Abstract:
Apparatus and a method for monitoring the performance of control algorithms, providing a safeing subsystem for a vehicle, particularly an agricultural windrower, for determining when a controlled system such as the propulsion system is no longer tracking a reference input signal sufficiently well. An appropriate action can then be executed, such as outputting a fault signal and/or shutting down the controlled system. An exponentially decaying integrator can be used to monitor the tracking errors.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/699,943, filed Jul. 16, 2005. 
    
    
     TECHNICAL FIELD 
     The present invention relates to vehicular safeing and, more particularly, to apparatus and a method providing a safeing sub-system for an agricultural windrower. 
     BACKGROUND OF THE INVENTION 
     U.S. Provisional Application No. 60/699,943, filed Jul. 16, 2005, is incorporated herein in its entirety by reference. U.S. Pat. No. 6,901,729 is also incorporated herein in its entirety by reference. 
     Vehicles, such as, but not limited to, agricultural windrowers, can utilize control algorithms for translating input signals, for instance, from operator controlled input devices such as a forward-neutral-reverse (FNR) lever, also sometimes referred to as a multi-function-handle (MFH), to systems to be controlled thereby, such as the propulsion driveline. 
     It is therefore desirable to have a capability to monitor the performance of such control algorithms, to ensure that the input commands are being accurately and safely translated into machine operations and movements. It is also desirable to have the capability to determine or sense when a controlled system, such as a propulsion driveline, is no longer tracking a reference input signal sufficiently well. A degradation in the tracking capability can occur for any of several reasons, such as an interrupted or corrupted communication path, such as due to electrical noise and/or damage to a conductive path such as a wiring harness, physical wear or damage, and the like. It is also desirable to have the ability to determine or sense when the controlled system is overshooting or undershooting a system bounds. For instance, a propulsion system may drive a vehicle such as a windrower at a speed greater than a set speed. A system can overshoot (measured system output exceeds the desired output value) or undershoot (measured system output is less than the desired output value), which may indicate that a controller for the output has become unstable. 
     SUMMARY OF THE DISCLOSURE 
     Accordingly, what is disclosed is apparatus and a method for monitoring the performance of control algorithms, providing a safeing subsystem for a vehicle, particularly an agricultural windrower. 
     A purpose of the invention is to sense when a controlled system is no longer tracking a reference input signal sufficiently well. Causes for this can be instability of the control system or a degradation in performance, as illustrated above. The invention can then take an appropriate action, such as outputting a fault signal and/or shutting down the controlled system. 
     According to a preferred aspect of the invention, an exponentially decaying integrator is used to monitor the tracking error. The tracking error is integrated and then multiplied by a time-dependent exponentially decaying function. This gives the algorithm a forgetting type property. That is, the most recent error signals are weighted more heavily than ones further in the past. A threshold can be set on this exponentially decaying integrator to indicate when the controlled system is no longer tracking sufficiently well. When the value of the exponentially decaying integrator exceeds the threshold, appropriate action can be taken to preserve the integrity and safety of the system, such as a fault indicator, an automatic system shutdown, or the like. 
     According to another preferred aspect of the invention, another algorithm for monitoring the controller stability, checks bounds. When the system is overshooting (measured system output exceeds the desired output value) or undershooting (measured system output is less than the desired output value) it is checked to make sure that the measured output value isn&#39;t at a corresponding saturation limit of the hardware, which would be an indication that the controller has become unstable. 
     The algorithms of the invention have applicability for the current control and position control loops of a propulsion system of an agricultural windrower. More particularly, in the design and operation of a windrower, and in all other similar equipment, it is important to consider the safety of the operator. Accordingly, the instant invention monitors the position of the propulsion cylinder (a cylinder and spring assembly) of the propulsion driveline relative to the FNR lever position. If there is a fault, the spring is allowed to take the drive shaft or propulsion rod of the propulsion driveline, to which pintel arms movable for stroking and destroking hydraulic pumps of the driveline are connected, to neutral, and the park brake is allowed to be applied. 
