Detection method and device thereof for charge balance type micro-accelerometer gauge head differential capacitor

Abstract

The invention provides a detection method and a device thereof for a charge balance type micro-accelerometer gauge head differential capacitor. A capacitance type micro-accelerometer gauge head is provided with two fixed plate electrodes and a movable plate electrode, and the three electrodes form the differential capacitor. Alternating current drive signals are exerted on the two fixed plate electrodes and coupled to the movable plate electrode, wherein the phase positions of the alternating current drive signals are complementary and the amplitude of the alternating current drive signals can be regulated dynamically, alternating current charges of a middle electrode is detected, the amplitude of the alternating current drive signals is adjusted after demodulation and control of proportional-integral, so that the two fixed plate electrodes are coupled to the movable plate electrode, the charges are offset automatically, rebalance of the charges is formed, and the proportional-integral controls the output voltage to be in direct proportion to the specific value of the capacitance difference and the capacitance sum of the gauge head differential capacitor. By adopting the detection device of the detection method, the problems that the scale stability and the zero stability of an accelerometer are poor due to the forward gain accuracy and the forward gain stability of an open loop detection circuit are solved, and the shortcoming that zero output of the accelerometer drifts in the electrostatic force balance micro-accelerometer due to medium charging effect is avoided. The detection device has the advantages of being high in measuring accuracy, good in stability, good in compatibility with different gauge heads, and the like.

Description

technical field [0001] The invention belongs to the technical field of micro-accelerometer signal detection, and in particular relates to a charge-balanced micro-accelerometer head differential capacitance detection method and device. Background technique [0002] The micro accelerometer is a device with a characteristic size in the micron level processed by micro-mechanical and electronic technology. It is used to measure the non-gravitational acceleration of the carrier. It is small in size, low in cost, suitable for batch processing and easy to integrate with ASIC. It is an inertial sensor and has With wide application prospects and urgent market demand, it has been successfully used in industrial fields such as automobiles and consumer electronics, civilian use, and military fields such as inertial guidance and tactical missiles. [0003] The capacitive micro-accelerometer head adopts a typical "spring-mass" structure. Under the action of inertial force, the mass block s...

AI Technical Summary

Problems solved by technology

The accumulation of charges on the surface may cause the drift of the accelerometer, and the accumulation of parasitic charges may also change the mechanical characteristics of the device;

[0007] 2) There may be electrostatic attraction failure

If the mechanical stiffness of the meter head is less than the electrostatic stiffness during this process, the electrostatic force on the moving piece exceeds the elastic restoring force of the elastic support beam, so that the moving piece is attracted by the electrostatic force and attached to the fixed pole plate and cannot return to the equilibrium position, resulting in Suction failure

In order to avoid electrostatic attraction, the design requires that the spring stiffness of the supporting mass block is greater than the maximum electrostatic stiffness that may be generated by the closed-loop system, which requires a high mechanical stiffness, and excessive mechanical stiffness will cause the zero output of the accelerometer to be unstable;

[0008] 3) Since the mechanical part with second-order transmission characteristics is inside the closed loop, it may affect the stability of the loop

In fact, the parasitic capacitance of the sensitive structure changes inevitably with temperature, and it is extremely difficult to achieve high stability of the excitation signal amplitude and high stability of the amplifier;

[0012] 2) Since the change of differential capacitance is not strictly proportional to the displacement of the movable plate, the output is non-linear, especially when the stroke of the movable plate is large, the nonlinearity is particularly serious;

[0013] 3) During differential capacitance detection, the excitation signal with a fixed amplitude acts on the upper and lower fixed plates. When there is an external acceleration, the movable plate deviates from the middle position and receives two unequal electrostatic forces, which will also lead to output nonlinearity

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