CN112573476B - MEMS sensor with adjustable sensitivity and bandwidth - Google Patents

Abstract

The invention belongs to the technical field of micro-electromechanical systems, and discloses a MEMS sensor with adjustable sensitivity and bandwidth, which comprises a sensitive module and a detection module, wherein the sensitive module comprises a negative stiffness structure and a stable structure; the negative stiffness structure is used for reducing the effective stiffness of the MEMS sensor and improving the sensitivity of device detection; the stabilizing structure is used for stabilizing the negative stiffness structure and realizing the adjustability of the total effective stiffness of the MEMS sensor. The stabilizing structure includes a first stabilizing electrode and a second stabilizing electrode, and stabilization of the negative stiffness structure is achieved by applying an alternating voltage across the first stabilizing electrode and the second stabilizing electrode to induce high frequency vibrations. The overall effective stiffness of the MEMS sensor is changed by changing the amplitude and frequency of the ac voltage, thereby changing the sensitivity of the sensor. The bandwidth of the MEMS sensor can be adjusted by adjusting the amplitude and frequency of the ac voltage.

Description

A MEMS sensor with adjustable sensitivity and bandwidth

Technical field

The invention belongs to the technical field of micro-electromechanical systems, and more specifically, relates to a MEMS sensor with adjustable sensitivity and bandwidth.

Background technique

The resonant accelerometer designed in the prior art 1 uses the first-order electrostatic negative stiffness generated by the electrostatic force between a set of parallel plate electrodes and the accelerometer test mass to reduce the mechanical stiffness of the entire accelerometer structure and improve the sensitivity. A set of comb electrodes is used to adjust the force balance of the accelerometer. This design requires a particularly high voltage to effectively reduce the stiffness of the device, achieve higher sensitivity, and have poor controllability.

In prior art 2, a parametric modulation method is used to control the coupling strength between two resonators to improve the sensitivity and resolution of the accelerometer. The purpose of parametric modulation here is to control the coupling strength between resonators with high-frequency AC voltage.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a MEMS sensor with adjustable sensitivity and bandwidth, which aims to stabilize the negative stiffness structure and realize real-time adjustment of the sensitivity and bandwidth of the device.

The invention provides a MEMS sensor with adjustable sensitivity and bandwidth, including a sensitive module and a detection module. The sensitive module includes a negative stiffness structure and a stable structure; the negative stiffness structure is used to reduce the effective stiffness of the MEMS sensor and improve The sensitivity of device detection; the stable structure is used to stabilize the negative stiffness structure and realize the controllability of the total effective stiffness of the MEMS sensor.

Furthermore, the stabilizing structure includes: a first stabilizing electrode and a second stabilizing electrode, and high-frequency vibration is introduced by applying AC voltage to the first stabilizing electrode and the second stabilizing electrode to achieve the stabilization of the negative stiffness structure.

Furthermore, the negative stiffness structure includes a first negative stiffness electrode N1 and a second negative stiffness electrode N2. The first negative stiffness electrode N1 and the second negative stiffness electrode N2 introduce electrostatic negative stiffness into the accelerometer through electrostatic force. .

Furthermore, the sensitive module also includes a first displacement control electrode D1 and a second displacement control electrode D2. The first displacement control electrode D1 and the second displacement control electrode D2 control the displacement of the detection mass through electrostatic force.

Furthermore, the negative stiffness structure includes a first negative stiffness arched beam C1 and a second negative stiffness arched beam C2. The first negative stiffness arched beam C1 and the second negative stiffness arched beam C2 are arched beams. Introducing negative stiffness in the accelerometer through buckling.

Furthermore, an AC voltage with frequency f and amplitude Vp is applied to the first stabilizing electrode and the second stabilizing electrode.

Furthermore, the frequency f of the AC voltage Vp depends on the negative stiffness introduced by the negative stiffness structure and the sensor sensitivity and bandwidth requirements of the actual application.

Among them, by adjusting the amplitude Vp and frequency f of the AC voltage, the sensitivity of the sensitive structure of the MEMS sensor is changed. By adjusting the amplitude Vp and frequency f of the AC voltage, the bandwidth of the MEMS sensor is adjusted.