     Also, two potentiometers are affixed or mounted in connection with the Propulsion Cylinder and positioned so that at all times the combined voltage output will equal a predetermined value, here, which is 5 V. If not, it is determined that one of the potentiometers is malfunctioning and requires replacement (dual Hall tracking). The sub-system of the invention uses electrical current error integration, position error integration, and dv/dt thresholding of the FNR and Propulsion Cylinders to identify/evaluate any faults. Additionally, the system can determine if the propulsion cylinder is stuck at either of its extents. 
     The following formulae are preferably used for integration of current and positional errors:
 
propulsion cylinder integrator=∫ e   a(T-t) *(position error) dT , with limits of integration 0 to  t.  
 
electrical current integrator=∫ e   a(T-t) *(current error) dT , with limits of integration 0 to  t.  
 
     The integrals are approximated (using integer math) via the following formula in discrete time: integral (k)=error(k)+[A*integral(k−1)] where, k is the sample time, and 0&lt;A&lt;1=decay rate. 
     According to another aspect of the invention, the control module can be programmed such that the FNR dv/dt monitoring and fault detection only reacts to faults that would cause rapid acceleration, therefore ignoring rapid deceleration commands. The logic of this is that it is not desirable to prevent the machine from decelerating. However, the control module is programmed such that Propulsion Cylinder dv/dt monitoring reacts to acceleration and deceleration. 
     As another aspect of the invention, the control module can be programmed such that if the FNR lever is in forward range, and being moved towards neutral, and if the Propulsion Cylinder is lagging behind the commanded position by more than a predetermined threshold, and the driveline is in high range, then a fault condition is determined, e.g., if the machine is sluggish to respond to an operator deceleration command, then the park brake is automatically applied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The advantages of this invention will be apparent upon consideration of the following detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein: 
         FIG. 1  is a partial side elevational view of a windrower of the type with which the invention may be used, including a header for severing crops from a field, mounted on a front end of the windrower; 
         FIG. 2  is a simplified diagrammatic representation of a propulsion driveline of the windrower incorporating aspects of the instant invention; 
         FIG. 3  is a schematic of circuitry of a multifunction handle of the windrower; 
         FIG. 4  is a schematic of other aspects of circuitry of the propulsion driveline; 
         FIG. 5  is another schematic of circuitry of the propulsion driveline; 
         FIG. 6  is a schematic of aspects of circuitry of the propulsion driveline for the PTO of the windrower; 
         FIG. 7  is a diagram illustrating a control system of the propulsion driveline and fault detection system embodying a preferred method of the instant invention; 
         FIG. 8  is a listing of code of a computer program incorporating steps of a preferred embodiment of the method of the invention; 
         FIG. 9  is a continuation of the listing; 
         FIG. 10  is a continuation of the listing; 
         FIG. 11  is a continuation of the listing; 
         FIG. 13  is a continuation of the listing; 
         FIG. 14  is a continuation of the listing; 
         FIG. 15  is a continuation of the listing; 
         FIG. 16  is a continuation of the listing; 
         FIG. 17  is a continuation of the listing; 
         FIG. 18  is a continuation of the listing; 
         FIG. 19  is a continuation of the listing; 
         FIG. 20  is a continuation of the listing; 
         FIG. 21  is a continuation of the listing; 
         FIG. 22  is a continuation of the listing; 
         FIG. 23  is a continuation of the listing; 
         FIG. 24  is a continuation of the listing; 
         FIG. 25  is a continuation of the listing; 
         FIG. 26  is a continuation of the listing; 
         FIG. 27  is a continuation of the listing; 
         FIG. 28  is a continuation of the listing; 
         FIG. 29  is a continuation of the listing; 
         FIG. 30  is a continuation of the listing; 
         FIG. 31  is a continuation of the listing; 
         FIG. 32  is a continuation of the listing; 
         FIG. 33  is a continuation of the listing; 
         FIG. 34  is a continuation of the listing; 
         FIG. 35  is a continuation of the listing; 
         FIG. 36  is a continuation of the listing; 
         FIG. 37  is a continuation of the listing; 
         FIG. 38  is a continuation of the listing; 
         FIG. 39  is a continuation of the listing; 
         FIG. 40  is a continuation of the listing; and 
         FIG. 41  is a continuation of the listing. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art, and they will not therefore be discussed in significant detail. Also, any reference herein to the terms “left” or “right” are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel. Furthermore, the various components shown or described herein for any specific application of this invention can be varied or altered as anticipated by this invention and the practice of a specific application of any element may already by widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail. Still further, in this description, the terms FNR lever, multi-function handle and MFH referred to the same item, and therefore are interchangeable. 
