Wand-axle zero set

• US 5,941,917 A
• Filed: 08/28/1996
• Issued: 08/24/1999
• Est. Priority Date: 08/31/1995
• Status: Expired due to Fees

• Current Assignee: GAR BAR Corporation
• Original Assignee: GAR BAR Corporation
• Inventors: Barnes, Ronny L., Mathews, H. Wayne
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): DONNELLY, ARTHUR D
• Application Number:
  US08/704,118
• Time in Patent Office: 1,091 Days
• Field of Search: 701/23, 701/41, 701/50, 701/116, 701/205, 180/167, 180/168, 180/169, 180/170, 180/179, 180/401, 172/191, 56/10.2 F
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0227 using mechanical sensing means, e.g. for sensing treated area

Abstract

A farm tractor is automatically guided along a row of stalks to harvest the crop from the stalks. Every 30 ms the average of 10 ms readings of the distance or deviation of the tractor from the row of stalks is calculated. The angles of the guiding wheels are measured. These two are compared. If the wheels are not angled correctly according to this comparison, a correction is made to the steering wheel, which is the manual steering wheel normally used to guide the tractor. For Auto-Track the deviation is averaged for 7/8ths of a second. If this average shows that the tractor is deviating consistently to one side or another the deviation will be corrected according to the controls. The 7/8ths second calculation is repeated every 7/8ths of a second. At any time that the 7/8ths calculation shows that there is a persistent deviation a correction will be made. These corrections will remain as a permanent correction until a subsequent correction changes them. Subsequent corrections may either add to or subtract from the correction. For Smart-Drive every 30 ms a determination is made as to whether the tractor is on the same side of the stalks as it was one second previously. Also, the determination will be made as to whether the tractor is closer to the row of stalks on the same side of the stalks than it was one second earlier. If the tractor is closer to the row of stalks, and on the same side as it was one second earlier, then the guiding wheels are adjusted to bring the tractor back to the row of stalks at a slower correction rate than before.

Claims

1. A method of guiding a land vehicle along a predetermined meandering path, said path having established physical boundaries, and said vehicle having a steerable axle;

said method of guiding including the steps of;

a) aligning the vehicle with respect to a portion of said predetermined path;

b) periodically determining the lateral position of said vehicle with respect to said path;

c) periodically determining the position of said steerable axle and thereby ascertaining a direction of draft with respect to a predetermined physical reference azimuth;

d) periodically adjusting the steering axle responsive to steps b) and c); and

e) periodically adjusting said steerable axle according to said steering corrections;

wherein the method includes the steps of;

f) periodically determining an axle correction factor based on the deviation between the direction of draft of the vehicle and the intended path over a predetermined interval of time;

g) using said axle correction factor to determine a corrected position of said steerable axle;

h) mathematically determining an offset steering correction with reference to said corrected axle position; and

i) applying said offset steering correction to said steerable axle.

2. An improved method of operating an automatic guidance system with the aid of a digital computer, for use in a land vehicle, at least two ground engaging wheels, at least one of said wheels attached to a steerable axle, said axle attached to the vehicle by a pivot, a steering means connected to the pivot, a sensing means attached to the steerable axle, a path sensing means attached to the vehicle, and an actuating means attached to the steering means, said method including:

a) providing a computer with a data base for said vehicle, including at least a constant representing the amount of physical input which must be applied to the steering means in order to effect a desired positional change in the steerable axle, and an adjustable sensitivity constant (R);

b) predetermining a path for said vehicle, said path being established with reference to a physical index;

c) imparting motion to the vehicle in a direction of draft;

d) placing the path sensing means in close proximity to the physical index;

e) repetitively performing a steering correction process, said process including the steps of;

1) initiating a first interval timer, and during said interval repetitively determining the deviation (SE) of the preestablished path from a predetermined reference azimuth using said path sensing means;

2) constantly providing the computer with said deviation (SE);

3) accumulating a set of said deviations (SE₁, . . . , SE_n) in a buffer;

4) upon the expiration of said interval, calculating in the computer a time averaged deviation (SE_av) between the reference azimuth and the predetermined path;

5) multiplying the time averaged deviation value (SE_av) by a sensitivity constant (R) to obtain a ratio adjusted deviation average (RSE)

6) determining the position of said axle (AE) according to a predetermined axle reference azimuth;

7) providing said axle position (AE) to the computer;

8) calculating a steering correction (M) to correlate the position of said axle necessary to move the vehicle along the preestablished path, by subtracting the axle position (AE) from the ratio adjusted deviation average (RSE);

9) applying a filter to said steering correction to ensure that it exceeds a minimum threshold value; and

10) transmitting said steering correction (M) to said actuating means;

wherein the improved method includes the steps of;

f) computing an axle zero correction factor (C₀) by;

