear from the wire coil. A net effect is a decrease in an apparent inductance of the wire coil proportional to the distance of the locking gear from the wire coil. The inductance of the wire coil is measured in the eddy current sensor. A microcontroller uses the measured inductance to calculate the distance of the locking gear from the wire coil. 
     It would be desirable to produce a sensor system and a method of temperature-compensation thereof, which enhances accuracy and efficiency of the sensor system. 
     SUMMARY 
     In concordance and agreement with the present disclosure, a sensor system and a method of temperature-compensation thereof, which enhances accuracy and efficiency of the sensor system, has surprisingly been discovered. 
     In one embodiment, a sensor system, comprises: a first sensor configured to generate at least one output; and a controller in electrical communication with the first sensor, the controller including a memory for storing data configured to store at least one offset value for the at least one output of the first sensor. 
     As aspects of certain embodiments, the first sensor is an eddy current sensor. 
     As aspects of certain embodiments, the at least one output of the first sensor is indicative of a distance of a conductive material from the first sensor. 
     As aspects of certain embodiments, the at least one output of the first sensor is a frequency signal. 
     As aspects of certain embodiments, the at least one offset value is a difference between at least one measured output of the first sensor and a predetermined output of the first sensor. 
     As aspects of certain embodiments, the at least one measured output of the first sensor is determined while a position of a conductive material is maintained and a temperature of surrounding atmosphere is varied. 
     As aspects of certain embodiments, the predetermined output of the first sensor is a frequency signal at an ideal ambient temperature. 
     As aspects of certain embodiments, further comprising a second sensor in electrical communication with the controller, wherein the second sensor is configured to measure a temperature of a desired input location. 
     As aspects of certain embodiments, the second sensor is a thermistor. 
     In another embodiment, a method of temperature-compensation of a sensor system, comprises the steps of: providing a first sensor configured to generate an output; providing a controller in electrical communication with the first sensor, wherein the controller includes a memory for storing data; providing an offset profile stored in the memory of the controller, wherein the offset profile provides a plurality of offset values for the output of the first sensor; transmitting the output of the first sensor to the controller; and calculating a temperature-compensated output of the first sensor by adjusting the output of the first sensor by one of the offset values stored in the memory of the controller. 
     As aspects of certain embodiments, further comprising the step of providing a second sensor in electrical communication with the controller, wherein the second sensor is configured to measure a temperature of a desired input location. 
     As aspects of certain embodiments, the one of the offset values is obtained from the offset profile based upon the output of the first sensor and the measured temperature from the second sensor. 
     As aspects of certain embodiments, further comprising the step of comparing the temperature-compensated output of the first sensor to calibrated values the output of the first sensor to determine a state of a differential of a vehicle. 
     As aspects of certain embodiments, the offset values are calculated using measured outputs of the first sensor determined while a position of a conductive material is maintained and a temperature of surrounding atmosphere is varied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are incorporated herein as part of the specification. The drawings described herein illustrate embodiments of the presently disclosed subject matter, and are illustrative of selected principles and teachings of the present disclosure. However, the drawings do not illustrate all possible implementations of the presently disclosed subject matter, and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  schematically depicts a vehicle according to an embodiment of the presently disclosed subject matter; 
         FIG. 2  is a cross-sectional view of a differential according to an embodiment of the presently disclosed subject matter; 
         FIG. 3  is a fragmentary cross-sectional view of a portion of the differential according to  FIG. 2 , wherein the differential is in an unlocked state; 
         FIG. 4  is a fragmentary cross-sectional view of a portion of the differential according to  FIG. 2 , wherein the differential is in a locked state. 
         FIG. 5  is a perspective view of a portion of an axle assembly according to an embodiment of the presently disclosed subject matter, wherein a portion of a differential carrier is not shown; 
         FIG. 6  is a fragmentary perspective view of a portion of the differential according to  FIG. 2 , wherein a differential case is not shown; 
         FIG. 7  is a fragmentary cross-sectional view of a portion of a differential having a transverse sensor according to an embodiment of the presently disclosed subject matter; 
         FIG. 8  is a block flow diagram of a temperature compensation method of a sensor system according to an embodiment of the presently disclosed subject matter; and 
         FIG. 9  is a block flow diagram of a method of sensing using the sensor system according to  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the presently disclosed subject matter may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific assemblies and systems illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless expressly stated otherwise. Also, although they may not be, like elements in various embodiments described herein may be commonly referred to with like reference numerals within this section of the application. 