Through the above technical solutions conceived by the present invention, compared with the existing technology, the following beneficial effects can be achieved:

(1) The existing technology uses negative stiffness structures to reduce the positive stiffness of the mechanical structure of MEMS devices. Due to machining errors, the negative stiffness structure does not match the positive and negative stiffness, which can easily make the system unstable. Therefore, based on the negative stiffness structure, the present invention introduces high-frequency oscillation based on the stability principle similar to the Kapitza pendulum to maintain the negative stiffness structure. steady state.

(2) By adding a high-frequency oscillation negative stiffness MEMS sensor, the sensitivity of the device can be adjusted in real time by adjusting the voltage amplitude and frequency of high-frequency oscillation according to actual application requirements.

(3) The negative stiffness MEMS sensor based on high-frequency oscillation can change the voltage amplitude and frequency of high-frequency oscillation and achieve adjustable bandwidth.

Description of the drawings

Figure 1 is a schematic structural diagram of a resonant accelerometer provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of the potential energy displacement curve of the resonant accelerometer provided by an embodiment of the present invention;

Figure 3 is a schematic diagram of the amplitude-frequency response curve of the resonant accelerometer provided by the embodiment of the present invention when the AC voltage at different frequencies is stable;

Figure 4 is a schematic structural diagram of a capacitive accelerometer based on the principle of the present invention provided by an embodiment of the present invention;

Among them, M is the inspection quality, L1, L2, L3 and L4 are four micro-lever structures respectively, R1 and R2 are two resonator beams respectively, S1, S2, S3 and S4 are four cantilever beams respectively, N1 and N2 is a set of negative stiffness electrodes, D1 and D2 are a set of displacement control electrodes, W1 and W2 are a set of stable electrodes; A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, and A16 are the anchor points for fixing the device on the substrate, among which A1, A3, A4, A5, A7, A9, A11, A12, A13, and A15 fix the microlever, resonator, and cantilever beam on On the substrate; the negative stiffness electrode is fixed on the substrate through anchor points A16 and A8; the displacement control electrode is fixed on the substrate through anchor points A2 and A6; the stable electrode is fixed on A10 and A14.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

The present invention provides a design and implementation method of a MEMS sensor that stabilizes the system by introducing high-frequency oscillation on the basis of negative stiffness, thereby achieving adjustable sensitivity and bandwidth; the design proposes a new type of MEMS sensor that stabilizes the negative stiffness structure. The method is to make the negative stiffness structure reach a stable state by introducing high-frequency oscillation according to the stability principle similar to the Kapitza pendulum on the basis of the negative stiffness structure; the MEMS sensor designed using this method not only has adjustable sensitivity, but also can Bandwidth is adjustable.

The MEMS sensor with adjustable sensitivity and bandwidth provided by the present invention includes a sensitive module and a detection module; the sensitive module is used to sense the displacement signal or force signal input from the outside; the detection module is used to convert the signal sensed by the sensitive module into an electrical signal. Output; the sensitive module includes a negative stiffness structure and a stable structure; the negative stiffness structure is used to reduce the effective stiffness of the MEMS sensor and improve the sensitivity of device detection; the stable structure is used to stabilize the negative stiffness structure and realize the controllability of the total effective stiffness of the MEMS sensor. Among them, the effective stiffness is the sum of the mechanical positive stiffness and negative stiffness of the sensor. In order to prevent the negative stiffness introduced by the negative stiffness structure from being unstable, exceeding the positive stiffness of the system will cause the effective stiffness of the entire system to be negative, thus making the entire system unstable. Therefore The present invention introduces a stable structure, and since sensitivity and stiffness are in an inverse relationship, the smaller the stiffness, the higher the sensitivity and the smaller the bandwidth. Therefore, the present invention realizes effective control of the sensitivity and bandwidth of the MEMS sensor by adjusting the effective stiffness of the system after stabilization.

In the embodiment of the present invention, the stabilizing structure includes: a first stabilizing electrode and a second stabilizing electrode, and high-frequency vibration is introduced by applying AC voltage on the stabilizing electrode to achieve the stabilization of the negative stiffness structure. Specifically, an AC voltage with frequency f and amplitude Vp can be applied to the first stable electrode and the second stable electrode; the frequency f of the AC voltage Vp depends on the size of the negative stiffness introduced by the negative stiffness structure and the actual application. Sensor sensitivity and bandwidth requirements. By adjusting the amplitude Vp and frequency f of the AC voltage, the sensitivity of the sensitive structure of the MEMS sensor can be changed, and the bandwidth of the MEMS sensor can be adjusted.

