Patent Publication Number: US-2023160981-A1

Title: Non-contact sensor arrangement for fifth wheel assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 63/264,415, filed on Nov. 22, 2021, entitled “NON-CONTACT SENSOR ARRANGEMENT FOR FIFTH WHEEL ASSEMBLY,” the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention is directed to an electronic system for monitoring the coupling of a trailer to a trailer hitch assembly that is mounted on a truck chassis, and in particular is directed to an electronic system that indicates whether the trailer is properly coupled to the trailer hitch assembly by determining between components of the trailer, components of the hitch assembly and foreign materials. 
     BRIEF SUMMARY OF THE INVENTION 
     One embodiment as disclosed herein may include an electronic system for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat, the electronic system determining whether the trailer hitch assembly is properly coupled to the trailer, where the electronic system includes at least one magnet creating a magnetic flux, the at least one magnet located on a first side of a throat of a hitch plate, a first Hall-effect sensor for sensing the position of a kingpin of a trailer relative to the throat of the hitch plate by measuring the magnetic flux of the at least one magnet, the first Hall-effect sensor located on a second side of the throat substantially opposite the first side, and a second Hall-effect sensor for sensing the position of the kingpin of the trailer relative to the throat of the hitch plate by measuring the magnetic flux of the at least one magnet, where the first Hall-effect sensor located on the second side of the throat substantially opposite the first side, and the second Hall-effect sensor spaced from the first Hall-effect sensor. 
     Another embodiment as disclosed herein may further or alternatively include an electronic system for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat, the electronic system determining whether the trailer hitch assembly is properly coupled to the trailer, where the electronic system includes a first magnet creating a first magnetic flux, the first magnet located on a first side of a throat of a hitch plate, a first Hall-effect sensor for sensing the position of a kingpin of a trailer relative to the throat of the hitch plate by measuring the first magnetic flux, the first Hall-effect sensor located on a second side of the throat substantially opposite the first side, and a circuit member comprising a magnetically permeable material, wherein the first magnet, the first Hall-effect sensor, and the circuit member are each in series with one another, and wherein the magnetically permeable material of the circuit member has a relative magnetic permeability of within a range of between about 30,000 and about 100,000. 
     Yet another embodiment as disclosed herein may further or alternatively include an electronic system for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat, the electronic system determining whether the trailer hitch assembly is properly coupled to the trailer, where the electronic system includes a plurality of magnets each creating a magnetic flux, at least one Hall-effect sensor for sensing the position of a kingpin of a trailer relative to the throat of the hitch plate by measuring the magnetic flux, and a circuit member comprising a magnetically permeable material, wherein the plurality of magnets, the at least one Hall-effect sensor, and the circuit member are each in series with one another. 
     Still yet another embodiment as disclosed herein may further or alternatively include an electronic system for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat, the electronic system determining whether the trailer hitch assembly is properly coupled to the trailer, where the electronic system includes at least one magnet creating a magnetic flux, at least one Hall-effect sensor for sensing the position of a kingpin of a trailer relative to a throat of a hitch plate by measuring the magnetic flux, and a circuit member comprising a magnetically permeable material, wherein the at least one magnet, the at least one Hall-effect sensor, and the circuit member are each in series with one another, and wherein the circuit member is tapered in an area proximate the at least one magnet or Hall-effect sensor. 
     Another embodiment as disclosed herein may further or alternatively include an electronic system for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat, the electronic system determining whether the trailer hitch assembly is properly coupled to the trailer, where the electronic system includes at least one magnet creating a magnetic flux, at least one Hall-effect sensor for sensing the position of a kingpin of a trailer relative to a throat of a hitch plate by measuring the magnetic flux, a circuit member comprising a magnetically permeable material, and a control arrangement configured to allow a user/microprocessor to adjust the magnetic flux between a first magnitude and a second magnitude that is greater than the first magnitude and/or to adjust the magnetic flux over a range of AC current frequencies. 
