CN110879303B

CN110879303B - Inertial sensor and control method thereof

Info

Publication number: CN110879303B
Application number: CN201911013165.1A
Authority: CN
Inventors: 汪建平
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2022-01-04
Anticipated expiration: 2039-10-23
Also published as: CN110879303A

Abstract

The application discloses an inertial sensor and a control method thereof, the inertial sensor comprises a sensor unit, the sensor unit comprises a movable mass block and a substrate, the movable mass block is opposite to a first surface of the substrate, corresponding displacement is generated in the direction of a sensing axis in response to acceleration in the direction of the sensing axis, a detection electrode positioned on the surface and an auxiliary electrode which is arranged in a way of being isolated from the detection electrode, the movable mass block provides a corresponding detection signal according to the position change of the movable mass block, the auxiliary electrode provides a corresponding reference signal, a processing circuit obtains and stores a plurality of reference values according to the detection signal and the reference signal which are collected under preset acceleration, then the acceleration to be detected is determined according to the reference values and the detection signal and the reference signal which are collected under the acceleration to be detected, and the effective capacitance change difference value contains offset error caused by the deformation of the substrate, therefore, the temperature drift of the inertial sensor can be reduced, and the accuracy of the inertial sensor is improved.

Description

Inertial sensor and control method thereof

Technical Field

The invention relates to the technical field of MEMS, in particular to an inertial sensor and a control method thereof.

Background

A Micro-Electro-mechanical System (MEMS) inertial sensor manufactured by adopting a surface process takes a silicon wafer as a substrate, and a three-dimensional micromechanical structure is prepared by multiple thin film deposition and graphic processing. Commonly used film layer materials are: polysilicon, silicon nitride, silicon dioxide, and metal.

The acceleration sensor is an electronic device capable of measuring acceleration, is one of common devices of a micro-electro-mechanical system (MEMS) inertial sensor, and is mainly applied to the aspects of position sensing, displacement sensing or motion state sensing and the like.

The inertial sensor mainly comprises a movable mass block, a fixed anchor point, an elastic structure, a fixed electrode and the like. One end of the elastic structure is connected with the fixed anchor point, the other end of the elastic structure is connected with the movable mass block, and a variable capacitor is formed between the fixed electrode and the movable mass block. When external acceleration acts on the movable mass block, inertial force is formed, the inertial force can enable the movable mass block to generate displacement, and the displacement variation is detected by sensing capacitance variation between the fixed electrode and the movable mass block, so that the magnitude of the external acceleration can be determined.

An important mechanical characteristic of the MEMS inertial sensor is temperature drift, and in the MEMS packaging process, the thermal expansion coefficients of the substrate and the substrate are different, and in the temperature change process such as welding, the MEMS substrate is deformed accordingly, and the deformation affects the distance between the fixed electrode and the movable mass block, thereby changing the capacitance between the fixed electrode and the movable mass block, and causing the output value to drift.

There is therefore a need for improvements to existing inertial sensors to reduce the temperature drift of the inertial sensor.

Disclosure of Invention

In view of the above, an object of the present invention is to provide an inertial sensor and a control method thereof, which further improve the accuracy of the inertial sensor.

According to an aspect of the present invention, there is provided an inertial sensor including: a sensor unit, the sensor unit comprising: a movable mass that undergoes a corresponding displacement in a sense axis direction in response to an acceleration in the sense axis direction; a substrate, the movable mass opposing a first surface of the substrate; the detection electrode is positioned on the first surface and used for providing a corresponding detection signal according to the position change of the movable mass; the auxiliary electrode is positioned on the first surface, is separated from the detection electrode and is used for providing a corresponding reference signal according to the position change of the movable mass block; and the processing circuit is connected with the sensor unit and used for acquiring and storing a plurality of reference values according to the detection signals and the reference signals acquired under the preset acceleration and determining the acceleration to be detected according to the reference values and the detection signals and the reference signals acquired under the acceleration to be detected.

Preferably, the sensor unit further includes: a central anchor fixed to a first surface of the substrate; the movable mass block comprises a first movable area and a second movable area, the first movable area and the second movable area are respectively and elastically connected with the central anchor point from two sides of the central anchor point, the detection electrode comprises a first detection electrode and a second detection electrode which respectively form a first detection capacitor and a second detection capacitor with the first movable area and the second movable area, the detection signal represents the difference value between the second detection capacitor and the first detection capacitor, the auxiliary electrode comprises a first auxiliary electrode and a second auxiliary electrode which respectively form a first reference capacitor and a second reference capacitor with the first movable area and the second movable area, the reference signal is used for representing the difference value between the second reference capacitor and the first reference capacitor, and the first movable area is arranged opposite to the first detection electrode and the first auxiliary electrode, the second movable region is disposed opposite to the second detection electrode and the second auxiliary electrode.

Preferably, the symmetry axis of the first auxiliary electrode coincides with the symmetry axis of the first detection electrode, and the symmetry axis of the second auxiliary electrode coincides with the symmetry axis of the second detection electrode.

Preferably, the plurality of reference values comprises at least a first to a fourth reference value, the processing circuit being configured to perform the following operations in a calibration phase: setting the preset acceleration to be zero, storing the received first detection signal as the first reference value, and obtaining a second reference value according to the ratio of the received first reference signal to the first detection signal; setting the preset acceleration as a non-zero first acceleration, and respectively storing the received reference signal and the received detection signal as a second reference signal and a second detection signal; setting the preset acceleration as a non-zero second acceleration, and respectively storing the received reference signal and the received detection signal as a third reference signal and a third detection signal; obtaining a first sum value from the second reference signal and the third reference signal, obtaining a second sum value from the second detection signal and the third detection signal, and obtaining a third reference value from the first sum value, the second sum value, and the first reference value and the second reference value; and obtaining a fourth reference value according to a first difference value between the second reference signal and the third reference signal and a second difference value between the second detection signal and the third detection signal, wherein the first acceleration and the second acceleration are equal in magnitude and opposite in direction.

Preferably, the first reference value is:

K1＝C20-C10

wherein C20-C10 is a difference between the second detection capacitance and the first detection capacitance when the preset acceleration is zero, and the first reference value is indicative of a mismatch parameter between the second detection capacitance and the first detection capacitance when the preset acceleration is zero.

Preferably, the second reference value is:

K2＝(C40-C30)/(C20-C10)

wherein C40-C30 is a difference between the second reference capacitance and the first reference capacitance when the preset acceleration is zero, C20-C10 is a difference between the second detection capacitance and the first detection capacitance when the preset acceleration is zero, and the second reference value is used for representing a ratio of a mismatch parameter of the reference capacitance to a mismatch parameter of the detection capacitance when the preset acceleration is zero.

Preferably, the third reference value is:

K3＝[(C41-C31)/2+(C42-C32)/2+K1×K2]/[(C21-C11)/2+(C22-C12)/2+K1]

wherein C41-C31 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the first acceleration, C21-C11 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the first acceleration, C42-C32 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the second acceleration, C22-C12 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the second acceleration, K1 is the first reference value, K2 is the second reference value, and the third reference value is used for representing a ratio between a sensitivity deviation value of the reference capacitor and a sensitivity deviation value of the detection capacitor when the preset acceleration is the first acceleration.

Preferably, the fourth reference value is:

K4＝[(C41-C31)/2-(C42-C32)/2]/[(C21-C11)/2-(C22-C12)/2]

wherein C41-C31 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the first acceleration, C21-C11 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the first acceleration, C42-C32 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the second acceleration, C22-C12 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the second acceleration, and the fourth reference value is used for representing a ratio between sensitivity of the reference capacitor and sensitivity of the detection capacitor when the preset acceleration is the second acceleration.

Preferably, the processing circuit comprises: the acquisition module is used for acquiring the corresponding detection signal and the reference signal under different accelerations; and the operation module is used for obtaining the first reference value, the second reference value, the third reference value, the fourth detection signal and the fourth reference signal which are acquired under the acceleration to be detected and the correlation coefficient corresponding to the acceleration to be detected, determining an effective capacitance change difference value between the second detection capacitor and the first detection capacitor under the acceleration to be detected, and determining the acceleration to be detected according to the effective capacitance change difference value.