       FIG. 1  shows a self-propelled windrower  10  incorporating the apparatus and method of the invention; however, it will be appreciated that the principles of the present invention are not limited to a self-propelled windrower, or to any specific type of harvesting machine. 
     In the illustrated embodiment, the self-propelled windrower  10  comprises a tractor  12  and a header  14 , the header  14  being attached to the front end of the frame  16  or chassis of the tractor  12 . The header may be of generally any suitable construction and design, and may include not only crop-harvesting mechanisms, but also crop conditioners such as elongate rolls  15 . Such attachment of the header  14  to the frame  16  is achieved through a pair of lower arms  18  (only the left one being shown, the right being generally the same) pivoted at one end to the frame  16  and at the other end to the header  14 , as well as through a central upper link  20 . 
     One or more cylinders, such as individual lift and flotation cylinders, or a single lift/flotation cylinder, interconnects the lower arm  18  and the frame  16  on each side of the header. 
     Typical features and operation of a system for controlling the lift and flotation functions for a header, such as header  14  depicted herein, are disclosed in U.S. Pat. No. 6,901,729, incorporated herein by reference. 
     Referring also to  FIGS. 2 ,  3 ,  4 ,  5  and  6 , windrower  10  includes a propulsion driveline  22  controllably operable using operator controls for rotatably driving a left wheel  24  and a right wheel  26  for propelling windrower  10  over a ground or other surface. Hydraulic motors (not shown) in connection with each wheel  24  and  26 , respectively, are provided with fluid under pressure by hydraulic pumps  28 , for driving the wheels. The pumps  28  can be differentially controlled for supplying different and varying amounts of pressurized fluid to the hydraulic motors, for effecting desired movements of windrower  10 , including steering movements, as effected by operation of a rotatable and longitudinally movable propulsion rod  30  in connection with pintel arms  32  and  34  movable for controlling displacement of pumps  28  in the well-known manner. Steering commands are inputted to driveline  22  by an operator via an operator control which is a steering wheel  36  disposed in an operator cab  38  of windrower  10 . Steering movements of windrower  10  are effected by rotating respective wheels  24  and  26  at different speeds. Propulsion speed and direction commands are inputted to driveline  22  by an operator via an operator control which is a FNR lever  40  also disposed in cab  38 . 
     FNR lever  40  is configured to operate a suitable sensor or sensors operable for generating varying information or outputs representative of the position of lever  40  when lever  40  is manipulated or moved, including one rotary potentiometer  42  and a neutral switch  44 , each of which is connected to a tractor control module  46  via a suitable conductive path or paths  48 , which can be, for instance, a wire or wires of a wiring harness, an optical path, a wireless path, or the like. Tractor control module  46  can comprise a single module or processor, or multiple modules connected by a controller area network (CAN). Movements of FNR lever  40  in relation to the neutral position will cause potentiometer  42  to output a varying signal representative of the position of lever  40 , which signal comprise voltage. It is desired for this voltage signal to very precisely indicate the position of lever  40 , such that precise control of the forward and rearward movements of windrower  10  can be achieved. 
     Neutral switch  44  is also mounted and configured such that movements of FNR lever  40  into the neutral position, and out of the neutral position, will cause changes in the operating state of switch  44 . Here, forward and rearward movements of FNR lever  40  from a generally straight up neutral position shown, will effect a change of state of switch  44  which will be outputted to control module  46 , which will responsively power up the propulsion driveline, control module  46  controlling the propulsion speed of windrower  10  as a function of the voltage output of the potentiometer  42 . Similarly, rearward movement of FNR lever  40  from the neutral position will effect a change of state of switch  44  outputted to control module  46  to affect operation of the propulsion driveline in the reverse direction, and the voltage output of the potentiometer  42  will be used to control reverse speed. It is also desired that, when lever  40  is moved into the neutral position, the propulsion system be controlled to positively de-stroke or otherwise transition into a non-propelling state over time, such that abrupt stoppage does not occur. 