       FIG. 1  illustrates an all-wheel-drive (AWD) vehicle  10  according to the presently disclosed subject matter. The vehicle  10  may be any vehicle type as desired such as a conventional fuel-powered vehicle, an electric vehicle, and an electric-hybrid vehicle, for example. In one embodiment, the vehicle  10  may include a driveline arrangement  12  with a power source  14 . The power source  14  may be, but is not limited to, an internal combustion engine or an electric motor. The driveline arrangement  12  may also include a transmission  16  having an input driveably connected to the power source  14  and an output driveably connected to a transfer case  18 . The transfer case  18  including a first output continuously driveably connected to a rear drive unit  19  and a second output selectively driveably connected to a front drive unit  20 . The rear drive unit  19  or the front drive unit  20  may further include an axle assembly  21  driveably connected to a wheel-set  22 . 
     As illustrated in  FIGS. 2-6 , the axle assembly  21  includes a differential  23  having a differential case  24 . The differential  23  provides improved fuel economy by disconnecting AWD driveline components when AWD functionality is not required. The differential case  24  is mounted for rotation within a differential carrier  10  via a pair of bearings  34 ,  36 . In certain embodiments, the differential  23  may be utilized within the axle assembly  21  the vehicle  10  shown in  FIG. 1 . However, methods utilized with the differential  23  as disclosed herein may be also be utilized with other movable components. The methods may have applications in both light-duty and heavy-duty vehicles, and for passenger, commercial, and off-highway vehicles. Further, the methods may also have industrial, locomotive, military, agricultural, and aerospace applications, as well as applications in passenger, electric, and autonomous or semi-autonomous vehicles. 
     As illustrated in  FIG. 5 , a ring gear  40  may be coupled with the differential case  24 . In an embodiment, the ring gear  40  may be integrally formed with the differential case  24 . In another embodiment, as illustrated in  FIGS. 2 and 5 , the differential case  24  may include a ring gear flange  42 . The ring gear flange  42  may define a plurality of fastener apertures (not shown) disposed circumferentially thereabout and formed therethrough. Mechanical fasteners  44 , such as bolts, may be disposed through the fastener apertures and into a first side of the ring gear  40  to couple the differential case  24  and the ring gear  40 . 
     The ring gear  40  includes a plurality of teeth (not depicted) on a second side  48  of the ring gear  40 . The ring gear teeth extend continuously circumferentially about the second side  48 . The ring gear teeth mesh with a set of teeth on a pinion gear  49  shown in  FIG. 1 . The pinion gear  49  is coupled with the transfer case  18 . The pinion gear  49  receives torque from the power source  14 . 
     As illustrated in  FIG. 2 , in an embodiment, a pinion shaft  50  is disposed within the differential case  24 . In an embodiment, additional pinion shafts  50 A may be located at 90 degrees and transverse to the pinion shaft  50 . The pinion shafts  50 ,  50 A may also be referred to as spider shafts. The pinion shaft  50  is connected to the differential case  24 . In an embodiment, the pinion shaft  50  may extend into the differential case  24  so that it is fixed therewith. Thus, the pinion shaft  50  rotates with the differential case  24 . 
     A first differential pinion gear  52  is located on one end of the pinion shaft  50  and a second differential pinion gear  54  is located on the other end of the pinion shaft  50 . The first and second differential pinion gears  52 ,  54  each include a plurality of teeth  56 ,  58  extending circumferentially about the first and second differential pinion gears  52 ,  54 . As noted above, if additional pinion shafts  50 A are provided, additional differential pinions may be located thereon. As illustrated in  FIG. 2 , a third differential pinion gear  52 A is disposed on the additional pinion shaft  50 A. The teeth  56 ,  58  of the first and second differential pinion gears  52 ,  54  are meshed with teeth  60 ,  62  on a first differential side gear  64  and a second differential side gear  66 . The differential side gear teeth  60 ,  62  extend circumferentially about the first and second differential side gears  64 ,  66 . 
