DIGITAL COMPASS

• US 3,634,946 A
• Filed: 02/10/1969
• Issued: 01/18/1972
• Est. Priority Date: 02/10/1969
• Status: Expired due to Term

• Current Assignee: Joseph Star
• Original Assignee: Joseph Star
• Inventors: Star, Joseph
• Primary Examiner(s): Hull, Robert B.
• Application Number:
  US04/797,843
• Time in Patent Office: 1,072 Days
• Field of Search: 33/204.3-204.44,125W,1PT 324/45,47 235/150.26 343/5DP,106
• US Class Current: 33/356
• CPC Class Codes: G01C 17/26 using electric pick-offs for transmission to final indicator, e.g. photocell
• CPC Class Codes: G01C 17/30 Earth-inductor compasses

Abstract

A digital compass system is provided by continuously and repetitively scanning a magnetic field with a field directionsensing device, producing a first signal when the device is aligned in a reference direction, and producing a second signal when the sensing device is aligned in a predetermined manner with the total magnetic field at the point of exposure. Spatially related pulses occurring between the two signals are counted to provide a digital output representative of heading.

Claims

1. A digital compass system, comprising magnetic field-sensing means for repetitively scanning in successive scanning intervals an established or slowly changing magnetic field and sensing the direction of said field once during each of said respective repetitive scanning intervals, means for sensing once during each such scanning interval a predetermined reference direction relative to the system, and means responsive to the sensing of the direction of said magnetic field and of said reference direction for producing a distinctive digital output coextensive with that part of each scanning interval which is representative of the heading of the reference direction relative to the direction of the established magnetic field.

2. A digital compass system as claimed in claim 1, further comprising means for converting said digital output to one or more direct visual representations of the heading.

3. A digital compass system for a vehicle adapted to travel within an established magnetic field, comprising magnetic field-sensing means for repetitively scanning in successive scanning intervals the established magnetic field and sensing the direction of said field once during each of said respective repetitive scanning intervals, means for scanning once during each such scanning interval a predetermined reference direction relative to the system, and means responsive to the sensing of the direction of said magnetic field and of said reference direction for producing a distinctive digital output coextensive with that part of each scanning interval representative of the heading of said reference direction relative to the magnetic field.

4. A digital compass system as claimed in claim 3, further comprising means for converting said digital output to a direct visual representation of the heading.

5. A digital compass system as claimed in claim 3 further comprising means for adjusting said digital Output in correspondence with the known magnetic field variation at the geographic location of the vehicle.

6. A digital compass system, comprising magnetic field-sensing means for producing a distinctive output signal when positioned within a magnetic field in a predetermined spatial relation thereto representative of the direction of the magnetic field through the sensing means, directional-sensitive means for producing an output signal when aligned in a predetermined reference direction relative to said system, and means responsive to said field-sensing means output signal and said reference direction output signal for producing a digital output representative of the relative angular difference of the magnetic field direction and said reference direction.

7. In a digital compass as claimed in claim 6, said digital output producing means including a source of spatially related count pulse signals representative of angular increments in space to determine said digital output, and means responsive to said field-sensing means output signal and said reference direction output signal for determining the quantity of count pulse signals controlling said digital output.

8. A digital compass system, comprising a housing, gimbal means mounted on said housing, a carrier shaft universally tiltably supported within the housing on said gimbal means, a magnetic field direction-sensing device fixedly positioned on the carrier shaft, means for continuously rotating said carrier shaft about its axis, means for producing a first output signal when said field direction-sensing device is substantially orthogonal with respect to the total magnetic field to which it is exposed, means for producing a second output signal when said sensing axis is positionally oriented in a reference direction, means for producing angularly spaced pulse signals in synchronism with the rotation of said carrier shaft representative of angular increments of rotation of said carrier shaft about its axis, counting means responsive to said pulse signals, means responsive to said first and second output signals for determining the number of said pulse signals to which said counting means is responsive, and means for producing a digital output representative of the count of said counting means.

9. A digital compass system as claimed in claim 8, said magnetic field direction sensing device being a Hall Effect device.

10. A digital compass system as claimed in claim 8, further comprising means for converting said digital output into a direct visual representation of heading.

11. A digital compass system as claimed in claim 8, further comprising means for adjusting the count of said counting means in correspondence with the known magnetic field variation at the system situs.

12. A digital compass system as claimed in claim 8, further comprising means for resetting said counting means once each revolution of said carrier shaft, and means for selectively, maintaining said digital output constant for readout purposes irrespective of changes in the count of said counting means.

13. A digital compass system as claimed in claim 8, further comprising means for limiting the maximum count registered in said counting means to a predetermined count, and means for resetting said counting means when said count exceeds said predetermined count.

14. A digital compass system as claimed in claim 8, in which said second output signal enables said counting means to be responsive to said pulse signals, and said first output signal disables said counting means from being responsive to additional ones of said pulse signals.

15. A method for determining the heading from a point of observation within an established magnetic field, comprising the steps of scanning the established magnetic field with a magnetic field direction sensing device which produces a null signal at the instant that its sensing axis is in a condition of orthogonality with the total magnetic field vector, producing in synchronism with thE scanning a repetitive series of spaced-apart signal pulses representative of predetermined angular scanning increments, and counting the number of such signal pulses occurring between a predetermined reference direction of said sensing axis relative to the compass and the condition of orthogonality to produce a digital output signal representative of the heading.

16. A method as claimed in claim 15, comprising the further step of providing a visual indication of heading as a function of the digital output.

17. A method as claimed in claim 15, further comprising the step of adjusting the signal pulse count in correspondence with the known magnetic field variation at the geographic location of the vehicle.