# US 8,783,103 B2 · Offset detection and compensation for micromachined inertial sensors > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,103 B2 - Document ID: US8783103B2 - Status: Granted - Kind: B2 - Application number: 12/545,334 - Filed: 2009-08-21 - Published: 2011-02-24 - Granted: 2014-07-22 - Earliest claimed: 2009-08-21 - Assignees: Analog Devices, Inc. - Applicants: William A. Clark; John A. Geen - Inventors: William A. Clark; John A. Geen - Web page: https://patentgrep.com/patent/US8783103B2 ## CPC - G01P 15/097: by vibratory elements - G01C 19/5712: the devices involving a micromechanical structure - G01P: MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT (measuring or recording blood flow A61B5/02, A61B8/06; monitoring speed or deceleration of electrically-propelled vehicles B60L3/00; vehicle lighting systems adapted to indicate speed B60Q1/54; determining position or course in navigation, measuring ground distance in geodesy or surveying G01C; combined measuring devices for measuring two or more variables of movement G01C23/00; measuring velocity of sound G01H; measuring velocity of light G01J7/00; measuring direction or velocity of solid objects by reception or emission of radiowaves or other waves and based on propagation effects, e.g. Doppler effect, propagation time, direction of propagation, G01S; measuring speed of nuclear radiation G01T; measuring acceleration of gravity G01V; {measuring or recording the speed of trains B61L23/00; speed indicators incorporated in motor vehicles B60K35/00; measuring frequency or phase G01R; traffic control G08G}) - G01C: MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY (measuring liquid level G01F; radio navigation, determining distance or velocity by use of propagation effects, e.g. Doppler effects, propagation time, of radio waves, analogous arrangements using other waves G01S) ## Abstract Error sources relating to the drive signal applied to the resonator of an inertial sensor, such as in-phase offset errors relating to the drive signal and/or electronic pass-through of the drive signal to accelerometer sense electronics, are detected by modulating the drive signal and sensing accelerometer signals that are induced by the modulated drive signal. Error sources related to aerodynamics of an inertial sensor resonator are detected by modulating the distance between the resonator and the underlying substrate and sensing accelerometer signals that are induced by such modulation. Compensating signals may be provided to substantially cancel errors caused by such error sources. ## Claims ### Claim 1 A method of detecting at least one error source relating to the magnitude of a drive signal applied to the resonator in an inertial sensor having a resonator and an accelerometer for measuring a Coriolis acceleration signal in a Coriolis acceleration signal band of a Coriolis channel, wherein the at least one error source induces corresponding error signals in the Coriolis channel that are in-phase with the drive signal and include error signals that affect the Coriolis acceleration signal, the method comprising: providing a modulated drive signal to the resonator, the modulated drive signal modulating the magnitude of the drive force applied to the resonator so as to modulate the magnitude of the at least one error source so as to induce corresponding modulated error signals in the Coriolis channel, wherein the error signals are modulated at a frequency outside of the Coriolis acceleration signal band; sensing the modulated error signals in the Coriolis channel; and providing at least one compensating signal responsive to the sensed modulated error signals to substantially cancel errors introduced by the at least one error source that affect the Coriolis acceleration signal. ### Claim 2 (depends on 1) A method according to claim 1, wherein providing the modulated drive signal to the resonator comprises: modulating a drive signal using one of amplitude modulation, frequency modulation, on/off keying, or a spread spectrum modulation. ### Claim 3 (depends on 1) A method according to claim 1, wherein sensing modulated error signals induced by the modulated drive signal includes demodulating accelerometer signals based on a modulation signal used to modulate the drive signal. ### Claim 4 (depends on 1) A method according to claim 1, wherein the at least one error source includes in-phase offset error that is substantially in-phase with the modulated drive signal, and wherein providing at least one compensating signal responsive to the sensed accelerometer signals comprises providing at least one compensating signal to substantially cancel the in-phase offset error. ### Claim 5 (depends on 4) A method according to claim 4, wherein providing at least one compensating signal to substantially cancel the in-phase offset error comprises providing a compensating signal to a set of in-phase-compensating electrodes to substantially cancel the in-phase offset error. ### Claim 6 (depends on 4) A method according to claim 4, wherein the at least one error source includes drive force misalignment. ### Claim 7 (depends on 1) A method according to claim 1, wherein the at least one error source includes electronic pass-through of the drive signal to the accelerometer, and wherein providing at least one compensating signal responsive to the sensed modulated error signals comprises providing at least one compensating signal to substantially cancel the pass-through. ### Claim 8 (depends on 7) A method according to claim 7, wherein providing at least one compensating signal to substantially cancel the pass-through comprises providing a compensating signal to the accelerometer to substantially cancel the pass-through. ### Claim 9 (depends on 1) A method according to claim 1, wherein the resonator includes a plurality of shuttles coupled to resonate at a single resonance frequency. ### Claim 10 (depends on 1) A method according to claim 1, wherein the accelerometer includes at least one of: a sense electrode in a plane of the resonator; or a sense electrode out of the plane of the resonator. ### Claim 11 An inertial sensor comprising: a resonator; an accelerometer for measuring a Coriolis acceleration signal in a Coriolis acceleration