US3663953A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Helicopter carried magnetometer assembly compensated for the parasitic field of the helicopter
Assignee: Commissariat à l'Énergie Atomique et Aux Énergies Alternatives
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Filing: 1970-09-17
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Granted: 1972-05-16
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Expires: 1990-09-17
Abstract
Abstract A magnetometer assembly for detection of ferromagnetic targets carried by a helicopter is compensated for the parasitic magnetic field generated by the helicopter. First and second magnetometer heads are carried by the helicopter and located at points aligned with the axis of the main rotor. An electric control signal representative of the difference of the total magnetic fields at the first and second heads is obtained and is used to compensate the parasitic component due to the helicopter in the magnetic field at one of the points. The distance between the heads and the rotor is large as compared to the variations of the position of the magnetic center of gravity of the helicopter and as compared to the distance between the heads.
Inventors
- 👤 Antoine Salvi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 20:39
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/02; G01R33/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
141 words
A method of compensating a magnetometer system carried by a helicopter having a single main rotor for parasitic magnetic fields associated with the helicopter, the steps of measuring the difference between the magnetic fields at two points connected to the helicopter and separated by a distance which is small compared with their distance from the barycenter of the magnetic masses of the helicopter, the latter distance being large compared with the amplitude of the displacements of said barycenter during maneuvering and changes in the loading of the helicopter, deriving from said difference an electric control signal proportional to the said difference, and compensating the parasitic component due to the helicopter in the magnetic field measured at one of the said points using the control signal, wherein said points are aligned on an axis which coincides with that of the rotor shaft.
Claim 2
Independent Claim
141 words
A method of compensating a magnetometer system carried by a helicopter having a single main rotor for parasitic magnetic fields associated with the helicopter, the steps of measuring the difference between the magnetic fields at two points connected to the helicopter and separated by a distance which is small compared with their distance from the barycenter of the magnetic masses of the helicopter, the latter distance being large compared with the amplitude of the displacements of said barycenter during maneuvering and changes in the loading of the helicopter, deriving from said difference an electric control signal proportional to the said difference, and compensating the parasitic component due to the helicopter in the magnetic field measured at one of the said points using the control signal, wherein said points are aligned on an axis which coincides with that of the rotor shaft.
Claim 3
Dependent Claim
41 words
A method as claimed in claim 1, wherein compensation is carried out by adjusting automatically and in proportion to the control signal a DC electric current in compensating coils situated substantially at the barycenter of the magnetic masses of the helicopter.
Claim 4
Dependent Claim
56 words
A method as claimed in claim 1, wherein compensation is carried out by multiplying said control signal by a predetermined value representing the ratio between the parasitic field at one of said points and said difference, and by subtracting the electric signal so obtained from an electric signal representing the field at one of said points.
Claim 5
Dependent Claim
173 words
A magnetometer assembly for a helicopter having a single main rotor carried by a shaft, said assembly being compensated for the parasitic magnetic field generated by the helicopter, comprising a first and a second magnetometer head carried by the helicopter, means for providing a signal representative of the value of the total magnetic field sensed by the first head, means for determining the difference between the respective values of the total magnetic field sensed by the first and second heads, means for generating a control voltage in direct proportion with said difference, and means responsive to said control voltage for modifying said signal, wherein the improvement consists in that the first head and the second head are located at points aligned with the axis of the shaft of said rotor, the length between each of said points and the shaft being large as compared to the variations of the position of the magnetic center of gravity of the helicopter and as compared to the length between the first head and the second head.
Claim 6
Dependent Claim
173 words
A magnetometer assembly for a helicopter having a single main rotor carried by a shaft, said assembly being compensated for the parasitic magnetic field generated by the helicopter, comprising a first and a second magnetometer head carried by the helicopter, means for providing a signal representative of the value of the total magnetic field sensed by the first head, means for determining the difference between the respective values of the total magnetic field sensed by the first and second heads, means for generating a control voltage in direct proportion with said difference, and means responsive to said control voltage for modifying said signal, wherein the improvement consists in that the first head and the second head are located at points aligned with the axis of the shaft of said rotor, the length between each of said points and the shaft being large as compared to the variations of the position of the magnetic center of gravity of the helicopter and as compared to the length between the first head and the second head.
Claim 7
Dependent Claim
57 words
An assembly according to claim 4, wherein the said heads are situated in a tube of non-magnetic material fiXed beneath the helicopter and in an extension of the axis of the rotor shaft. 6.A magnetometer assembly according to claim 5, wherein the tube is pivotally connected to the helicopter around a flange mounted on the floor thereof.
Claim 8
Dependent Claim
48 words
A magnetometer assembly according to claim 5, wherein the tube is telescopic and the lower portions can be extended from a fixed upper portion offset relative to the rotor shaft and so positioned angularly that the lower portion containing the heads is substantially in line with the shaft.
Claim 9
Dependent Claim
60 words
A magnetometer assembly as claimed in claim 4, for detecting anomalies in the earth''s magnetic field, characterized in that the distances x between the heads and the rotor shaft and delta x between the two heads are such that the values for the earth''s magnetic field disturbed by the anomalies are not equal at the level of the two heads.
Claim 10
Dependent Claim
24 words
A device as claimed in claim 8, wherein x is between 7 and 10 m and delta x is between 0.5 and 1 m.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-05-16 | 1975-11-15 | 1976-05-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-05-16 | 1979-11-15 | 1980-05-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-05-16 | 1983-11-15 | 1984-05-16 | $7700.00 | Window Closed / Lapsed |