     The first and second differential side gears  64 ,  66  include a hollow interior portion  68 ,  70 , respectively. The hollow interior portions  68 ,  70  may each include radially extending splines  72 ,  74 . The splines  72  of the first differential side gear  64  may be engaged with splines on a first axle half shaft (not depicted) to transfer rotation to the shaft. The splines  74  of the second differential side gear  66  may be engaged with splines on a second axle half shaft (not depicted) to transfer rotation to the shaft. The first and second axle half shafts extend from the differential case  24  and through the axle assembly  21  to the wheel-set  22 . 
     In certain embodiments illustrated in  FIGS. 2-4 and 6 , the differential  23  may be an electrical differential locker (EDL). The EDL may be utilized in applications across multiple industries including automotive, aerospace, industrial automation equipment, and instrumentation applications. In one embodiment, the subject matter disclosed herein may be utilized in an operation  9   f  the AWD vehicle  10  shown in  FIG. 1 . In certain embodiments, the second differential side gear  66  may include a set of locking teeth  76  disposed on an axially outboard surface  78 . In an embodiment, the locking teeth  76  are integrally formed with the second differential side gear  66 . The locking teeth  76  extend circumferentially about the axially outboard surface  78 . 
     As illustrated in  FIGS. 2-6 , an actuator assembly  80  may be mounted on the second differential case flange  28 . The actuator assembly  80  is coupled with the differential carrier  10  so that the actuator assembly  80  is fixed against rotation relative to the differential carrier  10 . In an embodiment, the actuator assembly  80  includes at least one radially extending pin  82 . The pin  82  is received within a slotted flange  84  fixedly connected to the differential carrier  10 . Receipt of the pin  82  within the slotted flange  84  militates against a rotation of the actuator assembly  80  with the differential case  24 . 
     In an embodiment, the actuator assembly  80  comprises a solenoid actuator.’ The actuator assembly  80  may include a housing  88 , an electromagnetic coil  90 , and an armature  92 . In an embodiment, the housing  88  may have an annular geometry such that an inner diameter of the housing  88  is coupled with a sleeve  89 . The sleeve  89  may be coupled with the differential case flange  28  such that the sleeve  89  may rotate relative to the differential case  24 . 
     The electromagnetic coil  90  may be molded, or set, within a resin and disposed within the housing  88 . The electromagnetic coil  90  may comprise a ring-shape with a hollow interior. The electromagnetic coil  90  is in electrical connection with a power source (not depicted), such as, but not limited to, a battery, that can selectively supply electricity to the electromagnetic coil  90 . The power source may also be connected with a controller (not shown) that determines when electricity is supplied to the electromagnetic coil  90 . In an embodiment, the controller may be mounted to an inboard portion of the housing  88 . In another embodiment, the controller may be mounted to a radially outer surface of the actuator housing  88 . In still another embodiment, the controller may be mounted to an outboard surface of the housing  88 . 
     With reference to  FIGS. 2-4 , in an embodiment, the armature  92  may be a generally hollow-cylinder disposed radially inward from the electromagnetic coil  90 . In some embodiments, at least a portion of the armature  92  is continuously radially surrounded by the electromagnetic coil  90 . The armature  92  may be formed from a ferromagnetic material. Disposed axially adjacent to the armature  92 , on an inboard side thereof, is an annular spacer  94 . The annular spacer  94  may be formed from of a polymeric material. 
     When electricity is applied to the electromagnetic coil  90 , the electromagnetic coil  90  generates a magnetic field which extends through the housing  88  and the armature  92 . The magnetic field extends into the armature  92  causing the armature  92  to move in the axial direction. In an embodiment, the armature  92  does not rotate. 
     In an embodiment, as illustrated in  FIGS. 2-4 , a sensor plate  124  may be positioned axially adjacent to an inboard side of the spacer  94 . The sensor plate  124  may also be disposed at least partially radially about the spacer  94 . In an embodiment, the sensor plate  124  abuts a plurality of legs  100  of a locking gear  96 . As more clearly illustrated in  FIG. 6 , the locking gear legs  100  extend axially outboard from a generally disk-shaped body portion  102  of the locking gear  96 . The legs  100  are located on an axially outboard side  104  of the body portion  102 . The locking gear body portion  102  includes a radially outer surface  106 . The radially outermost surfaces of the legs  100  may extend from the outer surface  106  such that the outer surface  106  and the radially outermost surfaces of the legs  100  have the same outer diameter. 
