Abstract:
An electrical circuit for a mobile machine, including an interface coupled between a controller and a plurality of sensors for accurately diagnosing faults in all of the sensor wires and the sensors themselves. This effective resolution reduces the downtime of the mobile machine and operator time by allowing faults to be timely isolated. The interface selectively couples a test signal to each of the sensor conductors, and also selectively couples a responsive returned characteristic signal to the controller, where the returned characteristic signal enables the controller to diagnose each of the plurality of conductors and sensors for faults. The electrical circuit may further include testing circuitry that can specifically determine a location of the determined fault in each of the plurality of conductors or each of the plurality of sensors.

Description:
BACKGROUND 
       [0001]    In many mobile machines, there are provided numerous wire harnesses and sensors. As machine size and complexity increases, the need for high levels of uptime and quick problem resolution becomes more and more valuable. The cost of operating machines may amount to hundreds of dollars per hour, not including operator or technician costs. Agricultural machines, such as combine harvesters are but one example of such mobile machines. 
         [0002]    There are many potential causes of wiring failure. For example, lack of quality control at production, or wear from use or from passing over debris (such as crop material during harvesting operations, for example), poor installation techniques, etc. Any one of these may cause a degradation or failure of the control system. 
         [0003]    Current controllers have some wiring/sensor diagnostic ability. For example, if the signal path to a sensor is broken, the controller may indicate “Error—left sensor voltage below normal”. Other examples of typical failure mode identifiers (FMI) from the SAE J1939-73 specification for defining messages to accomplish diagnostic services are identified below:
       0—Data valid but above normal operation range   1—Data valid but below normal operational range   2—Data erratic, intermittent or incorrect   3—Voltage above normal, or shorted to high source   4—Voltage below normal, or shorted to low source   5—Current above normal or open circuit   6—Current below normal or grounded circuit   7—Mechanical system not responding or out of adjustment   8—Abnormal frequency or pulse width or period   9—Abnormal update rate   10—Abnormal rate of change   11—Failure code not identifiable   12—Bad intelligent device   13—Out of Calibration       
 
         [0018]    While this information is helpful in identifying the type of failure that has occurred, it is far from complete and does not specifically identity where the failure has occurred or other information that will lead to an effective resolution. Accordingly, there is a need for on-board diagnostic abilities which will both quickly and accurately identifies the failure and which is presented to the operator or technician in a way that leads to effective resolution. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a simplified combined schematic and block diagram of a combine illustrating a head controller and controller interface according to one embodiment of the invention; 
           [0020]      FIG. 2  is combined schematic and block diagram of the controller and controller interface according to one embodiment of the invention; 
           [0021]      FIG. 3  is combined schematic and block diagram of the controller and controller interface during normal operation, with sensor signals configured to be routed back to the controller; 
           [0022]      FIG. 4  is combined schematic and block diagram illustrating the interface configured in a testing mode to selectively deliver a test signal to each conductor of each sensor, whereby a generated characteristic signal is returned back to the controller for analysis; 
           [0023]      FIG. 5  is combined schematic and block diagram illustrating the fault analysis circuit configured to perform time domain reflectometry (TDR) on the sensor conductors identified to have a fault to determine an specific location of the fault in the conductor; 
           [0024]      FIG. 6  is an algorithm executed by the controller to test the sensor conductors and the sensors to accurately identify a fault, and the location of the fault; and 
           [0025]      FIG. 7  is a table showing an example of test results generated signals from tests of lines A, B and C on a single sensor. 
       
    
    
     DESCRIPTION 
       [0026]    Referring to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  illustrates, in simplified schematic and block diagram form, a machine (such as an agricultural combine harvester) indicated generally by reference numeral  10  having an attachment  12  (such as a “header”) mounted thereon. Sensors  14  (such as height sensors) are mounted on the attachment  12  and are in electrical communication with a controller interface  18  and a controller  20 . The controller  20  is responsive to signal outputs from the sensors  14  mounted to the attachment  12  and provides suitable electrical control signals to an electrically actuated, hydraulic control system  38 . In this embodiment, the signal outputs from the height sensors  14  are variable in magnitude with respect to changes in height of the header attachment  12  relative to the ground surface  16  to effect raising and lowering of the header attachment  12  with respect to the ground surface  16  or to effect lateral tilt of the header attachment as the combine harvester  10  traverses a field in the direction of arrow  56 . 
