A gas medium driven MEMS gyroscope

Abstract

The present invention discloses a gas medium driven MEMS gyroscope, comprising a gyroscope body and a mass block arranged in the inner cavity of the gyroscope body, wherein a pair of detection capacitor plates are arranged in the Y-axis direction of the mass block in the gyroscope body, and the mass block is arranged between the pair of detection capacitor plates, and a vibration amplitude detection plate and a driving sound source are arranged in the X-axis direction of the mass block in the gyroscope body, and the mass block is arranged between the vibration amplitude detection plate and the driving sound source, and a gap is arranged between the driving sound source and the mass block, and the gap is filled with a gas medium for transmitting the sound of the driving sound source to drive the mass block. The present invention aims to solve the problems that the mass block and the driving electrode of the electrostatically driven MEMS gyroscope need a very small spacing to meet the driving force requirements, resulting in great difficulty in processing, the need for vacuum packaging and difficulty in maintaining performance indicators, and the existence of electrical coupling between driving and detection, resulting in insufficient performance and great difficulty in control.

Description

Technical Field

[0001] The invention relates to a gyroscope, and in particular to a gas medium driven MEMS gyroscope. Background Art

[0002] A gyroscope is an inertial sensing device used to measure and control the angular motion of an object in relative inertial space. Figure 1 The following is a schematic diagram of the working principle of the gyroscope, where f is the Coriolis force, m is the mass of the mass block, Ω is the angular velocity, v is the speed, and x, y, and z are three-dimensional coordinate axes. When a mass block (mass is m) moves along the x-axis and applies an angular rotation rate in the z-axis direction, the object will be subjected to a force in the y-axis direction. The formula for calculating the Coriolis force f is: f=2mΩv. Because the Coriolis force f is proportional to the angular velocity Ω, the mass m and the speed v are both controlled as constants, and the magnitude of the Coriolis force f is detected to obtain the value of the angular velocity Ω.

[0003] The structure of the commonly used electrostatically driven and capacitively detected MEMS gyroscope is as follows: Figure 2 As shown, its mass block is provided with an independent pair of driving capacitors and a pair of detection capacitors, and a common capacitor is required for driving force loading and vibration amplitude detection. However, the existing MEMS gyroscopes have the following problems: 1. The current MEMS gyroscope drive requires a very small spacing (less than 10um), which is difficult to process. 2. The current precision MEMS gyroscope requires a vacuum to increase the Q value, otherwise the gas resistance will make movement difficult. 3. The current driving part and the driving amplitude detection share a common capacitor, which interferes with each other and affects performance. 4. The MEMS gyroscope device is very small, and the electric driving signal is coupled to the angular velocity detection side through parasitic capacitance, which seriously affects the angular velocity resolution. Decoupling has become the key performance improvement method of the current MEMS gyroscope. Summary of the invention

[0004] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a gas medium driven MEMS gyroscope is provided. The present invention aims to solve the problems that a very small spacing between the mass block and the driving electrode of the electrostatically driven MEMS gyroscope is required to meet the driving force requirements, resulting in great difficulty in processing, the need for vacuum packaging and difficulty in maintaining performance indicators, and the existence of electrical coupling between driving and detection, resulting in insufficient performance and great difficulty in control.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A gas medium driven MEMS gyroscope comprises a gyroscope body and a mass block arranged in an inner cavity of the gyroscope body, wherein a pair of detection capacitor plates are arranged in the gyroscope body in the Y-axis direction of the mass block, and the mass block is arranged between the pair of detection capacitor plates, and a vibration amplitude detection plate and a driving sound source are arranged in the gyroscope body in the X-axis direction of the mass block, and the mass block is arranged between the vibration amplitude detection plate and the driving sound source, and a gap is arranged between the driving sound source and the mass block, and the gap is filled with a gas medium for transmitting the sound of the driving sound source to drive the mass block.

[0007] Optionally, resonance is formed between the driving sound source and the mass block so that the inner cavity of the gyroscope body and the gas medium in the gap between the driving sound source and the mass block form a gas medium resonance flute cavity.

[0008] Optionally, the amplitude of the gas medium is greater than the amplitude of the mass block.

[0009] Optionally, the calculation function expression of the amplitude of the gas medium is:

[0010] ξ =0.481 SQR ( P e η o ) / ( af ) 2

[0011] In the above formula, ξ is the amplitude of the gas medium, SQR is the square root function, P e is the power driving the sound source, η o is the conversion efficiency, a is the sound source radius of the driving sound source, f is the frequency of the driving sound source.

[0012] Optionally, the driving force F generated by the driving sound source on the mass block is 90° out of phase with the displacement of the mass block in the X-axis direction.

