Inertial sensor

Patent metadata

Field	Value
Publication number	US-10551192-B2
Application number	US-201515313242-A
Country	US
Kind code	B2
Filing date	Apr 8, 2015
Priority date	May 23, 2014
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

An inertial sensor having a simple configuration by vacuum sealing a resonator which detects acceleration and exploits a resonance vibration using a high Q value MEMS device. The sensor includes: a detecting proof mass and beam which detects acceleration; a driving electrode which excites the detecting proof mass and beam; a resonant frequency tuning electrode which changes the resonant frequency of the detecting proof mass and beam; and a detecting circuit which applies voltage to the resonant frequency tuning electrode for changing the resonant frequency to cancel a change of the resonant frequency of the detecting proof mass and beam when the acceleration is applied to the detecting proof mass and beam during the vibration of the detecting proof mass and beam by the voltage applied to the detecting proof mass and beam, and outputs the acceleration based on a value of the voltage applied to resonant frequency tuning electrode.

First claim

The invention claimed is:

1. An inertial sensor comprising:
at least two first resonators which detects acceleration;
at least two second resonators which detect angular velocity;
a capacitive first electrode which excites the at least two first resonators;
a capacitive second electrode which changes a resonant frequency of the at least two first resonators;
a detecting circuit which applies a first voltage to the second electrode to change the resonant frequency such that a change of the resonant frequency of the at least two first resonators are canceled when the acceleration is applied to the at least two first resonators during a vibration of the at least two first resonators due to application of the first voltage to the at least two first resonators,
the detecting circuit applies a second voltage to the second electrode, which decreases a spring constant of the first resonator, and
the detecting circuit outputs the acceleration based on a value of the first voltage applied to the second electrode; and
a diagnostic circuit which diagnoses failure based on comparison of resonant frequencies between the at least two first resonators before acceleration is applied and the at least two second resonators.

2. The inertial sensor according to claim 1 , wherein the second voltage is a bias voltage which changes the resonant frequency of the at least two first resonators and the bias voltage is applied in advance to the second electrode in a steady state in which the acceleration is not applied to the at least two first resonators, and
the resonant frequency of the at least two first resonators in the steady state are to be a resonant frequency lower than that in a state in which the bias voltage is not applied.

3. The inertial sensor according to claim 1 , wherein before acceleration is applied the detecting circuit controls the first voltage applied to the second electrode such that the resonant frequency of the at least two first resonators which detects the acceleration is matched with the resonant frequency of the at least two second resonators which detects the angular velocity.

4. The inertial sensor according to claim 2 , wherein before the acceleration is applied the at least two first resonators which detects the acceleration are arranged,
a plurality of the first electrodes, a plurality of the second electrodes, and a plurality of the detecting circuits are arranged to correspond to the at least two first resonators, and
each of the detecting circuits controls the first voltage applied to a plurality of second electrodes such that the resonant frequency of the at least two first resonators which detects the acceleration is to be the same frequency as the at least two second resonators.

5. The inertial sensor according to claim 4 , further comprising the at least two second resonators which detects angular velocity,
wherein before the acceleration is applied each of the detecting circuit controls the first voltage applied to the second electrode such that the resonant frequency of the at least two first resonators which detects the acceleration is matched with the resonant frequency of the at least two second resonators which detects the angular velocity.

6. The inertial sensor according to claim 4 , further comprising the at least two second resonators which detects the angular velocity,
wherein before the acceleration is applied each of the detecting circuits controls the first voltage applied to the second electrode such that the resonant frequency of the at least two first resonators which detects the acceleration are matched with the resonant frequency of one of the at least two second resonators which detect the angular velocity.

7. The inertial sensor according to claim 4 , wherein before the acceleration is applied, each of the detecting circuits compares the resonant frequency of the at least two first resonators which detects the acceleration with the resonant frequency of an outside resonator having a higher Q value than a Q value of the at least two first resonators, and controls such that the resonant frequency of the at least two first resonators are matched to the resonant frequency of the outside resonator having the high Q value.

8. The inertial sensor according to claim 1 , comprising the at least two first resonators which detects the acceleration,
the at least two second resonators which detects the angular velocity, and
one oscillation circuit which generates a clock signal which excites the at least two first resonators and the at least two second resonators.

9. The inertial sensor according to claim 1 , wherein the diagnostic circuit diagnoses the failure based on comparison of the first voltage which excites the at least two first resonators and the at least two second resonators at a predetermined amplitude, or amplitude obtained during the vibration of the at least two first resonators by a predetermined voltage.

10. The inertial sensor according to claim 9 , wherein the diagnostic circuit diagnoses the failure based on the comparison of the resonant frequency of the at least two first resistors and the at least two second resistors based on a change of temperature obtained by a temperature sensor arranged on an integrated circuit of the inertial sensor.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Maeda Daisuke
• Jeong Heewon
• Hayashi Masahide

Classifications

• G01C19/5726 Primary

  Signal processing · CPC title

• G01P15/125

  by capacitive pick-up · CPC title

• G01P15/097

  by vibratory elements · CPC title

• G01C19/5776

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• G01C19/5769

  Manufacturing; Mounting; Housings · CPC title