         [0027]    While this description and drawing figures reference and depict an agricultural combine harvester and height sensors used to effect raising and lowering of the header attachment, it should be understood that the system and method described herein is suited for any machine having a plurality of sensors configured to sense parameters where it may desirable to determining faults between a controller and the sensors. Accordingly, as used herein, the term “machine” should be understood to include any type of agricultural, industrial, or other machine. Additionally, for purposes of this description, the term “sensor” should be understood to include any type of contact sensor or non-contact sensor that is capable of generating output signals, which may or may not be variable in magnitude depending on what parameters are being sensed. For example, contact sensors may include, but are not limited to, surface contacting pivoting arms coupled to rotational or position sensors for detecting the angular or linear position of the arms. Non-contact sensors may include, but are not limited to ultrasonic or laser sensors. Furthermore, as used herein, the term “signal output” should be understood as meaning or including any signal value or signal characteristic generated by a sensor  14 , including voltage, current, pulse width, etc. as well as digital signals. 
         [0028]    Referring to  FIG. 2 , there is shown a schematic and block diagram of one embodiment of the controller interface  18  and controller  20 . As shown in  FIG. 3 , during normal operation of the machine  10 , sensor signals from sensors  14  are routed back to controller  20  via switches and Muxs. 
         [0029]    During a testing mode, as shown in  FIG. 4 , the interface  18  is configured to generate and selectively couple a test signal to each of the sensor conductors, namely, the wires of the wire harness extending between the controller interface  18  and the plurality of sensors  14 . The test signal, such as a 5V pulse, is communicated, to each of the wires A, B, C of each of the sensors  14  labeled Sensor  1 -n, one at a time, whereby a returned characteristic signal generated by the respective sensor  14  or wiring in response to the test pulse is then selectively routed via one of the other wires back to the controller  20  for diagnostic testing of faults. Many different faults may be detected, including, but not limited to, a “sensor power wire open” which may indicate a poor connection, a “sensor signal wire shorted to the sensor power wire” which may indicate wire damage from a pinch point, and “sensor power and ground wires swapped” which may indicate improper installation technique. By providing for the selective routing of a test signal to each of the wires, whereby the other wires of the respective sensor are used to retrieve/route the returned characteristic signal, each and every sensor wire, as well as each and every sensor, can be analyzed by controller  20  to provide a more accurate and robust diagnostic system allowing operators to better isolate faults, more quickly to reduce down time and costs. 
         [0030]    Referring back to  FIG. 2 , interface  18  is operably connected between controller  20  and each of the sensors  14 . Each of the sensors  14  has an associated power source  22  that can be selectively coupled to line C of the respective sensor via an associated switch. Switch banks S 1 -Sn have associated individually controllable switches controlled by controller  20 , where switch bank S 1  has associated switches S 1 -A, S 1 -B and S 1 -C, while the remaining switch banks have two switches since the grounds are tied together, where switch S 2  has individual switches S 2 -B and S 2 -C, and switch Sn likewise has individually controllable switches Sn-B and Sn-C. Power Switched ground  24  is selectively coupled to line A of each of the sensors  14  by controller  20  by switch S 1 -A, where each of these ground lines are tied together to form a ground bar. This switched power and switched ground enables each to be removed from the sensors during the diagnostic testing of the sensors and sensor lines as will now be described in more detail. 
         [0031]    Associated with each sensor  14  is a TriState Drive Hi/LO generally shown at  26 ,  28  and  30 . Each of the TriState circuits  26 ,  28  and  30  may comprise of a pull-up resistor selectively coupled to power, which may generate, for instance, a 5V pulse that is generated in response to a control signal provided on respective control lines  32 ,  34  and  36  generated by controller  20 . Alternatively, other test signals may be generated by the circuits  26 ,  28  and  30 , such as analog signals, and limitation to a TriState Drive providing a digital pulse and so forth is not to be inferred. Still referring to  FIG. 2 , interface  18  includes a controllable Mux  40 , labeled Mux for C, configured to selectively couple the test signal from TriState Drive HI/LO  26  to each of the lines C of the sensors  14  via the respective switch C of switch bank S 1 -Sn. For instance, the controller  20  can generate a control signal on line  44  to instruct Mux  40  to couple the test signal from TriState Drive HI/LO  26  to the line C of Sensor  2  via switch S 2 -C, or the test signal to the line C of sensor n via switch Sn-C. The controller  20  controls each of the switches of switch banks S 1 -Sn as it controls the output of the Mux  40  to selectively control the coupling of the test signal to each of the lines C, whereby line C is configured as the power line of each sensor  14 . 