[0013] Optionally, it also includes a phase compensation driving circuit for compensating for the air break phase delay caused by the gap between the driving sound source and the mass block, and the phase compensation driving circuit is respectively connected to the vibration amplitude detection plate and the driving sound source.

[0014] Optionally, the calculation function expression of the air breath phase delay is:

[0015] P = Df 360 / 330,

[0016] In the above formula, P is the air break phase delay, D To drive the gap between the sound source and the mass block, f is the frequency of the driving sound source.

[0017] Optionally, the phase compensation driving circuit includes a capacitor voltage amplifier circuit, an amplitude phase detection circuit, a phase shift amplitude adjustment amplifier and a driving module, the vibration amplitude detection plate is connected to the input end of the capacitor voltage amplifier circuit, the capacitor voltage amplifier circuit, the amplitude phase detection circuit, the phase shift amplitude adjustment amplifier and the driving module are connected in sequence, and the driving module is used to drive a dynamic coil or piezoelectric generator to drive a sound source to emit sound.

[0018] Optionally, the amplitude phase detection circuit includes a digital-to-analog conversion circuit ADC, a phase-locked loop PLL and a multiplication switch, the output end of the capacitor voltage amplifier circuit is connected to the input end of the digital-to-analog conversion circuit ADC, and the output end of the digital-to-analog conversion circuit ADC is respectively connected to the phase-locked loop PLL and the multiplication switch to output a phase signal through the phase-locked loop PLL and output an amplitude signal through the multiplication switch.

[0019] Optionally, the phase-shift amplitude adjustment amplifier includes a multiplication module, a delay module, a digital-to-analog conversion circuit DAC and an amplifier, the output end of the multiplication switch of the amplitude phase detection circuit is connected to an input end of the delay module through the multiplication module, the other input end of the delay module is connected to the output end of the phase-locked loop PLL of the amplitude phase detection circuit, and the output end of the delay module, the digital-to-analog conversion circuit DAC and the amplifier are connected in sequence.

[0020] Compared with the prior art, the present invention mainly has the following advantages:

[0021] 1. In the conventional electrostatically driven MEMS gyroscope, the mass block and the driving electrode need a very small spacing (less than 10 μm) to meet the driving force requirements. In the gas medium driven MEMS gyroscope of the present invention, a vibration amplitude detection plate and a driving sound source are provided in the gyroscope body in the X-axis direction of the mass block, the mass block is arranged between the vibration amplitude detection plate and the driving sound source, a gap is arranged between the driving sound source and the mass block, and the gap is filled with a gas medium to transmit the sound of the driving sound source to drive the mass block. Since the gas medium driving method is adopted, the width of the gas medium has little effect on the transmitted energy and can reach the centimeter level, so it has the advantage of easy structural processing.

[0022] 2. The air in the cavity of the mass block of the traditional electrostatically driven MEMS gyroscope will produce resistance and thus affect the movement of the mass block and cause movement difficulties. Therefore, it is necessary to evacuate the MEMS gyroscope to improve the Q value. The vacuum-encapsulated MEMS gyroscope is not only difficult to produce, but also difficult to maintain vacuum for a long time. The vacuum drop seriously affects the performance index. The resonant frequency of the MEMS gyroscope covers hundreds of Hz to tens of kHz, which is exactly the audio range. As long as the mass block can produce submicron to micron-level vibrations, the mass block can detect the angular velocity. However, in the gas medium driven MEMS gyroscope of the present invention, since the gas medium driving method is adopted, the gas is no longer the resistance to the movement of the mass block but the driving force. The mass block is placed in the gas, and the driving sound source generates an excitation wave to drive the moving parts to vibrate. The conventional capacitor detects the movement of the moving parts and feeds back to the driving source to form resonance. This completely replaces the traditional electrostatic drive and other driving methods, and there is no need to evacuate the MEMS gyroscope, so the packaging is simpler and conducive to maintaining performance indicators.

[0023] 3. The driving part and driving amplitude detection of the conventional electrostatically driven MEMS gyroscope share a common capacitor, which interferes with each other and affects the performance. In addition, the MEMS device is very small, and the electric driving signal is coupled to the angular velocity detection side through the parasitic capacitance, which seriously affects the angular velocity resolution. Decoupling has become the key performance improvement method of the current MEMS gyroscope. In the gas medium driven MEMS gyroscope of the present invention, a vibration amplitude detection plate and a driving sound source are provided in the X-axis direction of the mass block in the gyroscope body, and the mass block is arranged between the vibration amplitude detection plate and the driving sound source. The present invention uses a gas medium for driving and a capacitor for detection, which overcomes the current electrical coupling phenomenon of driving and detection, greatly improves the performance and reduces the control difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figure is a schematic diagram of the working principle of a gyroscope in the prior art.