Preferably, the operation module determines the correlation coefficient according to the following formula:

pa is a ratio between the reference signal and the detection signal under the acceleration to be detected, Pg is a ratio between the reference signal and the detection signal under the first acceleration, Δ Ca _ ref is a sensitivity deviation value of the reference capacitor under the acceleration to be detected, Δ Ca _ det is a sensitivity deviation value of the detection capacitor under the acceleration to be detected, and K3 is the third reference value.

Preferably, the operation module determines an effective capacitance change difference value between the second detection capacitor and the first detection capacitor under the acceleration to be detected according to the following formula:

ΔC2a-ΔC1a＝[Ka*K3*(C2a-C1a)-(C4a-C3a)-(Ka*K3-K2)*K1]/(Ka*K3-K4)

Δ C2a- Δ C1a represent an effective change capacitance difference between the second detection capacitor and the first detection capacitor, K1-K4 represent the first to fourth reference values, respectively, Ka represents the correlation coefficient corresponding to the acceleration to be measured, C2a-C1a represent a difference between the second detection capacitor and the first detection capacitor at the acceleration to be measured, and C4a-C3a represent a difference between the second reference capacitor and the first reference capacitor at the acceleration to be measured.

Preferably, the fourth reference value is a constant value over the range of the inertial sensor.

Preferably, the first detection electrode has a first notch region and a symmetry axis of the first detection electrode is located in the first notch region, the first auxiliary electrode is disposed in the first notch region, the second detection electrode has a second notch region and a symmetry axis of the second detection electrode is located in the second notch region, and the second auxiliary electrode is located in the second notch region.

Preferably, the first and second detection electrodes are U-shaped electrodes, and the first and second auxiliary electrodes are strip-shaped electrodes.

Preferably, the first detection electrode and the first auxiliary electrode form a shape-matched comb-tooth electrode structure, and the second detection electrode and the second auxiliary electrode form a shape-matched comb-tooth electrode structure.

Preferably, the area ratio of the first detection electrode to the first auxiliary electrode is 1:1 to 3:1, and the area ratio of the second detection electrode to the second auxiliary electrode is 1:1 to 3: 1.

According to another aspect of the present invention, there is provided a control method of an inertial sensor including a sensor unit including a movable mass, and a detection electrode and an auxiliary electrode which are located on a first surface of a substrate and are placed apart from each other, the movable mass being disposed opposite to the detection electrode and the auxiliary electrode, wherein the control method includes: acquiring a detection signal provided by the detection electrode and a reference signal provided by the auxiliary electrode under a preset acceleration, wherein the detection signal is provided by the detection electrode according to the position change of the movable mass block, and the reference signal is provided by the auxiliary electrode according to the position change of the movable mass block; acquiring and storing a plurality of reference values according to the detection signal and the reference signal acquired under the preset acceleration; and acquiring the detection signal and the reference signal under the acceleration to be detected, and determining the acceleration to be detected according to the reference value and the detection signal and the reference signal acquired under the acceleration to be detected.

Preferably, the movable mass includes a first movable region and a second movable region, the first movable region and the second movable region are elastically connected to a central anchor point of the sensor unit from two sides of the central anchor point, the detection electrode includes a first detection electrode and a second detection electrode, a first detection capacitor and a second detection capacitor are formed with the first movable region and the second movable region respectively, the detection signal represents a difference between the second detection capacitor and the first detection capacitor, the auxiliary electrode includes a first auxiliary electrode and a second auxiliary electrode, a first reference capacitor and a second reference capacitor are formed with the first movable region and the second movable region respectively, the reference signal is used for representing a difference between the second reference capacitor and the first reference capacitor, and the first movable region is disposed opposite to the first detection electrode and the first auxiliary electrode, the second movable region is disposed opposite to the second detection electrode and the second auxiliary electrode.

Preferably, the step of obtaining and storing a reference value according to the detection signal and the reference signal acquired at the preset acceleration includes: setting the preset acceleration to be zero, storing the received first detection signal as the first reference value, and obtaining a second reference value according to the ratio of the received first reference signal to the first detection signal; setting the preset acceleration as a non-zero first acceleration, and respectively storing the received reference signal and the received detection signal as a second reference signal and a second detection signal; setting the preset acceleration as a non-zero second acceleration, and respectively storing the received reference signal and the received detection signal as a third reference signal and a third detection signal; obtaining a first sum value from the second reference signal and the third reference signal, obtaining a second sum value from the second detection signal and the third detection signal, and obtaining a third reference value from the first sum value, the second sum value, and the first reference value and the second reference value; and obtaining a fourth reference value according to a first difference value between the second reference signal and the third reference signal and a second difference value between the second detection signal and the third detection signal, wherein the first acceleration and the second acceleration are equal in magnitude and opposite in direction.

Preferably, the first reference value is:

K1＝C20-C10

the reference value C20-C10 is a difference value between a second detection capacitor and a first detection capacitor when the preset acceleration is zero, and the first reference value is used for representing a mismatch parameter between the second detection capacitor and the first detection capacitor when the preset acceleration is zero.

Preferably, the second reference value is:

K2＝(C40-C30)/(C20-C10)

the reference capacitance detection circuit comprises a reference capacitance detection circuit, a reference capacitance detection circuit and a reference capacitance detection circuit, wherein C40-C30 are difference values between a second reference capacitance and a first reference capacitance when the preset acceleration is zero, C20-C10 are difference values between a second detection capacitance and a first detection capacitance when the preset acceleration is zero, and the second reference value is used for representing the ratio of mismatch parameters of the reference capacitance and mismatch parameters of the detection capacitance when the preset acceleration is zero.

Preferably, the third reference value is:

K3＝[(C41-C31)/2+(C42-C32)/2+K1×K2]/[(C21-C11)/2+(C22-C12)/2+K1]

wherein C41-C31 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the first acceleration, C21-C11 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the first acceleration, C42-C32 are differences between the second reference capacitor and the first reference capacitor when the preset acceleration is the second acceleration, C22-C12 are differences between the second detection capacitor and the first detection capacitor when the preset acceleration is the second acceleration, and the third reference value is used for representing a ratio between a sensitivity deviation value of the reference capacitor and a sensitivity deviation value of the detection capacitor when the preset acceleration is the first acceleration.

Preferably, the fourth reference value is:

K4＝[(C41-C31)/2-(C42-C32)/2]/[(C21-C11)/2-(C22-C12)/2]

Preferably, the step of determining the acceleration to be measured according to the reference value, the detection signal and the reference signal acquired under the acceleration to be measured includes: storing the detection signal and the reference signal acquired under the acceleration to be detected as a fourth detection signal and a fourth reference signal respectively; determining the correlation coefficient corresponding to the acceleration to be detected according to the third reference value, the fourth detection signal and the fourth reference signal; determining an effective capacitance change difference value between a second detection capacitor and a first detection capacitor under the acceleration to be detected according to the first to fourth reference values, the fourth detection signal, the fourth reference signal and the correlation coefficient; and determining the current acceleration according to the effective capacitance change difference.

Preferably, the correlation coefficient is determined according to the following formula:

pa represents a ratio between the reference signal and the detection signal at the acceleration to be detected, Pg represents a ratio between the reference signal and the detection signal at the first acceleration, Δ Ca _ ref represents a sensitivity deviation value of the reference capacitor at the acceleration to be detected, Δ Ca _ det represents a sensitivity deviation value of the detection capacitor at the acceleration to be detected, and K3 is the third reference value.

Preferably, the effective capacitance change difference between the second detection capacitor and the first detection capacitor under the acceleration to be detected is determined according to the following formula:

ΔC2a-ΔC1a＝[Ka*K3*(C2a-C1a)-(C4a-C3a)-(Ka*K3-K2)*K1]/(Ka*K3-K4)

wherein Δ C2a- Δ C1a represent an effective change capacitance difference between the second detection capacitance and the first detection capacitance, K1-K4 represent the first to fourth reference values, Ka represents the correlation coefficient corresponding to the acceleration to be measured, C2a-C1a represent a difference between the second detection capacitance and the first detection capacitance at the acceleration to be measured, and C4a-C3a represent a difference between the second reference capacitance and the first reference capacitance at the acceleration to be measured.