1) periodically initiating a second interval timer for a time substantially larger than the interval of said first interval timer;

2) accumulating a set of deviation values (SE₁, . . . , SE_kn) in a correction factor buffer during said second interval;

3) calculating the product (C₀) of a time averaged value of said deviation values accumulated during said second interval (SE_kav)and a variable sensitivity constant (R);

4) storing the value of said product (C₀) in a zero correction register;

g) calculating the difference between the axle position value (AE) and the value of said zero correction register (C₀), and storing the value of said difference as a corrected axle reference azimuth value (CAE); and

h) calculating the steering correction (M) needed to adjust the direction of draft of the vehicle to correspond to its intended path by calculating the difference between the current ratio adjusted deviation average (RSE) and the corrected axle reference azimuth value (CAE)

j) transmitting said steering correction to said actuating means.

3. The method as defined in claim 2 wherein said land vehicle is an agricultural tractor.

4. The method as defined in claim 3 wherein said path is a crop row.

5. An improved method of guiding a land vehicle along a predetermined meandering path, said vehicle having a steerable axle, said path having established physical boundaries, and said path having non-periodic oscillations deviating from a hypothetical linear path, said method comprising:

a) aligning the vehicle with respect to a portion of said predetermined path;

b) periodically determining the position of said vehicle with respect to said path;

c) determining the position of said steerable axle and thereby ascertaining the direction of draft with respect to a predetermined physical reference azimuth;

d) mathematically determining a steering correction to be applied to said steerable axle to correct the direction of draft to correlate with said predetermined path; and

e) adjusting said steerable axle according to said steering corrections;

wherein the improved method includes the steps of;

f) calculating a slope of previous positions of the vehicle with respect to the desired path as a function of time;

g) comprising said slope to the current position of said vehicle with respect to the desired path;

h) mathematically determining whether said vehicle is moving along said desired path toward or away from said predetermined path; and

i) upon concluding that the vehicle is moving toward the predetermined path and has previously moved away from the predetermined path, automatically applying a steering factor to move the vehicle away from the predetermined path.

10. The method as defined in claim 5 further comprising:

j) periodically determining an axle correction factor based on the deviation between the direction of the draft of the vehicle and the intended path over a predetermined interval of time;

k) using said axle correction factor to determine a corrected position of said steerable axle;

l) mathematically determining an offset steering correction with reference to said corrected axle position; and

m) applying said offset steering correction to said steerable axle.

6. An improved method of operating an automatic guidance system for use in a land vehicle with the aid of a digital computer, at least two ground engaging wheels, at least one of said wheels attached to a steerable axle, said axle attached to the vehicle by a pivot, an automatic steering means connected to the pivot, an axle position sensing means attached to the steerable axle, a path sensing means attached to the frame, and a mechanical actuating means attached to the steering means, said method including:

a) providing said computer with a data base for said vehicle, including at least a constant representing the amount of physical input which must be applied to the steering means in order to effect a desired change in the steerable axle,

b) preestablishing a path for said vehicle, said path having established physical boundaries, and said path having non-periodic oscillations deviating from a hypothetical linear path, and said path being defined with reference to a physical index;

c) imparting motion to the vehicle in a direction of draft;

d) placing the path sensing means in close proximity to the physical index;

e) initiating a steering correction process, said process including the steps of;

1) initiating a first interval timer, and during said interval repetitively determining the deviation (SE) of the preestablished path from a predetermined reference azimuth using said path sensing means;

2) constantly providing the computer with said deviation (SE);

3) accumulating a set of said deviations (SE₁, . . . , SE_n) in a buffer;

4) upon the expiration of said interval, calculating in the computer a time averaged deviation (SE_av) between the reference azimuth and the predetermined path;

5) multiplying the time averaged deviation value (SE_av) by a sensitivity constant (R) to obtain a ratio adjusted deviation average (RSE)

6) determining the position of said axle (AE) according to a predetermined axle reference azimuth;

7) providing said axle position (AE) to the computer;

8) calculating a steering correction (M) to correlate the position of said axle necessary to move the vehicle along the preestablished path, by subtracting the axle position (AE) from the ratio adjusted deviation average (RSE);

9) applying a filter to said steering correction to ensure that it exceeds a minimum threshold value; and

10) transmitting said steering correction (M) to said actuating means;

wherein the improved method includes the steps of;

f) accumulating a designated number of previous deviations (SE_n-119, SE_n-118, . . . , SE_n-100) representing a preset past interval of time in a buffer;

g) calculating a slope (S) of said deviation readings with respect to time as the difference between the time averaged value of the previous deviation readings (ASE100) and the time averaged value of the set of current deviations (ASE0);

h) comparing the sense of the slope (S) to the sense of the current time averaged deviation of the vehicle; and

j) upon determining that the current deviation are of the same sense, concluding that the vehicle has moved away from a hypothetical linear path and begun moving back towards said hypothetical linear path;

thereupon

k) engaging an automatic path correction process, including the steps of;

1) substituting a zero value for the time averaged deviation value (RSE);

2) calculating a steering factor (M) necessary to steer the vehicle back to its intended path; and

3) transmitting the steering correction (M) to said steering actuating means.

