Method and apparatus for correcting the output of an onboard vehicle terrestrial magnetism sensor

• US 5,151,872 A
• Filed: 07/24/1990
• Issued: 09/29/1992
• Est. Priority Date: 10/17/1989
• Status: Expired due to Fees

• Current Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Original Assignee: Pioneer Electronic Corporation (Pioneer Corporation)
• Inventors: Suzuki, Kiyomi, Chijiiwa, Masaru
• Primary Examiner(s): Trans, Vincent N.
• Application Number:
  US07/556,545
• Time in Patent Office: 798 Days
• Field of Search: 364/454, 364/460, 364/571.02, 364/571.03, 364/571.04, 364/571.05, 364/457, 73/178 R, 340/988, 33/320, 33/356, 33/357
• US Class Current: 702/92
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01V 3/40 specially adapted for measuring magnetic field characteristics of the earth
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165

Abstract

Method and apparatus for correcting the output of an onboard vehicle terrestrial magnetism sensor. An azimuth computation reference circle is obtained from the terrestrial magnetism sensor output, the circle in turn being used to correct the sensor output. When the reference circle is dislodged, the least square method is used to fine a true azimuth computation reference circle.

Claims

1. A method for correcting the output of a terrestrial magnetism sensor mounted on a vehicle comprising the steps of:

generating an output from the terrestrial magnetism sensor;

detecting an error in the output of the terrestrial magnetism sensor caused by extraneous magnetic influence;

selecting a plurality of data pairs x_o, y_o form the output of the terrestrial magnetism sensor;

determining from said plurality of data pairs x_o, y_o an initial radius r_o and initial center coordinates x_o, y_o of an initial azimuth computation reference circle;

computing a distance r_o between each of said plurality of data pairs x_o, y_o and said initial center coordinates x_o, hd o;

calculating a difference between each distance r_o and said initial radius r_o ;

obtaining a variance σ

² from squares of the calculated differences;

determining an updated radius r'"'"'_o and updated center coordinates x'"'"'_o, y'"'"'_o of the azimuth computation reference circle such that said variance σ

² is minimized with respect to changes in coordinates x, y and radius r;

establishing an updated azimuth computation reference circle from said updated radius r'"'"'_o and said updated center coordinates x'"'"'_o, y'"'"'_o ; and

correcting the output of the terrestrial magnetism sensor using said updated azimuth computation reference circle.

2. An apparatus for correcting the output of an onboard vehicle terrestrial magnetism sensor mounted on a vehicle using an azimuth computation reference circle obtained form said output, said apparatus comprising:

vehicle terrestrial magnetism sensor for generating an output signal;

detecting means for detecting an error in the output of the vehicle terrestrial magnetism sensor caused by extraneous magnetic influence;

input means responsive to said detecting means for inputting a plurality of data pairs x_i, x_i from the output of the terrestrial magnetism sensor when an error is detected;

initial value setting means for setting an initial radius r_o and initial center coordinates x_o, y_o from an initial azimuth computation reference circle on the basis of said plurality of data pairs x_i, y_i ;

distance calculating means for calculating a distance r_i between each of said plurality of data pairs x_i, y_i and said initial center coordinates x_o, y_o ;

difference calculating means for calculating a difference between each distance r and said initial radius r_o ;

variance calculating means for calculating a variance σ

² from squares of the calculated differences;

updated value determining means for determining an updated radius r'"'"'_o and updated center coordinates x'"'"'_o, y'"'"'_o of the azimuth computation reference circle such that said variance σ

² is minimized with respected to changes in coordinates x, y and radius r;

updated reference circle determining means for determining an updated azimuth computation reference circle from said updated radius r'"'"'_o and said updated center coordinates x'"'"'_o, y'"'"'_o ; and

correction means for correcting the output of the terrestrial magnetism sensor using updated azimuth computation reference circle.