     In an embodiment, the legs  100  may be circumferentially located such that they are separated from one another by arcs of the same length. The legs  100  may taper down from the body portion  102  to their ends. In an embodiment, the locking gear body portion  102  may be entirely located within the differential case  24 . The locking gear legs  100  may be located mostly within the differential case  24 ; however, the end portions of the legs  100  axially extend through differential case apertures  108  dedicated to each leg  100 . The end portions of the legs  100  extend outside of the differential case  24  to contact the armature  92 , the spacer  94 , or the sensor plate  124 . 
     A plurality of teeth  112  are located on the axially inboard side  110  of the locking gear body portion  102 . The teeth  112  extend circumferentially about the locking gear body portion inboard side  110 . The locking gear teeth  112  are complementary with and selectively mesh with the second differential side gear locking teeth  76 . 
     In an embodiment, the locking gear  96  defines an annular groove  118  located in an inboard surface thereof. The locking gear groove  118  may be axially aligned with a groove  121  on the axially outboard surface  78  of the second differential side gear  66 . A biasing member  122  may be at least partially located within the locking gear groove  118  and the second differential side gear groove  121 . The biasing member  122  axially biases the locking gear  96  apart from the second differential side gear  66  when the actuator assembly  80  is in a disengaged position. The biasing member  122  may be, but is not limited to, a spring, a plurality of springs, one or more Bellville-type washers, or one or more wave springs. 
     Being located within the differential case  24 , it can be appreciated that the locking gear  96  rotates with the differential case  24 . The locking gear  96  is preferably one piece, unitary and integrally formed out of a robust material, such as metal. The locking gear  96  may be constructed of a conductive material. 
     In an embodiment, as illustrated in  FIGS. 2-4 , the sensor plate  124  may be coupled with the locking gear  96 . The sensor plate  124  may comprise a generally discoid geometry and have a radially inner surface  126 , a radially outer surface  128 , an axially inboard surface  130 , and an axially outboard surface  132 . The axially inboard and outboard surfaces  130 ,  132  may be substantially parallel and equally spaced from one another. In the embodiment illustrated in  FIGS. 2-4 , the axially inboard and outboard surfaces  130 ,  132  define a substantially constant sensor plate  124  thickness therebetween. The sensor plate  124  may have a radial dimension much greater than its axial dimension. In other words, the thickness of the plate  124  may be much less than the distance between the radially inner and outer surface  126 ,  128 . 
     As illustrated in  FIGS. 2-4 , the sensor plate  124  may comprise tabs  134  extending axially, or transverse, to the axially inboard surface  130 . A radially inner surface of the tabs  134  may be contiguous with the sensor plate radially inner surface  126 . The tabs  134  may be regularly spaced from one another about the circumference of the radially inner surface  126 . In an embodiment, a portion of the tabs  134  may be disposed in a radially extending annular groove  135  defined by the locking gear  96  to frictionally lock the sensor plate  124  to the locking gear  96 . In one embodiment, the groove  135  is disposed in a radially inner side of the locking gear legs  100 . 
     At least a portion of the sensor plate  124  is located substantially outside of the differential case  24 ; however, the sensor plate tabs  134  may extend into the differential case  24 . More particularly, the tabs  134  may extend at least partially through the differential case apertures  108 . In other embodiments (not depicted), the sensor plate  124  may be coupled with the locking gear  96  in other ways such as, but not limited to, mechanical fasteners. Thus, in certain embodiments, the armature  92  or the annular spacer  94  may not directly contact the sensor plate  124 , but instead the armature  92  or annular spacer  94  may directly contact the locking gear  96 . 
     In an embodiment, a body portion  136  of the sensor plate  124  may comprise a substantially continuous surface. In another embodiment, as illustrated in  FIG. 6 , the sensor plate body portion  136  may have one or more apertures extending axially therethrough. The apertures may permit fluid, such as air and lubricant, to flow within the differential carrier  10 . In an embodiment (not depicted), the sensor plate  124  may comprise a plurality of apertures having a small diameter, versus having fewer apertures with a relatively large diameter. The sensor plate  124 , being coupled with the locking gear  96 , moves axially with and rotates with the locking gear  96 . Further, the sensor plate  124  may comprise a conductive material. 
