Abstract:
A method for calibrating a proportional solenoid valve used in the propulsion system of a windrower, wherein a programmable control module in connection with a valve and a sensor is programmed as part of an automatic calibration routine for directing test control signals to the valve for causing a predetermined displacement of the hydraulic cylinder, the test control signals having values which vary based on the actual displacement of the hydraulic cylinder as compared with a predetermined value of displacement, and operating the hydraulic cylinder using the test control signal that causes the predetermined displacement of the element. The predetermined displacements correspond to the crack points, or the electrical signal levels at which two ports of interest are just beginning to open to one another from a closed position. Of particular interest are the crack points from the supply pressure port to each of the work ports and from the tank port to each of the work ports.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 60/777,180, filed Feb. 27, 2006. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to equipment calibration and, more particularly, to a method embodied in a computer program for calibration of a valve, more particularly to calibration of a proportional solenoid valve, and even more particularly to calibration of a proportional solenoid valve used in the propulsion system of an agricultural windrower. 
       BACKGROUND OF THE INVENTION 
       [0003]    U.S. Pat. No. 6,901,729, is incorporated herein by reference in its entirety. This patent describes a windrower. While other embodiments are possible, it is this general type of windrower that provides the best example of the type of system with which the apparatus and method of the instant invention can/should be used. U.S. Provisional Application No. 60/777,180, filed Feb. 27, 2006, is also incorporated herein by reference in its entirety. 
         [0004]    In any modern windrower, and much other similar equipment, proportional solenoid controlled valves, activated by electrical currents, are used to control hydraulic devices such as cylinders in the actuation of various systems including the propulsion system. Associated with these valves is a range of current values that causes movement of a movable element of the valve such as a spool or barrel, without creating a path for hydraulic fluid flow between ports. The current value required to move the valve sufficiently to allow fluid communication between ports is referred to as an offset value. An offset of particular interest is the input current required to move the valve to a point in which hydraulic fluid first begins to flow. 
         [0005]    It is important to efficient and effective operation of the system to calibrate the valve based on the offset values required to directly activate a proportional valve using electrical current. These offset values can determine the “crack” points between various ports. The “crack” points are the electrical signal levels at which two ports of interest are just beginning to open to one another from a closed position. Of particular interest are the crack points from the supply pressure port to each of the work ports and from the tank port to each of the work ports. 
         [0006]    Therefore, it would be desirable to have a method which enables calibration of a valve based on the electrical current offset required to determine the crack points, for instance, those from the supply port to each of the working ports and from the tank port to each of the working ports. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    What is disclosed is an apparatus and method which enables calibration of a proportional solenoid valve activated by electrical current, by determining the crack points from the supply port to the working ports and from the tank port to each of the working ports by automatically deriving the electrical current offsets associated with these crack points. 
         [0008]    According to a preferred aspect of the invention, the method utilizes a programmable control module in connection with at least one proportional solenoid valve and a sensor for detection of hydraulic cylinder displacement. The displacement of the moveable element of the hydraulic cylinder is variably controllable as a function of the electrical current signals. The electrical current signals are varied based on an actual displacement of the moveable element of the hydraulic cylinder as compared to a predetermined displacement corresponding to the initial electrical current signal. The current value associated with the offsets can be found by applying levels of input current to the valve and monitoring the hydraulic cylinder for initiation of movement as an indication of fluid flow. 
         [0009]    A control module is programmed as part of an automatic calibration routine for directing control signals to the signal controlled device and receiving sensor inputs representative of an actual displacement of the hydraulic cylinders. The solenoid controlling the valve receives test control signals having values which will vary based the actual displacement of the hydraulic cylinder as compared to a predetermined displacement. 
         [0010]    According to a preferred aspect of the invention, the signals comprise electrical current values within a range anticipated to encompass the current values required for the displacement of the hydraulic cylinder through its range of displacements. Additionally the sensor provides information representative of displacement of the hydraulic cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    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: 
           [0012]      FIG. 1  is a side elevational view of a crop harvesting machine of the type with which the invention may be used; 
           [0013]      FIG. 2  includes a diagram, schematic and a representative relationship between flow rate and input current for a valve of the type with which the invention may be used; 
           [0014]      FIG. 3  is a top level block diagram including the interconnections of the invention; 
           [0015]      FIG. 4  is a high level flow diagram of steps of a preferred embodiment of a computer program of the invention; 
           [0016]      FIG. 5  is another high-level flow diagram of steps of a preferred embodiment of a computer program of the invention; 
           [0017]      FIG. 6  is another high-level flow diagram of steps of a preferred embodiment of a computer program of the invention; 
           [0018]      FIG. 7  is another high-level flow diagram of steps of a preferred embodiment of a computer program of the invention; 
           [0019]      FIG. 8  is a written listing of steps of the preferred program of the invention; 
           [0020]      FIG. 9  is a written listing of still further steps of the preferred program of the invention; and 
           [0021]      FIG. 10  is a written listing of still further steps of the preferred program of the invention; 
           [0022]      FIG. 11  is a written listing of still further steps of the preferred program of the invention; 
           [0023]      FIG. 12  is a written listing of still further steps of the preferred program of the invention; 
           [0024]      FIG. 13  is a written listing of still further steps of the preferred program of the invention; 
           [0025]      FIG. 14  is a written listing of still further steps of the preferred program of the invention; 
           [0026]      FIG. 15  is a written listing of still further steps of the preferred program of the invention; 
           [0027]      FIG. 16  is a written listing of still further steps of the preferred program of the invention; 
           [0028]      FIG. 17  is a written listing of still further steps of the preferred program of the invention; 
           [0029]      FIG. 18  is a written listing of still further steps of the preferred program of the invention; 
           [0030]      FIG. 19  is a written listing of still further steps of the preferred program of the invention; 
           [0031]      FIG. 20  is a written listing of still further steps of the preferred program of the invention; 
           [0032]      FIG. 21  is a written listing of still further steps of the preferred program of the invention; 
           [0033]      FIG. 22  is a written listing of still further steps of the preferred program of the invention; 
           [0034]      FIG. 23  is a written listing of still further steps of the preferred program of the invention; 
           [0035]      FIG. 24  is a written listing of still further steps of the preferred program of the invention; 
           [0036]      FIG. 25  is a written listing of still further steps of the preferred program of the invention; 
           [0037]      FIG. 26  is a written listing of still further steps of the preferred program of the invention; 
           [0038]      FIG. 27  is a written listing of still further steps of the preferred program of the invention; 
           [0039]      FIG. 28  is a written listing of still further steps of the preferred program of the invention; 
           [0040]      FIG. 29  is a written listing of still further steps of the preferred program of the invention; 
           [0041]      FIG. 30  is a written listing of still further steps of the preferred program of the invention; 
           [0042]      FIG. 31  is a written listing of still further steps of the preferred program of the invention; 
           [0043]      FIG. 32  is a written listing of still further steps of the preferred program of the invention; 
           [0044]      FIG. 33  is a written listing of still further steps of the preferred program of the invention; 
           [0045]      FIG. 34  is a written listing of still further steps of the preferred program of the invention; 
           [0046]      FIG. 35  is a written listing of still further steps of the preferred program of the invention; 
           [0047]      FIG. 36  is a written listing of still further steps of the preferred program of the invention; 
           [0048]      FIG. 37  is a written listing of still further steps of the preferred program of the invention; 
           [0049]      FIG. 38  is a written listing of still further steps of the preferred program of the invention; and 
           [0050]      FIG. 39  is a written listing of still further steps of the preferred program of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0051]    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” is used as a matter of mere convenience, and is 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. 
         [0052]      FIG. 1  shows the present invention utilized in connection with a self-propelled windrower  10 ; 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. 
         [0053]    In the illustrated embodiment, the self-propelled windrower  10  comprises a tractor  12  and a header  14  attached to the front end of a frame  18  or chassis of the tractor  12 .  FIG. 3  shows a top level block diagram  30  of the interconnections of exemplary valve apparatus that can be calibrated using the method embodied in the invention. The method of the present invention describes a routine programmed in a control module  32  that calibrates the input current offsets of a proportional solenoid valve controlled hydraulic actuator as represented by hydraulic actuator  20  which is a common hydraulic cylinder. Application of the input current offsets to a solenoid  24 ,  26  causes movement in the valve to the point at which two ports are just beginning to open to one another. This offset current can be identified by monitoring a motion or displacement of a moveable element  42  of the actuator  20 , which can be, for instance, a piston and rod assembly. A sensor  22  is used to sense cylinder  42  motion and/or position, embodied by motion or displacement of element  42 . The offset values to be sensed can be, but are not necessarily limited to:
       1. The ‘cracking’ of a supply pressure port (P)  34  to each of the work ports 36, 38.   2. The ‘cracking’ of a tank port (T)  40  to each of the work ports  36 ,  38 .       
 
