Automotive drive guide system with error monitor for a magnetic compass therein

• US 4,622,754 A
• Filed: 02/10/1983
• Issued: 11/18/1986
• Est. Priority Date: 02/15/1982
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Mitamura, Kenichi, Chujo, Satoru
• Primary Examiner(s): Haroian, Harry N.
• Application Number:
  US06/465,492
• Time in Patent Office: 1,377 Days
• Field of Search: 33/361, 33/357, 33/356
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 21/28 with correlation of data from several navigational instruments

Abstract

A drive guide system for an automotive vehicle indicates the remaining distance to a destination and the direction to the destination. In order to indicate the remaining distance and the direction in which to travel, travelling direction and travelling distance are detected. A direction sensor for detecting the terrestrial magnetic field is employed in the drive guide system. The direction sensor can be easily influenced by background noises in its surroundings. The background noise thus affects the detection of the direction of the terrestrial magnetism and thus causes errors in the calculation of the remaining distance and the direction to travel. Therefore, the variation of the background noise is sequentially monitored to detect the magnitude of the background noise affecting the detection of the direction, and when the variation exceeds acceptable limits, an error signal is produced.

Claims

1. A direction sensor with an error monitor comprising:

first means for detecting the orientation of the terrestrial magnetism and producing a periodic first signal indicative of the direction of terrestrial magnetism, said first signal having a signal phase which varies with a change in said orientation relative to said sensor and said first signal having a signal level proportional to the magnitude of the terrestrial magnetic field;

second means for producing a second signal having a level representative of a predetermined reference value, which predetermined reference value is determined based on an initial signal level of said first signal under conditions in which an initial background noise exists at a predetermined signal phase of said first signal; and

third means for detecting a subsequent signal level of said first signal at said predetermined signal phase thereof, said third means comparing said detected subsequent first signal level to said second signal level to determine the difference between the signal levels, and said third means producing a third signal when said first signal level is above said second signal level.

2. The sensor as set forth in claim 1, which further comprises fourth means for producing an alarm in response to said third signal.

3. The sensor as set forth in claim 1, wherein said first means is adapted to produce a direction-indicative reference signal having a signal phase different from the signal phase of said first signal, which difference corresponds to the orientation of the sensor with respect to a predetermined direction, and produces a phase difference-indicative signal.

4. The sensor as set forth in claim 3, wherein said third means is responsive to the phase difference-indicative signal corresponding to the difference between the signal phase of said direction-indicative reference signal and said predetermined signal phase of the first signal to compare said first signal level with said second signal level.

5. The sensor as set forth in claim 4, which further comprises fourth means, responsive to said phase difference-indicative signal, for producing a correction signal having a value corresponding to a background noise level, which fourth means determines said correction signal value based on said first signal level, and fifth means for correcting said first signal level with said correction signal.

6. A direction sensor with an error monitor comprising:

first means for producing a first signal having a value proportional to the magnitude of a first component of the terrestrial magnetic field and a second signal having a value proportional to the magnitude of a second component of the terrestrial magnetic field, phase of said second component being offset from the phase of said first component by 90°

;

second means for determining a background noise component in the value of the terrestrial magnetic field indicated by said first and second signal values and producing a correction signal for correcting said first and second signal values to eliminate the background noise component therefrom; and

third means for producing a direction-indicative signal having a value corresponding to a detected direction, said third means being responsive to said first and second signals to arithmetically determine said direction-indicative signal value based on said first and second signal values.

7. The sensor as set forth in claim 6, wherein said first means includes a first magnetic element and second magnetic element which are cyclically excited by application of power which alternates between a high level and a low level at a given interval, said first and second elements being adapted to produce signals respectively having harmonic components depending upon an external magnetic field.

8. The sensor as set forth in claim 7, wherein said first means comprises a magnetic core, a first magnetic coil transversely wound around said magnetic core, a second magnetic coil transversely wound around said magnetic core at right angles to said first geomagnetic coil, and a magnetic coil adapted to receive said power to be cyclically excited to induce said first and second signals.

9. The sensor as set forth in claim 8, wherein said third means receives said correction signal to correct said first and second signal values by said correction signal value.

