Abstract: Embodiments are disclosed for active cancellation of noise in motion sensor signals. In some embodiments, a method comprises: obtaining a motion sensor signal from a motion sensor; obtaining a reference signal indicative of parasitic vibration from a vibration source mechanically coupled to the motion sensor; generating, using an adaptive noise canceller, an estimate of the parasitic vibration; and using the estimated parasitic vibration to cancel the parasitic vibration from the motion sensor signal.

Abstract: A head-mountable device can include a display, a housing, a processor, and a camera module. The camera module can include a lens assembly, an optical sensor, a substrate, and a motion sensor attached to the camera module to determine a motion of the camera module. The processor can be communicatively coupled to the motion sensor, and can generate a signal based on the motion.

Abstract: According to some aspects of the subject technology, an apparatus includes an accelerometer including one or more sense electrodes to sense an input acceleration, and an unstick device to free the accelerometer from a stuck state due to a saturating acceleration input. The unstick device includes at least one unstick electrode and a control circuitry to cause the unstick electrode to generate vibrational energy to free the accelerometer.

Abstract: According to some aspects of the subject technology, an apparatus includes an accelerometer including one or more sense electrodes to sense an input acceleration, and an unstick device to free the accelerometer from a stuck state due to a saturating acceleration input. The unstick device includes at least one unstick electrode and a control circuitry to cause the unstick electrode to generate vibrational energy to free the accelerometer.

Abstract: An in-situ test calibration system and method are disclosed where a perpetual out-of-band electrostatic force induced excitation is used to dither the proof-mass of a MEMS based accelerometer where the amount of deflection change is proportional to sensitivity changes. The supplier of the accelerometer would exercise the accelerometer in a calibration station to determine initial sensitivity values. After the calibration and before removing the accelerometer from the calibration station, the supplier would start the dither and calibrate the acceleration equivalent force (FG) to drive voltage transfer function (FG/V). After installation of the accelerometer into a system or sometime later in the field, any changes in the FG/V transfer function due to changes in the sensitivity are observable and can be used for re-calibrating the accelerometer.

Abstract: An in-situ calibration system, method and apparatus is disclosed that uses test electrodes to stimulate a proof-mass of a MEMS based gyroscope at a drive frequency as quasi-Coriolis forces to extract the electromechanical gain, and uses a non-resonant carrier signal on the proof-mass to extract the additional changes in the sense and drive capacitance. Additionally, an in-situ calibration system, method and apparatus is disclosed that uses quadrature electrodes to apply a known force stimulus to the proof-mass as part of a calibration procedure, where the known force is applied again after installation into a system or further into the life of the gyroscope. Differences in the proof-mass response to the force are proportional to changes in sensitivity, which allows the sensitivity to be corrected in-field.

Abstract: A quadrature ADC feedback compensation system and method for MEMS gyroscope is disclosed. In an embodiment, a MEMS gyroscope comprises an analog processing chain including a drive circuit for generating an analog drive signal and a sense circuit that is configured to generate an analog rate signal and an analog quadrature signal in response to a change in capacitance output by the MEMS gyroscope. A compensation circuit coupled to the sense circuit is configured to null the analog quadrature signal using the analog drive signal and a compensation value, and to adaptively compensate, in a digital processing chain, a quadrature-induced rate offset of a digital rate signal over temperature using a digital quadrature signal, the compensation value and temperature data.

Abstract: A MEMS sensor is disclosed that includes dual pendulous proof masses comprised of sections of different thickness to allow simultaneous suppression of vertical and lateral thermal gradient-induced offsets in a MEMS sensor while still allowing for the normal operation of the accelerometer. In an embodiment, the structure and different sections of the MEMS sensor is realized using multiple polysilicon layers. In other embodiments, the structure and different thickness sections may be realized with other materials and processes. For example, plating, etching, or silicon-on-nothing (SON) processing.