         [0032]    Similarly, a Mux for B shown at  42  is configured to selectively provide the test signal from the TriState Drive HI/LO  28  to a selected line B of one of the sensors  14  via the corresponding switch B of switch bank S 1 -Sn. For instance, the controller  20  can instruct the Mux for B via control line  46  to selectively provide the test signal from TriState Drive HI/LO  28  to the line B of Sensor  1  via switch S 1 -B, whereby line B of each sensor  14  is the sensor signal line. It is noted there is not provided a Mux for lines A because the TriState Drive HI/LO  30 , when instructed by controller  20  via control line  36 , provides the test control signal to each commonly tied lines A of sensors  14  via switch S 1 -A. 
         [0033]    Still referring to  FIG. 2 , a Mux for Analog Input is generally shown at  50 . Mux  50  is configured to be controlled by controller  20  via control line  60  so as to receive and route a received characteristic signal from lines A, B and C of the sensors  14  to the controller  20  via line  62 . In addition, the Mux for Analog Input  50  can also selectively receive the test signal generated by the respective TriState Drive HI/LO  26 ,  28  and  30  and route it to the controller  20  via line  62 , such that the controller  20  can compare the generated test signal to the returned characteristic signal to perform signal processing analysis and determined the specifics of any detected faults or irregularities in the conductors/wires and the sensors  14 . Thus, for instance, the controller  20  is configured to send a test signal to each of the signal lines A, B, C for each of the sensors  14  as described above, and monitor the other two lines to which the test signal is not injected, to determine the returned characteristic signal. For instance, this test signal could be injected to the power line C of a sensor, and the characteristic signal can be sensed from other lines A or B of the respective sensor. Likewise, the test signal could be injected into line B, which is the sensor signal of the sensor, and the returned characteristic signal can be sensed from either or both lines A or C of the respective sensor. The test signal can be routed to each of lines A, and the returned characteristic signal can be sensed from either or both lines B or C of the respective sensor. Advantageously, the interface circuitry  18  is configured such that a test signal can be injected into each line of the sensor, and each of the other lines can be sensed such that two returned characteristic signals are generated for each injected signal, allowing the controller  20  to analyze the signal lines, and the sensors, to determine a fault as well as the type of fault and the possible location thereof. In addition to providing test pulses to each of the sensor lines A, B and C, each of the sensor lines A, B and C may be allowed to float by the respective TriState Drive HI/LO, allowing the controller  20  to read each of the lines A, B and C and compare the results from all readings to known and/or expected values. 
         [0034]    Referring now to  FIG. 5 , there is shown an additional testing circuitry at  70  shown to be a time domain reflectometer (TDR) including a signal generator and analyzer configured to test each of the sensor lines A, B, C of sensors  14  via the respective switches of switch banks S 1 -Sn, as shown. Advantageously, the TDR  70  is configured to perform a test on the sensor and/or sensor line that is determined by controller  20  and interface  18  to have a fault or irregularity as previously described in reference to  FIGS. 2-4 . For instance, if controller  20  and interface  18  determine there is fault or irregularity with sensor line B of sensor  2 , controller  20  switches switch S 2 -B and generates a control signal on control line  72  such that TDR analyzer  70  responsively generates a TDR test signal via switch S 2 -B on line B to determine an exact location of a fault between TDR  70  on the respective line B of sensor  2 . For instance, at location X as shown in  FIG. 5 , which is reported on line  74  to controller  20 . Likewise, a fault can be precisionally determined in each of the power lines C and ground lines A of the respective sensors, such as shown at location Y. The TDR circuitry  70  provides, for instance, a very accurate distance of the fault X and Y from the TDR signal source to allow a technician to more quickly isolate that portion of the wire harness that may have a fault. An example of a suitable TDR is a PIC18F25K22-I/ML microchip made by Microchip and available from Digikey. The advantageous application of TDR analysis in a mobile controller, and in conjunction with the fault analysis control and interface as previously described, allows technicians and operators to quickly identify and repair faults in equipment. 