     The housing  88  comprises an inboard surface  138 , an outboard surface  140 , and a radially outer surface  142 . The radially outer surface  142  may be curvilinear and define a substantially constant outer diameter of the ring-shaped housing  88 . The inboard and outboard surfaces  138 ,  140  define a substantially constant distance, or thickness, between them. The inboard and outboard surfaces  138 ,  140  are substantially parallel one another. The inboard and outboard surfaces  138 ,  140  may extend substantially transverse to an axis of rotation  144  of the differential case  24 . 
     Similarly, the inboard and outboard surfaces  130 ,  132  of the sensor plate  124  may extend substantially transverse the axis of rotation  144  of the differential case  24 . The inboard and outboard surfaces  130 ,  132  of the sensor plate  124  are substantially parallel to the inboard and outboard surfaces  138 ,  140  of the housing  88 . 
     In an embodiment, a position sensor  148  of a sensor system  152  (shown in  FIG. 1 ) may be disposed on the inboard surface  138  of the housing  88 . In another embodiment, the position sensor  148  may be disposed in a recess in the inboard surface  138  of the housing  88 . The position sensor  148  may be located anywhere radially along the inboard surface  138 . In one embodiment, the position sensor  148  is located near a radially outward portion of the inboard surface  138 . In an embodiment, more than one position sensor  148  may be located at more than one radial location on the inboard surface  138 . In another embodiment, the position sensor  148  may comprise a ring disposed on the inboard surface  138 . 
     In yet another embodiment, as illustrated in  FIG. 7 , the position sensor  148  may be located transverse to the sensor plate  124 . For example, the position sensor  148  may be located radially outward from the sensor plate  124 . In this embodiment, the position sensor  148  is fixed a constant distance from the radially outer surface  128  of the sensor plate  124 . 
     The transverse position sensor  148  works essentially the same as described herein. In one embodiment, the transverse position sensor  148  senses the percentage it is covered by the sensor plate radially outer surface  128  so that a microcontroller can determine the position of the sensor plate  124  based on the percentage of coverage. 
     In still another embodiment, as illustrated in  FIG. 7 , a first transverse position sensor  148  may be located radially above the sensor plate  124  and a second transverse position sensor  148 A may be located radially below the sensor plate  124 . By “above” and “below” is it meant that the first and second sensors are fixed radially opposite one another. 
     In another embodiment (not depicted), a first position sensor  148  may be located axially adjacent the sensor plate inboard surface  130  and a second position sensor  148  may be located axially adjacent the sensor plate outboard surface  132 . Thus, the first and second sensors  148 ,  148  are located on either side of the sensor plate  124 ; the first position sensor  148  faces the sensor plate inboard surface  130  and the second position sensor  148  faces the sensor plate outboard surface  132 . The second position sensor  148  may be radially aligned with the first sensor. In other words, the first and second sensors  148 ,  148  may be located the same distances from the differential axis of rotation  144 . In this embodiment, the data from the first and second sensors  148 ,  148  may be used by the controller microprocessor either in conjunction or separately. When used separately, the data can be compared to act as a double check on the sensor plate  124  position. When used together, the data can be used to detect any variation in the distance between the sensor plate  124  and the first and second sensors  148 ,  148 . 
     Various types of sensors  148  may be used. A brief summary of some of the possible sensors  148  follows, but the device is not limited to just these sensors  148  or the operation described below. 
     In one embodiment, the position sensor  148  may be a two-wire sensor. A voltage is provided to the position sensor  148  (for example, approximately 4-9 volts), and a draw of current is fixed. The current may be such as either 7 milliamps or 14 milliamps depending on the state of the system. For example, one current may be associated with a locked condition of the differential  23  and another current can be associated with an unlocked condition of the differential  23 . 