The inertial sensor and the control method thereof of the embodiment of the invention have the following beneficial effects.

The inertial sensor comprises a movable mass, a detection electrode and an auxiliary electrode, wherein the detection electrode and the auxiliary electrode are positioned on a substrate, the detection electrode is used for providing a corresponding detection signal according to the position change of the movable mass, and the auxiliary electrode is isolated from the detection electrode and is used for providing a corresponding reference signal according to the position change of the movable mass. The inertial sensor further comprises a processing circuit, wherein the processing circuit is used for obtaining detection signals and reference signals under different preset accelerations according to the detection electrodes and the auxiliary electrodes in a calibration stage, obtaining a plurality of reference values related to temperature drift errors according to the detection signals and the reference signals, then determining effective capacitance change difference values according to the reference values, the detection signals and the reference signals collected under the acceleration to be detected in a test stage, and obtaining the acceleration to be detected according to the effective capacitance change difference values. Because the effective capacitance change difference value contains offset error caused by substrate deformation, the temperature drift of the inertial sensor can be reduced, and the precision of the inertial sensor is improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.

FIG. 1 shows a schematic structural diagram of an inertial sensor according to an embodiment of the invention;

FIG. 2 shows a schematic diagram of a processing circuit according to an embodiment of the invention;

fig. 3 shows a schematic cross-sectional view of a sensor unit according to a first embodiment of the invention in the Y-direction;

fig. 4 shows a top view of a sensor unit according to a first embodiment of the invention;

FIG. 5 shows a schematic cross-sectional view of a sensor unit according to a second embodiment of the invention in the Y-direction;

fig. 6 shows a top view of a sensor unit according to a second embodiment of the invention;

FIG. 7 shows a flow chart diagram of a method of controlling an inertial sensor according to an embodiment of the invention;

FIG. 8 shows a system diagram of a sensor unit according to a first embodiment of the invention when subjected to acceleration in the Z-axis direction;

fig. 9 shows another system diagram of the sensor unit according to the first embodiment of the present invention when subjected to acceleration in the Z-axis direction.

Detailed Description

The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.

In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of components, are set forth in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.

It will be understood that when a layer, region or layer is referred to as being "on" or "over" another layer, region or layer in describing the structure of the component, it can be directly on the other layer, region or layer or intervening layers or regions may also be present. Also, if the component is turned over, one layer or region may be "under" or "beneath" another layer or region.

Fig. 1 shows a schematic structural diagram of an inertial sensor according to an embodiment of the invention. It should be noted that although a particular configuration is shown in fig. 1, it should be understood that any suitable combination of sensors, processing circuitry, memory, and other circuitry may be used in different applications and systems as desired.

In an exemplary embodiment of the present invention, a micro-electromechanical system (MEMS) inertial sensor includes a sensor unit 10 formed using semiconductor processing techniques and processing circuitry 20.

The sensor unit 10 may include a substrate, anchor points, a movable mass that "teeter-totter" about the anchor points in response to acceleration in the direction of the sensing axis, and elastic elements connecting the anchor points and the movable mass.

Further, fig. 3 and 4 respectively show a schematic cross-sectional view and a top view of the sensor unit according to the first embodiment of the present invention along the Y direction, and as shown in the figure, the sensor unit 10 of the present embodiment includes a substrate 11, a detection electrode 12, a movable mass 13, an auxiliary electrode 14, a central anchor point 15, and an elastic element 16. Wherein the substrate 11 comprises a first surface opposite to the movable mass 13 and the detection electrodes 12, the auxiliary electrodes 14 and the central anchor point 15 are arranged on this surface of the substrate 11.

For convenience of description, in the embodiment of the present invention, the extending direction of the elastic element 16 is referred to as a Y-axis direction, a direction perpendicular to the Y-axis direction and located on a plane of the movable mass 13 is referred to as an X-axis direction, and a direction perpendicular to the plane of the movable mass is referred to as a Z-axis direction.

The central anchor point 15 is used to support the movable mass 13 above the substrate 11. In particular, the central anchor point 15 is connected to the side wall of the mobile mass 13 by means of an elastic element 16, so that the mobile mass 13 floats above the substrate 11, and the direction of extension of the elastic element 16 coincides with the direction of extension of the central anchor point 15. The elastic element 16 may be a leaf spring or a spring or an equivalent member. The connection of the movable mass 13 to the substrate 11 is well known to those skilled in the art and will not be described in detail here.

The detection electrode 12 in the sensor unit 10 is adjacent to the movable mass 13 in the direction of the acceleration, and can provide a corresponding detection signal Se according to the movement of the movable mass 13. Further, the detection electrode 12 and the movable mass 13 form a detection capacitor, the capacitance value of the detection capacitor varies according to the distance between the detection electrode 12 and the movable mass 13, and the distance between the detection electrode 12 and the movable mass 13 varies with the acceleration, so that the acceleration on the sensing axis can be detected based on the variation of the capacitance value of the detection capacitor.

An important mechanical characteristic of the micro-electromechanical inertial sensor is temperature drift, and due to different thermal expansion coefficients of materials such as a substrate and a substrate, the substrate can be correspondingly deformed in the process of temperature change such as welding in the process of packaging the MEMS, and the deformation can affect the distance between the detection electrode and the movable mass block, so that the capacitance value between the detection electrode and the movable mass block is changed, and the output value is caused to drift.

In order to solve the above technical problem, the embodiment of the present invention further includes an auxiliary electrode 14, where the auxiliary electrode 14 is configured to provide a corresponding reference signal Sa according to the movement of the movable mass 13. Further, each auxiliary electrode 14 forms with the movable mass 13 a reference capacitance whose capacitance value varies with the distance between the auxiliary electrode 14 and the movable mass 13.

With continued reference to fig. 1, the processing circuit 20 obtains and stores a reference value according to the detection signal Se and the reference signal Sa collected under the preset acceleration in the calibration stage, and determines the acceleration a to be measured according to the reference value and the detection signal Se and the reference signal Sa collected under the acceleration to be measured in the test stage.

Further, the processing circuit 20 stores the received detection signal and the reference signal as the first detection signal Se1 and the first reference signal Sa1, respectively, and stores the first detection signal Se1 as the first reference value K1 when the preset acceleration is zero, and obtains the second reference value K2 according to the ratio of the received first reference signal Sa1 and the received first detection signal Se 1. The received reference signal and detection signal are stored as the second reference signal Sa2 and the second detection signal Se2, respectively, at a first acceleration at which the preset acceleration is non-zero, the received reference signal and detection signal are stored as the third reference signal Sa3 and the third detection signal Se3, respectively, at a second acceleration at which the preset acceleration is non-zero, the third reference value K3 is obtained from a first addition value between the second reference signal Sa2 and the third reference signal Sa3, a second addition value between the second detection signal Se2 and the third detection signal Se3, and the first reference value K1 and the second reference value K2, and the fourth reference value K4 is obtained from a first difference value between the second reference signal Sa2 and the third reference signal Sa3 and a second difference value between the second detection signal Se2 and the third detection signal Se 3. And finally, determining an effective capacitance change difference value under the acceleration to be detected according to the first to fourth reference values K1-K4, the fourth detection signal Se4 and the fourth reference signal Sa4 which are acquired under the acceleration to be detected and the correlation coefficient corresponding to the acceleration to be detected, and determining the acceleration a to be detected according to the effective capacitance change difference value, wherein the first acceleration and the second acceleration are equal in magnitude and opposite in direction.

The processing circuitry 20 may comprise one or more modules for providing the necessary signal processing based on the output signal of the sensor unit 10. In some embodiments, the processing circuitry 20 may include hardware control logic, which may be integrated within the chip of the sensor unit 10, for controlling the operation of the sensor unit 10 and performing various aspects of processing on the output signal of the sensor unit 10. In some embodiments, the inertial sensor further comprises a memory 30, the memory 30 being used to store various reference values output by the processing circuitry 20. In other embodiments, processing circuitry 20 may also include a processor (e.g., a microprocessor) that executes software instructions stored, for example, in memory 30. The microprocessor may control the operation of the sensor unit 10 by interacting with hardware control logic and process the measurement signals from the sensor unit 10.

