Resonant MEMS force sensor and device with temperature compensation

Abstract

The invention belongs to the field of MEMS (micro electro mechanical system) sensors, and particularly relates to a resonant MEMS force sensor and device with temperature compensation, which comprises a resonant force probe, a resonant temperature sensor, a resonator reading circuit and a temperature compensation upper computer, the resonant force probe and the resonant temperature sensor are connected in a monolithic integration manner; the resonator reading circuit maintains the resonance state of the resonant force probe and the resonance state of the resonant temperature sensor. The resonator reading circuit respectively reads the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor and inputs the resonant frequencies to the temperature compensation upper computer; and a force measurement result is output in the temperature compensation upper computer based on the corresponding relation between the resonant frequency of the pre-calibrated resonant force probe and the resonant frequency of the resonant temperature sensor. The invention provides a force sensor which can reduce the influence of environment temperature and has a larger measurable range.

Description

Technical Field

[0001] The present invention belongs to the field of micro-electromechanical system sensors, and in particular relates to a resonant MEMS force sensor with temperature compensation and a device thereof. Background Art

[0002] Space science experiments and satellite applications often use the vacuum, microgravity, and strong radiation characteristics of the space environment to carry out tasks such as gravitational wave detection, Earth gravity field measurement, and microgravity research. To achieve the accuracy of such experiments, satellite platforms need to perform drag-free control through micro-thrusters to offset external disturbances such as solar wind and cosmic radiation. To ensure the stability and accuracy of the thrust output of micro-thrusters, their performance needs to be tested with high precision in a ground environment. Existing ground thrust testing schemes are divided into direct and indirect methods. The direct method calibrates by measuring the thrust generated by the thruster itself; the indirect method calculates the thrust by measuring physical quantities related to the thrust (such as reverse thrust, working fluid flow, etc.). The reverse thrust of each target disk is read by a high-precision force probe, and the thrust magnitude and direction angle can be obtained simultaneously through vector synthesis.

[0003] At present, force probes usually use capacitive MEMS micro-force sensors, but the output range of capacitive MEMS force probes is limited. When the cold gas thruster operates within a large dynamic range, the sensor output is prone to saturation, making it difficult to achieve both high resolution and a large range. Resonant sensors can have a larger dynamic range through frequency readout. However, existing resonant force sensors mostly use quartz crystals as resonant structures, which have a high temperature frequency coefficient and are easily affected by ambient temperature fluctuations, resulting in frequency output drift and reduced measurement stability. In a vacuum test environment, the temperature drift problem of the quartz resonator will be further amplified, limiting its application in wide temperature range and long-term testing scenarios. Summary of the Invention

[0004] In order to overcome the defect of the existing force probe in the prior art that is easily affected by temperature, the present invention provides a resonant MEMS force sensor and device with temperature compensation.

[0005] In order to achieve the above technical effects, the technical solutions of the present invention are as follows:

[0006] The present invention provides a resonant MEMS force sensor with temperature compensation, comprising:

[0007] A resonant force probe, a resonant temperature sensor, a resonator readout circuit, and a temperature compensation host computer; the resonant force probe and the resonant temperature sensor are monolithically integrated and connected;

[0008] The resonator readout circuit maintains the resonant state of the resonant force probe and the resonant temperature sensor;

[0009] The resonator readout circuit reads out the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor respectively and inputs them into the temperature compensation host computer;

[0010] The force measurement result is outputted in the temperature compensation host computer based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor which are pre-calibrated.

[0011] As a preferred embodiment, the resonant force probe includes an electrically connected force amplifying structure and a resonant force sensitive structure; when the force sensor measures external force, the force to be measured generates tension or pressure on the resonant force sensitive structure through the force amplifying structure.

[0012] As a preferred embodiment, the force amplification structure includes a probe support structure and a force probe connected to the probe support structure, a force amplification lever and a force amplification structure anchor point, and the force amplification lever is electrically connected to the resonant force sensitive structure; when the force sensor measures external force, the force probe receives the external force and transmits it to the probe support structure, and applies the amplified external force to the first resonant beam of the force sensitive structure through the force amplification lever.

