Location equipment

• US 20030163255A1
• Filed: 02/26/2003
• Published: 08/28/2003
• Est. Priority Date: 02/28/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Shimotani, Mitsuo, Mikuriya, Makoto, Ishigami, Tadatomi, Matsuo, Toshiyuki, Akamatsu, Teruki
• Granted Patent: US 6,856,903 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/52 Determining velocity

Abstract

A location equipment includes a calibration unit (14) for calibrating scale factors used for calculating the distances traveled by left and right wheels of a vehicle from pulse signals delivered from wheel sensors (11) respectively installed in the left and right wheels based on GPS signals received by a GPS receiver (12), and an estimation unit (15 and 16) for estimating vehicle position and movement from the GPS signals received by the GPS receiver and the pulse signals delivered from the wheel sensors by using the scale factors calibrated by the calibration unit.

Claims

1. A location-equipment comprising:

wheel sensors installed in left and right wheels of a vehicle, each for generating a pulse signal as a corresponding one of the left and right wheels rotates;

a GPS receiver for receiving GPS signals sent from GPS satellites;

a calibration means for calibrating scale factors used for calculating distances traveled by the left and right wheels from the pulse signals delivered from said wheel sensors based on the GPS signals received by said GPS receiver; and

an estimation means for estimating vehicle position and movement from the GPS signals received by said GPS receiver and the pulse signals delivered from said wheel sensors by using the scale factors calibrated by said calibration means.

2. The location equipment according to claim 1, wherein said calibration means performs Kalman filter processing on the scale factors so as to calibrate the scale factors.

3. The location equipment according to claim 1, wherein said estimation means performs Kalman filter processing so as to estimate the vehicle position and movement.

4. The location equipment according to claim 1, wherein said calibration means calibrates the scale factors based on information on a heading or velocity of the vehicle included in the GPS signals received by said GPS receiver.

5. The location equipment according to claim 3, wherein said calibration means calculates a probability of occurrence of slipping of the left and right wheels from the GPS signals received by said GPS receiver and the pulse signals delivered from said wheel sensors, and enlarges a Kalman gain that said estimation means uses when the probability of occurrence of slipping becomes larger than a reference value.

6. The location equipment according to claim 3, wherein said calibration means calculates a change in the heading of the vehicle from the pulse signals delivered from said wheel sensors, and enlarges a Kalman gain that said estimation means uses when the change in the heading becomes larger than a reference value.

7. The location equipment according to claim 3, wherein said calibration means determines an acceleration of the vehicle from the GPS signals received by said GPS receiver and calculates an acceleration-equivalent value of the vehicle from the pulse signals delivered from said wheel sensors, and enlarges a Kalman gain that said estimation means uses when a difference between the acceleration and the acceleration-equivalent value becomes larger than a reference value.

8. The location equipment according to claim 1, wherein said calibration means calculates a probability of occurrence of slipping of the left and right wheels from the GPS signals received by said GPS receiver and the pulse signals delivered from said wheel sensors, and stops calibrating the scale factors when the probability of occurrence of slipping becomes larger than a reference value.

9. The location equipment according to claim 1, wherein said calibration means calculates a change in the heading of the vehicle from the pulse signals delivered from said wheel sensors, and stops calibrating the scale factors when the change in the heading becomes larger than a reference value.

10. The location equipment according to claim 1, wherein said calibration means determines an acceleration of the vehicle from the GPS signals received by said GPS receiver and calculates an acceleration-equivalent value of the vehicle from the pulse signals delivered from said wheel sensors, and stops calibrating the scale factors when a difference between the acceleration and the acceleration-equivalent value becomes larger than a reference value.

11. The location equipment according to claim 1, wherein said calibration means calculates an error involved in a velocity of the vehicle and either an error involved in a heading of the vehicle or an error involved in a change in the heading of the vehicle from the GPS signals received by said GPS receiver and the pulse signals delivered from said wheel sensors, and calibrates a distance between the wheels (i.e., a wheel track) without calibrating the scale factors when either the error involved in the heading of the vehicle or the error involved in the change in the heading of the vehicle is equal to or greater than a predetermined value even though the error involved in the velocity of the vehicle is equal to or less than a reference value.

12. The location equipment according to claim 3, wherein said estimation means calculates a change in a bearing of the vehicle and a distance traveled by the vehicle per unit time based on the pulse signals from said wheel sensors so as to update a position and heading of the vehicle, and modifies the updated position and heading of the vehicle based on information on the position and heading of the vehicle which is included in the GPS signals received by said GPS receiver.

13. The location equipment according to claim 12, wherein said estimation means stores the information on the position and heading of the vehicle that is included in the GPS signals applied thereto at predetermined intervals from said GPS receiver, calculates a direction in which the vehicle is moved from stored time-series pieces of information on the position of the vehicle, and calculates an error involved in the heading of the vehicle from the time-series pieces of position information and stored time-series pieces of information on the heading of the vehicle.

14. The location equipment according to claim 12, wherein said estimation means stores the information on the position of the vehicle that is included in the GPS signals applied thereto at predetermined intervals from said GPS receiver and the change in the bearing of the vehicle and the distance traveled by the vehicle per unit time that are calculated based on the pulse signals from said wheel sensors, and calculates an error involved in the information on the position of the vehicle that is included in said GPS signals by comparing per-unit-time movement-vectors each obtained from the stored information on the position of the vehicle that is included in the GPS signals with those each obtained from the stored change in the bearing of the vehicle and the stored distance traveled by the vehicle per unit time, respectively.

15. The location equipment according to claim 13, wherein said estimation means stops modifying the updated position and heading of the vehicle when errors in the position and heading of the vehicle that are included in the GPS signals applied thereto from said GPS receiver become larger than reference values, respectively.

16. The location equipment according to claim 14, wherein said estimation means stops modifying the updated position and heading of the vehicle when errors in the position and heading of the vehicle that are included in the GPS signals applied thereto from said GPS receiver become larger than reference values, respectively.