Apparatus for determining positional coordinates utilizing the terrestrial magnetism as a directional reference

• US 4,300,390 A
• Filed: 09/14/1979
• Issued: 11/17/1981
• Est. Priority Date: 01/24/1979
• Status: Expired due to Term

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Shimizu, Sachinobu
• Primary Examiner(s): Martin, Jr., William D.
• Application Number:
  US06/075,421
• Time in Patent Office: 795 Days
• Field of Search: 33/356, 33/342, 33/352, 33/333, 33/316, 33/317 R, 33/317 D, 33/361, 33/362, 33/1 M, 73/178 R
• US Class Current: 73/178.00R
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments

Abstract

Apparatus for determining the positional coordinates of a moving object including a plurality of magnetic field vector detecting devices, an inclination detecting device for detecting inclination of the magnetic field vector detecting devices, a distance detecting device for detecting the distance that the moving object has travelled, and arithmetic means which receives outputs from the magnetic field vector detecting devices as well as from the inclination detecting device, calculates the horizontal component force vector of the geomagnetic field by using the outputs from the magnetic field vector detecting devices and from the inclination detecting device, further calculates the vector in the progress direction of the moving object by referring to the horizontal component force vector, and integrates the product of the vector in the progress direction and the output from the distance detecting device, whereby the positional coordinates are obtained as the output of the arithmetic means, and the coordinates which have been set at an arbitrary point are replaced by the newly determined coordinates when turning to the right or left is carried out at the arbitrary point correctly as ordered.

Claims

1. Apparatus for determining the positional coordinates of a moving object comprising:

a plurality of magnetic field vector detecting devices each having a rotary magnetic piece and a fixed coil, said detecting devices being disposed in spaced apart fixed relationships to each other;

an inclination detecting device for detecting the inclination of said magnetic field vector detecting devices relative to a vertical direction;

a distance detecting device for detecting the distance that the moving object has travelled during a particular period of time; and

arithmetic means which receives output from said magnetic field vector detecting devices as well as from said inclination detecting device, calculates the horizontal component force vector of the geomagnetic field by using said output from said magnetic field vector detecting devices and from said inclination detecting device, further calculates the vector in the progress direction of the moving object referring to said horizontal component force vector, and integrates the product of said vector in the progress direction and the output from said distance detecting device, whereby the positional coordinates are obtained as the output of said arithmetic means, and coordinates which have initially been set at an arbitrary point are replaced by the newly determined coordinates when turning to the right or left is carried out at said arbitrary point correctly as ordered.

2. Apparatus according to claim 1, wherein each said coil of said magnetic field vector detecting device is disposed around the rotary axis of its corresponding rotary magnetic piece such that the magnetic flux density in the magnetic piece becomes maximum with respect to the magnetic field vector within a plane perpendicular to said rotary axis, and said coil is provided with such a cross section that becomes maximum within the maximum cross section of said magnetic piece but its contour does not extend out of said maximum magnetic piece cross section.

3. Apparatus according to claim 1, wherein the rotary magnetic piece of each magnetic field vector detecting device is alinged along the rotary axis of a motor which is synchronizingly rotated by means of a synchronizing circuit comprising signal extracting means for extracting a signal having pulse widths corresponding to the difference between the reference input signal and the rotary phase of the motor, signal detecting means for detecting a signal having an amplitude corresponding to the rotational speed of said motor, an amplitude control circuit which varies its output in compliance with the result of comparison between the output of said signal detecting means and a reference voltage, and a multiplying circuit for developing a pulse signal corresponding to the product of the pulse width obtained by said signal extracting means and the amplitude of the output signal developed by said amplitude control circuit, whereby said motor is synchronizingly driven by the pulse signal, the amplitude of which is changed in response to the rotational speed of the motor and the pulse width of which is varied in compliance with the difference between the reference input signal and the rotary phase of the motor.

4. Apparatus according to claim 1, and further comprising a motor for rotating said rotary magnetic pieces, the rotary magnetic pieces of said magnetic field vector detecting devices being disposed in series along the rotary axis of said motor, said apparatus having an angular position detecting device for detecting the rotated position of said rotary magnetic pieces, said angular position detector comprising a rotary plate disposed along the rotary axis and having a slit provided therein, light emitting and receiving elements which are disposed at both sides of said plate so as to face to each other, a circuit for performing peak detection of the output from said light receiving element, a circuit for generating a reference voltage in response to the output of said peak detection circuit, and a level slice circuit for performing a level slice operation in respect of the output of said peak detection circuit, whereby the output from said level slice circuit is used as the rotated position information of the rotary magnetic piece for determining the positional coordinates.

5. Apparatus accordingly to claim 1, wherein there are provided three magnetic field vector detecting devices.

6. Apparatus according to claim 5 wherein a plurality of difference signals are developed from the outputs of said plurality of magnetic field vector detecting devices by setting one of said outputs as a common subtrahend or a minuend to the others, and the magnetic field due to the magnetic body is calculated using the ratio of said difference signal and an arbitrary difference signal, thereby eliminating the influence of the magnetic field on said magnetic body.

7. Apparatus according to claim 1, wherein said arithmetic means comprises a DA converter which receives an analog signal from each said magnetic field vector detecting device as well as a digital signal consisting of the digital value for the crest value of a reference since wave and develops an output proportional to the product of said analog and digital input signals;

an AD converter which performs AD conversion by means of integrating the output of said DA converter over a period equal to an integer multiple of said reference sine wave period; and

a vector component arithmetic circuit which is adapted to obtain the digital value with respect to the preset phase component vector of the input signal from said AD converter.

8. Apparatus according to claim 1, wherein said inclination detecting device is provided with a magnet and a coil arranged so as to be subject to displacement when inclined, and supplies said coil with an electric current having a direction and magnitude sufficient to eliminate said displacement.