The MEMS sensors with adjustable sensitivity and bandwidth provided by the present invention include: force- or displacement-based sensors such as capacitive accelerometers, magnetometers, and pressure gauges using negative stiffness structures.

In order to further explain the MEMS sensor with adjustable sensitivity and bandwidth provided by the embodiment of the present invention, the details are as follows with reference to the accompanying drawings and specific examples:

Figure 1 shows the specific structure of a resonant accelerometer, a MEMS sensor based on force sensing provided by the first embodiment of the present invention, including a sensitive module and a detection module. Among them, the detection module uses a resonator as the detection device, and the sensitive module includes the inspection mass M, the first displacement control electrode D1 and the second displacement control electrode D2, the first negative stiffness electrode N1 and the second negative stiffness electrode N2, the first stable Electrode W1 and second stabilizing electrode W2. Among them, the first negative stiffness electrode N1 and the second negative stiffness electrode N2 introduce electrostatic negative stiffness into the accelerometer through electrostatic force; the first displacement control electrode D1 and the second displacement control electrode D2 control the displacement of the detection mass through electrostatic force; The first stabilizing electrode W1 and the second stabilizing electrode W2 generate high-frequency vibration by applying AC voltage to stabilize the negative stiffness introduced by the negative stiffness electrode.

Figure 4 shows the specific structure of a capacitive negative stiffness accelerometer, a MEMS sensor based on displacement sensing provided by the second embodiment of the present invention, including a sensitive module and a detection module. Among them, the detection module specifically adopts the method of capacitive displacement detection, and the sensitive module is specifically the inspection mass M, the first negative stiffness arched beam C1 and the second negative stiffness arched beam C2, the first stable electrode W1 and the second stable electrode W2 ; Among them, the first negative stiffness arched beam C1 and the second negative stiffness arched beam C2 introduce negative stiffness into the accelerometer through buckling; the first stable electrode W1 and the second stable electrode W2 generate high-frequency vibration by applying AC voltage. , stabilizing the negative stiffness introduced by the negative stiffness electrode.

The principle and specific implementation method of the adjustable sensitivity and bandwidth of the present invention are as follows:

The structure of the electrostatic negative stiffness resonant accelerometer is shown in Figure 1, which includes a traditional resonant accelerometer structure, a set of negative stiffness comb electrodes and a set of displacement control electrodes; when no voltage is applied to each electrode, it is a traditional For a resonant accelerometer, the accelerometer system is in an equilibrium position.

Among them, anchor points A1, A3, A4, A5, A7, A9, A11, A12, A13, A15 are used to fix the micro-lever, resonator and cantilever beam on the substrate; the first negative stiffness electrode N1 and the second negative The stiffness electrode N2 is fixed on the substrate through anchor points A16 and A8; the first displacement control electrode D1 and the second displacement control electrode D2 are fixed on the substrate through anchor points A2 and A6; the first stable electrode W1 and the second stable electrode W2 is fixed on the substrate via anchor points A10 and A14.

When the DC voltage V1 is applied to the first negative stiffness electrode N1 and the second negative stiffness electrode N2, the DC voltage V2 is applied to the first displacement control electrode D1 and the second displacement control electrode D2, and the bias voltage V4 is applied to the inspection quality, it is a Resonant accelerometer using electrostatic negative stiffness structure.

Since the mechanical restoring force generated by the positive stiffness of the accelerometer's mechanical structure pulls the system back to the equilibrium position, the electrostatic force is the attraction force that causes the accelerometer system to deviate from the equilibrium position. Therefore, contrary to the positive mechanical stiffness, the electrostatic force produces a negative Stiffness. Negative stiffness structures can also be implemented using arched beams, such as the capacitive negative stiffness accelerometer shown in Figure 4. When the electrostatic negative stiffness is greater than the positive mechanical stiffness, the stiffness of the entire system is negative, and the potential energy curve is shown as the dotted line in Figure 2, which is in an unstable state. Applying the working principle similar to the Kapitza pendulum, an AC voltage with frequency f and amplitude Vp is applied to the stable electrodes W1 and W2 to introduce high-frequency vibration.