[0013] As a preferred embodiment, the resonant force-sensitive structure includes a first DC bias electrode, a first sensing electrode, a first driving electrode, a first resonant beam, and a force-sensitive structure anchor point; one end of the first resonant beam is connected to the force amplification structure, and the other end is connected to the first DC bias electrode; the first sensing electrode and the first driving electrode are placed opposite each other on both sides of the first resonant beam; the force-sensitive structure anchor point is placed outside the first sensing electrode and the first driving electrode and is connected to the force amplification structure; when the force sensor measures external force, the first DC bias electrode receives a DC bias voltage, the first driving electrode receives an AC voltage signal output by the resonator readout circuit, the AC voltage causes the first resonant beam to start resonant motion, and the first sensing electrode senses the vibration signal of the first resonant beam and outputs it to the resonator readout circuit.

[0014] As a preferred solution, there are two resonant temperature sensors, which are symmetrically distributed on both sides of the resonant force-sensitive structure.

[0015] As a preferred embodiment, the resonant temperature sensor includes a second DC bias electrode, a second drive electrode, a second sensing electrode, a second resonant beam, and a resonant beam anchor point; one end of the second resonant beam is connected to the resonant beam anchor point, and the other end is connected to the second DC bias electrode, and the second sensing electrode and the second drive electrode are placed opposite each other on both sides of the second resonant beam; when the force sensor measures external force, the second DC bias electrode receives a DC bias voltage, and the second drive electrode receives an AC voltage signal output by the resonator readout circuit, and the AC voltage causes the second resonant beam to start resonant motion, and the second sensing electrode senses the vibration signal of the second resonant beam and outputs it to the resonator readout circuit.

[0016] As a preferred solution, the material of the first resonant beam and the second resonant beam includes single crystal silicon.

[0017] As a preferred embodiment, the step of outputting the force measurement result based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor that have been pre-calibrated includes: subtracting the resonant frequency of the resonant force probe from the resonant frequency of the resonant temperature sensor to obtain the characteristic frequency; and obtaining the force measurement result based on the pre-calibrated force-characteristic frequency sensitivity.

[0018] The present invention further provides a resonant MEMS force measurement device with temperature compensation, comprising at least one resonant MEMS force sensor with temperature compensation.

[0019] The present invention further provides a force measurement method with temperature compensation, which is applied to the resonant MEMS force sensor with temperature compensation, and includes the following steps:

[0020] The resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor are read out respectively by the resonator readout circuit and input into the temperature compensation host computer;

[0021] The force measurement result is outputted in the temperature compensation host computer based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor which are pre-calibrated.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention measures force magnitude based on the resonance principle, and can effectively increase the dynamic range of force measurement under the condition of the same force resolution; by integrating a monolithic resonant temperature sensor, combining the temperature calculation of the resonant temperature sensor with the common-mode subtraction of the temperature response of the resonant force probe, the influence of ambient temperature fluctuations on the resonant silicon MEMS force probe is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1FIG. 1 is a structural diagram of a resonant MEMS force measurement device with temperature compensation according to Example 1.

[0025] Figure 2 This is a structural diagram of the resonant force probe of Example 1.

[0026] Figure 3 This is a structural diagram of the resonant MEMS force sensor with temperature compensation in Example 1.

[0027] Figure 4 This is a structural diagram of the resonant temperature sensor of Example 1.

[0028] Figure 5 This is the simulation result of a resonant MEMS force sensor with temperature compensation in Example 2. DETAILED DESCRIPTION

[0029] The accompanying drawings are for illustrative purposes only and are not to be construed as limiting the present invention;

[0030] It is understandable to those skilled in the art that some well-known descriptions may be omitted in the drawings.

[0031] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0032] Example 1

[0033] This embodiment proposes a resonant MEMS force sensor with temperature compensation, such as Figure 1 FIG. 1 is a structural diagram of a resonant MEMS force measurement device with temperature compensation according to an embodiment of the present invention.