     Yet another embodiment as disclosed herein may further or alternatively include a method for monitoring a trailer hitch assembly having a hitch plate with a throat for receiving a kingpin of a trailer and a locking mechanism for locking the kingpin in the throat and determining whether the trailer hitch assembly is properly coupled to the trailer, where the method includes providing at least one magnet configured to create a magnetic flux at first magnitude and a second magnitude that is greater than the first magnitude, providing at least one Hall-effect sensor for sensing the position of a kingpin of a trailer relative to a throat of a hitch plate by measuring the magnetic flux, providing a circuit member comprising a magnetically permeable material and electrically coupled to the at least one magnet and the at least one Hall-effect sensor, providing a control arrangement configured to allow a user to adjust the magnetic flux between the first magnitude and a second magnitude, adjusting the magnetic flux between the first and second magnitudes, and sensing the magnet flux via the at least one Hall-effect sensor. 
     These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a truck and trailer arrangement; 
         FIG.  2    is a bottom plan view of a fifth wheel hitch plate and an electronic sensing system; 
         FIG.  3    is a side elevation view of the fifth wheel hitch plate and the electronic sensing system; 
         FIG.  4    is an inverted side elevation view of the fifth wheel hitch plate and the electronic sensing system; 
         FIG.  5    is a schematic perspective view of an output device; 
         FIG.  6    is a bottom perspective view of the fifth wheel hitch plate and a first embodiment of the electronic sensing system; 
         FIG.  7    is a bottom plan view of the fifth wheel hitch plate and the first embodiment of the electronic sensor assembly; 
         FIG.  8    is an enlarged plan view of the area VIII,  FIG.  7   ; 
         FIG.  9    is a schematic top plan view of the first embodiment of the electronic sensor assembly, where the electronic sensor assembly is at a zero state; 
         FIG.  10    is an electronic schematic view of the electronic circuit of the electronic sensor assembly, including a power supply and over current/reverse current protection; 
         FIG.  11    is a schematic top plan view of the first embodiment of the electronic sensor assembly indicating a location of the kingpin in proper alignment with the hitch plate; 
         FIG.  12    is a schematic top plan view of the first embodiment of the electronic sensor assembly with a ferromagnetic material positioned within the throat of the hitch plate; 
         FIG.  13    is a schematic view of a second embodiment of the electronic sensor assembly; 
         FIG.  14    is a schematic view of a third embodiment of the electronic sensor assembly; 
         FIG.  15    is a schematic view of a fourth embodiment of the electronic sensor assembly at a zero state; 
         FIG.  16    is a schematic view of the fourth embodiment of the electronic sensor assembly indicating a location of the kingpin in proper alignment with the hitch plate; 
         FIG.  17    is a schematic view of the fourth embodiment of the electronic sensor assembly with a ferromagnetic material located within the throat of the hitch plate; 
         FIG.  18    is an electrical schematic view of the electronic circuit of the fourth embodiment of the electronic sensor assembly; and 
         FIG.  19    is an electrical schematic view of an alternative embodiment of the electronic circuit of the fourth embodiment of the electronic sensor assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in  FIGS.  1 - 3   . However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     The reference numeral  10  ( FIGS.  1 - 3   ) generally designates an electronic monitoring and sensing system incorporated within a towing and towed vehicle arrangement  9  that includes a towing truck  10  and a towed trailer  17 . A hitch assembly  14  includes a base  16  securely mounted to a chassis  18  of the truck  10 , a trailer hitch plate or fifth wheel hitch plate  20  pivotally mounted on the base  16  on a transverse axis  19 , and a locking mechanism  22  for locking a conventional trailer kingpin  15  of the trailer  17  in place. The electronic sensing system  10  preferably includes a non-contact kingpin sensor assembly  24  mounted to the hitch assembly  14 , a tilt sensor assembly  25 , a lock sensor  27 , and an output device  26  mounted in the cab of the tractor  12 . A contact sensor (not shown) configured to sense contact of the fifth wheel hitch plate  20  with a contact surface on an underside of the towed trailer  17  may be utilized in conjunction with or as an alternative to the sensor assembly  25 . The tilt sensor assembly  25  and the lock sensor assembly  27  are described in U.S. Pat. Nos. 5,861,802; 6,285,278; and 6,452,485 which are incorporated herein by reference in their entirety. The sensor assemblies  24 ,  25 ,  27  are coupled to the output device  26  by a multi-conductor cable  28 . In one embodiment, the non-contact kingpin proximity sensor  24  includes an inductive-type sensor, however, other proximity sensors may be utilized, including Hall-effect type sensors, and the like, as discussed below. 
