CN100483136C - Dual-axis capacitance type micromechanical accelerometer - Google Patents

Abstract

The invention discloses a dual-axle capacitor micro mechanical accelerometer, which comprises a basic plate, a weigh block, a flexible support, a driving electrode, a detecting electrode, a tooth axle and a backstop, while it uses the weight block to sense the accelerators at two orthogonal directions. Wherein, the weight block is at the center of said device, while the flexible support, backstop, driving electrode, and detecting electrode are outside the weight block; the flexible support can realize decouple in two orthogonal directions to improve the sensitivity and resolution in said two directions; the flexible support uses the four corners of square as anchor points, with better structure stability; and it uses comb capacitor to realize differential static driving and capacitor detection, to improve the sensitivity and resolution of accelerator. The invention can easily realize two-dimension accelerator detection with high accuracy.

Description

A dual-axis capacitive micromachined accelerometer

technical field

The invention relates to a capacitive micro-machine accelerometer, in particular to a two-axis capacitive micro-machine accelerometer, which belongs to the field of micro-mechanical sensors in micro-electro-mechanical systems (MEMS). It is widely used as a micro-inertial device in automotive electronics, aerospace, and weapons. equipment etc.

Background technique

MEMS is in the development period, its technology and market are not yet mature, but its broad development prospects, huge social and economic benefits are well known to the world, and the micro-mechanical accelerometer is the most successful representative. The research on micro-machined accelerometers began in the early 1970s, and formed single-axis micro-machined accelerometer products in the 1980s. In the late 1990s, multi-axis micro-machined accelerometers appeared. The most representative one on the market is the American AD The company's ADXL series of micromachined accelerometers. Micromachined accelerometers have developed rapidly, and there are various forms such as piezoresistive, capacitive, piezoelectric, force balance, thermal convection, resonance, and tunnel current. Compared with many forms, capacitive micromachined accelerometers have high sensitivity, small temperature drift, good stability, strong resistance to overload, easy self-test, and easy to achieve low-cost high-precision measurement. Capacitive micromachined accelerometers are relatively mature in foreign countries and have been successfully industrialized. In China, they are still in the stage of laboratory prototypes, and there is still a certain distance from industrialization. Most of the existing micro-mechanical accelerometer products are of medium and low precision, and the measurement accuracy cannot meet the requirements of the inertial level, which seriously restricts its application range, and is only used in commercial fields where the accuracy is not high. Micromachined accelerometer products are mostly uniaxial, but in practical applications, biaxial or triaxial accelerometers are often required to measure the acceleration vector. less. At present, the research direction of micromachined accelerometers is mainly focused on high precision, multi-axis integration and digital output. Improving the performance of accelerometers is to achieve multi-axis high sensitivity, low noise, low drift and large dynamic range measurement.

Contents of the invention

The technology of the present invention solves the problem: overcomes the deficiencies of the prior art, and provides a high-precision dual-axis capacitive micro-machined accelerometer to solve the problems that the existing micro-machined accelerometers are mostly single-axis, and the sensitivity and resolution are not high enough. Realize high-precision two-dimensional acceleration measurement.

The technical solution of the present invention is a two-axis capacitive micromachined accelerometer, which is characterized in that it includes a substrate, a mass block, an elastic support, a drive electrode, a detection electrode and a tooth pivot. Acceleration in an orthogonal direction, the mass block is located in the center of the structure, and the periphery of the mass block is elastic support, driving electrodes and detection electrodes. The elastic support is composed of four double-end fixed beams and four cantilever beams, and the four The beams form a square, and the four corners of the square are anchor points. One end of each cantilever beam is fixedly connected to the mass block, and the other end is fixedly connected to the middle of the corresponding double-ended fixed beam; the movable plate of the driving electrode and the detecting electrode is connected to the mass The block is fixedly connected, and the fixed plate of the electrode is fixedly connected with the tooth hub, and the differential electrostatic drive and capacitance detection are realized with the comb-tooth offset structure.

In addition, stoppers are arranged around the periphery of the mass block, which can effectively realize overload protection and prevent the elastic support structure from breaking under strong impact.

Compared with the prior art, the present invention has the advantages that: the present invention adopts one mass block to be sensitive to accelerations in two directions, realizes the decoupling of two orthogonal directions with an ingenious elastic support structure, and makes the sensitivity and resolution of two directions The rate is high; the center symmetric structure with the four corners of the square as the anchor point is very stable and has a large impact resistance; the structure of the comb tooth offset realizes differential electrostatic drive and capacitance detection, effectively eliminating Common mode interference, improved sensitivity and resolution, easy to achieve high-precision two-dimensional acceleration measurement.

Description of drawings

Fig. 1 is a schematic diagram of the planar structure of the biaxial capacitive micromachined accelerometer of the present invention.