         [0035]    Referring now to  FIG. 6  in view of  FIG. 4 , there is shown an algorithm at  80  illustrating a testing sequence for analyzing the sensors and the sensor wires according to the present invention. 
         [0036]    The algorithm is configured during normal operation of the mobile machine at step  82  such that the controller  20  controls the sensors  14  and reads the sensor values thereof as the mobile machine traverses. When a testing mode is manually selected by a user at step  84 , or automatically enabled by the controller  20 , controller  20  disables power and ground from each of the sensors S 1 -Sn by disabling each switched power  22  and switched ground  24 . 
         [0037]    Next, at step  86 , the controller  20  instructs the TriState Drive HI/LO  26  via control line  32  to provide a test pulse, such as 5V, via Mux for C  40  as configured by control line  44 , and switch S 1 -C as controlled by controller  20 , to line C of sensor  1 . The controller  20  also configures the Mux for B  42  via control line  46  to route a generated characteristic signal from line B of the sensor  1  via switch S 1 -B to the Mux for Analog Input  50 , and configures the Mux for Analog Input  50  via control line  60  to route the characteristic signal to controller  20  via line  62  for analysis. Thereafter, a generated characteristic signal from line A of sensor  1  is routed via switch S 1 -A and the Mux for Analog input  50  to the controller  20  for analysis, as controlled by control line  60 . As previously mentioned, the generated characteristic signals generated from lines B and A are compared to expected voltage levels, waveforms or other predetermined characteristics. 
         [0038]    The following tests are illustrative examples of tests that may be performed on the sensor lines A, B and C of each of the sensors  14 .  FIG. 7  is a table showing an example of the results that are analyzed from performing these tests on a single sensor. These tests are run in response to a user request, or automatically enabled by the controller  20 , wherein the controller  20  runs through a series of initial tests concerning three values A=Sensor Ground circuit, B=Signal Line and C=Power Line. The tests consist of:
       Test  0 : driving power to A (Gnd) and reading B (Sig).   Test  1 : driving power to A (Gnd) and reading C (Pwr).   Test  2 : driving power to B (Sig) and reading A (Gnd).   Test  3 : driving power to B (Sig) and reading C (Pwr).   Test  4 : driving power to C (Pwr) and reading A (Gnd).   Test  5 : driving power to C (Pwr) and reading B (Sig).   Test  6 : while none are driven, reading A (Gnd).   Test  7 : while none are driven, reading B (Sig).   Test  8 : while none are driven, reading C (Pwr).       
 
         [0048]    Additionally, if unique results are not identified by controller  20  that isolate a fault, then the controller  20  will perform additional tests  9 - 14 .
       Test  9 : driving power to A (Gnd) and reading B (Sig) and driving ground to C (Pwr).   Test  10 : driving power to A (Gnd) and reading C (Pwr) and driving ground to B (Sig).   Test  11 : driving power to B (Sig) and reading A (Gnd) and driving ground to C (Pwr).   Test  12 : driving power to B (Sig) and reading C (Pwr) and driving ground to A (Gnd).   Test  13 : driving power to C (Pwr) and reading A (Gnd) and driving ground to B (Sig).   Test  14 : driving power to C (Pwr) and reading B (Sig) and driving ground to A (Gnd).       
 
         [0055]    These additional tests run above tests for one sensor and store the “read” values in an array of structures. When the tests are run for sensors, then this test will be called in a loop for all sensors. A normal Diagnostic Sensor test collects the readings for all sensors first, because while the test is reading the sensors, the controller  20  cannot read the sensors  14 . During the test mode, the controller  20  uses the last known value of the sensors  14  during operation. By taking all of the readings first, the system is able to read the sensors sooner and shorten the diagnostic time. During a normal test, after all readings are taken, a separate function analyzes the readings and reports the results. 
