Pulse-driven accelerometer arrangement

• US 4,987,779 A
• Filed: 02/28/1989
• Issued: 01/29/1991
• Est. Priority Date: 02/28/1989
• Status: Expired due to Term

• Current Assignee: VTI Holding Oy
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: McBrien, Gregory J.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US07/317,217
• Time in Patent Office: 700 Days
• Field of Search: 73/517 B
• US Class Current: 73/514.18
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means

Abstract

An accelerometer arrangement includes an acceleration sensor that includes two capacitor plates having respective parallel mutually facing major surfaces which bound a sensing gap therebetween. A plate-shaped electrically chargeable proof mass is resiliently mounted in the gap in parallelism with the major surfaces for displacement in response to the action of acceleration forces thereon out of a substantially central rest position toward one or the other of the major surfaces depending on the direction of the acceleration forces. An electrical potential difference is established between the capacitor plates to generate respective electrostatic fields between the capacitor plates and the proof mass which cause a proof mass electrical potential variation having a magnitude and sense depending on the extent and direction of the displacement of the proof mass out of its rest position. The variation is evaluated and an a pulse train that is proportionate to the variation is generated and supplied to the proof mass to esatablish thereat a voltage sufficient for electrostatic forces caused thereby between the proof mass and the capacitor plates to return the proof mass to the rest position thereof against the action of the acceleration forces on the proof mass.

Claims

1. An accelerometer arrangement comprising

at least one acceleration sensor including two capacitor plates having respective parallel mutually facing major surfaces which bound a sensing gap therebetween, a plate-shaped electrically chargeable proof mass, and means for resiliently mounting said proof mass in said gap in parallelism with said major surfaces for displacement in response to the action of acceleration forces thereon out of a substantially central rest position toward one or the other of said major surfaces depending on the direction f said acceleration forces;

means for establishing an electrical potential difference between said capacitor plates to generate respective electrostatic fields between said capacitor plates and said proof mass which cause a proof mass electrical potential variation having a magnitude and sense depending on the extent and direction of said displacement of said proof mass out of said rest position thereof, including means for applying to said capacitor plates respective D.C. voltages which are at substantially constant different levels; and

means for evaluating said variation and for supplying to said proof mass an electrical control signal sufficient to establish on said proof mass a voltage that is proportionate to said variation and at which electrostatic forces caused thereby between said proof mass and said capacitor plates return said proof mass to said rest position thereof against said action of said acceleration forces thereon, including means for generating a train of pulses which alternate between at least two voltage levels and the succession, duration and sense of which are such that the time average of said pulses substantially establishes said voltage on said proof mass,

said generating means including a D.C. source, switching means connected to said source and having an output connected to said proof mass, means for controlling said switching means to issue said pulse train at said output thereof; and

said evaluating means further including means for detecting the effects of said pulse train on the potentials appearing at said capacitor plates and issuing an output signal representative thereof, means for demodulating said output signal with said pulse train, and means for supplying the thus demodulated signal to said controlling means to cause the latter to control the waveform of said pulse train in dependence on the value of said demodulated signal.

2. An arrangement for driving at least one acceleration sensor which includes two capacitor plates having respective parallel mutually facing major surfaces which bound a sensing gap with one another and a plate-shaped electrically chargeable proof mass that is resiliently mounted in the gap in parallelism with the major surfaces for displacement in response to the action of acceleration forces thereon out of a substantially central rest position toward one or the other of the major surfaces depending on the direction of the acceleration forces, comprising

means for establishing an electrical potential difference between the capacitor plates to generate respective electrostatic fields between the capacitor plates and the proof mass which cause a proof mass electrical potential variation having a magnitude and sense depending on the extent and direction of the displacement of the proof mass out of its rest position, including means for applying to the capacitor plates respective D.C. voltages which are at substantially constant different levels;

and

means for evaluating said variation and for supplying to the proof mass an electrical control signal sufficient to establish on the proof mass a voltage that is proportionate to said variation and at which electrostatic forces caused thereby between the proof mass and the capacitor plates return the proof mass to the rest position thereof against the action of said acceleration forces thereon, including means for generating a train of pulses which alternate between at least two voltage levels and the succession, duration and sense of which are such that the time average of said pulses substantially establishes said voltage on the proof mass,

said generating means including a D.C. source, switching means connected to said source and having an output connected tot he proof mass, means for controlling said switching means to issue said pulse train at said output thereof; and

said evaluating means further including means for detecting the effects of said pulse train on the potentials appearing at the capacitor plates and issuing an output signal representative thereof, means for demodulating said output signal with said pulse train, and means for supplying the thus demodulated signal to said controlling means to cause the latter to control the waveform of said pulse train in dependence on the value of said demodulated signal.