Compass

• US 4,539,760 A
• Filed: 10/12/1983
• Issued: 09/10/1985
• Est. Priority Date: 10/12/1982
• Status: Expired due to Fees

• Current Assignee: ROKE Manor Research Limited (Chemring Group PLC)
• Original Assignee: Plessey Overseas Limited (Marconi Holdings Company Limited)
• Inventors: Foster, Michael R., Marchent, Brian G.
• Primary Examiner(s): Little, Willis
• Application Number:
  US06/541,026
• Time in Patent Office: 699 Days
• Field of Search: 33/363 R, 33/352, 33/355 R, 33/356, 33/357, 33/361, 33/362
• US Class Current: 33/356
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses

Abstract

An electronic compass for vehicles comprising three magnetic sensors arranged in use to be respectively responsive to orthogonal components of a magnetic field which includes the earth'"'"'s magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, tilt sensor means responsive to vehicle tilt with respect to the horizontal plane, data processor and storage means arranged to store signals derived from the sensors as the vehicle is turned through a compass setting cycle, and signal processor means responsive to electrical signals produced by the sensors after the setting cycle has been completed and to the signals stored during the setting cycle, for providing compensated signals related to the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for and further processor means to which the compensated signals are applied and which is responsive to the tilt sensor means for modifying the compensated signals to produce output signals appertaining to vehicle heading in which the effects of tilt are compensated for.

Claims

1. A navigation system for vehicles which includes an electronic compass comprising three magnetic sensors arranged in use to be respectively responsive to orthogonal components of a magnetic field which includes the earth'"'"'s magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, tilt sensor means responsive to vehicle tilt with respect to the horizontal plane, data processor and storage means arranged to store signals derived from the sensors as the vehicle is turned through a compass setting cycle, and signal processor means responsive to electrical signals produced by the sensors after the setting cycle has been completed and to the signals stored during the setting cycle, for providing compensated signals related to the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for and further processor means to which the compensated signals are applied and which is responsive to the tilt sensor means for modifying the compensated signals to produce compass output signals appertaining to vehicle heading in which the effects of tilt are compensated for, the system including also, means for sensing the velocity of the vehicle in which the compass is mounted, data infeed means operable for providing data appertaining to an original map reference, navigation computer means responsive to data signals derived from the velocity indicator, the compass output signals, and the data infeed means for providing data for display means whereby the display means is arranged to provide a display indicative of the position or location of the vehicle.

2. A navigation system for vehicles as claimed in claim 1 wherein the tilt sensor means comprises mechanical or electro-mechanical tilt sensors responsive to vehicle tilt to which the two magnetic sensors are subject, to provide signals appertaining to the tilt of the magnetic sensors in two orthogonal planes.

3. A navigation system for vehicles as claimed in claim 1 wherein the data storage means includes capacity to store data corresponding to or derived from nine values sensed by each of the sensors during the setting cycle and wherein the signal processor means is adapted to solve an equation utilizing these values to provide the bearing indication.

4. A navigation system for vehicles which includes an electronic compass comprising three magnetic sensors arranged in use to be respectively responsive to orthogonal components of a magnetic field which includes the earth'"'"'s magnetic field and a spurious magnetic field which is associated with the vehicle, for producing electrical signals corresponding to said components, tilt sensor means responsive to vehicle tilt with respect to the horizontal plane, data processor and storage means arranged to store signals derived from the sensors as the vehicle is turned through a compass setting cycle, and signal processor means responsive to electrical signals produced by the sensors after the setting cycle has been completed and to the signals stored during the setting cycle, for providing compensated signals related to the bearing appertaining to the heading of the vehicle in which the effects of the spurious magnetic field are compensated for and further processor means to which the compensated signals are applied and which is responsive to the tilt sensor means for modifying the compensated signals to produce compass output signals appertaining to vehicle heading in which the effects of tilt are compensated for, the system including also, distance measuring apparatus, and a computer responsive to said apparatus and to signals derived from the compass for providing output signals indicative of location in terms of map co-ordinates.