Detailed ways

As shown in Figure 1, the present invention includes a substrate 1, a mass block 2, an elastic support, a drive electrode and a detection electrode, tooth pivots 15, 25, 35, 45, tooth pivots 15, 25, 35, 45, stoppers 17, 27 , 37 , 47 , anchor points 16 , 26 , 36 , 46 are connected to the substrate 1 through bonding, the structure is center-symmetric, and a mass 2 is used to sense accelerations in two orthogonal directions. The mass block 2 is located in the center of the structure, and the periphery of the mass block 2 is elastic support, stoppers 17, 27, 37, 47, tooth hubs 15, 25, 35, 45, drive electrodes and detection electrodes. The elastic support is composed of four double-ended fixed beams 12, 22, 32, 42 and four cantilever beams 11, 21, 31, 41, and the four double-ended fixed beams 12, 22, 32, 42 form a square. The four corners are anchor points 16,26,36,46. One end of each cantilever beam 11 , 21 , 31 , 41 is fixedly connected to the mass block 2 , and the other end is fixedly connected to the middle of the corresponding double-ended support beam 12 , 22 , 32 , 42 . The movable pole plates 14, 24, 34, 44 of the drive electrodes and the detection electrodes are fixedly connected with the mass block 2, the fixed pole plates 13, 23, 33, 43 of the electrodes are fixedly connected with the tooth hubs 15, 25, 35, 45, and the drive electrodes The detection electrodes are all composed of comb-tooth bias structure, and the electrostatic drive and capacitance detection are realized in the form of differential capacitance. The stoppers 17, 27, 37, 47 can effectively realize overload protection and prevent the elastic support structure from breaking under strong impact.

The working principle of the present invention: the acceleration is converted into an inertial force through the sensitive mass block, and the inertial force causes the displacement of the sensitive mass block, the movable plate of the capacitor is fixedly connected with the mass block, and the displacement of the movable plate causes the distance between the capacitor plates to change. Measure the capacitance to calculate the measured acceleration. At the same time, in order to reduce the nonlinearity of the accelerometer and improve the test accuracy, the electrostatic force feedback is used to form a force balance closed-loop system, so that the mass works at the zero balance position. When there is an acceleration input in the vertical direction, the inertial force generated by the mass block 2 deforms the elastic support, and the mass block 2 is fixedly connected with the electrode movable plates 24, 44 on the left and right sides, and they are displaced in the vertical direction together to make the capacitor The distance between the movable pole plates 24, 44 and the fixed pole plates 23, 43 changes, and the measured acceleration in the vertical direction is deduced by measuring changes in capacitance. The measured information is fed back as the voltage on the driving electrode plate, and the electrostatic force acting on the capacitive movable plate 24, 44 is controlled to balance the electrostatic force and the inertial force, so that the mass block 2 works in a zero displacement balance in the vertical direction position; when there is an acceleration input in the horizontal direction, the mass block 2 generates an inertial force in the horizontal direction, and the elastic support deforms, and the mass block 2 is fixedly connected with the electrode movable plates 14, 34 on the upper and lower sides, and they together generate a horizontal displacement , the distance between the movable plate 14, 34 and the fixed plate 13, 33 is changed, and the measured acceleration in the horizontal direction is deduced by measuring the change of capacitance. The measured information is fed back as the voltage on the driving electrode plate, and the electrostatic force acting on the capacitive movable plate 14, 34 is controlled to balance the electrostatic force and the inertial force, so that the mass block 2 works in a zero-displacement balance in the horizontal direction Location.

In summary, the present invention proposes a dual-axis capacitive micromachined accelerometer with a novel structure. It is small in size and light in weight, and can realize two-dimensional acceleration measurement with high sensitivity and high resolution. Applications in the field of high precision.

Claims (2)

1, dual-axis capacitance type micromechanical accelerometer, its characteristics are: comprise substrate, mass, resiliency supported, drive electrode, detecting electrode and tooth pivot, total is a centrosymmetric image, by the acceleration of responsive two orthogonal directionss of a mass; Mass occupy the center of structure, the mass periphery is resiliency supported, drive electrode and detecting electrode, resiliency supported is made of four two-end fixed beams and four semi-girders, foursquare four angles of four two-end fixed beam formations are anchor points, one end and the mass of each semi-girder are connected, and the two-end fixed beam that the other end is corresponding with it is middle to be connected; Drive electrode and detecting electrode constitute differential capacitor with the broach bias structure, and the movable pole plate of differential capacitor is connected with mass, and the fixed polar plate of differential capacitor is connected with the tooth pivot.

2, dual-axis capacitance type micromechanical accelerometer according to claim 1 is characterized in that: in the periphery of described mass, be provided with two backstops axisymmetrically.