     In another embodiment, the position sensor  148  may be a three-wire sensor. This embodiment may transmit an output such as a fixed frequency signal around 250 Hz, but other frequencies may be used. The duty cycle of the output may vary with the position of the sensor plate  124  or locking gear  96 . The output may be either a continuous signal relative to the position of the sensor plate  124  or locking gear  96 , or the output may be a signal having fixed values based on specific positions of the sensor plate  124  or locking gear  96 . For example, the output may be a signal indicating 10% when the sensor plate  124  or locking gear  96  is closest to the position sensor  148 , and indicating 90% when the sensor plate  124  or locking gear  96  is furthest from the position sensor  148 . In addition, the output may be include percentage signals that may be fixed for specific positions at every instance between the closest and furthest positions. In yet another embodiment of this position sensor  148 , the output may be a signal that may be fixed at a particular amount in the closest position (unlocked) and a different particular amount in the furthest position (locked) with no other signals. 
     In another embodiment, the output of the position sensor  148  may be a serial digital signal. By way of example, the output may be a serial digital signal such as a UART-style or LIN-bus output with a predetermined baud rate (such as, by way of example 9600 baud). 
     In any of the above-described embodiments, the position sensor  148  may be an inductive sensor comprising an inductive coil  149 . The sensor inductive coil  149  may include, but is not limited to, a bobbin-wound length of wire, a printed circuit board (PCB) trace spiral, or a printed trace of metal (if the inboard surface is non-conductive). In an embodiment, the inductive coil  149  may be substantially planar and rigid. In another embodiment, the inductive coil  149  may be flexible, non-planar and/or curvilinear. 
     In embodiments where planar and rigid, the inductive coil  149  may be set in, or located on, a substrate. The substrate may be the housing  88 , or a material attached to the housing  88  in which the position sensor  148  is embedded. 
     In embodiments where flexible, non-planar and curvilinear, the inductive coil  149  may similarly be set in, or located on, a substrate. The substrate may be a flexible material that can be adapted to a curvilinear surface. In one embodiment, the substrate may be a flexible circuit board. Alternatively, the inductive coil  149 , in whole or in part, may be curved or flexed so that it is curvilinear. The inductive coil  149  may then be located on a curvilinear shape, such as the differential case  24  or the differential carrier  10  or a structure connected to either. 
     The inductive coil  149  generates a high-frequency alternating magnetic field when a conductive material is nearby. The magnetic field causes eddy currents to form within the conductive material. The eddy currents create a magnetic field in the conductive material opposite to the magnetic field in the inductive coil  149 . An amplitude of the eddy currents in the conductive material measured by the position sensor  148  is proportional to a distance of the conductive material therefrom. The position sensor  148  is configured to generate and transmit the output indicative of the distance of the conductive material therefrom to a controller  150  of the sensor system  154  (shown in  FIG. 1 ) such as a microcontroller or a controller area network (CAN) system, for example, in electrical communication with the position sensor  148 . In certain embodiments, the controller  150  may be located on or within the actuator assembly housing  88 . In other embodiments, however, the controller  150  may be located at other suitable locations within the vehicle  10  shown in  FIG. 1  as desired. 
     In an embodiment, the conductive material may be the sensor plate  124 . In another embodiment, the position sensor  148  instead senses the location of the locking gear  96 . It can be appreciated that the position sensor  148  senses the exact position of the locking gear  96 , whether position sensor  148  senses the locking gear  96  directly, or the sensor plate  124 . As can be appreciated from the foregoing, the location of the locking gear  96  and/or the sensor plate  124  can be known so that a reliable determination of whether the differential  23  is in a locked or unlocked condition can also be reliably known. 
       FIGS. 2 and 3  illustrate the differential  23  in an unlocked state. In an unlocked state, the locking gear  96  is not engaged with the second side gear  66 . Additionally, the electromagnetic coil  90  is not sufficiently energized to actuate the armature  92 . Further, the biasing member  122  biases the locking gear  96  to an axially outboard position. 
     Upon the detection of a condition wherein it may be desirable to lock the differential  23 , electrical current is supplied to the electromagnetic coil  90  in an amount sufficient for the electromagnetic coil  90  to create a magnetic flux in the electrically conductive armature  92 . There may be a variety of conditions that warrant locking the differential  23 . These conditions may be monitored by one or more vehicle sensors (not depicted). 
