Current position calculating system having a function for correcting a distance factor

• US 5,899,954 A
• Filed: 04/09/1996
• Issued: 05/04/1999
• Est. Priority Date: 04/21/1995
• Status: Expired due to Term

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Xanavi Informatics Corporation (Hitachi, Ltd.)
• Inventors: Sato, Hiroyuki
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): ARTHUR JEANGLAUDE, GERTRUDE
• Application Number:
  US08/629,853
• Time in Patent Office: 1,120 Days
• Field of Search: 701/201, 701/202, 701/206, 701/207, 701/208, 701/209, 701/210, 701/212, 701/214, 701/216, 701/200, 701/94, 340/990, 340/995, 340/988, 73/178 R
• US Class Current: 701/207
• CPC Class Codes: G01C 21/30 Map- or contour-matching
• CPC Class Codes: G01C 22/02 by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator G01C22/002, G01C22/004, G01C22/006 take precedence

Abstract

A current position calculation system is provided for adequately correcting a distance factor which is used for obtaining a travelled distance by utilizing various information at the time when a vehicle turns left or right. According to an output from a headed direction detecting device, an output from a travelled distance calculating device and road data of a road map, at the time when the vehicle turns left or right from a first road to a second road, there is obtained a distance error amount d which is an error in an output from the travelled distance calculating device with respect to an actual value it should be. The distance error amount d is corrected so as to be reduced. In order to obtain the distance error amount d, a moving path of the vehicle position is estimated without considering whether the position is on or off a road after completing the left or right turn, it is checked whether the estimated moving path of the vehicle position is an overshoot or an undershoot with respect to the second road on the road map, and the amount of the overshoot or the undershoot is obtained as the aforementioned distance error amount d.

Claims

1. A current position calculating system for installation on a vehicle moving in accordance with a wheel rotation and calculates a current position of the vehicle, said system comprising:

means for storing road data representing a road map;

a headed direction detecting means for detecting a headed direction of the vehicle;

a rotational speed detecting means for detecting a wheel rotational speed;

a travelled distance calculating means for calculating a travelled distance of the vehicle in accordance with the wheel rotational speed detected by the rotational speed detecting means and a predetermined distance factor;

a current position estimating means for estimating a current position on a road where the vehicle exists thereon, in accordance with the detected ravelled distance, the detected head direction and the road map represented by the road data;

a left/right turning determining means for determining whether the vehicle turns left or right from a first road to a second road;

a distance factor correcting means for obtaining at a time of turning left or right, based on the detected travelled distance, the detected headed direction and the road data of the road map, a distance error amount which is an error in an output from the travelled distance calculating means with respect to an actual value it should be, and for correcting the distance factor in order to reduce the distance error amount;

a storing means for accumulating a combination of data items obtained at a plurality of previous sequential points in time, said data items including the detected travelled distance, the detected headed direction and the current position where the vehicle exists,

said distance factor correcting means estimating a moving path of vehicle positions whether the positions are on or off a road, according to the combination of said data items, after completing a left or a right turn, checking whether said moving path overshoots or undershoots the second road on the road map, and obtaining an amount of either of the overshoot and the undershoot as said distance error amount;

means for obtaining a width of said second road according to the road data; and

means for correcting said distance error amount in accordance with the width of said second road.

2. A current position calculating system as defined in claim 1, wherein said left/right turning determining means determines that the vehicle turns left or right, when it is detected according to at least one of an output from the current position estimating means and an output from the headed direction detecting means that the vehicle has moved to the second road from the first road and that either of the angle formed by the headed directions before and after the moving and the angle formed by the directions of the first and the second roads, is approximately 90 degrees.

3. A current position calculating system as defined in claim 1, wherein:

a detection of the headed direction and the wheel rotational speed, and an estimation of the current position of the vehicle are performed every predetermined travelled distance which is constant.

4. A current position calculating system as defined in claim 2, wherein:

a detection of the headed direction and the wheel rotational speed, and an estimation of the current position of the vehicle are performed every predetermined travelled distance, which is constant.

5. A current position calculating system according to claim 1, wherein said means for correcting said distance error amount includes a table in which correction amounts are pre-stored corresponding to ranges of the width of said second road.

6. A method for correcting a distance factor for obtaining a vehicle travelled distance based on a wheel rotational speed, in a current position calculating system for installation on the vehicle to obtain a current position of the vehicle, comprising:

when the vehicle turns left or right at approximately right angle and moves from a first road to a second road, estimating a moving path of vehicle positions on or off a road according to the travelled distance determined based on headed directions sequentially obtained by a headed direction detecting means and a travelled distance determined based on travelled distances sequentially obtained according to the distance factor and the wheel rotational speed;

checking whether the estimated moving path of vehicle positions overshoots or undershoots the second road on a road map; and

decreasing the distance factor depending on an amount of the overshoot when the moving path is an overshoot, and increasing the distance factor depending on an amount of the undershoot, when the moving path is an undershoot,

wherein a width of said second road is checked according to the road data, and each amount of the overshoot and the undershoot is corrected in accordance with the width of said second road.

7. A method for correcting a distance factor according to claim 6, wherein the correction of each amount of the overshoot and the undershoot is performed referring to a predetermined table in which correction amounts are pre-stored corresponding to ranges of the width of said second road.