Abstract: A multi-stage MEMS accelerometer is disclosed that includes a MEMS sensor that has two suspended structures (proof masses) suspended by suspension members. The suspended structures move together in response to input acceleration when less the acceleration is less than a threshold value. When the input acceleration is greater than the threshold value, one of the suspended structures makes contact with a mechanical stop while the other suspended structure continues to move with increased stiffness due to the combined stiffness of the suspension members. The contact with the mechanical stop contributes a nonlinear mechanical stiffening effect that counteracts the nonlinear capacitive effect inherent in capacitive based MEMS accelerometers. In some embodiments, more than two suspended structures can be used to allow for optimization of sensitivity for multiple full-scale ranges, and for higher fidelity tuning of mechanical sensitivity with nonlinear capacitance.

Abstract: An architecture is disclosed for an angular rate sensor that includes a duty-cycled phase shifter for generating a clock with high resolution delay for use in synchronized demodulation of a sensor output signal. In an embodiment, a sensor comprises: a mechanical resonator; a drive circuit coupled to the mechanical resonator and operable to actuate the mechanical resonator into resonant vibration; a sense circuit mechanically coupled to the mechanical resonator, the sense circuit operable to generate a sense signal having an in-phase signal component and a quadrature signal component; a demodulator circuit operable to receive the sense signal and a first clock for demodulating the sense signal to separate the in-phase signal component from the quadrature signal component; and a duty-cycled phase shifter coupled to the demodulator, the duty-cycled phase shifter operable to generate the first clock.

Abstract: An in-situ calibration system, method and apparatus is disclosed that uses test electrodes to stimulate a proof-mass of a MEMS based gyroscope at a drive frequency as quasi-Coriolis forces to extract the electromechanical gain, and uses a non-resonant carrier signal on the proof-mass to extract the additional changes in the sense and drive capacitance. Additionally, an in-situ calibration system, method and apparatus is disclosed that uses quadrature electrodes to apply a known force stimulus to the proof-mass as part of a calibration procedure, where the known force is applied again after installation into a system or further into the life of the gyroscope. Differences in the proof-mass response to the force are proportional to changes in sensitivity, which allows the sensitivity to be corrected in-field.

Abstract: An in-situ test calibration system and method are disclosed where a perpetual out-of-band electrostatic force induced excitation is used to dither the proof-mass of a MEMS based accelerometer where the amount of deflection change is proportional to sensitivity changes. The supplier of the accelerometer would exercise the accelerometer in a calibration station to determine initial sensitivity values. After the calibration and before removing the accelerometer from the calibration station, the supplier would start the dither and calibrate the acceleration equivalent force (FG) to drive voltage transfer function (FG/V). After installation of the accelerometer into a system or sometime later in the field, any changes in the FG/V transfer function due to changes in the sensitivity are observable and can be used for re-calibrating the accelerometer.

Abstract: A quadrature ADC feedback compensation system and method for MEMS gyroscope is disclosed. In an embodiment, a MEMS gyroscope comprises an analog processing chain including a drive circuit for generating an analog drive signal and a sense circuit that is configured to generate an analog rate signal and an analog quadrature signal in response to a change in capacitance output by the MEMS gyroscope. A compensation circuit coupled to the sense circuit is configured to null the analog quadrature signal using the analog drive signal and a compensation value, and to adaptively compensate, in a digital processing chain, a quadrature-induced rate offset of a digital rate signal over temperature using a digital quadrature signal, the compensation value and temperature data.

Abstract: A multi-stage MEMS accelerometer is disclosed that includes a MEMS sensor that has two suspended structures (proof masses) suspended by suspension members. The suspended structures move together in response to input acceleration when less the acceleration is less than a threshold value. When the input acceleration is greater than the threshold value, one of the suspended structures makes contact with a mechanical stop while the other suspended structure continues to move with increased stiffness due to the combined stiffness of the suspension members. The contact with the mechanical stop contributes a nonlinear mechanical stiffening effect that counteracts the nonlinear capacitive effect inherent in capacitive based MEMS accelerometers. In some embodiments, more than two suspended structures can be used to allow for optimization of sensitivity for multiple full-scale ranges, and for higher fidelity tuning of mechanical sensitivity with nonlinear capacitance.