Referring to fig. 2, as a non-limiting example, the processing circuit 20 includes an acquisition module 201 and an arithmetic module 202. The acquisition module 201 is configured to obtain corresponding detection signals Se and reference signals Sa at different accelerations. The operation module 202 is configured to obtain first to fourth reference values K1-K4 according to the detection signal Se and the reference signal Sa at different accelerations, output and store the first to fourth reference values K1-K4 to the memory 30, determine an effective capacitance change difference value at the acceleration to be measured according to the first to fourth reference values K1-K4, the detection signal Se and the reference signal Sa acquired at the acceleration to be measured, and the correlation coefficient corresponding to the acceleration to be measured, and determine the acceleration a to be measured according to the effective capacitance change difference value.

Further, referring to fig. 3 and 4, in order to detect the acceleration in the Z-axis direction, a surface of the substrate 11 opposite to the movable mass 13 is provided with a detection electrode 12, and the detection electrode 12 can provide a corresponding detection signal according to the position change of the movable mass 13. Further, the detection electrode 12 and the movable mass 13 form a differential capacitance structure, and the acceleration in the Z-axis direction can be obtained by detecting the capacitance value change of the capacitance. In particular, the movable mass 13 comprises at least a first movable zone 131 and a second movable zone 132, the first movable zone 131 and the second movable zone 132 performing a "seesaw movement" around the central anchor point 15 under the effect of acceleration. The detection electrode 12 includes a first detection electrode 121 opposed to the first movable region 131 and a second detection electrode 122 opposed to the second movable region 132. The first sensing electrode 121 and the first movable area 131 form a first sensing capacitance, the second sensing electrode 122 and the second movable area 132 form a second sensing capacitance, and the sensing signal is used to characterize the difference between the second sensing capacitance and the first sensing capacitance.

In addition, an auxiliary electrode 14 is disposed on the substrate 11, and the auxiliary electrode 14 can provide a corresponding reference signal according to the position change of the movable mass 13. Further, the auxiliary electrode 14 and the movable mass 13 form a differential capacitance structure. Specifically, auxiliary electrode 14 includes at least a first auxiliary electrode 141 opposite first movable region 131 and a second auxiliary electrode 142 opposite second movable region 132, where first auxiliary electrode 141 and first movable region 131 form a first reference capacitance, second auxiliary electrode 142 and second movable region 132 form a second reference capacitance, and the reference signal can be used to characterize a difference between the second reference capacitance and the first reference capacitance.

The first detection electrode 121, the second detection electrode 122, the first auxiliary electrode 141, and the second auxiliary electrode 142 may adopt a capacitor plate structure known to those skilled in the art.

Further, the ratio of the projected area of the first detection electrode 121 to the first auxiliary electrode 141 in the plan view direction is 1:1 to 3:1, and the ratio of the projected area of the second detection electrode 122 to the second auxiliary electrode 142 in the plan view direction is 1:1 to 3: 1.

Further, the first auxiliary electrode 141 coincides with the symmetry axis of the first detection electrode 121, and the second auxiliary electrode 142 coincides with the symmetry axis of the second detection electrode 122, so that the ratio of the difference value of the reference capacitance to the difference value of the detection capacitance of the inertial sensor at the external acceleration of the acceleration a and the first acceleration (or the second acceleration) and the ratio of the reference sensitivity deviation value to the detection sensitivity deviation value are in equal ratio, thereby obtaining:

pa represents a ratio between a reference signal and a detection signal under the external acceleration a, Pg represents a ratio between a reference signal and a detection signal under the first acceleration, Δ Ca _ ref represents a sensitivity deviation value of the reference capacitor under the acceleration a to be detected, Δ Ca _ det represents a sensitivity deviation value of the detection capacitor under the acceleration to be detected, K3 is a third reference value representing a ratio between the sensitivity deviation values of the reference capacitor and the detection capacitor under the acceleration to be detected, Ka is a correlation coefficient when the external acceleration is the acceleration a, and represents a proportionality coefficient between the ratio between the reference signal and the detection signal under the external acceleration a and the ratio between the reference signal and the detection signal under the external acceleration is the first acceleration.

Further, the first detection electrode 121, the second detection electrode 122, the first auxiliary electrode 141, and the second auxiliary electrode 142 may have any shape of electrode structure. Further, the first detection electrode 121 and the second detection electrode 122 are shaped electrodes, the first detection electrode 121 has a first notch area, the center of the first detection electrode 121 is located in the first notch area, and the first auxiliary electrode 141 is disposed in the first notch area; the second detection electrode 122 has a second cut-out region and the center of the second detection electrode 122 is located in the second cut-out region, and the second auxiliary electrode 142 is located in the second cut-out region. As shown in fig. 4, in the present embodiment, the first detection electrode 121 and the second detection electrode 122 are both U-shaped electrodes, the first auxiliary electrode 141 and the second auxiliary electrode 142 are both strip-shaped electrodes, and the first auxiliary electrode 141 and the second auxiliary electrode 142 are respectively located in the U-shaped notch regions of the first detection electrode 121 and the second detection electrode 122, that is, the first auxiliary electrode 141 and the first detection electrode 121, and the second auxiliary electrode 142 and the second detection electrode 122 are staggered in the X-axis direction.

In some embodiments, the first and

second detection electrodes

121 and 122 have the same structure, and the first and second

auxiliary electrodes

141 and 142 have the same structure.

In other embodiments, the first detection electrode 121 and the second detection electrode 122 are symmetrically disposed about a centerline of the central anchor point 15; similarly, the first auxiliary electrode 141 and the second auxiliary electrode 142 are symmetrically disposed about a centerline of the central anchor point 15.

In addition, the mass of the two sides of the movable mass 13 is not equal, that is, the mass of the first movable region 131 and the second movable region 132 of the movable mass 13 on the two sides of the elastic element 16 in the X-axis direction is not equal, so as to ensure that the movable mass 13 can form a "seesaw" effect when the acceleration exists in the Z-axis direction.

In a particular embodiment of the present invention, as shown in fig. 3 and 4, the areas of first movable area 131 and second movable area 132 are not equal and thus have different corresponding masses. Illustratively, the area of first movable area 131 is greater than the area of second movable area 132, such that when acceleration in the Z-axis direction is present, first movable area 131 and second movable area 132 perform a "seesaw motion" about the elastic member coupled thereto.

In other embodiments of the present invention, the areas of the first movable area 131 and the second movable area 132 are equal, so that in order to make the masses of the first movable area 131 and the second movable area 132 unequal, at least one of the first movable area 131 and the second movable area 132 is provided with a plurality of lightening holes distributed in an array. The lightening hole can be a through hole and is formed by an etching method during manufacturing; or blind holes, and can be etched by adding a layer of mask. In another embodiment, the masses of first movable area 131 and second movable area 132 may also be made unequal by adding a counterweight to at least one of first movable area 131 and second movable area 132.

It should be noted that the shapes, the number and the combination relationship of the lightening holes on the movable mass and the counterweight block in the present embodiment are not limited thereto, and those skilled in the art can select the number of the lightening holes on the mass according to specific situations.

Fig. 5 and 6 show a schematic cross-sectional view and a top view, respectively, of a sensor unit according to a second embodiment of the invention in the Y-direction.

Likewise, the sensor unit of the present embodiment includes a substrate 21, a detection electrode 22, a movable mass 23, an auxiliary electrode 24, a central anchor point 25, and an elastic element 26.

The central anchor point 25 is used to support the movable mass 23 above the substrate 21. Specifically, the central anchor point 25 is connected to the sidewall of the movable mass 23 through the elastic element 26, so that the movable mass 23 floats above the substrate 21, and the extending direction of the elastic element 26 coincides with the extending direction of the central anchor point 25. The elastic element 26 may be a leaf spring or a spring or an equivalent member. The connection of the movable mass to the substrate is well known to those skilled in the art and will not be described in detail here.

