Invensense, Inc.

Panasonic Corporation

Giacomo Gafforelli

Luca Coronato

Adolfo Giambastiani

Jaakko Ruohio

Federico Mazzarella

Massimiliano Musazzi

Michele Folz

Edoardo Belloni

A microelectromechanical (MEMS) sensor, such as an accelerometer, has one more proof masses that respond to movement of the sensor, the movement of which is measured based on a distance between the one or more proof masses and on one or more sense electrodes. The accelerometer also has a plurality of auxiliary electrodes and a signal generator configured to apply an auxiliary signal having a first harmonic frequency to the plurality of auxiliary electrodes. Circuitry receives a sensed signal from the plurality of sense electrodes and identifies a portion of the sensed signal having the first harmonic frequency. Based on this identified portion of the sensed signal, the circuitry determines whether a residual voltage is present on the one or more proof masses or on the one or more sense electrodes, and the circuitry modifies the operation of the accelerometer when the residual voltage is determined to be present in order to compensate for the residual voltage.

MEMS sensor with compensation of residual voltage

A microelectromechanical system (MEMS) test structure includes a plurality of capacitors formed from sense electrodes and capacitive plates having a predetermined geometry and size associated with a related MEMS device such as a MEMS sensor. Based on the predetermined relationships between the capacitors of the test structure, and between the test structure and the MEMS devices, an effect of fringing fields on the sensed capacitances of the MEMS devices may be eliminated, and the capacitive gap of the MEMS device may be accurately measured.

Capacitance gap measurement

A gyroscope includes drive portions, lever arms, and proof masses located in a device plane. The lever arms are caused to rotate about an anchoring point based on anti-phase movement of the drive portions along a first axis in the device plane, and are coupled to the proof masses to cause the proof masses to move in anti-phase along an axis perpendicular to the first axis in the device plane. In response to a Coriolis force applied to the proof masses, the lever arm rotates out of plane and the proof masses move relative to sense electrodes. The movement of the proof masses with respect to the sense electrodes is used to measure angular velocity.

Out-of-plane sensing gyroscope robust to external acceleration and rotation

A microelectromechanical (MEMS) accelerometer has a proof mass, a sense electrode, and an auxiliary electrode. The sense electrode is located relative to the proof mass such that a capacitance formed by the sense electrode and the proof mass changes in response to a linear acceleration along a sense axis of the accelerometer. The auxiliary electrode is located relative to the proof mass such that a capacitance formed by the auxiliary electrode and proof mass is static in response to the linear acceleration. A sense drive signal is applied at the sense electrode and an auxiliary drive signal is applied at the auxiliary electrode. The sense drive signal and the auxiliary drive signal have different frequencies. An error is identified based on a portion of a signal that is received from the accelerometer and that is responsive to the auxiliary drive signal. Compensation is performed at the accelerometer based on the identified error.

Identification and compensation of MEMS accelerometer errors

A gyroscope includes four drive masses and four sense masses. Each drive mass is adjacent to two other drive masses and opposite the fourth drive mass, and each sense mass is adjacent to two other sense masses and opposite the fourth sense mass. Each drive mass may oscillate in a manner that is perpendicular to its adjacent drive mass and parallel and anti-phase to its opposite mass. The sense motion of the each sense mass may be coupled in a manner that prevents motion due to linear acceleration or angular acceleration.

Yaw rate gyroscope robust to linear and angular acceleration

A MEMS sensor includes a substrate and a MEMS layer. A plurality of anchoring points within the MEMS layer suspend a suspended spring-mass system that includes active micromechanical components that respond to a force of interest such as linear acceleration, angular velocity, pressure, or magnetic field. Springs and rigid masses couple the active components to the anchoring points, such that displacements of the anchoring points do not substantially cause the active components within the MEMS layer to move out-of-plane.

Anchoring structure for a sensor insensitive to anchor movement

A sensor such as an accelerometer includes a proof mass located opposite a plurality of electrodes located on a substrate. Some of the electrodes are auxiliary electrodes that apply an alternating current auxiliary signal to the proof mass while other electrodes are sense electrodes that sense movement of the proof mass. When a residual voltage is not present on the proof mass or on the sense electrodes, the forces imparted by the auxiliary signal onto the proof mass are substantially balanced. When the residual voltage is present on the proof masses, forces at a first harmonic frequency of the auxiliary signal are sensed by a sense electrode of the sensor. A self-test is failed if the sensed forces exceed a threshold.

Residual voltage self test

A microelectromechanical (MEMS) accelerometer has a proof mass, a sense electrode, and an auxiliary electrode. The sense electrode is located relative to the proof mass such that a capacitance formed by the sense electrode and the proof mass changes in response to a linear acceleration along a sense axis of the accelerometer. The auxiliary electrode is located relative to the proof mass such that a capacitance formed by the auxiliary electrode and proof mass is static in response to the linear acceleration. A sense drive signal is applied at the sense electrode and an auxiliary drive signal is applied at the auxiliary electrode. The sense drive signal and the auxiliary drive signal have difference frequencies. A portion of a sensed signal at the sense drive frequency is used to determine linear acceleration while a portion of the sensed signal at the auxiliary drive frequency is used to identify damage within a sense path from the proof mass.

Accelerometer sense path self-test

An accelerometer has a plurality of proof masses and a plurality of sense electrodes, which collectively form at least two capacitors. A first sense drive signal is applied to a first capacitor and a second sense drive signal is applied to a second capacitor. Both of the sense drive signals have the same sense drive frequency. Capacitance signals are sensed from each of the first capacitor and second capacitor, and a common mode component of the capacitance signals is determined. A capacitor error is identified based on the common mode component.

Accelerometer common mode self-test

A microelectromechanical sensor (MEMS) package includes a gyroscope and an accelerometer. The gyroscope is located within a low-pressure cavity that is sealed from an external pressure. The accelerometer is located within a cavity, and the seal for the accelerometer cavity is entirely within the gyroscope cavity. Under normal operating conditions, the accelerometer seal holds the accelerometer cavity at a higher pressure than the pressure of the enclosing gyroscope cavity. In the event that one of the gyroscope seal or the accelerometer seal is broken, the gyroscope senses the change in pressure.

Dual-sealed MEMS package with cavity pressure monitoring

A gyroscope includes drive electrodes that drive a drive mass at a drive frequency. A sense mass is responsive to a Coriolis force caused by rotation of the gyroscope and oscillates based on the drive frequency. Electrodes adjacent to the sense mass drive the sense mass at test frequencies. The response to the driving at the test frequencies is measured and a gyroscope failure is identified based on this response.

Gyroscope with auxiliary self-test

A gyroscope is driven at a drive frequency and senses a Coriolis force caused by rotation of the gyroscope. The response of the gyroscope to a given Coriolis force may change due to changes in the gyroscope over time. A plurality of test frequencies are applied to the gyroscope, and the response of the gyroscope to those test frequencies is analyzed in order to track changes in the response of the gyroscope. Operational parameters of the gyroscope may be altered in order to compensate for those changes.

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Casatenovo, Italy

Giacomo Gafforelli