         [0056]    The ‘crack’ points are defined as the electrical signal levels at which two ports  34 ,  36 ,  38 ,  40  of interest are just beginning to open to one another from a closed position. The profile  43  of the ‘crack’ points in relation to hydraulic fluid flow and current applied to solenoid  24 ,  26  is shown in  FIG. 2 . Points iAp, iAt, iBp, and iBt can be defined as crack points. A crack point is detected via motion of actuator  20  which is directly correlated to flow. To calibrate a ‘cracking’ point, a binary divide algorithm is used. 
         [0057]    The binary divide routine uses a set of predetermined parameters. These parameters must be defined before execution of the algorithm. These parameters are:
       1. Upper limit of electrical signal value (i_ul).   2. Lower limit of electrical signal value (i_ll).   3. Nominal value of electrical signal (i_nom).   4. Dwell time  1  (dt 1 ).   5. Dwell time  2  (dt 2 ).   6. A predetermined distance of cylinder motion (dp).   7. Tolerance on predetermined distance of cylinder motion (dp_tol).   8. Value of electrical signal to be held between stages of calibration (i_null).   9. Number of loops through calibration (n_loops). Other variables used in the algorithm are:   10. High signal history value (i_hh).   11. Low signal history value (i_hl).   12. Electrical test signal value (i_test).   13. initial cylinder position (p_i).   14. Final cylinder position (p_f).   15. Cylinder position difference (dp_diff).   16. Loop counter (count).   17. Number of time cylinder moved (num_mv).   18. Number of times cylinder didn&#39;t move (num_nomv).       
 