     Other operator controls include a park brake switch  50  also connected to tractor control module  46  via a conductive path  48 , and via another conductive path  48  to a key switch  52  and a start relay  54  in connection with a starter of engine  22  and with tractor control module  46 . A 2-speed switch  56  is connected to tractor control module  46  via another conductive path  48 , as is a field cruise switch  58 . 
     Tractor control module  46  is in connection with a dual rotary potentiometer  62  via a conductive paths  48 , potentiometer  62  being operable for outputting information representative of the position of a propulsion cylinder  64 . Propulsion cylinder  64  is extendable and retractable by solenoids controlled by tractor control module  46 , based on the voltage outputs of potentiometer  42 , to move propulsion rod  30  longitudinally for changing the stroke of the hydraulic pumps  28  via the angle of the pintel arms  32  and  34 , for effecting propulsion of the windrower. A rotary potentiometer  66  is operable for outputting information representative of the position of pintel arm  32  to module  46  via another conductive path  48 , providing information representative of differential stroking of pumps  28  to effect steering movements. Information representative of speed of respective wheels  24  and  26  is determined by reluctance speed sensors ( FIG. 2 ) and communicated via conductive paths  48  to module  46 . Differences in the speed readings is also indicative of steering movements. 
       FIG. 3  schematically illustrates circuitry  68  of FNR lever  40 . 
       FIG. 4  schematically illustrates aspects of propulsion driveline  22  associated primarily with the operator controls, including potentiometer  42 ; neutral switch  44 ; control module  46 ; park brake switch  50 ; speed switch  56 ; and additionally, a park brake latch relay  70 ; a propulsion enable relay  72 , also sometimes referred to as a propulsion latching relay; and a propulsion interlock relay  74 . Other illustrated elements of propulsion driveline  22  include a brake valve solenoid  76  and a ground speed high solenoid  78 . 
       FIG. 5  schematically illustrates other aspects of propulsion driveline  22 , including aspects of tractor control module  46  in connection with propulsion cylinder position sensors  80  and  82  which incorporate rotary potentiometers  62  ( FIG. 2 ); a pintel arm position sensor  84  incorporating rotary potentiometer  66  (also  FIG. 2 ); left and right ground speed sensors  86  and  88 ; a propulsion forward solenoid  90 ; and a propulsion reverse solenoid  92 . 
       FIG. 6  schematically illustrates circuitry of propulsion driveline  22  for powering a PTO of windrower  10 . Briefly, this portion of the driveline in one embodiment includes a header PTO forward/reverse solenoid  154  (where a header PTO forward solenoid  156  and a header PTO reverse solenoid  158  are not used). In another embodiment (where a header PTO forward/reverse solenoid  154  is not used), a header PTO forward solenoid  156 , and a header PTO reverse solenoid  158  are provided. Each of solenoids  154 ,  156  and  158  is controlled by an electrical signal. In the embodiment where the header PTO forward/reverse solenoid  154  is used, the electrical current value of which can be very precisely controllably varied through a range between zero and a greater amount, such as 65 milliamps (ma) or greater. The driveline is operated by programmable control module  46  connected to header PTO forward/reverse solenoid  154 , or header PTO forward solenoid  156  and reverse solenoid  158 , by suitable conductive paths  162 , which can be, for instance, wires of a wiring harness, depending on which embodiment of the driveline is being utilized. Other pertinent elements of the PTO aspects of driveline  22  include a header PTO switch  170  selectably operable by an operator for selecting a forward or reverse direction of operation of the PTO; in the embodiment where the header PTO forward/reverse solenoid  154  is used, a header speed switch  172  selectably operable by an operator for increasing or decreasing the speed of operation of the header; a header PTO emergency stop switch  174 ; and a seat switch  176 . 
     As noted above, the instant invention utilizes control module  46  to monitor the propulsion command inputted thereto by potentiometer  42  indicative of the position of FNR lever  40 . Essentially, the output of only one of the potentiometers  62  is required for signaling the position of the propulsion cylinder  64 , but two are used (dual Hall tracking) and the voltage outputs are continually summed. If the sum does not equal a predetermined value, here 5 V, it is determined that an error in the voltage signal of one or both of the potentiometers is determined. The output of potentiometer  62  is indicative of the position of propulsion cylinder  64  of the propulsion driveline  22 . The position of propulsion cylinder  64  (and thus the output of potentiometer  62 ) should, if normally operating, correspond to or track the inputted command from potentiometer  42 , modified by a transfer function, with consideration of normal deviations such as due to hysteresis, time lag in executing the propulsion commands, and the like. dv/dt (changing voltage over time) thresholding of the FNR potentiometer is used to identify/evaluate any faults. 