signal band of a Coriolis channel, wherein the at least one error source induces corresponding error signals in the Coriolis channel that are in-phase with the drive signal and include error signals that affect the Coriolis acceleration signal; a resonator driver configured to provide a modulated drive signal to the resonator, the modulated drive signal modulating the magnitude of the drive force applied to the resonator so as to modulate the magnitude of the at least one error source so as to induce corresponding modulated error signals in the Coriolis channel, wherein the error signals are modulated at a frequency outside of the Coriolis acceleration signal band; an offset detector configured to sense the modulated error signals in the Coriolis channel; and a servo configured to provide at least one compensating signal responsive to the sensed modulated error signals to substantially cancel errors introduced by the at least one error source that affect the Coriolis acceleration signal. ### Claim 12 (depends on 11) An inertial sensor according to claim 11, wherein the resonator driver is configured to modulate the drive signal using one of amplitude modulation, frequency modulation, on/off keying, or a spread spectrum modulation. ### Claim 13 (depends on 11) An inertial sensor according to claim 11, wherein the offset detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the drive signal to sense modulated error signals induced by the modulated drive signal. ### Claim 14 (depends on 11) An inertial sensor according to claim 11, wherein the at least one error source includes in-phase offset error that is substantially in-phase with the modulated drive signal, and wherein the servo is configured to provide at least one compensating signal responsive to the sensed accelerometer signals to substantially cancel the in-phase offset error. ### Claim 15 (depends on 14) An inertial sensor according to claim 14, wherein the servo is configured to provide a compensating signal to a set of in-phase-compensating electrodes to substantially cancel the in-phase offset error. ### Claim 16 (depends on 14) An inertial sensor according to claim 14, wherein the at least one error source includes drive force misalignment. ### Claim 17 (depends on 11) An inertial sensor according to claim 11, wherein the at least one error source includes electronic pass-through of the drive signal to the accelerometer, and wherein the servo is configured to provide at least one compensating signal responsive to the sensed modulated error signals to substantially cancel the pass-through. ### Claim 18 (depends on 17) An inertial sensor according to claim 17, wherein the servo is configured to provide a compensating signal to the accelerometer to substantially cancel the pass-through. ### Claim 19 (depends on 11) An inertial sensor according to claim 11, wherein the resonator includes a plurality of shuttles coupled to resonate at a single resonance frequency. ### Claim 20 (depends on 11) An inertial sensor according to claim 11, wherein the accelerometer includes at least one of: a sense electrode in a plane of the resonator; or a sense electrode out of the plane of the resonator. ### Claim 21 A controller for detecting at least one error source relating to the magnitude of a drive signal applied to a resonator of an inertial sensor including the resonator and an accelerometer for measuring a Coriolis acceleration signal in a Coriolis acceleration signal band of a Coriolis channel, wherein the at least one error source induces corresponding error signals in the Coriolis channel that are in-phase with the drive signal and include error signals that affect the Coriolis acceleration signal, the controller comprising: a resonator driver configured to provide a modulated drive signal to the resonator, the modulated drive signal modulating the magnitude of the drive force applied to the resonator so as to modulate the magnitude of the at least one error source so as to induce corresponding modulated error signals in the Coriolis channel, wherein the error signals are modulated at a frequency outside of the Coriolis acceleration signal band; an offset detector configured to sense the modulated error signals in the Coriolis channel; and a servo configured to provide at least one compensating signal responsive to the sensed accelerometer signals to the inertial sensor to substantially cancel errors introduced by the at least one error source that affect the Coriolis acceleration signal. ### Claim 22 (depends on 21) A controller according to claim 21, wherein the resonator driver is configured to modulate the drive signal using one of amplitude modulation, frequency modulation, on/off keying, or a spread spectrum modulation. ### Claim 23 (depends on 21) A controller according to claim 21, wherein the offset detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the drive signal to sense modulated error signals induced by the modulated drive signal. ### Claim 24 (depends on 21) A controller according to claim 21, wherein the at least one error source includes in-phase offset error that is substantially in-phase with the modulated drive signal, and wherein the servo is configured to provide at least one compensating signal responsive to the sensed modulated error signals to substantially cancel the in-phase offset error. ### Claim 25 (depends on 24) A controller according to claim 24, wherein the servo is configured to provide a compensating signal to a set of in-phase-compensating electrodes to substantially cancel the in-phase offset error. ### Claim 26 (depends on 24) A controller according to claim 24, wherein the at least one error source includes drive force misalignment. ### Claim 27 (depends on 21) A controller according to claim 21, wherein the at least one error source includes electronic pass-through of the drive signal to the accelerometer, and wherein the servo is configured to provide at least one compensating signal responsive to the sensed accelerometer signals to substantially cancel the pass-through. ### Claim 28 (depends on 27) A controller according to claim 27, wherein the servo is configured to provide a compensating signal to the accelerometer to substantially cancel the pass-through.