[0025] Figure 2 The schematic diagram is a structural diagram of a MEMS gyroscope with electrostatic drive and capacitance detection in the prior art.

[0026] Figure 3 Schematic diagram of the structure of a gas medium driven MEMS gyroscope in an embodiment of the present invention.

[0027] Figure 4 Schematic diagram of the structure of the phase compensation driving circuit in an embodiment of the present invention.

[0028] Figure 5 Schematic diagram of the structure of the amplitude phase detection circuit in an embodiment of the present invention.

[0029] Figure 6 Schematic diagram of the structure of the phase-shift amplitude adjustment amplifier in an embodiment of the present invention.

[0030] Legend: 1. Mass block; 2. Detection capacitor plate; 3. Vibration amplitude detection plate; 4. Driving sound source; 5. Gas medium; 6. Phase compensation driving circuit; 61. Capacitor voltage amplifier circuit; 62. Amplitude phase detection circuit; 63. Phase shift amplitude adjustment amplifier; 64. Driving module. DETAILED DESCRIPTION

[0031] like Figure 3 As shown, this embodiment provides a gas medium driven MEMS gyroscope, including a gyroscope body (omitted and not drawn in the figure) and a mass block 1 arranged in the inner cavity of the gyroscope body, a pair of detection capacitor plates 2 are provided in the gyroscope body in the Y-axis direction of the mass block 1, and the mass block 1 is arranged between the pair of detection capacitor plates 2, a vibration amplitude detection plate 3 and a driving sound source 4 are provided in the gyroscope body in the X-axis direction of the mass block 1, and the mass block 1 is arranged between the vibration amplitude detection plate 3 and the driving sound source 4, a gap is arranged between the driving sound source 4 and the mass block 1, and the gap is filled with a gas medium 5 for transmitting the sound of the driving sound source 4 to drive the mass block 1.

[0032] In this embodiment, resonance is formed between the driving sound source 4 and the mass block 1, so that the inner cavity of the gyroscope body and the gas medium 5 in the gap between the driving sound source 4 and the mass block 1 form a gas medium resonance flute cavity. At this time, resonance is formed between the driving sound source 4 and the mass block 1, so that the energy transfer efficiency is the highest.

[0033] In this embodiment, the amplitude of the gas medium 5 is greater than the amplitude of the mass block 1. As long as the amplitude of the gas medium 5 is greater than the amplitude of the mass block 1, the gas medium 5 is a driving force rather than a resistance.

[0034] In this embodiment, the calculation function expression of the amplitude of the gas medium 5 is:

[0035] ξ =0.481 SQR ( P e η o ) / ( af ) 2

[0036] In the above formula, ξ is the amplitude of the gas medium 5, SQR is the square root function, P e is the power driving the sound source 4, η o is the conversion efficiency, a is the sound source radius of driving sound source 4, fis the frequency of the driving sound source 4. In this embodiment, P e =5mW, η o =50%, a =3mm, f =10k, substitute into the above formula to calculate the amplitude of gas medium 5 ξ = 26.7 μm, indicating the power of the driving sound source 4 of 5 mw P e You can use a 6mm diameter air column (the sound source radius of the driving sound source 4 a =3mm), which is much larger than the micron-submicron amplitude requirement of conventional MEMS gyroscopes. It is much larger than the micron-submicron amplitude requirement of conventional MEMS gyroscopes. The driving power of conventional MEMS gyroscopes is at the μW level. Although the power of the driving sound source 4 in this embodiment is at the mW level, the driving sound source 4 at the mW level is a conventionally achievable level, indicating that the gas medium driven MEMS gyroscope in this embodiment is easy to implement.

[0037] The vibration of the mass block 1 in the gas medium driven MEMS gyroscope of this embodiment is a typical second-order system (spring damping system), and its function expression is shown in the following formula:

[0038] ,

[0039] In the above formula, is the mass of the mass block, is the displacement of the mass block in the X-axis direction, for The second-order position of for The first-order differential of The driving force generated by the driving sound source 4 on the mass block 1 is: is the elastic coefficient. Solving the equation, we can see that when the phase of the force driving force F during the movement of the second-order system differs by 90° from the phase of the displacement in the X-axis direction, the vibration can be strengthened (resonance) or weakened (attenuation), and the vibration will increase the fastest, that is, the positive feedback will be the strongest. Exceeding 90° will act in the opposite direction to accelerate the attenuation of the movement, and the phase delay generated by the cavity is compensated and adjusted by the sound source circuit. Therefore, in this embodiment, the driving force F generated by the driving sound source 4 on the mass block 1 differs by 90° from the phase of the displacement of the mass block 1 in the X-axis direction. In order to maintain constant vibration of the mass block, in addition to sufficient driving force, certain phase requirements must also be met, so the cavity size needs to be taken into account.

