System and method for determining a position of a vehicle with compensation for noise or measurement error

• US 7,720,598 B2
• Filed: 08/19/2005
• Issued: 05/18/2010
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Hunt, Kenneth Edward, Schmidt, Mark Alvin, Holm, David Roy, Stephens, Scott Adam
• Primary Examiner(s): Tran; Khoi
• Assistant Examiner(s): SAMPLE, JONATHAN L
• Application Number:
  US11/208,255
• Publication Number:
  US 20060224307A1
• Time in Patent Office: 1,733 Days
• Field of Search: 701/207, 701/200
• US Class Current: 701/207
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• CPC Class Codes: G01S 5/0215 Interference
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

A mobile transmitter transmits a transmission signal from a vehicle to beacons. An estimator determines elapsed times for corresponding propagation paths between the vehicle and the beacons. Each propagation path includes at least one of a first propagation duration of a transmission signal and a second propagation duration of a return signal. A compensator compensates for noise or measurement error associated with a corresponding propagation path by invoking a linear fit scheme. The linear fit scheme applies a generally linear fit over fixed intervals of noisy measurements such that the noisy position measurements generally conform to a linear portion of a path plan of a vehicle. A data processor estimates a position of a vehicle at a confluence or intersection of the position curves or temporal curves based on elapsed times for the propagation paths.

Claims

1. A method for determining a position of a vehicle, the method comprising:

transmitting a transmission signal from a mobile transmitter at the vehicle to beacons at different sites associated with a work area;

determining respective elapsed times for corresponding propagation paths between the vehicle and the beacons, each propagation path including at least one of a first propagation duration and a second propagation duration, the first propagation duration referring to a first propagation time of the transmission signal from the vehicle to a particular beacon, the second propagation duration referring to a second propagation time of a return signal from the particular beacon to the vehicle;

compensating for error associated with a corresponding propagation path by invoking a linear fit scheme, the linear fit scheme applying a generally linear fit over fixed intervals of noisy position measurements to generally conform to a linear portion of a path plan of a vehicle to be tracked; and

estimating the position of the vehicle at least near a confluence of position curves based on elapsed times for the propagation paths, where the position curves are fitted to a generally linear progression of a planned path of the vehicle in accordance with the compensation to obtain the estimated position.

2. The method according to claim 1, wherein if the linear portion of the path plan is defined by the line equation:

y=mx+b, where m is the estimated slope to be optimized and b is the estimated y axis intercept (of the line) to be optimized, where the x axis and y axis are perpendicular to each other, then the least squares estimates for the parameter values are

$m=\frac{\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>\left(x_i-\stackrel{\_}{x}\right)<br><br>\left(y_i-\stackrel{\_}{y}\right)}{\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>{\left(x_i-\stackrel{\_}{x}\right)}^2}$

and b= y−

m x, where the bar over the x and y indicate an arithmetic mean value of x and y, respectively, where n is the total number of measurement values averaged, values of x_i are the predictor variables, and i is a measurement value which ranges from 1 to n, where n is positive whole number.

3. The method according to claim 1 wherein the estimating comprises assigning an approximately equal weight to the position curves or equal weight to the temporal curves to estimate the position of the vehicle.

4. The method according to claim 1 wherein the estimating comprises assigning differential weights to the position curves based on at least one probability density function for the position curves to estimate the position of the vehicle.

5. The method according to claim 1 wherein the estimating comprises collecting a series of first position curves and averaging the series of first position curves over time;

collecting a series of second position curves and averaging the series of first position curves over time; and

collecting a series of third position curves and averaging the series of position curves over time to estimate the position of the vehicle.

6. The method according to claim 1 wherein the estimating comprises collecting a series of first position curves and fitting the first position curves to a generally linear progression over time, collecting a series of second position curves and fitting the second position curves to a generally linear progression over time, collecting a series of third position curves and fitting the third position curves to a generally linear progression over time in accordance with at least one of a least squares approach and a weighted least squares approach, where the generally linear progression is consistent with a generally linear path portion of a vehicle.

7. The method according to claim 1 wherein the compensating further comprises applying bias delay compensation to a turn-around paging scenario, in which a transmission is transmitted from the vehicle to one of the beacons, and then a return transmission is transmitted from the beacon back to the vehicle, by making a deduction for lag within each beacon.