     In the illustrated example, the sensor assembly  24  is mounted to the hitch plate  20  near a throat  30  formed in the hitch plate  20 , into which a trailer kingpin  15  is positioned and locked.  FIG.  4    provides an upside-down or inverted side view in partial cross section illustrating the location of the trailer kingpin  15  when properly disposed within the throat  30  of the hitch plate  20 , which includes sensing that the kingpin  15  is fully inserted into the throat of the hitch plate  20  and that the height of the head portion of the kingpin  15  is properly positioned with respect to the relative height location of the hitch plate  20 . In the illustrated example, the sensor assembly  24  outputs a detection signal when the kingpin  15  is disposed within the throat  30 . The calibration of the sensor assembly  24  prevents it from indicating that the kingpin  15  is present when a misaligned coupling occurs, which prevents the locking mechanism  22  from securing the kingpin  15  to the hitch plate assembly  14  (i.e., the trailer  17  to the truck  12 ), or further from providing “false-positives” or untrue readings of a proper coupling, as discussed below. The locking mechanism  22  of the hitch plate assembly  14  is biased by a compression spring to automatically lock-in and secure the trailer kingpin  15  as soon as the trailer kingpin  15  enters the hitch throat  30 . Those of ordinary skill in the art will appreciate that the present invention may be used in connection with any type of locking mechanism. It should further be noted that the present invention may be applied to tractor hitch assemblies having other constructions and is not limited to particular mounting locations as shown for the embodiments of the sensor assembly  24  described herein. 
       FIG.  5    illustrates an exemplary output device  26 . A multiple conductor cable  28  couples the sensor assembly  24  to the output device  26 . The internal components (i.e., the control circuitry) of the output device  26  are further shown and described in U.S. Pat. No. 6,285,278, which is incorporated by reference herein in its entirety. The output device  26  includes a display panel  34  for providing coupling status information to the driver/operator of the tractor or truck  12 . It is noted that the output device  26  may also or alternatively include indicator lamps/lights (not shown) mounted on or proximate to the fifth wheel hitch plate  20 , and/or may include electronic messaging communicated to a computerized autonomous algorithm by CANbus (Control Area Network) or other electronic communication arrangements. In a preferred embodiment, the display panel  34  includes an “unlocked” icon  36 , a “locked” icon  38 , a “fifth wheel” icon  40  and seven-segment display  42 . In the embodiment, the display  42  provides an error code indicating possible sources of a coupling malfunction, again as further described in U.S. Pat. No. 6,285,278. Preferably, a red light diode (LED) is provided behind the “unlocked” icon  36 . Further, a yellow, a red, and green LED are provided behind the “fifth wheel” icon  40  and a green LED is provided behind the “lock” icon  38 . One of ordinary skill in the art will appreciate that the individual LEDs could be replaced by an LED array capable of providing multiple colors. While output device  26  as shown only indicates visual indicators, one of ordinary skill in the art will readily appreciate that and audio output may be provided. For example, by adding a speaker and appropriate voice processing circuitry, the output device  26  may provide voice output to instruct a driver as to possible causes of a coupling malfunction. Additionally, a warning buzzer may be activated in addition to, or as an alternative, providing an unlocked icon  36 . 