       FIG. 7  includes a diagram  94  illustrating the flow of operator input commands and hardware outputs utilized in error monitoring and fault detection according to the invention. Essentially, reference input commands r (e.g., voltage inputted through the position of FNR lever  40  by potentiometer  42 ) is matched with responsive system/hardware outputs y (e.g., voltages outputted by potentiometers  62 ) to derive tracking errors e by control module  46  (Controller H). Tracking errors e are processed to determine any faults (Fault Detection F). This is preferably done using the following exponentially decaying integrator, also used for integration of current errors:
 
propulsion cylinder integrator=∫ e   a(T-t) *(position error) dT , with limits of integration 0 to  t.  
 
electrical current integrator=∫ e   a(T-t) *(current error) dT , with limits of integration 0 to  t.  
 
     The integrals are approximated (using integer math) via the following formula: integral (k)=error(k)+[A*integral(k−1)] where 0&lt;A&lt;1=decay rate to give the algorithm a forgetting type property wherein the most recent error signals are weighted more heavily than ones further in the past. A predetermined threshold is set on this exponentially decaying integrator to indicate when the controlled system is no longer tracking sufficiently well. When the value of the exponentially decaying integrator exceeds the threshold, appropriate action is taken to preserve the integrity and safety of the system, which can include outputting of a fault signal to the operator, an automatic system shutdown, or the like. 
     Another algorithm for monitoring the controller stability checks bounds. When the system is overshooting (measured system output exceeds the desired output value) or undershooting (measured system output is less than the desired output value) it is checked to make sure that the measured output value isn&#39;t at a corresponding saturation limit of the hardware, which would be an indication that the controller has become unstable. 
     If there is a fault, solenoids A and B ( FIG. 2 ) controlling the valve which directs hydraulic fluid to the chambers of propulsion cylinder  64  are de-energized, to allow the spring associated with 
     Control module  46  can be programmed such that the FNR dv/dt monitoring and fault detection only reacts to faults that would cause rapid acceleration, therefore ignoring rapid deceleration commands. However, control module  46  can be programmed such that Propulsion Cylinder dv/dt monitoring reacts to acceleration and deceleration. 
     Control module  46  can additionally be programmed such that if FNR lever  40  is in a forward range, that is, it is moved in the direction for commanding the windrower to move forward, and is being moved towards neutral, and if the Propulsion Cylinder  64  is lagging behind the commanded position by more than a predetermined threshold, and driveline  22  is in high range, then a fault condition is determined, e.g., if the machine is sluggish to respond to an operator deceleration command, then the park brake is automatically applied. 
     Referring also to  FIGS. 8-41 , lines of code of an actual computer program embodying the above described steps of the method of the invention is disclosed. The notes accompanying the lines of code describe many features of the method of the invention. In the code, the FNR lever is identified as the MFH. Lines  1 - 118  initialize operation. Lines  119 - 248  monitor the exponentially decaying integrators of position and current tracking errors of propulsion cylinder  64  relative to commanded set points, including steps for the disablement of the propulsion system if the set points are exceeded. Lines  250 - 265  calculate the exponentially decaying integrator of absolute cylinder position tracking errors. Lines  266 - 283  calculate the exponentially decaying integrator of absolute valve current tracking errors. 
     Lines  284 - 345  look for rapid transitioning errors (MFH velocity and propulsion cylinder velocity exceeds limit) for both forward and reverse directions. 
     Lines  348 - 379  look at whether propulsion cylinder  64  is stuck at either of its forward and rearward extents. Lines  381 - 402  look for propulsion cylinder position verses MFH position mismatch. 
     Lines  1 - 1200  beginning in  FIG. 16  provide steps, among other things, for calibrating MFH position commands with outputted control currents, for determining the reference values for tracking and set point error determination according to the invention. 
     It will be understood that changes in the details, materials, steps and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the inventions. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.