Abstract: A MEMS sensor is disclosed that includes dual pendulous proof masses comprised of sections of different thickness to allow simultaneous suppression of vertical and lateral thermal gradient-induced offsets in a MEMS sensor while still allowing for the normal operation of the accelerometer. In an embodiment, the structure and different sections of the MEMS sensor is realized using multiple polysilicon layers. In other embodiments, the structure and different thickness sections may be realized with other materials and processes. For example, plating, etching, or silicon-on-nothing (SON) processing.

Abstract: An architecture is disclosed for an angular rate sensor that includes a duty-cycled phase shifter for generating a clock with high resolution delay for use in synchronized demodulation of a sensor output signal. In an embodiment, a sensor comprises: a mechanical resonator; a drive circuit coupled to the mechanical resonator and operable to actuate the mechanical resonator into resonant vibration; a sense circuit mechanically coupled to the mechanical resonator, the sense circuit operable to generate a sense signal having an in-phase signal component and a quadrature signal component; a demodulator circuit operable to receive the sense signal and a first clock for demodulating the sense signal to separate the in-phase signal component from the quadrature signal component; and a duty-cycled phase shifter coupled to the demodulator, the duty-cycled phase shifter operable to generate the first clock.

Abstract: In some implementations, a control system for a resonating element comprises: a resonating element being driven by an oscillating drive signal and configured to generate a sense signal proportional to an amplitude of motion; a phase comparator coupled to the resonating element and to an oscillating drive signal, the phase comparator configured to compare the sense signal and the oscillating drive signal and to generate an error signal proportional to the phase difference; an oscillator coupled to the phase comparator and configured for generating the oscillating drive signal, the oscillator configured to receive the error signal and to adjust a phase of the oscillating signal based on the error signal; and an automatic gain control coupled to the resonating element and the oscillator, the automatic gain control configured to adjust the gain of the oscillating drive signal based on the signal generated by the resonating element.

Abstract: In some implementations, a control system for a resonating element comprises: a resonating element being driven by an oscillating drive signal and configured to generate a sense signal proportional to an amplitude of motion; a phase comparator coupled to the resonating element and to an oscillating drive signal, the phase comparator configured to compare the sense signal and the oscillating drive signal and to generate an error signal proportional to the phase difference; an oscillator coupled to the phase comparator and configured for generating the oscillating drive signal, the oscillator configured to receive the error signal and to adjust a phase of the oscillating signal based on the error signal; and an automatic gain control coupled to the resonating element and the oscillator, the automatic gain control configured to adjust the gain of the oscillating drive signal based on the signal generated by the resonating element.

Abstract: A strain measurement platform that comprises of a strain die that can be embedded inside a package substrate or have its own substrate with through silicon vias (TSVs) is disclosed. The strain die comprises a body and a base. The base is coupled to the body with strain enhancing structures. Strain enhancing structures are formed on the strain die to amplify the strain signals locally, while also acting as strain and vibration isolators. Strain sensors are formed on or around the strain enhancing structures at locations of maximum strain. The strain sensors can be piezo-resistors, piezo-junctions or piezo-electrics. Strain enhancing structures are implemented either as compliant springs or as a thin membrane over which the base is suspended. A package stack can be mounted on top of the strain die and electrically connected to a strain measuring platform. Some example process flows for fabricating strain die are also disclosed.

Abstract: Due to restrictive tolerancing, structural imperfections that reduce performance of fabricated micro gyroscopes are typical. While feedback control is normally used to compensate for these imperfections, there are limitations to how large of errors for which this strategy can compensate without interfering with the performance of the sensor. A multi stage control architecture comprising in situ self-diagnostic capabilities, electronic “trimming” of errors, and feedback control allows for the compensation of all magnitudes of errors without interfering with the performance of the device. The self-diagnostic capabilities include an algorithm for determining structural imperfections based on the dynamic response of the system. The feedforward portion of the control is used to “trim” large imperfections, while the feedback portion compensates for the remaining non-idealities and small perturbations. A control architecture is shown in a gyroscope using nonlinear electrostatic parallel plate actuation.