     In a first embodiment, the sensor assembly  24  ( FIGS.  6 - 9   ) includes a bridge circuit arrangement  50  that includes a housing  52  configured to at least partially extend about the kingpin  15  when the kingpin  15  is positioned within the throat  30  of the hitch plate  20 . In the illustrated example, the housing  52  ( FIG.  9   ) is further configured to house the sensor assembly  24  that includes a plurality of magnets and a plurality of Hall-effect sensors in series with a circuit member as described below. Specifically, the sensor assembly  24  may include one or more magnets  56  including a first magnet  58 , a second magnet  60 , a third magnet  62  and a fourth magnet  64 , and a sensor such as a Hall-effect sensor  68 , each interspaced and sandwiched within a circuit member  70 . In the illustrated example, the first magnet  58  is positioned within a first side portion  76  of the circuit member  70 , the second magnet  60  is positioned within a forward portion  78  of the circuit member  70 , the third magnet  62  is positioned within a second side portion  80  of the circuit member  70 , and the fourth magnet  64  is positioned proximate a first end  82  of the circuit member  70  such that the fourth magnet  64  is located proximate a first side  85  of the throat  30  of the hitch plate  20 . The magnetic flux created by each of the magnets  56  may be controllable by an operator, as described below. 
     The Hall-effect sensor  68  is located proximate a second end  86  of the circuit member  70  such that the Hall-effect sensor  68  is located proximate a second side  88  of the throat  30  of the hitch plate  20 . It is noted that the magnetic circuit member  70  may be tapered on one or both sides of the magnetic circuit element  70  proximate the Hall-effect sensor(s)  68  to funnel the associated magnetic flux therethrough. While a Hall-effect sensor is shown within the described example, other non-contact sensor arrangements may also be utilized. 
     The circuit member  70  may comprise a highly magnetically permeable material that has a relative magnetic permeability preferably of within a range of between 30,000 and about 100,000, and more preferably within a range of between 50,000 and 100,000, where the relative magnetic permeability is the ratio of the magnetic permeability of the material relative to the permeability of free space. The circuit member  70  may also comprise about 99.95% pure iron particles. The circuit member  70  may further comprise about 80% Ni and about 20% Fe (a.k.a. permalloy), and/or a packed iron powder of high purity (e.g., 95% or greater). 
     As described above, the sensor assembly  24  may include the analog Hall-effect sensor  68  with an integrated circuit, the biasing magnets  56  each having a magnetic axis  90  and producing a magnetic flux  92 , and a threshold adjustment and a switching circuit  94  ( FIG.  10   ). The Hall-effect sensor  68  is sensitive to magnetic flux in a direction perpendicular to the larger dimension thereof. As best illustrated in  FIG.  9   , the biasing magnets  56  provide a base or zero level flux  96  when the kingpin  15  is not properly located within the throat  30 . The strength of the bias magnets  56  and the dynamic range of the Hall-effect device within the sensor  68  determine the effective range of the sensor  68 . As illustrated in  FIG.  11   , with the kingpin  15  moved in a direction as illustrated and represented by directional arrow  98  and positioned proximate the sensor assembly  68 , the flux  96  of the magnets  56  as read by the Hall-effect sensor  68  is greater in strength due to the proximity of the ferromagnetic material comprising the kingpin  15 . A positive signal is then generated indicating proper location of the kingpin  15  within the throat  30  of the hitch plate  20 . As illustrated in  FIG.  12   , a foreign material, such as grease, water, ice, and the like containing shavings or particles of a ferromagnetic material, commonly referred to as swarf, does not provide an adequate amount of flux  96 , per proper calibration of the adjustment and switching circuit  94 , in order to indicate a positive and proper location of the kingpin  15  within the throat  30 . 
     The schematic view of the sensor assembly  24  as illustrated in  FIG.  10    includes a power supply  100  and a ground  102  each coupled to the Hall effect sensor  68 , and the switching circuit  94  configured to supply power to the Hall effect sensor  68 . In the illustrated example, the switching circuit  94  includes a voltage regulator  104  configured to supply a constant dc voltage to the Hall effect sensing element, and other components to refine the power produced, or protect the remaining elements of the switching circuit  94 . It is noted that most vehicles provide/produce approximately 12 volts as a power input and the switch circuit  94  regulates the power as supplied to the Hall effect sensor to the range of 3.3-5 volts. The illustrated switching circuit  94  is also configured to protect for overvoltage and possible reverse voltage, i.e., improper incoming power connection, although alternatively configured circuits may be utilized. 