In order to detect the acceleration in the Z-axis direction, the substrate 21 is provided with a detection electrode 22, the detection electrode 22 and the movable mass 23 form a differential capacitance structure, and the acceleration in the Z-axis direction can be obtained by detecting a change in capacitance value of the capacitance. Specifically, the detection electrode 22 includes at least a first detection electrode 221 opposed to the first movable region 231 and a second detection electrode 222 opposed to the second movable region 232. The first detection electrode 221 and the first movable region 231 form a first detection capacitance, and the second detection electrode 222 and the second movable region 232 form a second detection capacitance. In addition, a first auxiliary electrode 241 and a second auxiliary electrode 242 are disposed on the substrate 21, the first auxiliary electrode 241 and the first movable region 231 form a first reference capacitor, and the second auxiliary electrode 242 and the second movable region 232 form a second reference capacitor.

Likewise, the detection electrodes 22 may provide respective detection signals according to the movement of the movable mass 23, which may be used to characterize the difference between the second detection capacitance and the first detection capacitance, and the auxiliary electrodes 24 may provide respective reference signals according to the movement of the movable mass 23, which may be used to characterize the difference between the second reference capacitance and the first reference capacitance.

The sensor in the second embodiment is substantially the same as that in the first embodiment except that in the second embodiment, the first detection electrode 221 and the first auxiliary electrode 241 form a comb-tooth electrode structure, and the second detection electrode 222 and the second auxiliary electrode 242 form a comb-tooth electrode structure. Similarly, the area ratio of the first detection electrode 221 to the first auxiliary electrode 241 is 1:1 to 3:1, and the area ratio of the second detection electrode 222 to the second auxiliary electrode 242 is 1:1 to 3: 1.

Fig. 7 shows a flow chart of a control method of an inertial sensor according to an embodiment of the invention. Fig. 8 and 9 are schematic views showing the structure of the sensor unit according to the embodiment of the present invention when subjected to acceleration in the Z-axis direction, and for convenience of explanation, the sensor unit according to the first embodiment is illustrated in fig. 8 and 9.

The method for controlling the inertial sensor according to the present embodiment will be described in detail below with reference to fig. 7 to 9. As shown in fig. 7, the control method of the inertial sensor includes steps S110 to S140.

In step S110, a preset acceleration is set to zero, the received detection signal is stored as a first reference value, and a second reference value is obtained according to a ratio of the reference signal to the detection signal at that time.

Specifically, when the external acceleration is zero, the processing circuit obtains the first detection signal Se1 and the first reference signal Sa1 at the time according to the capacitance values of the first detection capacitor, the second detection capacitor, the first reference capacitor and the second reference capacitor at the time, and stores the first detection signal Se1 as the first reference value K1. The first reference value K1 is used to represent a mismatch parameter between the second detection capacitor and the first detection capacitor when the external acceleration is zero. Specifically, the first reference value K1 is:

K1＝ΔC2-ΔC1

in addition, the processing circuit is further configured to obtain a second reference value K2 according to the first detection signal Se1 and the first reference signal Sa1 at this time. Wherein the second reference value K2 is used to characterize the ratio of the mismatch parameter of the reference capacitance to the mismatch parameter of the detection capacitance when the external acceleration is zero. Specifically, the second reference value K2 is:

K2＝(ΔC4-ΔC3)/(ΔC2-ΔC1)

wherein, Δ C4- Δ C3 represent mismatch parameters of the reference capacitance, and Δ C2- Δ C1 represent mismatch parameters of the detection capacitance. Further, Δ C1 represents an additional capacitance between the first detection electrode and the first movable region due to the deformation, Δ C2 represents an additional capacitance between the second detection electrode and the second movable region due to the deformation, Δ C3 represents an additional capacitance between the first auxiliary electrode and the first movable region due to the deformation, and Δ C4 represents an additional capacitance between the second auxiliary electrode and the second movable region due to the deformation.

Further, in the present embodiment, when the external acceleration is zero, the capacitance value of the first detection capacitor is equal to the sum of the ideal capacitance value of the first detection capacitor and the additional capacitance between the first detection electrode and the first movable region due to deformation, so that it can be obtained that when the external acceleration is zero, the capacitance value of the first detection capacitor is equal to:

C10＝C1+ΔC1

wherein C10 represents the capacitance of the first detection capacitor when the external acceleration is zero, and C1 represents the ideal capacitance of the first detection capacitor, that is, the capacitance of the first detection capacitor when the external acceleration is zero without deformation of the substrate.

Similarly, it can be respectively obtained that the capacitance value of the second detection capacitor is equal to:

C20＝C2+ΔC2

wherein C20 represents the capacitance of the second detection capacitor when the external acceleration is zero, and C2 represents the ideal capacitance of the second detection capacitor, that is, the capacitance of the second detection capacitor when the external acceleration is zero without deformation of the substrate.

The capacitance value of the first reference capacitance is equal to:

C30＝C3+ΔC3

wherein C30 represents the capacitance of the first reference capacitor when the external acceleration is zero, and C3 represents the ideal capacitance of the first reference capacitor, i.e. the capacitance of the first reference capacitor when the external acceleration is zero without deformation of the substrate.

The capacitance value of the second reference capacitance is equal to:

C40＝C4+ΔC4

wherein C40 represents the capacitance of the second reference capacitor when the external acceleration is zero, and C4 represents the ideal capacitance of the second reference capacitor, that is, the capacitance of the second reference capacitor when the external acceleration is zero without deformation of the substrate.

In this embodiment, when the substrate is not deformed, the ideal capacitance value of the first detection capacitor is equal to the ideal capacitance value of the second detection capacitor when the external acceleration is zero, and the ideal capacitance value of the first reference capacitor is equal to the ideal capacitance value of the second reference capacitor, so that the first reference value and the second reference value obtained according to the above formula are:

K1＝C20-C10

K2＝(C40-C30)/(C20-C10)

wherein C40-C30 are the first reference signal Sa1, and represent the difference between the second reference capacitance and the first reference capacitance when the external acceleration is zero. C20-C10 are the first detection signal Se1, which represents the difference between the second detection capacitance and the first detection capacitance when the external acceleration is zero.

In step S120, the preset acceleration is set as the first acceleration and the second acceleration, and the third reference value and the fourth reference value are obtained according to the reference signal and the detection signal at this time. The first acceleration and the second acceleration are equal in magnitude and opposite in direction.

Specifically, as shown in fig. 8, when there is a first acceleration + g in the Z-axis direction, since the weights of the first movable region 131 and the second movable region 132 are not equal to each other, the distance between the first movable region 131 and the substrate 11 decreases, and the distance between the second movable region 132 and the substrate 11 increases, so that the first detection capacitance and the second detection capacitance form a differential capacitance structure, and the first reference capacitance and the second reference capacitance form a differential capacitance structure.

As shown in fig. 9, when there is the second acceleration-g in the Z-axis direction, since the weights of the first movable region 131 and the second movable region 132 are not equal, the distance between the first movable region 131 and the substrate 11 increases, and the distance between the second movable region 132 and the substrate 11 decreases, so that the first detection capacitance and the second detection capacitance form a differential capacitance structure, and the first reference capacitance and the second reference capacitance form a differential capacitance structure.

The processing circuit stores the reference signal and the detection signal received at the time of acceleration of the first acceleration + g as a second reference signal Sa2 and a second detection signal Se2, respectively, and stores the reference signal and the detection signal received at the time of second acceleration-g as a third reference signal Sa3 and a third detection signal Se3, respectively. And obtains a first sum value between the second reference signal Sa2 and the third reference signal Sa3, a second sum value between the second detection signal Se2 and the third detection signal Se3, then obtains a third reference value K3 from the first sum value, the second sum value, and the first reference value K1 and the second reference value K2, and obtains a fourth reference value K4 from a first difference value between the second reference signal Sa2 and the third reference signal Sa3, and a second difference value between the second detection signal Se2 and the third detection signal Se 3.

