Navigator for use aboard a vehicle

• US 4,688,176 A
• Filed: 04/22/1985
• Issued: 08/18/1987
• Est. Priority Date: 04/27/1984
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Hirata, Seiichiro
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/725,631
• Time in Patent Office: 848 Days
• Field of Search: 364/424, 364/443, 364/449, 364/521, 364/561, 364/571, 73/178 R, 340/988, 340/995, 343/451, 342/451
• US Class Current: 701/208
• CPC Class Codes: G01C 21/04 by terrestrial means G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 21/30 Map- or contour-matching

Abstract

A navigator for use aboard a vehicle includes means for detecting the running distance of the vehicle, means for detecting the angle of the advancing direction of the vehicle with reference to terrestrial magnetism, arithmetic operational means for calculating the coordinates of the position of the vehicle in response to the detected running distance and angle of direction, a memory for storing data regarding the coordinates of the points of correction set at intersections of roads on a map corresponding to an area in which the vehicle is traveling, the distances between the points of correction, and the angles of roads branching from the points of correction with reference to terrestrial magnetism, a locating means for judging whether the vehicle is within a predetermined distance from a point of correction by comparing the coordinates of the present position of the vehicle with the coordinates of the points of correction stored in the memory, a means for judging whether the vehicle has made a turn, and a second arithmetic operational means for calculating the ratio of a reference distance between first and second reference points of correction to the measured distance between the first and second reference points of correction from the means for detecting the running distance, to obtain a compensation coefficient in determining the actual distance traveled by the vehicle.

Claims

1. A navigator for use aboard a vehicle, comprising:

first means for detecting the running distance of the vehicle and producing an output signal corresponding thereto;

second means for detecting an angle of the advancing direction of the vehicle relative to terrestrial magnetism and producing an output signal corresponding thereto;

arithmetic operational means for performing an arithmetic calculation of the coordinates of the position of the vehicle in response to said output signals from said first and second detecting means and a compensation coefficient;

memory means for storing data on the coordinates of points of correction set at intersections of roads on a map of the area in which the vehicle is traveling, the distances between said points of correction, and the angles of roads branching from the points of correction relative to terrestrial magnetism;

locating means for judging whether the vehicle is within a predetermined distance from a point of correction by comparing the coordinates of the position of the vehicle from the arithmetic operational means with the coordinates of said points of correction stored in said memory means;

means for judging whether the vehicle has made a turn in a first area, when the position of the vehicle is judged to be within the first area by comparing the advancing direction of the vehicle with directions of the branching roads stored in said memory means, and specifying the point of correction in said first area as a first reference point of correction and a point of correction in a second area in the advancing direction of the vehicle as a second reference point of correction; and

second arithmetic operational means for performing an arithmetic calculation of the ratio of the distance between the first and second reference points of correction obtained from the memory means to the distance between the first and second reference points of correction obtained from said first detecting means, to obtain said compensation coefficient.

2. A navigator as defined in claim 1, wherein said running distance detecting means detects the running distance of the vehicle at predetermined time intervals or at irregular time intervals, and incrementally adds the distances so detected to obtain the running distance.

3. A navigator for use aboard a vehicle, comprising:

first means for detecting the advancing direction of the vehicle including,

a terrestrial magnetism sensor, an A/D converter, and

means for detecting the X- and Y-components of the terrestrial magnetism as digital signals Xd and Yd at predetermined time intervals so as to obtain the advancing direction θ

of the vehicle;

second means for detecting the running distance of the vehicle S, by multiplying a number of pulses N generated in accordance with the distance travelled by the vehicle for a predetermined period of time T by a constant Q and a compensation coefficient K to obtain the running distance S for the time T,

arithmetic operational means for performing an arithmetic calculation to obtain the coordinates of the position of the vehicle by calculating incremental changes X and Y in the X- and Y-axis direction for a predetermined time interval T in response to the digital signals Xd and Yd from the first means, and the value of S from the second means, and adding the changes X and Y to the coordinates of the present position;

memory means for storing data on the coordinates of points of correction set at intersections of roads on a map of the area in which the vehicle is travelling, the distances between said points of correction, and the angles of roads branching from the points of correction relative to terrestrial magnetism;

locating means for locating the point of correction whose coordinates are within a predetermined distance from the present position, the locating means reading out the coordinates of the points of correction from the memory means, and receiving the coordinates of the present position (X, Y) from the arithmetic operational means, thereby comparing the aimed coordinates of the points of correction against those of the present position;

turn detecting means for judging whether the vehicle has made a turn and outputting a turn judging signal corresponding thereto, said turn detecting means receiving the angle θ

m stored in the memory means corresponding to the coordinates of the point of correction searched by the locating means, receiving the advancing direction θ

from said first means, and judging that the vehicle has made a turn when the advancing direction θ

is within a predetermined direction range with respect to the angle θ

m; and

second arithmetic operational means for obtaining said compensation coefficient K by calculating the ratio of a reference distance between the point of correction for the present turn judging signal and that for the immediately preceding turn judging signal, the reference distance being stored in the memory means, to the measured distance between the point of correction for the present turn judging signal and the point of correction for the immediately preceding turn judging signal, on the basis of the running distance S from the distance detecting means, as said compensation coefficient K.

4. A navigator as defined in claim 3, wherein the second arithmetic operational means comprises:

a first memory for storing a reference distance between the point of correction for the present turn judging signal and the point of correction for the immediately preceding turn judging signal calculated on the basis of the distance between the points of correction stored in the memory means;

a second memory for storing a measured distance from the point of correction for the immediately preceding turn judging signal to the point at which the present turn judging signal from the turn detecting means is outputted;

means for adding the running distance S to said measured distance stored in the second memory upon receipt of the running distance S from the distance detecting means, thereby updating the measured distance in the second memory; and

compensation coefficient arithmetic operational means for arithmetically calculating the ratio of the measured distance stored in the second memory upon outputting of the turn judging signal to the reference distance stored in the first memory to output said compensation coefficient K.