     The reference numeral  24   a  ( FIG.  13   ) generally designates another embodiment of the sensor assembly. Since the sensor assembly  24   a  is similar to the previously described sensor assembly  24 , similar parts appearing in  FIGS.  9 - 12    and  FIG.  13    respectively, are represented by the same, corresponding reference numeral, except for the suffix “a” in the numerals of the latter. In the illustrated example, the sensor assembly  24   a  includes a first Hall-effect sensor  150 , a second Hall-effect sensor  152 , first, second and third biasing magnets  154 ,  156 ,  158  each having a magnetic axes  90   a  and creating a magnetic flux  92   a.  In the illustrated example, the first side portion  76   a  of the circuit member  70   a  includes a first branch  158  and a second branch  160  while the second side portion  80   a  of the circuit member  70   a  includes a first branch  162  and a second branch  164 . The circuit member  70   a  and the overall circuit assembly  54   a  are configured such that the first Hall-effect sensor  150 , the first bias magnet  154 , the second bias magnet  156 , the first branch  158  of the first side portion  76   a  of the circuit member  70   a  and the first branch  162  of the second side portion  80   a  of the circuit member  70   a  cooperate to form a first circuit adapted to sense the proper positioning of the kingpin trailer (not shown) within the throat  30   a  similar to as discussed above with respect to the sensor assembly  24 , and where the second Hall-effect sensor  152 , the first bias magnet  154 , the third bias magnet  158 , the second branch  160  of the first side portion  76   a  of the circuit member  70   a  and the second branch  164  of the second side portion  80   a  of the circuit member  70   a  form a second circuit configured to sense the proper positioning of a second element relative to a given ground, such as the fifth wheel hitch plate or mounting structure thereof. The second circuit arrangement may be configured to sense the proper positioning of elements such as other primary or locking arrangements either associated with the locking of the kingpin within the throat of the fifth wheel, secondary locking arrangements, landing gear, suspension arrangements or components, and the like. 
     The reference numeral  24   b  ( FIG.  14   ) generally designates another embodiment of the sensor assembly. Since the sensor assembly  24   b  is similar to the previously described sensor assembly  24 , similar parts appearing in  FIGS.  9 - 12    and  FIG.  14   , respectively, are represented by the same, corresponding reference numeral, except for the suffix “b” in the numerals of the latter. In the illustrated example, the sensor assembly  24   b  includes a circuit member  70   b  having a general U-shaped or bridge configuration, including a first side portion  170 , a second side portion  172  and a forward portion  174 . In the illustrated example, the sensor assembly  24   b  includes a plurality of Hall-effect sensors including a first Hall-effect sensor  176 , a second Hall-effect sensor  178 , a third Hall-effect sensor  180  and a fourth Hall-effect sensor  182  interspaced within the second side portion  172  of the circuit member  70   b,  and a plurality of bias magnets, including a first bias magnet  184 , a second bias magnet  186 , a third bias magnet  188  and a fourth bias magnet  190  interspaced within the first side portion  170  of the circuit member  70   b,  and positioned such that the first, second, third and fourth bias magnets  184 ,  186 ,  188 ,  190  are spaced across from the first, second, third and fourth Hall-effect type sensors  176 ,  178 ,  180 ,  182 , respectively. While the illustrated example includes four Hall-effect type sensors  176 ,  178 ,  180 ,  182  and four bias magnets  184 ,  186 ,  188 ,  190 , other pluralities of the Hall-effect sensors and/or bias magnets may be utilized, including less than or more than four. Further, although the bias magnets  184 ,  186 ,  188 ,  190  are illustrated as being positioned directly across from corresponding Hall-effect type sensors  176 ,  178 ,  180 ,  182 , the bias magnets  184 ,  186 ,  188 ,  190  may be misaligned from the corresponding sensors  176 ,  178 ,  180 ,  182 . It is still further noted that the number of magnets  182 ,  186 ,  188 ,  190  do not necessarily need to correspond with the number of sensors  176 ,  178 ,  180 ,  182 . In use, the kingpin  15   b,  or other element may be moved in a direction  192  relative to the sensor assembly  24   b,  whereby the sensors may be utilized to sense the magnetic flux  92   b  as it passes through the kingpin  15   b  while the kingpin  15   b  is in motion, such that the relative location and motion of the kingpin  15   b  can be sensed. 