Wherein the third reference value K3 is used to characterize the ratio between the reference capacitance sensitivity deviation value and the detection capacitance sensitivity deviation value when the external acceleration is acceleration g (including the first acceleration + g and the second acceleration-g). Specifically, the third reference value is:

K3＝(ΔC4g0-ΔC3g0)/(ΔC2g0-ΔC1g0)

wherein Δ C4g0- Δ C3g0 represent reference capacitance sensitivity deviation values, and Δ C2g0- Δ C1g0 represent detection capacitance sensitivity deviation values. Further, Δ C1g0 represents an additional capacitance between the first detection electrode and the first movable region due to deformation under acceleration g, Δ C2g0 represents an additional capacitance between the second detection electrode and the second movable region due to deformation under acceleration g, Δ C3g0 represents an additional capacitance between the first auxiliary electrode and the first movable region due to deformation under acceleration g, and Δ C4g0 represents an additional capacitance between the second auxiliary electrode and the second movable region due to deformation under acceleration g.

The fourth reference value K4 is used to characterize the ratio between the reference capacitance sensitivity and the detection capacitance sensitivity when the external acceleration is acceleration g (including the first acceleration + g and the second acceleration-g). Specifically, the fourth reference value K4 is:

K4＝(ΔC4g-ΔC3g)/(ΔC2g-ΔC1g)

where Δ C4g- Δ C3g represent reference capacitance sensitivity, and Δ C2g- Δ C1g represent detection capacitance sensitivity. Further, Δ C1g represents an effective change capacitance between the first detection electrode and the first movable region due to acceleration g, Δ C2g represents an effective change capacitance between the second detection electrode and the second movable region due to acceleration g, Δ C3g represents an effective change capacitance between the first auxiliary electrode and the first movable region due to acceleration g, and Δ C4g represents an effective change capacitance between the second auxiliary electrode and the second movable region due to acceleration-g.

Further, in the present embodiment, when the external acceleration is g (including the first acceleration + g and the second acceleration-g), the capacitance value of the first detection capacitor is equal to:

C11＝C10+ΔC1g0+ΔC1g

C12＝C10+ΔC1g0-ΔC1g

where C11 represents the capacitance of the first detection capacitor when the external acceleration is the first acceleration + g, and C12 represents the capacitance of the first detection capacitor when the external acceleration is the second acceleration-g.

C21＝C20+ΔC2g0+ΔC2g

C22＝C10+ΔC2g0-ΔC2g

where C21 represents the capacitance value of the second detection capacitor when the external acceleration is the first acceleration + g, and C22 represents the capacitance value of the second detection capacitor when the external acceleration is the second acceleration-g.

The capacitance value of the first reference capacitance is equal to:

C31＝C30+ΔC3g0+ΔC3g

C32＝C30+ΔC3g0-ΔC3g

wherein, C31 represents the capacitance of the first reference capacitor when the external acceleration is the first acceleration + g, and C32 represents the capacitance of the first reference capacitor when the external acceleration is the second acceleration-g.

The capacitance value of the second reference capacitance is equal to:

C41＝C40+ΔC4g0+ΔC4g

C42＝C40+ΔC4g0-ΔC4g

wherein, C41 represents the capacitance of the second reference capacitor when the external acceleration is the first acceleration + g, and C42 represents the capacitance of the second reference capacitor when the external acceleration is the second acceleration-g.

The third reference value can thus be obtained according to the above equation:

K3＝[(C41-C31)/2+(C42-C32)/2-(ΔC4-ΔC3)]/[(C21-C11)/2+(C22-C12)/2+(ΔC2-ΔC1)]

and because:

K1＝ΔC2-ΔC1＝C20-C10

K2＝(ΔC4-ΔC3)/(ΔC2-ΔC1)＝(C40-C30)/(C20-C10)

then, the third reference value is:

K3＝[(C41-C31)/2+(C42-C32)/2-K1×K2]/[(C21-C11)/2+(C22-C12)/2+K1]

the fourth reference value is:

K4＝[(C41-C31)/2-(C42-C32)/2]/[(C21-C11)/2-(C22-C12)/2]

wherein, C41-C31 are the second reference signal Sa2, which represents the difference between the second reference capacitance and the first reference capacitance when the external acceleration is the first acceleration + g, and C21-C11 are the second detection signal Se2, which represents the difference between the second detection capacitance and the first detection capacitance when the external acceleration is the first acceleration + g. C42-C32 are third reference signals Sa3 indicating the difference between the second reference capacitance and the first reference capacitance when the external acceleration is the second acceleration-g, and C22-C12 are third detection signals Se3 indicating the difference between the second detection capacitance and the first detection capacitance when the external acceleration is the second acceleration-g. (C41-C31)/2+ (C42-C32)/2 is a first sum of the second reference signal Sa2 and the third reference signal Sa3, and (C21-C11)/2+ (C22-C12)/2 is a second sum of the second detection signal Se2 and the third detection signal Se 3. (C41-C31)/2- (C42-C32)/2 is a first difference value of the second reference signal Sa2 and the third reference signal Sa4, and (C21-C11)/2- (C22-C12)/2 is a second difference value of the second detection signal Se2 and the third detection signal Se 3.

Further, the control method of the inertial sensor further comprises the step of storing the obtained first to fourth reference values K1-K4 in a memory so as to retrieve the first to fourth reference values K1-K4 in the subsequent test process.

In step S130, the inertial sensor is tested under the condition that the external acceleration is any acceleration, so as to obtain the current detection signal and the reference signal, and obtain the correlation coefficient under the current acceleration according to the detection signal and the reference signal.

Specifically, when the external acceleration is the acceleration a, the processing circuit obtains the current fourth detection signal Se4 and the fourth reference signal Sa4 according to the capacitance values of the first detection capacitor, the second detection capacitor, the first reference capacitor and the second reference capacitor at this time, and obtains the correlation coefficient Ka at the current acceleration according to the fourth detection signal Se4 and the fourth reference signal Sa 4.

In this embodiment, when the external acceleration is an acceleration a, the capacitance value of the first detection capacitor is equal to:

C1a＝C1+ΔC1+ΔC1a0+ΔC1a

where C1a represents a capacitance value of the first detection capacitor when the external acceleration is the acceleration a, C1 represents an ideal capacitance value of the first detection capacitor, Δ C1 represents an additional capacitance between the first detection electrode and the first movable region due to deformation at zero acceleration, Δ C1a0 represents an additional capacitance between the first detection electrode and the first movable region due to deformation at the acceleration a, and Δ C1a represents an effective change capacitance between the first detection electrode and the first movable region due to the acceleration a.

C2a＝C2+ΔC2+ΔC2a0+ΔC2a

where C2a represents a capacitance value of the second detection capacitor when the external acceleration is the acceleration a, C2 represents an ideal capacitance value of the second detection capacitor, Δ C2 represents an additional capacitance between the second detection electrode and the second movable region due to deformation at zero acceleration, Δ C2a0 represents an additional capacitance between the second detection electrode and the second movable region due to deformation at the acceleration a, and Δ C2a represents an effective change capacitance between the second detection electrode and the second movable region due to the acceleration a.

The capacitance value of the first reference capacitance is equal to:

C3a＝C3+ΔC3+ΔC3a0+ΔC3a

where C3a represents a capacitance value of the first reference capacitor when the external acceleration is the acceleration a, C3 represents an ideal capacitance value of the third detection capacitor, Δ C3 represents an additional capacitance between the first auxiliary electrode and the first movable region due to deformation at zero acceleration, Δ C3a0 represents an additional capacitance between the first auxiliary electrode and the first movable region due to deformation at the acceleration a, and Δ C3a represents an effective change capacitance between the first auxiliary electrode and the first movable region due to the acceleration a.

The capacitance value of the second reference capacitance is equal to:

C4a＝C4+ΔC4+ΔC4a0+ΔC4a

where C4a represents a capacitance value of the second reference capacitor when the external acceleration is the acceleration a, C4 represents an ideal capacitance value of the fourth detection capacitor, Δ C4 represents an additional capacitance between the second auxiliary electrode and the second movable region due to deformation at zero acceleration, Δ C4a0 represents an additional capacitance between the second auxiliary electrode and the second movable region due to deformation at the acceleration a, and Δ C4a represents an effective change capacitance between the second auxiliary electrode and the second movable region due to the acceleration a.