         [0056]    Tests  0 - 8  are used to determine opens and shorts of the plurality of conductors. The Values in each test are in tenths of a volt, i.e. Value 44=4.4V. The voltage is correlated to the status of a conductor, such as an open conductor or a shorted conductor. Tests  9 - 14  are used for potentiometer sensors and are run with caution on the hall effect sensors. The tests are run at intervals and may be, in one example, once per second. 
         [0057]    The following are logic rules for analyzing the Values/results table, although other logic rules may apply in other embodiments:
       1. A range of Values less than 15 are used as valid pull to values for an open conductor.   2. A range of Values greater than 45 are valid numbers for a shorted conductor.       
 
         [0060]    Thereafter, the controller  20  tests line C of Sensor  2  by configuring Mux for C  40  via control line  44  to output the test signal to switch S 2 -C, and configures switch S 2 -C to provide the test signal to line C of Sensor  2 . The controller  20  configures the Mux for B  42  via control line  46  to route the generated characteristic signal from line B of Sensor  2  via Switch S 2 -B to the Mux for Analog Input  50 , and configures the Mux for Analog Input  50  via line  62  to provide the characteristic signal to controller  20  for analysis. Thereafter, the generated characteristic signal from line A of Sensor  2  is routed to via switch S 1 -A to controller  20  by controlling the Mux for Analog Input  50 . This algorithm  80  continues to test line C of each sensor such that the characteristic signals from lines B and A of each sensor are routed to controller  20  for testing. 
         [0061]    At step  88 , the controller  20  tests line B of Sensor  1  by configuring the Mux for B  42  to send a test signal from TriState Drive HI/LO  28  via Switch S 1 -B to line B of the Sensor  1 , and then the generated characteristic signal is routed from line C of Sensor  1  via switch S 1 -C to the Mux to C  40  and the Mux for Analog Input  50  to controller  20  using control lines  44  and  60  for analysis. Thereafter, the controller  20  routes the generated characteristic signal from line A of Sensor  1  via switch S 1 -A to the Mux for Analog Input  50  to the controller  20  for analysis. Thereafter, the controller  20  tests line B of Sensor  2  by controlling the Mux for B  42  and switch S 2 -B to deliver the test signal. The generated characteristic signal from each of lines C and A of Sensor  2  are routed via respective Switches S 2 -C and S 1 -A to controller  20  for analysis as described above. This algorithm  80  continues to test line B of each sensor such that the characteristic signals from lines C and A of each sensor are routed to controller  20  for testing. 
         [0062]    At step  90 , the line A of each sensor  14  is tested. The controller  20  instructs the TriState Drive HI/Lo  30  to generate the test signal, and controls the switch S 1 -A to provide the test signal to line A of each sensor simultaneously as the line A of each sensor is tied together. The controller  20  then routes the generated characteristic signal from line C of Sensor  1  via Switch S 1 -C back to the controller for analysis via Mux for C  40  and Mux for Analog Input  50  as described. The controller  20  then routes the generated characteristic signal from line B of Sensor  1  via Switch S 1 -B and Mux for B  42  and Mux for Analog Input  50  to controller  20  for analysis. Then, controller  20  routes the characteristic signal from line C of Sensor  2  via Switch S 2 -C, then from line B of Sensor  2  via Switch S 2 -B, and so on for each sensor including Sensor Sn. 
         [0063]    At step  92 , controller  20  controls TDR  70  to perform TDR analysis on each of the lines and sensors that are determined to have a fault during any of the steps  84 ,  86 ,  88  and  90  as previously described. Thereafter, the algorithm routes back to normal operation at step  82 , as shown in  FIG. 6 . It is noted that each of the switches of switch banks S 1 -Sn are shown in  FIGS. 2-5  in their normal position for normal operation of the sensors and also for testing of the conductors A, B and C, whereby each switch is individually switched only when the TDR test is performed to select an individual conductor associated with a switch for testing. 
         [0064]    The foregoing description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment of the system, and the general principles and features of the system and methods described herein will be readily apparent to those of skill in the art. Thus, the present invention is not to be limited to the embodiments of the system and methods described above and illustrated in the drawing figures, but is to be accorded the widest scope consistent with the spirit and scope of the appended claims.