     The magnetic flux in the armature  92  causes the armature  92  to move in an axially inboard direction. The flux in the armature  92  is sufficient that it moves the armature  92  against the biasing force of the biasing member  122 . In other words, the axial inboard movement of the armature  92  axially moves the locking gear  96  in an inboard direction. As noted above, because the sensor plate  124  is coupled with the locking gear  96 , the sensor plate  124  also moves in an axial inboard direction. 
       FIG. 4  illustrates the differential  23  in the locked state. In the locked state, the armature  92 , the locking gear  96 , and the sensor plate  124 , move in an axial inboard direction so that the second side gear locking teeth  76  and the locking gear teeth  112  engage with one another. When the second side gear locking teeth  76  and the locking gear teeth  112  are fully engaged the differential  23  is locked. In the locked condition, the second side gear  66  is locked against rotation relative to the differential case  24 . This prevents the second side gear  66  from rotating independently from the first side gear  64 ; instead, the first and second side gears  64 ,  66  can only rotate together. The locked state of the differential  23  has the effect of dividing power equally to both the first and second side gears  64 ,  66 , both axle half shafts, and both wheel ends. 
     When a locked differential  23  is no longer required, the electrical current to the electromagnetic coil  90  is ended, or reduced. The termination or reduction in power to the electromagnetic coil  90  causes the biasing member  122  to urge the locking gear  96  in the axial outboard direction from the second side gear  66 . This results in the locking teeth  76  of the second side gear  66  and the teeth  112  of the locking gear  96  to disengage. Once disengaged, the second side gear  66  can rotate with respect to the first side gear  64 . 
     As illustrated in  FIG. 1 , the sensor system  152  may further include a temperature sensor  154  for measuring and/or estimating a temperature T 1  of a desired input location  156  (e.g. a component or fluid of the vehicle  10 ). It is understood that additional temperature sensors  154  may be employed for measuring temperatures at a plurality of input locations  156 . By way of example, the desired input location  156  may be a location within the controller  150 , a clutch assembly of a rear drive unit, the differential  23 , a vehicle engine, an engine fluid, a vehicle transmission, a transmission fluid, ambient air, and the like. Various types of controllers or microcontrollers may be employed with the sensor system  152 . In the embodiment shown, the sensor system  152  facilitates electrical communication amongst the position sensor  148 , the controller  150 , and the temperature sensor  154 . In certain embodiments, the controller  150  may be in electrical communication with the position sensor  148 , the controller  150 , and the temperature sensor  154  to facilitate such communication there amongst. 
     In certain embodiments, the controller  150  includes a memory  158  for storing data. The memory  158  may be in electrical communication with the position sensor  148  and the temperature sensor  154 . The memory  158  may be configured to store an offset profile of the position sensor  148  determined during development of the position sensor  148 . The offset profile may be a look-up table which provides an offset value for the output (e.g. the frequency signal) of the position sensor  148  based upon a temperature. 
     In one embodiment, the temperature sensor  154  is thermistor. Various types of thermistors may be employed as the temperature sensor  154  such as a negative temperature coefficient (NTC) thermistor and a positive temperature coefficient (PTC) thermistor, for example. With an NTC thermistor, when the temperature increases, resistance of the NTC thermistor decreases. Conversely, when temperature decreases, resistance of the NTC thermistor increases. On the other hand with a PTC thermistor, when temperature increases, the resistance of the PTC thermistor increases, and when temperature decreases, resistance of the PTC thermistor decreases. 
     Unlike other temperature sensors, the temperature sensor  154  may be a nonlinear thermistor, meaning a relationship between a resistance and a temperature is not a 1:1 ratio. As such, the temperature to resistance values plotted on a graph representing such relationship form a curve rather than a straight line. It is understood that the temperature sensor  154  may have a variety of shapes and sizes such as a disk, chip, bead, rod, surface-mounted, for example. The temperature sensor  154  can also be encapsulated in epoxy resin, glass, baked-on phenolic, and painted, if desired. 