     The reference numeral  24   c  ( FIG.  15   ) generally designates another embodiment of the sensor assembly. Since the sensor assembly  24   c  is similar to the previously described sensor assembly  24 , similar parts appearing in  FIGS.  9 - 12    and  FIGS.  15 - 17   , respectively, are represented the same, corresponding reference numeral, except for the suffix “c” in the numerals of the latter. In the illustrated example, the sensor assembly  24   c  includes a first bias magnet  200 , a second bias magnet  202 , a Hall-effect type sensor  68   c,  and a circuit member  70   c.  As illustrated in  FIG.  16   , with the kingpin  15   c  moved in a direction as illustrated in or represented by directional arrow  98   c  and positioned proximate the sensor assembly  24   c,  the flux  96  of the magnets  56   c  and  200  as read by the Hall-effect sensor  68   c  is greater in strength due to the proximity of the ferromagnetic material comprising the kingpin  15   c.  A positive signal is then generated indicating proper location of the kingpin  15   c  within the throat  30   c  of the hitch plate. As illustrated in  FIG.  17   , a foreign material, commonly referred to as swarf, does not provide an adequate amount of flux  96   c,  per proper calibration of the adjustment and switching circuit  94   c,  in order to indicate a positive and proper location of the kingpin  15   c  within the throat  30   c.    
     In the illustrated example, the second bias magnet  202  is similar to the previously described bias magnets  58 ,  60 ,  64  and is provided proximate to the end  82   c  of the circuit member  70   c,  while the Hall-effect sensor  68   c  is provided proximate to the end  86   c  of the circuit member  70   c.  The first bias magnet  200  may include a magnet arrangement providing a magnetic flux that is controllable by an operator or controller. In the illustrated example, the first bias magnet  200  comprises a coil or solenoid-type magnet that extends about the forward portion  78   c  of the circuit member  70   c.  The coil-type magnet  200  allows a user or controller, such as a controller associate with an autonomous vehicle control arrangement, to control the amount and/or frequency of current, particularly an AC current, and change the strength of the magnetic field as provided thereby, thereby allowing fine tuning of the overall magnetic frequency to avoid false positives caused by swarf located within the throat  30   c  and the air gap of the electronic sensor system  10 . It is noted that the relative permeability of the various elements within the system, such as the kingpin  15   c  and any potential contaminating swarf material is frequency dependent, such that controlling the frequency of the coil magnet  200  may allow the user to tune the sensor assembly  24   c  to sense only the permalloy material of the circuit member  70   a  and the material of the kingpin  15   c,  thereby reducing the likelihood of false-positives. Still further, the coil magnet  200  may be configured such that an operator or controller may pass a relatively large current in alternating directions, such as the normal operating forward direction  204  and a reversed direction  206 , thereby minimizing the effect of the swarf on the overall sensor reading from the Hall-effect type sensor  68   c.  Currents generated by the coil magnet  200  may also be utilized to force contaminants, such as metal debris, from within the overall swarf material or force the swarf material from either within or to a different position within the throat  30   c,  thereby minimizing the effects of the swarf on the sensor  68   c.  Still further, the controllability of the coil magnet  200  would allow a controller or user to activate the coil magnet  200  only during coupling and/or uncoupling of the kingpin with the associated fifth wheel hitch plate, thereby reducing or eliminating the magnetic flux and attraction force as associated therewith generated by the coil magnet  200 , and as a result reducing the effects of contamination and swarf buildup caused by the magnetic flux during general vehicle operations. 