[0034] The resonant MEMS force sensor with temperature compensation proposed in this embodiment includes:

[0035] A resonant force probe 1, a resonant temperature sensor 2, a resonator readout circuit 3, and a temperature compensation host computer 4; the resonant force probe and the resonant temperature sensor are monolithically integrated and connected;

[0036] The resonator readout circuit 3 maintains the resonant state of the resonant force probe 1 and the resonant temperature sensor 2;

[0037] The resonator readout circuit 3 reads the resonant frequency of the resonant force probe 1 and the resonant frequency of the resonant temperature sensor 2 respectively and inputs them to the temperature compensation host computer 4;

[0038] The force measurement result is outputted in the temperature compensation host computer 4 based on the correspondence between the resonant frequency of the resonant force probe 1 and the resonant frequency of the resonant temperature sensor 2 which are pre-calibrated.

[0039] In this embodiment, the resonant force probe 1 and the resonant temperature sensor 2 are monolithically integrated, and the temperature calculation of the resonant temperature sensor 2 and the common-mode subtraction of the temperature response of the resonant force probe 1 are combined to reduce the impact of ambient temperature fluctuations on the resonant silicon MEMS force probe.

[0040] In an optional embodiment, the resonant force probe 1 includes an electrically connected force amplifying structure 101 and a resonant force sensitive structure 102; when the force sensor measures external force, the force to be measured generates tension or pressure on the resonant force sensitive structure 102 through the force amplifying structure 101.

[0041] More specifically, when the force amplifying structure 101 is affected by an external force, it will displace, amplify the force and transfer it to the resonant force sensitive structure 102. The applied force will cause the resonant frequency of the resonant force sensitive structure 102 to change, thereby achieving the measurement of the external force.

[0042] In this embodiment, the external force can be amplified by the force amplification structure 101, thereby improving the measurement sensitivity and response accuracy, and can still provide accurate measurement results under lower input forces, which is suitable for the detection of weak forces.

[0043] In an optional embodiment, the force amplification structure 101 includes a probe support structure 1011 and a force probe 1012 connected to the probe support structure, a force amplification lever 1013 and a force amplification structure anchor point 1014, and the force amplification lever 1013 is electrically connected to the resonant force sensitive structure 102; when the force sensor measures external force, the force probe 1012 receives the external force and transmits it to the probe support structure 1012, and applies the amplified external force to the force sensitive structure 102 through the force amplification lever 1013.

[0044] like Figure 2 , which is a structural diagram of the resonant force probe 1 .

[0045] In this embodiment, the force probe 1012 responds to external force by contact or fixation, and transmits the external force to the probe support structure 1011. Due to the lever principle, the force amplifying lever 1013 will amplify the external force and generate axial tension or pressure on the force sensitive structure 102. This tension or pressure will cause the resonant frequency of the force sensitive structure 102 to change.

[0046] In an optional embodiment, the resonant force-sensing structure 102 includes a first DC bias electrode 1021, a first sensing electrode 1022, a first driving electrode 1023, a first resonant beam 1024, and a force-sensing structure anchor 1025. One end of the first resonant beam 1024 is connected to the force amplification structure, and the other end is connected to the first DC bias electrode 1021. The first sensing electrode 1022 and the first driving electrode 1023 are positioned opposite each other on either side of the first resonant beam 1024. The force-sensing structure anchor 1025 is positioned outside the first sensing electrode 1022 and the first driving electrode 1023 and is connected to the force amplification structure. When the force sensor measures external force, the first DC bias electrode 1021 receives a DC bias voltage, the first driving electrode 1023 receives an AC voltage signal output by the resonator readout circuit 3, the AC voltage causes the first resonant beam 1024 to begin resonant motion, and the first sensing electrode 1022 senses a vibration signal of the first resonant beam 1024 and outputs it to the resonator readout circuit 3.

[0047] More specifically, the first sensing electrode 1022 and the first driving electrode 1023 form a capacitor with the first resonant beam 1024 .

