Actuation And Sensing Platform For Sensor Calibration And Vibration Isolation

Patent metadata

Field	Value
Publication number	US-2016245667-A1
Application number	US-201615051752-A
Country	US
Kind code	A1
Filing date	Feb 24, 2016
Priority date	Feb 24, 2015
Publication date	Aug 25, 2016
Grant date	—

Abstract

A micro-system with integrated multi-axis actuation and sensing capabilities for in-situ calibration of long-term scale-factor drifts in the output signal of attached or monolithically integrated inertial sensors. The micro-system comprises a piezoelectric actuator, integrated position sensors, and a controller. The controller provides the electrical excitation signals to the actuator and receives and processes signals from the inertial sensors and the position sensors. The electrical excitation signals are adjusted to reduce undesired off-axis motion resulting from environmental vibration during operation or from misalignment and digressions from the process tolerance during fabrication. Capacitive position sensors allow for determination of the trajectory of the piezoelectric actuator and for electrostatic pull-down and lock-down of an actuation plate. Piezoelectric signals and piezoresistive signals are used to improve position sensing precision. The actuator trajectory and the corresponding output of the inertial sensors are used by the controller to determine the device parameters of the inertial sensors.

First claim

What is claimed is:

1 . A micro-system for in situ calibration having integrated multi-axis actuation and position sensing capabilities, comprising:
a plate; a primary frame defining an inner space in which the plate is disposed; a plurality of connecting members disposed within the inner space and arranged around the plate, wherein each connecting member, in response to an applied stimuli, allows for movement of the plate in any of three geometric axes that are perpendicular to each other, each connecting member has a first end and a second end with the first end being attached to the plate, each connecting member is elastic and includes a piezoelectric element having a first surface opposing a second surface, where a plurality of partitioned surface electrodes are disposed on at least the first surface of the piezoelectric element; at least one primary sensor coupled to or integrated into the plate; a plurality of sensing elements that detect a motion trajectory of the plate; and a controller electrically connected to each of the connecting members and to each of the sensing elements in the plurality of sensing elements, wherein the controller is configured to actuate the plate by providing the applied stimuli to one or more of the plurality of connecting members while concurrently sensing motion of the plate from input received from the plurality of sensing elements.

2 . The micro-system of claim 1 , wherein a common geometric plane passes through the plate, the primary frame, each of the plurality of connect members, and the two largest dimensions of one of the plurality of connecting members defines a geometric plan parallel to the common geometric plane.

3 . The micro-system of claim 1 , further comprising:
a fixed member having a first surface opposing a second surface, wherein the first surface of the fixed member opposes the plate, the plurality of sensing elements includes a plurality of capacitive sensing elements, the plurality of capacitive sensing elements are disposed on the first surface of the fixed member, the plurality of capacitive sensing elements faces the plate, and the plurality of capacitive sensing elements is symmetrically arranged to provide position sensing outputs that the controller uses to estimate the motion trajectory of the plate.

4 . The micro-system of claim 1 , wherein the plurality of sensing elements, further comprises:
a plurality of piezoresistive sensing elements, wherein the plurality of piezoresistive sensing elements are integrated into the plurality of connecting members, and the controller uses signals from the plurality of piezoresistive sensing elements for estimation of the motion trajectory of the plate.

5 . The micro-system of claim 1 , wherein the plurality of connecting members includes:
a first group of connecting members that provides vibratory tilting motion of the plate around a predetermined reference axis; a second group of connecting members that is used for integrated sensing of the applied reference stimuli; and a third group of connecting members that is used for compensation of any off-axis motion of the plate other than the desired motion around the predetermined reference axis, wherein
a piezoelectric sensing signal is obtained from one of the plurality of partitioned surface electrodes or from the difference between the outputs of two partitioned surface electrodes from the second group of connecting members, and
the controller uses piezoelectric sensing signals to estimate the motion trajectory of the plate.

6 . The micro-system of claim 1 , further comprising:
a feedback control system, wherein the feedback control system interacts with the connecting members, the plate, and the plurality of sensing elements to create a motion trajectory of the plate and to determine at least one device parameter, including a scale-factor, a bias, a cross-axis sensitivity, a linearity and frequency response, or the angular rate and linear acceleration of the primary sensor.

7 . The micro-system of claim 1 , further comprising:
a feedback control system, wherein the feedback control system interacts with the connecting members, the plate, and the plurality of sensing elements to dampen undesired motion of the plate with respect to the primary frame and to improve the performance of the micro-system.

8 . The micro-system of claim 1 , wherein electrical connections are formed by a plurality of flexible cables extending from the plate to the primary sensor.

9 . The micro-system of claim 1 , wherein each connecting member has an L-shape layout or a U-shaped layout.

10 . The micro-system of claim 1 , wherein each connecting member has a rectangular cross-section or a T-shaped cross-section.

11 . The micro-system of claim 1 , further comprising:
a secondary frame disposed within the inner space, a first set of connecting members that attach the plate to the secondary frame; and a second set of connecting members that attach the secondary frame to the primary frame.

12 . The micro-system of claim 1 , wherein the system is encapsulated in a single device package.

13 . The micro-system of claim 1 , wherein the system is hermetically sealed.

14 . A micro-system for in situ calibration having integrated multi-axis actuation and position sensing capabilities, comprising:
a plate; a frame defining an inner space in which the plate is disposed; a plurality of connecting members disposed within the inner space and arranged around the plate, wherein each connecting member, in response to a reference signal, allows for movement of the plate in any of three geometric axes that are perpendicular to each other, each connecting member has a first end and a second end, the first end being attached to the plate, each connecting member is elastic and includes a piezoelectric element having a first surface opposing a second surface, where a plurality of surface electrodes are disposed on at least the first surface of the piezoelectric element; an inertial sensor coupled to or integrated into the plate; a fixed member having a first surface opposing a second surface, wherein the first surface opposes the plate, and a plurality of capacitive sensing elements is disposed on at least the first surface of the fixed member and the plurality of capacitive sensing elements are specifically arranged to allow the reference signal to be determined; a feedback control system, wherein the feedback control system interacts with the connecting members, the plate, and the plurality of capacitive sensing elements to create a specific motion trajectory of the plate; and a controller electrically coupled to the each of the connecting members and each of the plurality of capacitive sensing elements, the controller is configured to actuate the plate by providing the reference signal to one or more of the plurality of partitioned surface electrodes and to concurrently receive sensing signals from the plurality of capacitive sensing elements and output signals from the inertial sensor, wherein the controller uses the signals obtained from the plurality of capacitive sensing elements to estimate the motion trajectory of the plate; uses the signals from the capacitive sensing elements to determine at least one device parameter; and uses the inertial sensor outputs, the reference signals, and the determined device parameter to calibrate the output signal of the inertial sensor, and wherein a common geometric plane passes through the plate, the primary frame, each of the plurality of connect members, and the two largest dimensions of the plurality of connecting members defines

Assignees

• Univ Michigan Regents

Inventors

• Najafi Khalil
• Aktakka Ethem

Classifications

• G01C19/5783

  Mountings or housings not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• G01C25/005 Primary

  initial alignment, calibration or starting-up of inertial devices · CPC title