     In the embodiment shown, the temperature sensor  154  is employed to measure the temperature T 1  of the desired input location  156 . The temperature sensor  154  has a minimal amount of electrical current (also commonly referred to as a bias current) flowing therethrough. The controller  150  is configured to cause an electrical source (not depicted) such as, by way of example a battery, to transmit the electrical current to the temperature sensor  154 . The temperature sensor  154  has a resistance associated with the temperature T 1  of the desired input location  156 . The electrical current flowing through the temperature sensor  154  converts the resistance of the temperature sensor  154  to a measured voltage difference across terminals of the temperature sensor  154 . The measured voltage difference is then transmitted from the temperature sensor  154  to the controller  150 . In certain embodiments, the controller  150  determines the temperature T 1  of the desired input location  156  based upon at least one determination method such as using the measured voltage difference and a tolerance band or function of the temperature sensor  154  stored within the memory  158  of the controller  150 , for example. A relationship between voltage and resistance is known, and may be calculated by utilizing a look-up table or other mathematical relationship therebetween. As such, in certain other embodiments, the determination method of the controller  150  utilizes the look-up table stored in the memory  158  to determine the temperature T 1  of the desired input location  156  based upon the measured voltage difference of the temperature sensor  154 . 
     Referring now to  FIG. 8 , a method of temperature-compensation  200  for the sensor system  152  according to an embodiment of the presently disclosed subject matter. In certain embodiments, at least one of the position sensor  148  and controller  150  is calibrated such that a value of the output of the position sensor  148  is determined to correspond with various switch points (e.g. a point of engagement of the second side gear locking teeth  76  and the locking gear teeth  112  associated with the differential  23  in the locked condition, and a point of disengagement the second side gear locking teeth  76  and the locking gear teeth  112  associated with the differential  23  in the unlocked condition) prior to operation of the vehicle  10 . Such calibrated values are then stored in the memory  158  of the controller  150 . 
     At step  202 , prior to an operation of the vehicle  10 , the output of the position sensor  148  is measured while a position of the conductive material is maintained and a temperature of a surrounding atmosphere is measured and varied. A difference between values of the measured output of the position sensor  148  at the measured temperatures and a predetermined output (i.e. a frequency at an ideal ambient temperature) is calculated at step  204 . In certain embodiments, the difference between each of the values of the measured output of the position sensor  148  at the measured temperatures and the predetermined output is an offset value of the output of the position sensor  148  at each of the measured temperatures representative of an effect of temperature on the position sensor  148 . The offset values are then stored within the memory  158  of the controller  150  at step  206 . As such, at step  208 , an offset profile of the position sensor  148 , or a look-up table, is created which provides the calculated offset value for the output of the position sensor  148  across numerous temperatures. 
     Referring now to  FIG. 9 , a method of sensing  300  of the sensor system  152  according to an embodiment of the presently disclosed subject matter. During the operation of the vehicle  10 , at step  302 , the position sensor  148  generates the output thereof indicative of the distance of the conductive material therefrom. At step  304 , the output of the position sensor  148  is transmitted to the controller  150 . 
     Simultaneously, at step  306 , an electrical current is supplied from an electrical source (e.g. a battery) to the temperature sensor  154  and flow therethrough, which generates the resistance. At step  308 , the resistance of the temperature sensor  154  is then converted to the measured voltage difference across the terminals of the temperature sensor  154  representative of the temperature T 1  of the desired input location  156 . At step  310 , the measured voltage difference is then transmitted to the controller  150  of the sensor system  152  to determine the temperature T 1  of the desired input location  156  using any suitable determination method as desired. At step  312 , the temperature T 1  of the desired input location  156  is used to obtain the associated offset value for the output of the position sensor  148  from the offset profile stored in the memory  158  of the controller  150 . Thereafter, at step  314 , a temperature-compensated output of the position sensor  148  is then calculated by subtracting the associated offset value for the output of the position sensor  148  of step  312  from the output of the position sensor  148  generated by the position sensor  148  at step  302 . The temperature-compensated output of the position sensor  148  is then utilized by the controller  150  and compared to the calibrated values of the output of the position sensor  148  to determine a state of the differential  23  (i.e. the locked or unlocked condition) at step  316 . 
     It is understood that the method of sensing  300  of the position sensor  148  may be repeated as desired. In certain embodiments, the method of sensing  300  of the position sensor  148  is continuously repeated. In other certain embodiments, however, that the method of sensing  300  of the position sensor  148  may be periodically repeated at predetermined intervals, if desired. 
     While various embodiments have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant arts that the disclosed subject matter may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments described above are therefore to be considered in all respects as illustrative, not restrictive.