[0048] In this embodiment, when the first resonant beam 1024 is subjected to axial pressure or tension, it produces changes in stiffness and resonant frequency, which are sensed by the capacitance formed by the first sensing electrode 1022 and the first driving electrode 1023. Accurately measuring external forces through vibration signal analysis offers significant advantages in high-precision applications such as micro-force measurement and dynamic force detection.

[0049] In an optional embodiment, there are two resonant temperature sensors 2 , which are symmetrically distributed on both sides of the resonant force-sensitive structure 102 .

[0050] like Figure 3 Shown is the structural diagram of a resonant MEMS force sensor with temperature compensation.

[0051] In this embodiment, the resonant temperature sensors 2 are symmetrically placed on either side of the resonant force-sensing structure, effectively improving the accuracy and stability of temperature measurement. The presence of two temperature sensors enables uniform temperature field acquisition, avoiding deviations caused by local temperature gradients.

[0052] In an optional embodiment, the resonant temperature sensor 2 includes a second DC bias electrode 201, a second drive electrode 202, a second sensing electrode 203, a second resonant beam 204, and a resonant beam anchor point 205; one end of the second resonant beam 204 is connected to the resonant beam anchor point 205, and the other end is connected to the second DC bias electrode 201, and the second sensing electrode 203 and the second drive electrode 202 are placed opposite each other on both sides of the second resonant beam 204; when the force sensor measures external force, the second DC bias electrode 201 receives a DC bias voltage, the second drive electrode 202 receives an AC voltage signal output by the resonator readout circuit 3, the AC voltage causes the second resonant beam 204 to start resonant motion, and the second sensing electrode 203 senses the vibration signal of the second resonant beam 204 and outputs it to the resonator readout circuit 3.

[0053] like Figure 4 As shown in FIG, it is a structural diagram of the resonant temperature sensor 2 .

[0054] In this embodiment, the change in temperature will directly affect the stiffness and vibration frequency of the resonant beam 204 , and the temperature change is measured by the vibration signal sensed by the second sensing electrode 203 .

[0055] In an optional embodiment, the material of the first resonant beam 1024 and the second resonant beam 204 includes single crystal silicon.

[0056] In this embodiment, the silicon material has a lower temperature coefficient than the quartz crystal material commonly used in the resonant beam, and is less affected by ambient temperature fluctuations.

[0057] In an optional embodiment, the step of outputting the force measurement result based on the correspondence between the resonant frequency of the resonant force probe 1 and the resonant frequency of the resonant temperature sensor 2 includes: subtracting the resonant frequency of the resonant force probe 1 and the resonant frequency of the resonant temperature sensor 2 to obtain the characteristic frequency; and obtaining the force measurement result based on the pre-calibrated force-characteristic frequency sensitivity.

[0058] In this embodiment, the effects of temperature fluctuations are eliminated through common-mode subtraction in data processing. This significantly improves the accuracy and stability of force measurement results. Even with large external temperature fluctuations, this compensation algorithm eliminates the impact of temperature on the measurement results, maintaining high accuracy.

[0059] Example 2

[0060] This embodiment provides implementation and principle explanation based on the first embodiment.

[0061] For the resonant force probe 1, a DC bias voltage is applied to the first DC bias electrode 1021. The force probe 1012 responds to the external force by contact or fixation, and transmits the external force to the probe support structure 1011. Due to the lever principle, the force amplification lever 1013 amplifies the external force and generates an axial tension or pressure on the first resonant beam 1024. This tension or pressure causes the resonant frequency of the first resonant beam 1024 to change. Taking a double-ended clamped tuning fork as an example, it can be expressed as:

[0062]

[0063] Where f0 is the resonant frequency of the first resonant beam 1024, F is the pressure or tension, L is the length of the first resonant beam 1024, t is the thickness of the first resonant beam 1024, w is the width of the first resonant beam 1024, and E is the Young's modulus of the material of the first resonant beam 1024. An AC voltage signal at the resonant frequency is inputted by the first drive electrode 1023, causing the first resonant beam 1024 to begin resonant motion. The vibration signal of the first resonant beam 1024 is sensed by the first sensing electrode 1022. By reading the resonant frequency of the first resonant beam 1024, force sensing can be achieved, including changes in the resonant frequency caused by changes in the temperature environment.