In this embodiment, the first detection capacitor is equal to the second detection capacitor when the external acceleration is zero without deformation of the substrate, and the first reference capacitor is equal to the second reference capacitor. Therefore, the difference between the effective variation capacitance of the second detection capacitance and the effective variation capacitance of the first detection capacitance can be obtained as follows:

ΔC2a-ΔC1a＝(C2a-C1a)-(ΔC2-ΔC1)-(ΔC2a0-ΔC1a0)

the effective change capacitance difference between the second reference capacitance and the first reference capacitance is:

ΔC4a-ΔC3a＝(C4a-C3a)-(ΔC4-ΔC3)-(ΔC4a0-ΔC3a0)

since the sensitivity of the inertial sensor varies linearly in the normal range, the ratio between the reference sensitivity and the detection sensitivity of the inertial sensor at different accelerations is constant, and therefore it is possible to obtain:

in addition, since the center position of the area where the first auxiliary electrode is located coincides with the center position of the area where the first detection electrode 121 is located, and the center position of the area where the second auxiliary electrode is located coincides with the center position of the area where the second detection electrode is located, the ratio of the difference value of the reference capacitance to the difference value of the detection capacitance of the inertial sensor at the external acceleration a and the external acceleration g, and the ratio of the reference sensitivity deviation value to the detection sensitivity deviation value are in an equal ratio relationship. The correlation coefficient Ka can thus be obtained as:

wherein, C41-C31 are the second reference signal Sa2, which represents the difference between the second reference capacitance and the first reference capacitance when the external acceleration is the first acceleration + g, and C21-C11 are the second detection signal Se2, which represents the difference between the second detection capacitance and the first detection capacitance when the external acceleration is the first acceleration + g. C4a-C3a are the fourth reference signal Sa4 indicating the difference between the second reference capacitance and the first reference capacitance when the external acceleration is acceleration a, and C2a-C1a are the fourth detection signal Se4 indicating the difference between the second detection capacitance and the first detection capacitance when the external acceleration is acceleration a.

In step S140, an effective capacitance change difference of the detected capacitance at the current acceleration is obtained according to the first to fourth reference values, the reference signal at the current acceleration a, the detection signal, and the correlation coefficient, and the current acceleration is determined according to the effective capacitance change difference.

From the above formula one can obtain:

ΔC4a0-ΔC3a0＝Ka*K3*(ΔC2a0-ΔC1a0)

and because:

ΔC4a-ΔC3a＝(C4a-C3a)-(ΔC4-ΔC3)-(ΔC4a0-ΔC3a0)

thus:

(ΔC2a-ΔC1a)*K4＝(C4a-C3a)-(ΔC2-ΔC1)*K2-(ΔC2a0-ΔC1a0)*Ka*K3

and because:

ΔC2a-ΔC1a＝(C2a-C1a)-(ΔC2-ΔC1)-(ΔC2a0-ΔC1a0)

it is thus possible to obtain:

ΔC2a-ΔC1a＝[Ka*K3*(C2a-C1a)-(C4a-C3a)-(Ka*K3-K2)*(ΔC2-ΔC1)]/(Ka*K3-K4)

and:

ΔC2-ΔC1＝K1

wherein, C4a-C3a are the fourth reference signal Sa4 when the external acceleration is the acceleration a, and C2a-C1a are the fourth detection signal Se4 when the external acceleration is the acceleration a.

In this embodiment, the capacitance values of the first reference capacitor, the second reference capacitor, the first detection capacitor and the second detection capacitor can be read at any acceleration a, the correlation coefficient Ka is obtained according to the capacitance values of the first reference capacitor, the second reference capacitor, the first detection capacitor and the second detection capacitor, and then the effective capacitance variation difference value is obtained according to the first to fourth reference values K1-K4 obtained in the calibration stage and the above formula, and the effective capacitance variation difference value includes an offset error caused by substrate deformation and a reference capacitance value during actual testing, so that errors caused by various types of deformation can be reduced.

In summary, in the inertial sensor and the control method thereof according to the embodiments of the present invention, in the calibration stage, the detection signal and the reference signal under different preset accelerations are obtained according to the detection electrode and the auxiliary electrode, the multiple reference values associated with the temperature drift error are obtained according to the obtained detection signal and the reference signal, then, in the test stage, the effective capacitance change difference is determined according to the multiple reference values and the detection signal and the reference signal acquired under the acceleration to be detected, and then, the corresponding acceleration to be detected is obtained through conversion according to the effective capacitance change difference. Because the effective capacitance change difference value contains offset error caused by substrate deformation, the temperature drift of the inertial sensor can be reduced, and the precision of the inertial sensor is improved.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An inertial sensor, comprising:

a sensor unit, the sensor unit comprising:

a movable mass that undergoes a corresponding displacement in a sense axis direction in response to an acceleration in the sense axis direction;

a substrate, the movable mass opposing a first surface of the substrate;

the detection electrode is positioned on the first surface and used for providing a corresponding detection signal according to the position change of the movable mass;

the auxiliary electrode is positioned on the first surface, is separated from the detection electrode and is used for providing a corresponding reference signal according to the position change of the movable mass block; and

a processing circuit connected to the sensor unit, the processing circuit being configured to obtain, in a calibration phase, a detection signal and a reference signal at different preset accelerations from the detection electrode and the auxiliary electrode, and to derive a plurality of reference values associated with a temperature drift error from the detection signal and the reference signal, an

And determining an effective capacitance change difference value according to the plurality of reference values and the detection signal and the reference signal acquired under the acceleration to be tested in the test stage, and obtaining the value of the acceleration to be tested according to the effective capacitance change difference value.

2. The inertial sensor of claim 1, wherein the sensor unit further comprises:

a central anchor fixed to a first surface of the substrate;

the movable mass comprises a first movable area and a second movable area, the first movable area and the second movable area are respectively and elastically connected with the central anchor point from two sides of the central anchor point,

the detection electrodes include a first detection electrode and a second detection electrode forming a first detection capacitance and a second detection capacitance with the first movable region and the second movable region, respectively, the detection signal representing a difference between the second detection capacitance and the first detection capacitance,

the auxiliary electrodes include a first auxiliary electrode and a second auxiliary electrode forming a first reference capacitance and a second reference capacitance with the first movable area and the second movable area, respectively, the reference signal being indicative of a difference between the second reference capacitance and the first reference capacitance,

the first movable region is disposed opposite to the first detection electrode and the first auxiliary electrode, and the second movable region is disposed opposite to the second detection electrode and the second auxiliary electrode.

3. An inertial sensor according to claim 2, wherein the axis of symmetry of the first auxiliary electrode coincides with the axis of symmetry of the first detection electrode and the axis of symmetry of the second auxiliary electrode coincides with the axis of symmetry of the second detection electrode.

4. An inertial sensor according to claim 3, wherein the plurality of reference values comprises at least first to fourth reference values, the processing circuitry being configured to perform the following operations in a calibration phase:

setting the preset acceleration to be zero, storing the received first detection signal as the first reference value, and obtaining a second reference value according to the ratio of the received first reference signal to the first detection signal;

setting the preset acceleration as a non-zero first acceleration, and respectively storing the received reference signal and the received detection signal as a second reference signal and a second detection signal;

setting the preset acceleration as a non-zero second acceleration, and respectively storing the received reference signal and the received detection signal as a third reference signal and a third detection signal;

obtaining a first sum value from the second reference signal and the third reference signal, obtaining a second sum value from the second detection signal and the third detection signal, and obtaining a third reference value from the first sum value, the second sum value, and the first reference value and the second reference value; and

obtaining a fourth reference value based on a first difference between the second reference signal and the third reference signal and a second difference between the second detection signal and the third detection signal,

wherein the first acceleration and the second acceleration are equal in magnitude and opposite in direction.

