Navigation instrument for the navigation of land vehicles

• US 4,114,437 A
• Filed: 07/22/1977
• Issued: 09/19/1978
• Est. Priority Date: 12/27/1976
• Status: Expired due to Term

• Current Assignee: Bodenseewerk
• Original Assignee: Bodenseewerk
• Inventors: Krogmann, Uwe
• Primary Examiner(s): Woodiel, Donald O.
• Application Number:
  US05/818,153
• Time in Patent Office: 424 Days
• Field of Search: 73/178 R, 364/450, 364/453, 364/444, 364/449, 364/424, 180/98, 244/175
• US Class Current: 73/178.00R
• CPC Class Codes: G01C 19/38 with north-seeking action by other than magnetic means, e.g. gyrocompasses using earth's rotation
• CPC Class Codes: G01C 21/12 executed aboard the object being navigated; Dead reckoning

Abstract

The vehicle is operated over land which is described by a grid coordinate system having a north direction offset from geographic north. The vehicle has a pick-up to determine its heading speed along its longitudinal center line. The spin axis of a free gyro establishes a reference axis. A meridian gyro determines the angle, if any, between said reference axis and geographic north at the start of a mission. At the start of the mission a computer is supplied with information as to the starting point in said grid coordinate system, the angle between geographic north and grid north, and an estimated corrective factor (based on the type of terrain to be traversed) to be applied to the measured heading speed. The computer continuously determines, for display, the position of the vehicle in said grid system. Upon the vehicle reaching a landmark whose coordinates in said grid system are known, the correct coordinates for the then location of the vehicle are supplied to the computer and the computer determines the error in the estimated corrective factor and thus determines a revised corrective factor to be employed upon leaving said landmark.

Claims

1. A navigation instrument for the navigation of land vehicles in a grid coordinate system having a north direction which does not necessarily coincide with geographic north but may differ therefrom by a grid convergence angle, said instrument being characterized by:

(a) movement pick-up means for generating a signal representing the magnitude of longitudinal movement of the vehicle;

(b) a gyro reference device including

free gyro means whose spin axis establishes a reference axis and which determines the angle α

_K between the reference axis and the longitudinal axis of the vehicle,

means for determining geographic north and, if said reference axis initially is offset from geographic north, for subsequently producing signals representing the angles between said reference axis and geographic north;

(c) a computer device for receiving said signals and said grid convergence angle and for generating output signals indicative of the vehicle position in said grid coordinate system; and

(d) means forming a part of at least one of said devices for correcting for the influence of the rotation of the earth on the spin axis and said free gyro means.

2. An instrument as set forth in claim 1, wherein said means for determining north is a north seeking meridian gyro means.

3. A navigation instrument as set forth in claim 2, wherein the last mentioned means generates a follow-up signal

4. A navigation instrument as set forth in claim 2, wherein the computer device computes the deviation rate ω

_ZG of the free gyro means from the grid coordinates and from the latitude φ

derived, in turn, therefrom and to integrate said rate with respect to time, taking the initial conditions into consideration, in order to determine the angle between said gyro reference axis and said grid north direction, and also takes this angle into consideration when determining the heading angle of the vehicle axis with respect to the grid during the generation of the vehicle position output signals.

5. A navigation instrument as set forth in claim 4, wherein

said meridian gyro means includes a gyro, a pick-off for producing signals responsive to the deviation of the gyro from wire zero position, means for highly amplifying said pick-off signals, and a torquer to exert counter torque to said gyro in response to said highly amplified signals;

and

said computer device multiplies a signal proportional to said amplified pick-off signal by the reciprocal value of the cosine of latitude of the vehicle to generate a signal indicative of the angle between said wire zero position and the grid north direction.

6. A navigation instrument as set forth in claim 1, wherein

said movement pick-up means is a velocity pick-up producing a velocity signal;

and

said computer device determines the heading angle of the vehicle axis with respect to the grid, multiplies the velocity signal by the sine and cosine, respectively, of said heading angle to produce products, and integrates said products with respect to time, in order to produce said output signals of the computer device.

7. A navigation instrument as set forth in claim 1, wherein

said movement pick-up means is a distance pick-up producing distance increment signals;

and

said computer device determines the heading angle of the vehicle axis with respect to the grid, multiplies a predetermined number of said distance increment signals by the sine and cosine, respectively, of said heading angle to produce products, and sums said products, in order to produce said output signals of the computer device.

8. A navigation instrument as set forth in claim 1, characterized in that the movement pick-up is a distance pick-up coupled to the vehicle drive means, said pick-up providing distance increment signals, the computer being arranged to multiply each distance increment signal or each predetermined number of distance increment signals by the size and cosine, respectively, of the respective grid angle and to sum the products thus obtained in order to derive the coordinates of the vehicle in the grid coordinate system.

9. A navigation instrument as set forth in claim 1, wherein the computer device carries out the following operations:

(a) applies a corrective factor W_A to the distance signal S_gem measured as said movement signal or derived by integrating the velocity to provide a corrected distance signal S on which the position computation is based,

(b) computes the coordinates x_F, y_F respecting the vehicle position in the grid coordinate system as output signals of the computer device from the grid heading angle signal α

_K and the corrected distance signal S,

(c) a reading in of the coordinates x_S, y_S of a known geodetic point defined in the grid coordinate system,

(d) forms the differences Δ

x, Δ

y of the coordinates x_F, y_F representing the vehicle coordinates and of the associated read in coordinates x_S, y_S of the geodetic point,

(e) determines the correction Δ

α

_K and Δ

W_A or Δ

K_v, respectively, of the grid heading angle signal and the corrective factor W_A, respectively, of the displacement signal S_gem in accordance with the equations;

##EQU5## wherein S_x and S_y are the coordinate differences between the start point of the vehicle and the said known geodetic point,

(f) corrects the output signals x_F, y_F by the said differences Δ

x and Δ

y, respectively, and

(g) continues to compute the coordinates representing the vehicle position in the grid coordinate system with the corrective factor W_A corrected by the correction Δ

W_A and with the grid heading angle corrected by the correction Δ

α

_K.