10. A direction sensor with an error monitor comprising:

first means for producing a first signal having a value proportional to the magnitude of a first component of a terrestrial magnetism and a second signal having a value proportional to the magnitude of a second component of the terrestrial magnetism, the phase of said second component being offset from that of said first component by 90°

;

second means for detecting a background noise component in the detected terrestrial magnetism based on said first and second signal values, said second means producing correction signals respectively corresponding to the background noise components in said first and second component phases;

third means for correcting said first signal value by the corresponding phase of said correction signal, and for correcting said second signal value by the corresponding phase of the other correction signal value; and

fourth means for receiving said corrected first and second signals to produce a direction-indicative signal based on said corrected first and second signal values.

11. The sensor as set forth in claim 10, wherein said first means includes a first magnetic element and a second magnetic element which are cyclically excited to induce signals which alternate between a high level and a low level at a given interval, said first and second elements being adapted to produce signals respectively having harmonic components depending upon an external magnetic field.

12. The sensor as set forth in claim 11, wherein said first means comprises a magnetic core, a first magnetic coil transversely wound around said magnetic core, a second magnetic coil transversely wound said magnetic core at right angles to said first geomagnetic coil, and a magnetic coil adapted to receive power to be cyclically excited to induce said first and second signals on said first and second magnetic coils.

13. The sensor as set forth in claim 11, wherein said fourth means comprises detectors connected to said first and second magnetic elements of said first means and also connected to said second means to receive said corrected first and second signal therefrom.

14. A compass comprising:

means for measuring terrestrial magnetism and for generating a first signal indicative of the direction of the terrestrial magnetism;

means for generating a second signal representative of a predetermined reference value, said second signal being based on an initial signal level of the first signal representing an initial background noise; and

means for detecting the signal level of said first signal at a predetermined phase thereof, and comparing said detected first signal level to said second signal to determine the difference between the first signal level and said reference value for producing a third signal when said first signal level is above the reference value.

15. A compass comprising:

means for producing a first signal representing a first component of a terrestrial magnetic field and a second signal representing a second component of the terrestrial magnetic field;

means for determining a background noise component of the terrestrial magnetic field indicated by values of said first and second signal and for producing a correction signal for correcting said first and second signal values; and

means for producing a direction-indicative signal on the basis of said first and second signal values and said correction signal.

16. A direction sensor with an error monitor comprising:

means for detecting the orientation of a horizontal component of terrestrial magnetism and producing a periodic first signal the phase of which corresponds to the direction of terrestrial magnetism, said first signal being indicative of the magnitude of the terrestrial magnetic field;

means for producing a second signal indicative of a predetermined reference value which corresponds to the magnetic field magnitude which should be indicated by said first signal at a predetermined signal phase at which a background noise exists; and

means for detecting the magnetic field magnitude indicated by said first signal at said predetermined phase thereof, comparing said detected magnitude to said reference value to determine the difference therebetween, and producing a third signal when said detected magnitude exceeds said reference value.

17. A direction sensor with an error monitor comprising:

means for producing a first signal indicative of the magnitude of a first component of a terrestrial magnetic field and a second signal indicative of the magnitude of a second component of the terrestrial magnetic field, the phase of said second component being offset from the phase of said first component by 90°

;

means for determining a predetermined background noise component in the terrestrial magnetic field indicated by said first and second signals and producing a correction signal for correcting said first and second signals to eliminate the background noise component therefrom; and

means responsive to said first and second signals to arithmetically determine a direction-indicative signal indicative of an orientation of the direction sensor within said terrestrial magnetic field.

18. A direction sensor with an error monitor comprising:

means for producing a first signal indicative of the magnitude of a first component of a terrestrial magnetism and a second signal indicative of the magnitude of a second component of the terrestrial magnetism, the phase of said second component being offset from that of said first component by 9°

;

means for detecting an invariant background noise component in the detected terrestrial magnetism based on said first and second signals, and producing correction signals respectively corresponding to the background noise components in said first and second component phases;

means for correcting said first signal by the corresponding phase of said correction signal, and for correcting said second signal by the corresponding phase of the other correction signal value; and

means for receiving said corrected first and second signals to produce a direction-indicative signal based on said corrected first and second values.