Temperature compensation of an accelerometer

• US 4,750,363 A
• Filed: 06/27/1986
• Issued: 06/14/1988
• Est. Priority Date: 06/27/1986
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Original Assignee: Sundstrand Data Control, Inc. (Rtx Corporation)
• Inventors: Norling, Brian L.
• Primary Examiner(s): Chapman, John
• Application Number:
  US06/879,262
• Time in Patent Office: 718 Days
• Field of Search: 73/497, 73/517 R, 73/517 AV, 310/329, 310/346
• US Class Current: 73/497
• CPC Class Codes: G01P 1/006 used for thermal compensation
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

Prior vibrating beam accelerometers are subject to errors caused by differential thermal expansion between the vibrating beams and other accelerometer components. This problem is overcome by the present accelerometer that comprises a housing (32), a proof mass (30), a support (34,36) for mounting the proof mass with respect to the housing, and first and second force sensing elements (38,40). The force sensing elements are connected between the proof mass and the housing such that differential thermal expansion or contraction between the force sensing elements and the proof mass, support and housing results in rotation of the proof mass about a compensation axis (CA) normal to the sensitive axis (SA). The force sensing elements may extend from their respective points of connection to the proof mass in opposite directions parallel to the sensitive axis to their respective points of connection to the housing, and the force sensing elements may be connected to the proof mass at spaced apart positions on opposite sides of the compensation axis.

Claims

1. An accelerometer for measuring acceleration along a sensitive axis, comprising:

a housing;

a proof mass;

support means for mounting the proof mass with respect to the housing; and

first and second vibrating beam force transducers connected between the proof mass and the housing such that an acceleration along the sensitive axis results in a compression force on one force transducer and a tension force on the other force transducer and such that differential thermal expansion or contraction between the force transducers and the other accelerometer components results in rotation of the proof mass about a compensation axis normal to the sensitive axis.

2. The accelerometer of claim 1, wherein the force transducers are connected to the proof mass at respective connection points and extend from their respective connection points in opposite directions parallel to the sensitive axis.

3. The accelerometer of claim 2, wherein the connection points are located at spaced-apart positions on opposite sides of the compensation axis.

4. The accelerometer of claim 3, wherein each force transducer is characterized by a thermal expansion coefficient such that for a given temperature change, the thermal expansion coefficient is equal to the change in position of the force transducer at the connection point divided by the temperature change, and wherein for each force transducer, the quotient of the thermal expansion coefficient divided by the distance between the force transducer'"'"'s connection point and the compensation axis is equal to the same quotient for the other force transducer.

5. The accelerometer of claim 4, wherein the length of the first force transducer is different from the length of the second force transducer.

6. The accelerometer of claim 3, wherein each force transducer is characterized by a stiffness, such that for a given force exerted on the force transducer along the sensitive axis, the stiffness is equal to the magnitude of the force divided by the resulting change of length of the force transducer, and wherein the product of the stiffness of each force transducer multiplied by the distance between the force transducer'"'"'s connection point and the compensation axis is equal to the same product for the other force transducer.

7. The accelerometer of claim 1, wherein the support means comprises flexure means attached between the proof mass and the housing, the flexure means permitting rotation of the proof mass with respect to the housing about a hinge axis normal to the sensitive axis and to the compensation axis.

8. The accelerometer of claim 7, wherein the force transducers are connected to the proof mass at respective connection points and extend from their respective connection points in opposite directions parallel to the sensitive axis, the connection points being located at spaced-apart positions on opposite sides of the compensation axis.

9. The accelerometer of claim 8, wherein the proof mass is rectangular in shape, one dimension of the proof mass being parallel to the sensitive axis and another dimension of the proof mass being parallel to the compensation axis.

10. The accelerometer of claim 8, wherein the proof mass is cylindrical in shape, the axis of the cylindrical proof mass coinciding with the compensation axis.

11. An accelerometer for measuring acceleration along a sensitive axis, comprising:

a housing;

a proof mass;

support means for mounting the proof mass with respect to the housing, the support means comprising a frame pivotally mounted to the housing for rotation about a compensation axis normal to the sensitive axis, and flexure means extending between the proof mass and the frame, the flexure means permitting rotation of the proof mass with respect to the frame about a hinge axis normal to the sensitive axis and to the compensation axis; and

,

first and second force transducers connected between the proof mass and the housing such that an acceleration along the sensitive axis results in a compression force on one force transducer and a tension force on the other force transducer and such that differential thermal expansion or contraction between the force transducers and the other accelerometer components results in rotation of the proof mass about the compensation axis.

12. The accelerometer of claim 11, wherein the force transducers are connected to the proof mass at respective connection points and extend from their respective connection points in opposite directions parallel to the sensitive axis, the connection points being located at spaced apart positions on opposite sides of the compensation axis.