[0064] For the resonant temperature sensor 2, a DC voltage is applied to the second DC bias electrode 201, so that the second DC bias electrode 201, the second resonant beam 204, and the resonant beam anchor point 205 have a DC voltage bias. The second drive electrode 202 inputs an AC voltage signal at the resonant frequency, causing the second resonant beam 204 to begin resonant motion. The vibration signal of the resonant beam is sensed by the second sensing electrode 203. Since the material of the second resonant beam 204 is single crystal silicon, the Young's modulus E(T) of single crystal silicon will change with temperature T. Taking a double-clamped beam as an example, its resonant frequency f(T) can be expressed as:

[0065]

[0066] Where f(T) is the temperature-dependent resonant frequency, E(T) is the temperature-dependent Young's modulus, I is the moment of inertia of the second resonant beam 204, L is the length of the second resonant beam 204, A = w*t is the cross-sectional area of the second resonant beam 204, ρ is the density of silicon, the material of the second resonant beam 204, and β is the vibration modal coefficient. Under different doping conditions, the TCE value of silicon material ranges from approximately -60 ppm / °C to -100 ppm / °C. When the resonator system exhibits negative temperature characteristics, the TCF coefficient is negative. Increasing temperature causes the resonant frequency to decrease, while decreasing temperature causes the resonant frequency to increase.

[0067] 11. The process is as follows: The first resonant temperature sensor and the second resonant temperature sensor are symmetrically distributed on both sides of the resonant force-sensitive structure 102. The temperatures of the first resonant temperature sensor and the second resonant temperature sensor can reflect the temperature fluctuation and temperature gradient at the resonant force-sensitive structure 102. Through electrical connection, the resonator readout circuit 3 can maintain the resonant state of the resonant force-sensitive structure 102, the first resonant temperature sensor, and the second resonant temperature sensor and read the resonant frequency signal. The resonator readout circuit 3 outputs the resonant frequency signal to the temperature compensation host computer 4. The output signal corresponds to the resonant force-sensitive structure 102, the first resonant temperature sensor, and the second resonant temperature sensor, respectively, which are force-sensitive structure data, first resonant temperature sensor data, and second resonant temperature sensor data. The force-sensitive structure data includes the resonant frequency change signal caused by external force and temperature fluctuations, and the first resonant temperature sensor data and the second resonant temperature sensor data respectively include the temperature information at the location. The first resonant temperature sensor data and the second resonant temperature sensor data are averaged to obtain the sensitive structure resonant beam temperature data, the force sensitive structure data and the sensitive structure resonant beam temperature data are subtracted to obtain the characteristic frequency, and the force measurement result is obtained based on the pre-calibrated force-characteristic frequency sensitivity. Figure 5 Figure 2 shows the force sensitivity simulation results of a resonant MEMS force sensor with temperature compensation.

[0068] Example 3

[0069] This embodiment provides a resonant MEMS force measurement device with temperature compensation, including at least one resonant MEMS force sensor with temperature compensation as provided in Embodiment 1.

[0070] Example 4

[0071] This embodiment provides a force measurement method with temperature compensation, which is applied to the resonant MEMS force sensor with temperature compensation provided in Example 1, and includes the following steps:

[0072] The resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor are read out respectively by the resonator readout circuit and input into the temperature compensation host computer;

[0073] The force measurement result is outputted in the temperature compensation host computer based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor which are pre-calibrated.