In the embodiment of the present invention, the amplitude Vp and frequency f of the AC voltage depend on the negative stiffness introduced by the negative stiffness structure, which is related to the inspection quality and the voltage applied to each electrode, generally 1 to 5V, 5Hz ~100Hz.

At this time, the potential energy curve of the system is shown as the solid line in Figure 2. The potential energy has a minimum value, and it is in a stable state within a displacement interval near the minimum value.

As shown in Figure 3, changing the frequency f of the AC voltage will change the resonant frequency of the system. Adjusting the amplitude Vp of the AC voltage can also adjust the bandwidth of the system. Therefore, the resonant accelerometer designed using the principle of the present invention not only has a stable and adjustable negative stiffness structure, but also has an adjustable bandwidth.

The present invention can also be used in sensors such as negative stiffness capacitive accelerometers and magnetometers. By adding stable electrodes and applying corresponding AC voltages to the stable electrodes, the effect of stabilizing the negative stiffness structure can also be achieved, and the sensitivity and bandwidth can be adjusted according to actual conditions. The application requires tuning. When the resonant accelerometer works with quasi-zero stiffness, the sensitivity is greatly improved. By adjusting the amplitude and frequency of the AC voltage on the stable electrode, the system can be placed at a stable quasi-zero stiffness, thereby improving the sensitivity. If the actual application does not require high sensitivity of the sensor but high bandwidth requirements, the AC voltage on the stable electrode can be adjusted to change the bandwidth of the sensor to meet the bandwidth requirements of the actual application. As shown in Figure 4, it is a capacitive accelerometer that uses high-frequency oscillation to stabilize a negative-stiffness arched beam. The control method of sensitivity and bandwidth is similar to the above-mentioned resonant accelerometer.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements, etc., made within the spirit and principles of the present invention, All should be included in the protection scope of the present invention.

Claims (6)

1. The MEMS sensor with adjustable sensitivity and bandwidth is characterized by comprising a sensitive module and a detection module, wherein the sensitive module comprises a negative stiffness structure and a stable structure; the negative stiffness structure is used for reducing the effective stiffness of the MEMS sensor and improving the sensitivity of device detection; the stabilizing structure is used for stabilizing the negative stiffness structure and realizing the adjustability and control of the total effective stiffness of the MEMS sensor;

the stabilizing structure comprises: a first stabilizing electrode and a second stabilizing electrode, wherein high-frequency vibration is introduced by applying alternating voltage to the first stabilizing electrode and the second stabilizing electrode to realize the stabilization of the negative stiffness structure;

the negative stiffness structure comprises a first negative stiffness electrode and a second negative stiffness electrode, wherein the first negative stiffness electrode and the second negative stiffness electrode introduce electrostatic negative stiffness into the accelerometer through electrostatic force;

the sensing module further comprises a first displacement control electrode and a second displacement control electrode, and the first displacement control electrode and the second displacement control electrode control the displacement of the detection mass through electrostatic force.

2. A MEMS sensor as claimed in claim 1 wherein the negative stiffness structure comprises a first negative stiffness arched beam and a second negative stiffness arched beam, the first negative stiffness arched beam and the second negative stiffness arched beam inducing a negative stiffness in the accelerometer by buckling.

3. The MEMS sensor of claim 1, wherein an alternating voltage of frequency f and amplitude Vp is applied across the first and second stabilizing electrodes.

4. A MEMS sensor according to claim 3, wherein the frequency magnitude of the ac voltage is dependent upon the magnitude of the negative stiffness introduced by the negative stiffness structure and the actual sensor sensitivity and bandwidth requirements.

5. The MEMS sensor of any one of claims 1-4, wherein the sensitivity of the sensitive structure of the MEMS sensor is altered by adjusting the amplitude and frequency of the ac voltage.

6. The MEMS sensor of any of claims 1-4, wherein the bandwidth of the MEMS sensor is adjusted by adjusting the amplitude and frequency of the ac voltage.