Heading sensor for vehicle dead reckoning system

• US 4,055,750 A
• Filed: 06/07/1976
• Issued: 10/25/1977
• Est. Priority Date: 06/07/1976
• Status: Expired due to Term

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: RCA Corporation (General Electric Company)
• Inventors: Jellinek, Ernest
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US05/694,043
• Time in Patent Office: 505 Days
• Field of Search: 235/150.2, 235/150.24, 235/150.26, 235/150.27, 340/22, 340/23, 340/24, 116/124 R, 116/35 R, 73/505, 73/178 R
• US Class Current: 701/207
• CPC Class Codes: G01C 22/025 Differential odometers

Abstract

A two-odometer heading sensor wherein an accumulator is incremented or decremented in response to detected increments of turn angle. Provisions are disclosed for avoiding errors due to spurious differences in the distance sensed by the respective odometers.

Claims

1. An apparatus for determining the heading of a vehicle with respect to a reference direction, said vehicle having a major longitudinal axis and a minor transverse axis, said system being of the type including first means for resettably generating a differential count indicative of the difference in distance traveled by first and second predetermined points on said vehicle, said differential count having a polarity in accordance with a predetermined convention, said first and second predetermined points being positioned at substantially equal distances from said transverse axis and separated by a predetermined distance in a direction parallel to said transverse axis;

wherein the improvement comprises;

quantizing means, responsive to said differential count, for generating output signals when the magnitude of said differential count reaches a first predetermiend threshold value;

said quantizing means output signals being indicative of the instantaneous polarity of said differential count, and being applied to first means to reset said distance count to zero;

accumulator mans, responsive to said quantizing means output signals, for generating an output signal indicative of the accumulated algebraic sum of said polarity signals;

first resetting means, responsive to said differential count, for generating an output signal when the average rate of accrual of increments of said differential count over a first predetermined time period does not exceed a first predetermined rate of accrual; and

second resetting means, responsive to said differential count for generating an output signal when the average rate of accrual of increments of said differential count over a second predetermined time period does not exceed a second predetermined rate of accrual;

said second time period being no greater than said first time period, said first and second resetting means output signals being applied to said first means to reset said differential count to zero.

2. The apparatus of claim 1, wherein said second resetting means comprises:

second means, responsive to said differential count and control signals applied thereto, for generating an output signal when the magnitude of said differential count does not exceed a second predetermined threshold value within said second predetermined time period, said second means being inhibited if said second threshold value is reached.

3. The apparatus of claim 2, wherein said first resetting means comprises:

third means, responsive to said quantizing means output signal, for generating an output signal if the magnitude of said differential count does not exceed said first predetermined threshold value within said first predetermined time period, said third means output signal being applied as a control signal to said second means to re-enable said second means.

4. The apparatus of claim 3 wherein the ratio of said first predetermined threshold value to said first predetermined time period is equal to the ratio of said second predetermined threshold value to said second time period.

5. The apparatus of claim 4 wherein said first predetermined threshold value is equal to said second predetermined threshold value.

6. The apparatus of claim 3 wherein said third means comprises:

second counter means, responsive to said quantizing means input signals and incremented at a predetermined frequency, for generating an output signal when the contents thereof equal a second predetermined value;

said counter means being reset by said quantizing means output signal;

said second counter means output signal being applied to said first means to reset said differential count to zero, and further being applied to said first counter means to re-enable said first counter means.

7. The apparatus of claim 2 wherein said second means comprises:

counter means, responsive to control signals applied thereto and incremented at a predetermined frequency, for generating an output signal when the contents thereof equal a first predetermined value, said counter means output signal being said second means ouput signal;

comparator means, responsive to said differential count, for generating an output signal when the magnitude of said differential count exceeds said second predetermined threshold value;

inhibiting means, responsive to said comparator means output signal, for generating a first control signal to said counter means to inhibit and reset said counter means in response to said comparator means output signal.

8. The apparatus of claim 1, wherein said first predetermined rate of accrual is equal to said second predetermined rate of accrual.

9. The apparatus of claim 1, wherein said second resetting means includes means for varying said second predetermined rate of accrual in accordance with the speed of said vehicle.

10. A method for determining the heading of a vehicle with respect to a reference direction comprising the steps of:

a. resettably generating a differential count indicative of the distance traveled by first and second laterally aligned points on said vehicle;

b. generating, in response to said differential count, a first reset signal when the magnitude of the differential count does not exceed a first predetermined threshold value within a predetermined period of time;

c. resetting said differential count to zero in response to said first reset signal;

d. generating, from said differential count, signals indicative of the instantaneous polarity of said differential count, when the magnitude of said differential count exceeds a second predetermined threshold value;

e. generating, in response to said polarity signals a count indicative of the algebraic sum of said polarity signals, said count being incremented in response to polarity signals indicative of one polarity and decremented in response to polarity signals indicative of the other polarity; and

f. resetting said distance count to zero in response to said polarity signals.