     The schematic view of an embodiment of an electronic circuit of the sensor assembly  24   c  is illustrated in  FIG.  18   , where the circuit  24   c  is configured to control varying levels of electrical current as an input into the first bias magnet  200  which may include a coil configured to induce a magnetic flux into the circuit member  70   c.  The power supply circuit as previously described supports the operation of the Hall effect sensor  68   c.  An output signal from the Hall effector sensor  68   c  may be utilized as input to a microprocessor  120  and logically used for determining the presence of the kingpin  15   c.  The microprocessor  120  is algorithmically configured to drive several outputs, including DIO1-D1O4  122 ,  124 ,  126 ,  128 , respectively. While four outputs  122 ,  124 ,  126 ,  128  are included in the illustrated example, it is noted that more or fewer outputs may be provided, as determined by the desired flux levels. In operation, powering an output  122 - 128  drives a current which is determined by the magnitude of resistance R1 through R4 130 ,  132 ,  134 ,  136  in each output circuit, respectively. The differing levels of current produces the desired levels of magnetic flux in the magnetic circuit. Sampling over different fluxes may be utilized to significantly improve the detection of the kingpin, or assist in discriminating between kingpin and contaminant swarf material. 
       FIG.  19    illustrates an alternative embodiment of an electronic circuit of the sensor assembly  24   d  where circuit  24   d  is configured to provide different frequencies of electric current to the first bias magnet or coil  200   d  that is used to induce magnetic flux into the circuit member  70   d.  In the illustrated example, changing the frequency of the electric current also changes the flux in the circuit member  70   d  in a similar manner. The circuit member  70   d  uses the same power supply circuit previously described for powering the Hall effect sensor  68   d.  A sensor output signal is supplied as an input to the control logic in the microprocessor  120   d  which is configured to use the sensor output signal as needed to detect the presence of the kingpin  15   d.  The microprocessor  120   d  also controls the direction of electric current by controlling a plurality of transistor switches Q1-Q4  240 ,  242 ,  244 ,  246 , respectively, that channel electric current into, and out of the coil  200   d  which induces flux into the circuit member  70   d.  To produce current in one direction and therefore magnetic flux in one direction in the circuit member  70   d  the microprocessor  120   d  controls the digital outputs D1O1-D1O4  122   d,    124   d,    126   d,    128   d,  respectively. In operation, when the microprocessor  120   d  activates DIO1  122   d  and DIO4  128   d  and does not activate D1O2  124   d  and D1O3  126   d  electric current flows into the coil  200   d,  through Q1  240  as controlled by DIO1  122   d,  from the upper left in the schematic diagram of  FIG.  19    and out of the coil  200   d  to ground  250 , through Q4  246  as controlled by DIO4  128   d.  This direction of current flow produces a flux in the circuit member  70   d  in one direction. To activate current flow in the opposite direction and produce magnetic flux in the circuit member  70   d  which is opposite to the first direction as described above, the microprocessor  120   d  deactivates DIO1  122   d  and DIO4  128   d  and activates DIO2  124   d  thereby allowing current to flow through Q2  242  into the coil  200   d  in an opposite direction and DIO3  126   d  thereby allowing current to flow out of coil  200  and to ground  250  through Q3  244 . By controlling the rate of the switching between these two states the frequency of the current, and the induced magnetic flux in the circuit member  70   d  may be controlled. This switching control can be done at several different frequencies thereby allowing the Hall effect sensor  68   d  to measure the output at the same time. It is noted that the different materials, namely the kingpin  15   d  and the contaminant swarf material have frequency dependent permeabilities, such that the desired switch control provides an improved ability to distinguish between the kingpin  15   d  and any confusing or unwanted output signals due to the contaminant swarf material. 
     In the foregoing description, it will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed herein. Such modifications are to be considered as included in the following claims, unless these claims by their language expressly state otherwise.