This patent (priority July 14, 2004) proposes reduction of shock sensitivity in micromechanical devices as a patentable concept. Representative claims include claims 1 and 9:
1. A method for reducing operational shock sensitivity of a MEMS device comprising: detecting a shock experienced by the MEMS device; and, altering closed-loop parameters of the MEMS device in dependence upon the detected shock such that effects of the shock are other than compensated for.
9. A method for reducing operational shock sensitivity of a MEMS device comprising: controlling the MEMS device using a closed-loop control circuit, the closed-loop control circuit including a movable MEMS structure, a detector for sensing a position of the MEMS structure and for providing a feedback signal related to the sensed position, and a processor for receiving the feedback signal and for providing a control signal used to control the MEMS device, the control signal determined in dependence upon the feedback signal; detecting a shock experienced by the MEMS device; and, altering the control signal in dependence upon the detected shock such that a response of the closed-loop control circuit to the shock is minimized.
Claim 1 refers to the alteration of the control parameters of the micromechanical structure to avoid prolonging the effects of shock. Ignoring the fact that this claim is poorly phrased in a contradictory fashion the purpose seems to avoid an overcompensation that would actually prolong the effects of shock (see column 5, lines 19-32 of '741).
Claim 9 (and several of the other independent claims) seems clearly directed to minimizing feedback response when shock is detected.
Unfortunately the patent examiner may have missed the following prior art patents which seem relevant:
US 6327909 (filed Nov. 30, 1999)
A bistable sensor with a tunable threshold for use in microelectromechanical systems. The sensor uses electrostatic force to modify the threshold and to disable the sensor in a deflected position once a sustained extreme in vibration is detected. Potential applications include mechanical implementations of signature analysis to automatically eliminate large amplitude noise at a specific frequency, shock detection without requiring quiescent DC power consumption, and determination of the magnitude of a shock.
US 6374677 (filed Feb 22, 2000)
A micromechanical resonator including a motion arresting mechanism to rapidly damp the vibration of a resonator beginning at any given moment in time to remove vibration caused by previous events. An electrostatic clamp uses a bias voltage between an electrode and the resonator to damp the resonator and return it to its equilibrium position. A mechanical clamp includes an actuator that forces the mechanical clamp to contact the resonator. These micromechanical resonators facilitate condition based monitoring of complex electromechanical machines and components by allowing signature analysis in multiple temporal and frequency domains.