7. The method as defined in claim 6 wherein said land vehicle is an agricultural tractor.

8. The method as defined in claim 7 wherein said predetermined physical path is an agricultural crop row.

9. The method defined in claim 6 and further comprising:

l) computing an axle zero correction factor (C₀) by;

1) periodically initiating a second interval timer for a time substantially larger than the interval of said first interval timer;

2) accumulating a set of deviation values (SE₁, . . . , SE_kn) in a correction factor buffer during said second interval;

3) calculating the product (C₀) of a time averaged value of said deviation values accumulated during said second interval (SE_kav)and a variable sensitivity constant (R);

4) storing the value of said product (C₀) in a zero correction register;

m) calculating the difference between the axle position value (AE) and the value of said zero correction register (C₀), and storing the value of said difference as a corrected axle reference azimuth value (CAE); and

n) calculating the steering correction (M) needed to adjust the direction of draft of the vehicle to correspond to its intended path by calculating the difference between the current ratio adjusted deviation average (RSE) and the corrected axle reference azimuth value (CAE)

o) transmitting said steering correction to said actuating means.

11. A computer program product comprising:

a computer useable medium having computer readable program code means embodied in said medium for causing a land vehicle to be automatically guided along a predetermined path, said path having physical boundaries and said path being determined with reference to a physical index;

said vehicle having at least two ground engaging wheels, at least one of said wheels attached to a steerable axle, a sensor on said axle, a steering means on said axle, an actuating means on said steering means, and a path sensing means on said vehicle, said computer program product having;

a) computer readable program code means for causing a computer to calculate a slope for previous positions of the vehicle with respect to the desired path as a function of time;

b) computer readable program code means for causing a computer to compare said slope to the current position of said vehicle with respect to the desired path;

c) computer readable program code means for causing a computer to mathematically determine whether said vehicle is moving along said path toward or away from said predetermined path; and

d) computer readable program code means for causing a computer to automatically apply a steering factor to move the vehicle away from the predetermined path, after concluding that the vehicle is moving toward the predetermined path and has previously moved away from the predetermined path;

e) computer readable program code means for receiving a value from said axle sensing means corresponding to the position of said steerable axle with respect to a reference azimuth;

f) computer readable program code means for calculating an axle position correction factor based on said time average of deviation over said long interval of time; and

g) computer readable program code means for calculating a steering correction based on said axle correction factor, said axle position, and said predetermined path.

12. A computer product comprising:

a computer useable medium having computer readable program code means embodied in said medium for causing a land vehicle to be automatically guided along a predetermined path, said path having physical boundaries and said path being determined with reference to a physical index;

said vehicle having at least two ground engaging wheels, at least one of said wheels attached to steerable axle, a sensor on said axle, a steering means on said axle, an actuating means on said steering means, and a path sensing means on said vehicle, said computer program having;

a) computer readable program code means for causing a computer to calculate a slope for previous positions of the vehicle with respect to the desired path as a function of time;

b) computer readable program code means for causing a computer to compare said slope to the current position of said vehicle with respect to the desired path;

c) computer readable program code means for causing a computer to mathematically determine whether said vehicle is moving along said path toward or away from said predetermined path; and

d) computer readable program code means for causing a computer to automatically apply a steering factor to move the vehicle away from the predetermined path, after concluding that the vehicle is moving toward the predetermined path and has previously moved away from the predetermined path.

13. The computer program as defined in claim 12 further comprising:

e) computer readable program code means for causing a computer to store a plurality of values representing the deviation of said predetermined path from a predetermined reference azimuth on the vehicle;

f) computer readable program code means for causing a computer to store a small array of said deviation values over a short first interval of time;

g) computer readable program code means for causing a computer to store a large array of said values over a longer interval of time;

h) computer readable program code means for calculating a timed average of said deviation values over said long interval of time and said short interval of time;

i) computer readable program code means for receiving a value from said axle sensing means corresponding to the position of said steerable axle with respect to a reference azimuth;

j) computer readable program code means for calculating an axle position correction factor based on said time average of deviation over said long interval of time; and

k) computer readable program code means for calculating a steering correction based on said axle correction factor, said axle position, and said predetermined path.