Noise removal method for an electronic compass

• US 5,323,336 A
• Filed: 12/27/1991
• Issued: 06/21/1994
• Est. Priority Date: 12/27/1991
• Status: Expired due to Term

• Current Assignee: Chrysler Group LLC (Stellantis NV)
• Original Assignee: Chrysler Corporation (Stellantis NV)
• Inventors: Cage, Russell E.
• Primary Examiner(s): Harvey, Jack B.
• Assistant Examiner(s): CHOI, KYLE JAEHUN
• Application Number:
  US07/815,269
• Time in Patent Office: 907 Days
• Field of Search: 364/559, 364/574, 364/581, 364/571.01-571.08, 73/1 E
• US Class Current: 702/193
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

A method for removing noise from data in an electronic compass system which discounts noise values or outliers (extreme headings far from average) by displaying median headings in the absence of a clear trend in the direction of change of sampled headings. If a clear trend is detected, extreme headings are displayed. Compass jitter is reduced by requiring two consecutive differences be on the same side of the displayed heading before the displayed heading is changed.

Claims

1. A method for noise and outliers from data values for an electronic compass, said method comprising:

(a) orienting first and second sense coils of a flux-gate sensor perpendicular to each other in the earth'"'"'s magnetic field;

(b) saturating said sense coils with a drive signal;

(c) measuring an induced voltage in said sense coils induced by said magnetic field;

(d) calculating a first heading related to said induced voltage using a processing unit and storing said first heading in a memory unit connected to said processing unit;

(e) calculating and storing a second heading related to said induced voltage using said processing and memory units;

(f) calculating and storing a third heading related to said induced voltage using said processing and memory units;

(g) determining a median heading of said three stored heading using said processing unit;

(h) displaying said median heading on a display unit when a currently displayed heading is less than said third stored heading and a last displayed heading is greater than said second stored heading;

(i) displaying said median heading on said display unit when said currently displayed heading is greater than said third stored heading and said last displayed heading is less than said second stored heading;

(j) displaying said third stored heading when said currently displayed heading is less than said third stored heading and said last displayed heading is less than said second stored heading; and

(k) displaying said third stored heading when said currently displayed heading is greater than said third stored heading and said last displayed heading is greater than said second stored heading,

wherein by selecting one of said median heading and said third stored heading for display using steps (h), (i), (j), and (k), noise and outliers are removed from said data values.

2. A method for removing noise and outliers from data values for an electronic compass, said method comprising:

(a) orienting first and second sense coils of a flux-gate sensor perpendicular to each other in the earth'"'"'s magnetic field;

(b) saturating said sense coils with a drive signal;

(c) measuring an induced voltage in said sense coils induced by said magnetic field;

(d) calculating a first current heading related to said induced voltage using a processing unit;

(e) displaying said first current heading on a display unit;

(f) calculating a second current heading related to said induced voltage using said processing unit;

(g) displaying said second current heading;

(h) calculating a third current heading related to said induced voltage using said computing means;

(i) displaying said third current heading when said third current heading is greater than said second displayed heading and said first displayed heading is less than said second current heading;

(j) displaying said third current heading when said third current heading is less than said second displayed heading and said first displayed heading is greater than said second current heading; and

(k) displaying said second displayed heading when steps (i) and (j) are not met,

wherein by selecting one of said third current heading and said second displayed heading for displaying using steps (i), (j), and (k), noise and outliers are removed from said data values.