[0074] The terms in the drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0075] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A resonant MEMS force sensor with temperature compensation, characterized in that: include: Resonant force probe, resonant temperature sensor, resonator readout circuit and temperature compensation host computer; The resonant force probe and the resonant temperature sensor are monolithically integrated and connected; The resonator readout circuit maintains the resonant state of the resonant force probe and the resonant temperature sensor; The resonator readout circuit reads out the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor respectively and inputs them into the temperature compensation host computer; The force measurement result is outputted in the temperature compensation host computer based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor which are pre-calibrated.

2. The resonant MEMS force sensor with temperature compensation according to claim 1, characterized in that: The resonant force probe includes an electrically connected force amplifying structure and a resonant force sensitive structure. When the force sensor measures external force, the force to be measured generates tension or pressure on the resonant force sensitive structure through the force amplifying structure.

3. The resonant MEMS force sensor with temperature compensation according to claim 2, characterized in that: The force amplification structure includes a probe support structure and a force probe connected to the probe support structure, a force amplification lever and a force amplification structure anchor point, and the force amplification lever is electrically connected to the resonant force sensitive structure; when the force sensor measures external force, the force probe receives the external force and transmits it to the probe support structure, and applies the amplified external force to the force sensitive structure through the force amplification lever.

4. The resonant MEMS force sensor with temperature compensation according to claim 2, characterized in that: The resonant force-sensitive structure includes a first DC bias electrode, a first sensing electrode, a first driving electrode, a first resonant beam, and a force-sensitive structure anchor point; One end of the first resonant beam is connected to the force amplifying structure, and the other end is connected to the first DC bias electrode; the first sensing electrode and the first driving electrode are placed opposite to each other on both sides of the first resonant beam; The anchor point of the force-sensitive structure is placed outside the first sensing electrode and the first driving electrode and is connected to the force amplification structure; when the force sensor measures external force, the first DC bias electrode receives a DC bias voltage, and the first driving electrode receives an AC voltage signal output by the resonator readout circuit. The AC voltage causes the first resonant beam to start resonant motion, and the first sensing electrode senses the vibration signal of the first resonant beam and outputs it to the resonator readout circuit.

5. The resonant MEMS force sensor with temperature compensation according to claim 2, characterized in that: There are two resonant temperature sensors, which are symmetrically distributed on both sides of the resonant force sensitive structure.

6. The resonant MEMS force sensor with temperature compensation according to claim 2, characterized in that: The resonant temperature sensor includes a second DC bias electrode, a second driving electrode, a second sensing electrode, a second resonant beam, and a resonant beam anchor point; One end of the second resonant beam is connected to the resonant beam anchor point, and the other end is connected to the second DC bias electrode. The second sensing electrode and the second driving electrode are placed opposite each other on both sides of the second resonant beam. When the force sensor measures external force, the second DC bias electrode receives a DC bias voltage, and the second driving electrode receives an AC voltage signal output by the resonator readout circuit. The AC voltage causes the second resonant beam to start resonant motion, and the second sensing electrode senses the vibration signal of the second resonant beam and outputs it to the resonator readout circuit.

7. The resonant MEMS force sensor with temperature compensation according to claim 6, characterized in that: The material of the first resonant beam and the second resonant beam includes single crystal silicon.

8. A resonant MEMS force sensor with temperature compensation according to any one of claims 1 to 7, characterized in that: The step of outputting the force measurement result based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor that has been pre-calibrated includes: subtracting the resonant frequency of the resonant force probe from the resonant frequency of the resonant temperature sensor to obtain a characteristic frequency; and obtaining the force measurement result based on the pre-calibrated force-characteristic frequency sensitivity.

9. A resonant MEMS force measurement device with temperature compensation, characterized in that: The device comprises at least one resonant MEMS force sensor with temperature compensation according to any one of claims 1 to 8.

10. A force measurement method with temperature compensation, characterized in that The resonant MEMS force sensor with temperature compensation according to any one of claims 1 to 8 comprises the following steps: The resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor are read out respectively by the resonator readout circuit and input into the temperature compensation host computer; The force measurement result is outputted in the temperature compensation host computer based on the correspondence between the resonant frequency of the resonant force probe and the resonant frequency of the resonant temperature sensor which are pre-calibrated.

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