         [0076]    Noted below is the step by step procedure involved in running a calibration for a single crack point: 
       Initialization of Binary Divide Algorithm: 
       [0000]    
       
         Step 1: Set Electrical test signal to nominal value, i_test=i_nom. 
         Step 2: Set high history value to upper limit of electrical signal value, i_hh=i_ul. 
         Step 3: Set low history value to lower limit of electrical value, i_hl=i_ll. 
         Step 4: Set counters to zero, Count=num_mv=num_nomv=0. 
       
     
       Binary Divide Algorithm: 
       [0000]    
       
         Step 1: Check position of cylinder by averaging sensor value over dt 1 . Set p_i to this value. 
         Step 2: Set hardware to the test value, i_test, and hold for dt 2 . 
         Step 3: While maintaining electrical signal at i_test, check cylinder position by averaging sensor value over dt 1 . Set p_f to this value. Set i_test to i_null. 
         Step 4: Check distance of cylinder motion d by comparing p_i and p_f. 
         Step 5: Did cylinder move?
       If cylinder moved greater than dp, increment num_mv counter. num_mv=num_v+1.   If cylinder moved less than dp, increment num_nomv counter. num_nomv=num_nomv+1.   Increment loop counter, count=count+1.   If loop counter (count) is greater than limit (n_loops), prepare to exit algorithm.   If either num_mv or num_nomv is equal to zero (cylinder either always moved or never moved),   
     
       
     
         [0091]    Calibration Failed.
       Otherwise record and/or return value of i_test and exit algorithm.       
 
         [0093]    Calibration Complete.
   Step 6: Determine new value of i_test.
       If distance of cylinder motion greater than dp, set next electrical test signal value to: i_test=i_test+(i_hh−i_test)/2.   If distance of cylinder motion greater than dp, set next electrical test signal value to: i_test=i_test−(i_test−i_hl)/2.   
       Step 7: Check to see if new i_test values are out of bounds.
       If i_test&gt;i_ul or i_test&lt;i_ll, then set warning flag and exit calibration.   
       
