LOCUS ESTIMATION DEVICE AND LOCUS ESTIMATING METHOD

• US 20150251662A1
• Filed: 01/29/2015
• Published: 09/10/2015
• Est. Priority Date: 03/06/2014
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: NAKAYAMA, Osafumi
• Granted Patent: US 9,511,776 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60W 2050/0034 Multiple-track, 2D vehicle model, e.g. four-wheel model
• CPC Class Codes: B60W 2520/14 Yaw
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2540/18 Steering angle
• CPC Class Codes: B60W 30/18145 Cornering
• CPC Class Codes: B60W 40/10 related to vehicle motion

Abstract

A processor of a locus estimation device accepts a measured value of a wheel speed of right and left front wheels of a moving object, and a measured value of a steering angle at which the traveling direction is changed. Based on a measured value of a wheel speed of the right and left front wheels, a measured value of a steering angle, a distance in the direction of the body of the moving object, a distance in the direction of the axle of the moving object, and a constant, the processor estimates an amount of rotation of the middle point of a rotation center of the right and left rear wheels on a circle having a center which is a point on a straight line passing through the rotation center of the right and left rear wheels, and an amount of translation of the middle point.

Claims

1. A locus estimation device, comprising:

a storage device which stores a distance between right and left front wheels and right and left rear wheels provided behind the front wheels in a moving object in a traveling direction of the moving object, a distance between the right and left front wheels in a direction of axles of the moving object, and a constant depending on a steering angle and a rotation radius of the moving object at the steering angle; and

a processor configured to accept a measured value of a wheel speed of the right and left front wheels, accept a measured value of a steering angle at which a traveling direction of the moving object is changed, and estimate an amount of a rotation of a middle point of a rotation center of the right and left rear wheels on a circle having a center which is a point on a straight line passing through the rotation center of the right and left rear wheels, and an amount of translation of the middle point on the basis of the measured value of the wheel speed of the right and left front wheels, the measured value of the steering angle, the distance in the direction of the body of the moving object, the distance in the direction of the axles of the moving object, and the constant.

2. The device according to claim 1, wherein

the processor further estimates the amount of rotation and the amount of translation by calculating the rotation radius of the circle by assuming that the left front wheel of the right and left front wheels is connected to a first axis which changes an angle of the left front wheel, the right front wheel is connected to a second axis which changes an angle of the right front wheel, the first and second axes are connected to a third axis at a right angle, and the steering angle is converted into a displacement in the direction of the third axis.

3. The device according to claim 1, wherein,

the processor further accumulates the wheel speed of the right and left front wheels measured at each specified time from a reference time of an estimation of the amount of rotation and the amount of translation until the reference time is updated;

estimates an average steering angle from the reference time to a latest measuring time;

updates the reference time;

calculates the amount of rotation and the amount of translation depending on the measuring time at each specified time on the basis of the accumulated wheel speed of the right and left front wheels and the average steering angle;

estimates the amount of rotation and the amount of translation from the reference time to the latest measuring time on the basis of the accumulated wheel speed of the right and left wheels, and the average steering angle;

updates the reference time at the latest measuring time when the estimated amount of translation satisfies a specified condition for suppression of an increasing error of the amount of rotation or the amount of translation; and

calculates the amount of rotation and the amount of translation of the moving object depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.

4. The device according to claim 3, wherein:

the condition is that the amount of translation of the moving object from the estimated reference time to the latest measuring time is not less than a reference time update threshold; and

the processor further calculates the amount of rotation and the amount of translation of the moving object from a measuring time immediately before the latest measuring time to the latest measuring time as the amount of rotation and the amount of translation depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.

5. The device according to claim 3, wherein

the processor further calculates backward a left wheel speed and a right wheel speed of the right and left front wheels from the amount of rotation and the amount of translation of the moving object from the estimated reference time to the latest measuring time, and compares a calculation result with the accumulated left wheel speed or the right wheel speed, and calculates the amount of rotation and the amount of translation of the moving object from a measuring time immediately before the latest measuring time to the latest measuring time as the amount of rotation and the amount of translation depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation;

and

the condition is that a difference between the backward calculated left wheel speed or right wheel speed of the right and left front wheels is within a second specified amount.

6. The device according to claim 1, wherein

the processor further estimates an amount of a rotation of a middle point of a rotation center of the right and left rear wheels on a circle having a center which is a point on a straight line passing through the rotation center of the right and left rear wheels, and an amount of translation of the middle point using a least squares method on the basis of the measured value of the wheel speed of the right and left front wheels, the measured value of the steering angle, the distance in the direction of the body of the moving object, the distance in the direction of the axles of the moving object, and the constant.