5. An inertial sensor according to claim 4, wherein the first reference value is:

K1＝C20-C10

wherein C20-C10 is a difference between the second detection capacitance and the first detection capacitance when the preset acceleration is zero,

the first reference value represents a mismatch parameter between the second detection capacitor and the first detection capacitor when the preset acceleration is zero.

6. An inertial sensor according to claim 4, wherein the second reference value is:

K2＝(C40-C30)/(C20-C10)

wherein C40-C30 is a difference between the second reference capacitance and the first reference capacitance when the preset acceleration is zero, C20-C10 is a difference between the second detection capacitance and the first detection capacitance when the preset acceleration is zero,

and the second reference value is used for representing the ratio of the mismatch parameter of the reference capacitor to the mismatch parameter of the detection capacitor when the preset acceleration is zero.

7. An inertial sensor according to claim 5, wherein the third reference value is: k3 ═ [ (C41-C31)/2+ (C42-C32)/2+ K1 XK 2]/[ (C21-C11)/2+ (C22-C12)/2+ K1]

Wherein C41-C31 is a difference value between a second reference capacitor and a first reference capacitor when the preset acceleration is the first acceleration, C21-C11 is a difference value between a second detection capacitor and a first detection capacitor when the preset acceleration is the first acceleration, C42-C32 is a difference value between the second reference capacitor and the first reference capacitor when the preset acceleration is the second acceleration, C22-C12 is a difference value between the second detection capacitor and the first detection capacitor when the preset acceleration is the second acceleration, K1 is the first reference value, and K2 is the second reference value,

and the third reference value is used for representing the ratio of the reference capacitance sensitivity deviation value and the detection capacitance sensitivity deviation value when the preset acceleration is the first acceleration.

8. An inertial sensor according to claim 4, wherein the fourth reference value is:

K4＝[(C41-C31)/2-(C42-C32)/2]/[(C21-C11)/2-(C22-C12)/2]

wherein C41-C31 is a difference value between a second reference capacitance and a first reference capacitance when the preset acceleration is the first acceleration, C21-C11 is a difference value between a second detection capacitance and a first detection capacitance when the preset acceleration is the first acceleration, C42-C32 is a difference value between the second reference capacitance and the first reference capacitance when the preset acceleration is the second acceleration, and C22-C12 is a difference value between the second detection capacitance and the first detection capacitance when the preset acceleration is the second acceleration,

and the fourth reference value is used for representing the ratio of the reference capacitance sensitivity to the detection capacitance sensitivity when the preset acceleration is the second acceleration.

9. The inertial sensor of claim 8, wherein the processing circuit comprises:

the acquisition module is used for acquiring the corresponding detection signal and the reference signal under different accelerations;

and the operation module is used for obtaining the first to fourth reference values according to the corresponding detection signals and the reference signals, determining an effective capacitance change difference value between the second detection capacitor and the first detection capacitor under the acceleration to be detected according to the first to fourth reference values, the fourth detection signals and the fourth reference signals which are acquired under the acceleration to be detected and the correlation coefficient corresponding to the acceleration to be detected, and determining the acceleration to be detected according to the effective capacitance change difference value.

10. The inertial sensor of claim 9, the arithmetic module determining the correlation coefficient according to the formula:

11. The inertial sensor of claim 9, wherein the arithmetic module determines the effective capacitance change difference between the second detected capacitance and the first detected capacitance at the acceleration under test according to the following equation:

ΔC2a-ΔC1a＝[Ka*K3*(C2a-C1a)-(C4a-C3a)-(Ka*K3-K2)*K1]/(Ka*K3-K4)

12. The inertial sensor of claim 4, wherein the fourth reference value is constant over the range of scales of the inertial sensor.

13. An inertial sensor according to claim 3, wherein the first detection electrode has a first cutout region and an axis of symmetry of the first detection electrode is located within the first cutout region, the first auxiliary electrode being disposed within the first cutout region,

the second detection electrode has a second cutout region and a symmetry axis of the second detection electrode is located in the second cutout region, and the second auxiliary electrode is located in the second cutout region.

14. An inertial sensor according to claim 13, wherein the first and second detection electrodes are U-shaped electrodes and the first and second auxiliary electrodes are strip electrodes.

15. An inertial sensor according to claim 3, wherein the first detection electrode and the first auxiliary electrode form a shape-matched comb-tooth electrode structure, and the second detection electrode and the second auxiliary electrode form a shape-matched comb-tooth electrode structure.

16. An inertial sensor according to any one of claims 13 to 15, wherein the area ratio of the first detection electrode to the first auxiliary electrode is from 1:1 to 3:1 and the area ratio of the second detection electrode to the second auxiliary electrode is from 1:1 to 3: 1.

17. A control method of an inertial sensor including a sensor unit including a movable mass, and a detection electrode and an auxiliary electrode which are located on a first surface of a substrate and are placed apart from each other, the movable mass being disposed opposite to the detection electrode and the auxiliary electrode, wherein the control method includes:

in the calibration stage, detection signals and reference signals under different preset accelerations are obtained according to the detection electrodes and the auxiliary electrodes, the detection signals are provided by the detection electrodes according to the position change of the movable mass block, and the reference signals are provided by the auxiliary electrodes according to the position change of the movable mass block;

deriving a plurality of reference values associated with temperature drift error from the detection signal and the reference signal, an

18. The control method of claim 17, wherein the movable mass comprises a first movable region and a second movable region, the first movable region and the second movable region being elastically connected with a central anchor point of the sensor unit from both sides of the central anchor point,

the auxiliary electrodes include a first auxiliary electrode and a second auxiliary electrode forming a first reference capacitance and a second reference capacitance with the first moveable region and the second moveable region, respectively, the reference signal being indicative of a difference between the second reference capacitance and the first reference capacitance,

19. The control method according to claim 18, wherein the step of obtaining and storing a reference value from the detection signal and the reference signal acquired at the preset acceleration includes:

setting the preset acceleration to be zero, storing the received first detection signal as a first reference value, and obtaining a second reference value according to the ratio of the received first reference signal to the first detection signal;

20. The control method according to claim 19, wherein the first reference value is:

K1＝C20-C10

the first reference value is used for representing a mismatch parameter between the second detection capacitor and the first detection capacitor when the preset acceleration is zero.

21. The control method according to claim 19, wherein the second reference value is:

K2＝(C40-C30)/(C20-C10)

wherein C40-C30 are differences between the second reference capacitance and the first reference capacitance when the preset acceleration is zero, C20-C10 are differences between the second detection capacitance and the first detection capacitance when the preset acceleration is zero,

22. The control method according to claim 21, wherein the third reference value is: k3 ═ [ (C41-C31)/2+ (C42-C32)/2+ K1 XK 2]/[ (C21-C11)/2+ (C22-C12)/2+ K1]

23. The control method according to claim 19, wherein the fourth reference value is:

K4＝[(C41-C31)/2-(C42-C32)/2]/[(C21-C11)/2-(C22-C12)/2]

24. The control method according to claim 23, wherein the step of determining the acceleration to be measured from the reference value and the detection signal and the reference signal acquired at the acceleration to be measured comprises:

storing the detection signal and the reference signal acquired under the acceleration to be detected as a fourth detection signal and a fourth reference signal respectively;

determining a correlation coefficient corresponding to the acceleration to be detected according to the third reference value, the fourth detection signal and the fourth reference signal;

determining an effective capacitance change difference value between a second detection capacitor and a first detection capacitor under the acceleration to be detected according to the first to fourth reference values, the fourth detection signal, the fourth reference signal and the correlation coefficient; and

and determining the current acceleration according to the effective capacitance change difference.

25. The control method according to claim 24, wherein the correlation coefficient is determined according to the following formula:

26. The control method of claim 24, wherein the effective capacitance change difference between the second detected capacitance and the first detected capacitance at the acceleration under test is determined according to the following equation: Δ C2a- Δ C1a ═ K3 (C2a-C1a) - (C4a-C3a) - (Ka × K3-K2) × K1]/(Ka × K3-K4)

27. The control method of claim 19, wherein the fourth reference value is a constant over the range of the inertial sensor's range of span.