Electromagnetic actuator equipped with means for adjusting its mobile polar element

• US 6,556,114 B1
• Filed: 06/21/2001
• Issued: 04/29/2003
• Est. Priority Date: 12/30/1998
• Status: Expired due to Fees

• Current Assignee: Thales Avionics SA (Thales SA)
• Original Assignee: Thales Avionics SA (Thales SA)
• Inventors: Guillemin, Pierre, Giroud, Pierre
• Primary Examiner(s): DONOVAN, LINCOLN D
• Application Number:
  US09/857,212
• Time in Patent Office: 677 Days
• Field of Search: 355/78-86, 355/222, 355/220, 355/228-9, 355/230, 355/234, 355/236-7, 355/244, 355/258, 355/274, 200/61.45 M, 200/61.53
• US Class Current: 335/229
• CPC Class Codes: G01V 1/181 Geophones
• CPC Class Codes: H01F 7/081 Magnetic constructions

Abstract

An electromagnetic accelerometer including a stationary stator element (12) associated with a movable polar element (14) securable to an external member (2), the stationary stator element (12) and the movable polar element (14) forming a magnetic circuit and defining between them at least two gaps (51), a magnet (5) helping to create magnetic field lines in the magnetic circuit, a coil (6) and a mechanism for energizing the coil for controlling the displacement of the movable polar element (14) through electromagnetic induction phenomena. The electromagnetic accelerometer further includes an adjustment polar element (15) for placing the movable polar element (14) in an adjusted position with respect to that of the stationary stator element (12), by deviating the magnetic field lines.

Claims

1. Electromagnetic accelerometer comprising a movable mass suspended from a peripheral frame, an electromagnetic actuator configured to compensate for displacements of the movable mass with respect to a reference position, the actuator comprising a stationary stator element associated with a movable polar element securable to the movable mass, the stationary stator element and the movable polar element forming a magnetic circuit and defining between them at least two gaps, a magnet helping to create magnetic field lines in the magnetic circuit, a coil for controlling the displacement of the movable polar element through electromagnetic induction phenomena, a position sensor detecting a position of the movable mass secured to the movable polar element, an adjustment polar element which cooperates with the stationary stator element so as to place the movable polar element in an adjusted position with respect to that of the stationary stator element, by deviating the magnetic field lines, placing the movable mass, in the absence of motion of the accelerometer, in the reference position.

2. Electromagnetic accelerometer according to claim 1, wherein the position sensor comprises strain gauges, the reference position corresponding to a strain-free state in respect of the gauges.

3. Electromagnetic accelerometer according to claim 1, wherein the adjustment polar element is engageable in an opening of the stationary stator element, insertion of the adjustment polar element causing a displacement of the movable polar element from an initial position to a desired adjusted position detected by the strain gauges, the movable polar element being closer to the opening in the initial position than in the adjusted position.

4. Electromagnetic accelerometer according to claim 1, wherein the adjustment polar element has a form of a plug.

5. Electromagnetic accelerometer according to claim 3, wherein the adjustment polar element comprises a longitudinally striated portion which cooperates with the opening whose edge is smooth.

6. Electromagnetic accelerometer according to claim 5, wherein the striated portion is followed by a conical portion in turn followed by an active portion of smaller diameter than that of the striated portion.

7. Electromagnetic accelerometer according to claim 1, wherein the adjustment polar element is made from a soft ferromagnetic material.

8. Electromagnetic accelerometer according to claim 3, wherein the insertion of the adjustment polar element is carried out utilizing a differential screw.

9. Electromagnetic actuator according to claim 2, wherein the strain gauges are associated with a system for slaving the position of the movable polar element which provides the coil with a slaving current.

10. Electromagnetic accelerometer according to claim 9, wherein, in the desired adjusted position of the movable polar element, the movable mass and the peripheral frame are in substantially a same plane.

11. Process for adjusting a position of a movable polar element of an electromagnetic accelerometer, the movable polar element being securable to a movable mass, the accelerometer comprising a stationary stator element associated with the movable polar element, the stationary stator element and the movable polar element forming a magnetic circuit and defining between them at least two gaps, a magnet helping to create magnetic field lines in the magnetic circuit, a coil for controlling displacement of the movable polar element through electromagnetic induction phenomena, comprising the following steps:

placement of the movable polar element in an initial position with respect to the stationary stator element,

orientation of the electromagnetic actuator such that a displacement of the movable polar element can occur substantially perpendicularly to gravity,

engagement into an opening of the stationary stator element of a polar element for adjusting a position of the movable polar element with respect to that of the stationary stator element, the engagement, by deviating the magnetic field lines, causing a displacement of the movable polar element until the movable polar element has reached a desired adjusted position, the desired adjusted position being detected by the strain gauges, the movable polar element being, in the initial position, nearer to the opening than in the desired adjusted position.