7. A locus estimating method, comprising:

accepting, by a processor, a measured value of a wheel speed of right and left front wheels of a moving object, and a measured value of a steering angle at which a traveling direction of the moving object is changed; and

estimating, by the processor, an amount of a rotation of a middle point of a rotation center of the right and left rear wheels on a circle having a center which is a point on a straight line passing through a rotation center of the right and left rear wheels, and an amount of translation of the middle point on the basis of a distance between the right and left front wheels and right and left rear wheels provided behind the front wheels in the moving object in a traveling direction of the moving object, a distance between the right and left front wheels in a direction of axles of the moving object, and a constant depending on the steering angle and a rotation radius of the moving object at the steering angle.

8. The method according to claim 7, wherein

in a process of estimating the amount of rotation and the amount of translation, the rotation radius of the circle is calculated by assuming that the left front wheel of the right and left front wheels is connected to a first axis which changes an angle of the left front wheel, the right front wheel is connected to a second axis which changes an angle of the right front wheel, the first and second axes are connected to a third axis at a right angle, and the steering angle is converted into a displacement in the direction of the third axis.

9. The method according to claim 7, further comprising:

accumulating, by the processor, the wheel speed of the right and left front wheels measured at each specified time from a reference time of an estimation of the amount of rotation and the amount of translation until the reference time is updated;

estimating, by the processor, an average steering angle from the reference time to a latest measuring time;

estimating the amount of rotation and the amount of translation from the reference time to the latest measuring time on the basis of the accumulated wheel speed of the right and left wheels, and the average steering angle;

updating, by the processor, the reference time at the latest measuring time when the estimated amount of translation satisfies a specified condition for suppression of an increasing error of the amount of rotation or the amount of translation; and

calculating, by the processor, the amount of rotation and the amount of translation of the moving object depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.

10. The method according to claim 9, wherein

the condition is that the amount of translation of the moving object from the estimated reference time to the latest measuring time is not less than a reference time update threshold;

and

the amount of rotation and the amount of translation of the moving object are calculated from a measuring time immediately before the latest measuring time to the latest measuring time as the amount of rotation and the amount of translation depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.

11. The method according to claim 9, further comprising:

calculating, by the processor, a left wheel speed and a right wheel speed of the right and left front wheels backward from the amount of rotation and the amount of translation of the moving object from the estimated reference time to the latest measuring time, wherein the condition is that a difference between the backward calculated left wheel speed or right wheel speed of the right and left front wheels is within a second specified amount; and

calculating, by the processor, the amount of rotation and the amount of translation of the moving object from a measuring time immediately before the latest measuring time to the latest measuring time as the amount of rotation and the amount of translation depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.

12. The method according to claim 7, further comprising

estimating, by the processor, an amount of a rotation of a middle point of a rotation center of the right and left rear wheels on a circle having a center which is a point on a straight line passing through a rotation center of the right and left rear wheels, and an amount of translation of the middle point using a least squares method on the basis of the measured value of the wheel speed of the right and left front wheels, the measured value of the steering angle, the distance in the direction of the body of the moving object, the distance in the direction of the axles of the moving object, and the constant.

13. A non-transitory computer-readable recording medium having stored therein a program for causing a computer to execute a process comprising:

accepting a measured value of a wheel speed of right and left front wheels of a moving object, and a measured value of a steering angle at which a traveling direction of the moving object is changed; and

estimating an amount of a rotation of a middle point of a rotation center of right and left rear wheels on a circle having a center which is a point on a straight line passing through a rotation center of the right and left rear wheels, and an amount of translation of the middle point on the basis of a distance between the right and left front wheels and right and left rear wheels provided behind the front wheels in the moving object in a traveling direction of the moving object, a distance between the right and left front wheels in a direction of axles of the moving object, and a constant depending on a steering angle and a rotation radius of the moving object at the steering angle.

14. The non-transitory computer-readable recording medium according to claim 13, wherein

in a process of estimating the amount of rotation and the amount of translation, the rotation radius of the circle is calculated by assuming that the left front wheel of the right and left front wheels is connected to a first axis which changes an angle of the left front wheel, the right front wheel is connected to a second axis which changes an angle of the right front wheel, the first and second axes are connected to a third axis at a right angle, and the steering angle is converted into a displacement in the direction of the third axis.

15. The non-transitory computer-readable recording medium according to claim 13, wherein the process further comprising:

accumulating the wheel speed of the right and left front wheels measured at each specified time from a reference time of an estimation of the amount of rotation and the amount of translation until the reference time is updated;

estimating an average steering angle from the reference time to a latest measuring time;

estimating the amount of rotation and the amount of translation from the reference time to the latest measuring time is estimated on the basis of the accumulated wheel speed of the right and left wheels, and the average steering angle;

updating the reference time at the latest measuring time when the estimated amount of translation satisfies a specified condition for suppression of an increasing error of the amount of rotation or the amount of translation; and

calculating the amount of rotation and the amount of translation of the moving object depending on the latest measuring time on the basis of the estimated amount of rotation and amount of translation.