8. The method according to claim 6 wherein the bias compensation deducts a delay for one or more of the following:

(a) processing of the transmission and generation of the return signal at the beacon, (b) receiving the return signal at the vehicle, and (c) processing of the return signal at the vehicle.

9. The method according to claim 1 wherein the compensating further comprises applying a received pulse or received pulse train to a phase locked loop circuit as a filter to reduce an input noise phase component of the input phase.

19. The method according to claim 1, further comprising:

measuring a frequency shift in the transmission signal at one or more of the beacons to estimate at least one of a vehicular speed and vehicular velocity.

20. The method according to claim 19, further comprising:

discarding the frequency shift at any beacon that exceeds a parameter of at least one of the vehicular speed and the vehicular velocity of the vehicle, wherein the parameter is set by at least one of a path planning module, physical constraints of the vehicle, and a user.

10. A system for determining the position of a vehicle, the system comprising:

a mobile transmitter for transmitting a transmission signal from a vehicle to beacons associated with the work area;

an estimator for determining elapsed times for corresponding propagation paths between the vehicle and the beacons, each propagation path including at least one of a first propagation duration and a second propagation duration;

the first propagation duration referring to a propagation time of the transmission signal from the vehicle to the particular beacon;

the second propagation duration referring to a propagation time of a return signal from the particular beacon to the vehicle;

a compensator for compensating for noise or measurement error associated with a corresponding propagation path by invoking a linear fit scheme, the linear fit scheme applying a generally linear fit over fixed intervals of noisy measurements such that the noisy position measurements generally conform to a linear portion of a path plan of a vehicle; and

a data processor for estimating a position of a vehicle at a confluence or intersection of the position curves or temporal curves based on elapsed times for the propagation paths.

11. The system according to claim 10, wherein if a linear portion of the path plan is defined by the line equation:

y=mx+b, where m is the estimated slope to be optimized and b is the estimated y axis intercept (of the line) to be optimized, where the x axis and y axis are perpendicular to each other, then the least squares estimates for the parameter values are

$m=\frac{\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>\left(x_i-\stackrel{\_}{x}\right)<br><br>\left(y_i-\stackrel{\_}{y}\right)}{\underset{i=1}{\overset{n}{\sum <br><br>}}<br><br>{\left(x_i-\stackrel{\_}{x}\right)}^2}$

and b= y−

m x, where the bar over the x and y indicate an arithmetic mean value of x and y, respectively, where n is the total number of measurement values averaged, values of xi are the predictor variables, and i is a measurement value which ranges from 1 to n, where n is positive whole number.

12. The system according to claim 10 wherein the estimator assigns an approximately equal weight to the position curves or equal weight to the temporal curves to estimate the position of the vehicle.

13. The system according to claim 10 wherein the estimator as signs differential weights to the position curves or differential weights to the temporal curves based on at least one probability density function for the position curves or the temporal curves to estimate the position of the vehicle.

14. The system according to claim 10 wherein the data processor collects a series of first position curves and averaging the series of first position curves over time;

collecting a series of second position curves and averaging the series of first position curves over time; and

collecting a series of third position curves and averaging the series of position curves over time to estimate the position of the vehicle.

15. The system according to claim 10 wherein the data processor collects a series of first position curves and fitting the first position curves to a generally linear progression over time, collecting a series of second position curves and fitting the second position curves to a generally linear progression over time, collecting a series of third position curves and fitting the third position curves to a generally linear progression over time in accordance with at least one of a least squares approach and a weighted least squares approach, where the generally linear progression is consistent with a generally linear path portion of a vehicle.

16. The system according to claim 10 wherein the compensator applies bias delay compensation to a turn-around paging scenario, in which a transmission is transmitted from a vehicle to a beacon, and then a return transmission is transmitted from the beacon back to the vehicle, by making a time or distance deduction for bias or processing lag within each beacon.

17. The system according to claim 16 wherein the compensator deducts a delay for one or more of the following:

(a) processing of the transmission and generation of the return signal at the beacon, (b) receiving the return signal at the vehicle, and (c) processing of the return signal at the vehicle.

18. The system according to claim 10 wherein the compensator applies a received pulse or received pulse train to a phase locked loop circuit as a filter to reduce an input noise phase component of the input phase.