 
         [0099]    Calibration Failed.
   Step 8: Return to Step 2.   
 
         [0101]    This algorithm is run for each of the defined calibration points. For example the crack points iAp, iAt, iBp, and iBt shown in  FIG. 3 , the binary divide routine would be run a total of four times. Each of the values 1-8 noted above would have to be redefined for each of the four runs. For the crack to tank calibrations, an external force would have to be applied to the cylinder to force oil flow from the hydraulic cylinder through the valve. One way of doing this is to use a spring centered cylinder and set the cylinder to a position away from the spring centered position at the beginning of the test. 
         [0102]    Referring also to  FIGS. 4-7 , a flow diagram  80  illustrating steps of a method of the instant invention for determining the offset values for control of a proportional solenoid valve operable for controlling movement of element  42  of hydraulic cylinder  20  is shown. The steps of flow diagram  80  are preferably programmed in, and executable by, control module  32  at appropriate times, such as, but not limited to, when changes in the hydraulic system are effected. The calibration routine will be initiated and automatically run in such situations. As shown in  FIG. 4 , block  82  initiates an offset calibration routine. The variables referenced above are initialized at block  82 . At block  84  a current input i_test is applied for a specified duration dt 2 . The actual responsive movement d of hydraulic cylinder element  42  is computed at block  86  as the final position p_f of cylinder  42  minus the initial position p_i of cylinder  42 . 
         [0103]    Following bubble A to  FIG. 5  module  32  checks for cylinder  42  movement at block  88 . Actual displacement d is compared to a predetermined displacement expected dp in response to the initial input i_test in the step shown in decision blocks  100 ,  102 . If actual displacement d of cylinder  42  exceeds predetermined displacement expected dp in response to the initial input i_test, a counter indicating cylinder element  42  movement, num_mv is incremented at block  104 . If actual displacement d of cylinder  42  is less than predetermined displacement expected dp in response to the initial input i_test, a counter indicating a lack of cylinder element  42  movement, num_nomv is incremented at block  106 . 
         [0104]    Following bubble B, a loop counter count is incremented at block  108  as shown in  FIG. 6 . Count is compared to a predetermined number of times n_loops as shown at block  110 . If count has reached n_loops, module  32  compares counters num_mv and num_nomv to zero at decision block  112 . If either num_mv or num_nomv are zero, cylinder  42  either moved for every value of i_test or for no value of i_test. Module  32  reports a calibration failure. If num_mv and num_nomv are nonzero, calibration is complete and the value of i_test is noted or stored by module  32 . If count has not reached n_loops, a new value of i_test is calculated by following bubble C to  FIG. 7  which represents additional steps of module  32 . 
         [0105]    In  FIG. 7  a new value of i_test is calculated as shown at block  114 . Decision block  116  compares actual displacement d to predetermined displacement dp. If actual displacement d is less than predetermined displacement dp, i_test is calculated to be a value half way between a previously set high history i_hh value of i_test according to a binary divide algorithm as indicated in block  118 . If actual displacement d is not less than predetermined displacement dp, i_test is calculated to be a value half way between a previously set low history i_hl value of i_test according to the binary divide algorithm as indicated in block  120 . The high history i_hh is initialized to the current upper limit, and updated with the value i_test when actual displacement d is greater than dp. The low history i_hl is initialized to the current lower limit, and updated with the value i_test when actual displacement d is less than dp. Once the new i_test is calculated, its value is checked against the input current upper limit and lower limit. If the new i_test is outside these limits, the calibration fails. If the new i_test is within these limits, module  32  follows bubble D to repeat application of i_test at block  84  of  FIG. 4  with the new i_test. 
         [0106]    As a result of execution of the calibration routine of the instant invention, registers of control module  32  will contain information representative of input electrical current values required to be directed to solenoid  24 ,  26  to determine current values corresponding to crack points such as iAp, iBp, iAt, and iBt. 
         [0107]    Referring also to  FIGS. 8-39 , 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. 
         [0108]    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.