[0040] In addition, the present embodiment further comprises a phase compensation driving circuit 6 for compensating the air break phase delay generated by the gap between the driving sound source 4 and the mass block 1, and the phase compensation driving circuit 6 is respectively connected to the vibration amplitude detection plate 3 and the driving sound source 4. In the present embodiment, the calculation function expression of the air break phase delay is:

[0041] P = Df 360 / 330,

[0042] In the above formula, P is the air break phase delay, D To drive the gap between the sound source 4 and the mass block 1, f is the frequency of driving sound source 4. D =3mm, f =10kSubstitute into the above formula, the air break phase delay can be calculated P =32.7°, this phase can be compensated in the circuit, factors such as temperature may cause errors of several degrees or more than 10 degrees, the phase has a certain range and does not affect the control stability. Calculations show that the method of this embodiment is easy to implement.

[0043] like Figure 4 As shown, the phase compensation driving circuit 6 of this embodiment includes a capacitor voltage amplifier circuit 61, an amplitude phase detection circuit 62, a phase shift amplitude adjustment amplifier 63 and a driving module 64, the vibration amplitude detection plate 3 is connected to the input end of the capacitor voltage amplifier circuit 61, the capacitor voltage amplifier circuit 61, the amplitude phase detection circuit 62, the phase shift amplitude adjustment amplifier 63 and the driving module 64 are connected in sequence, and the driving module 64 is used to drive the dynamic coil or piezoelectric generator that drives the sound source 4 to make sound.

[0044] like Figure 5 As shown, the amplitude phase detection circuit 62 of this embodiment includes a digital-to-analog conversion circuit ADC, a phase-locked loop PLL and a multiplication switch. The output end of the capacitor voltage amplifier circuit 61 (the output is a CV signal, i.e., a capacitor voltage signal) is connected to the input end of the digital-to-analog conversion circuit ADC, and the output end of the digital-to-analog conversion circuit ADC is respectively connected to the phase-locked loop PLL and the multiplication switch to output a phase signal through the phase-locked loop PLL and output an amplitude signal through the multiplication switch.

[0045] like Figure 6As shown, the phase-shift amplitude adjustment amplifier 63 of this embodiment includes a multiplication module, a delay module, a digital-to-analog conversion circuit DAC and an amplifier. The output end of the multiplication switch of the amplitude phase detection circuit 62 is connected to an input end of the delay module through the multiplication module, and the other input end of the delay module is connected to the output end of the phase-locked loop PLL of the amplitude phase detection circuit 62. The output end of the delay module, the digital-to-analog conversion circuit DAC and the amplifier are connected in sequence, and finally a driving signal for driving the excitation driving sound source 4 is obtained through the amplifier.

[0046] The working process of the gas medium driven MEMS gyroscope of this embodiment is as follows: During the working process of the gas medium driven MEMS gyroscope of this embodiment, the driving sound source 4 replaces the driving capacitor (driving electrode) of the traditional MEMS gyroscope to drive the mass block 1 to move, and the detection capacitor plate 2 is used to detect the angular velocity (the same as the traditional MEMS gyroscope). At the same time, the vibration amplitude detection plate 3 is used to detect the oscillation amplitude of the mass block 1 and input it to the phase compensation driving circuit 6, and the phase compensation driving circuit 6 is used to compensate for the air break phase delay caused by the gap between the driving sound source 4 and the mass block 1 and control the stable amplitude.

[0047] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A gas medium driven MEMS gyroscope, comprising a gyroscope body and a mass block (1) disposed in an inner cavity of the gyroscope body, wherein a pair of detection capacitor plates (2) are disposed in the gyroscope body in the Y-axis direction of the mass block (1), and the mass block (1) is arranged between the pair of detection capacitor plates (2), characterized in that: A vibration amplitude detection plate (3) and a driving sound source (4) are provided in the gyroscope body in the X-axis direction of the mass block (1); the mass block (1) is arranged between the vibration amplitude detection plate (3) and the driving sound source (4); a gap is arranged between the driving sound source (4) and the mass block (1); and a gas medium (5) is filled in the gap to transmit the sound of the driving sound source (4) to drive the mass block (1); and the amplitude of the gas medium (5) is greater than the amplitude of the mass block (1).

2. The gas medium driven MEMS gyroscope according to claim 1, characterized in that: Resonance is formed between the driving sound source (4) and the mass block (1), so that the inner cavity of the gyroscope body and the gas medium (5) in the gap between the driving sound source (4) and the mass block (1) form a gas medium resonance flute cavity.

3. The gas medium driven MEMS gyroscope according to claim 2, characterized in that: The calculation function expression of the amplitude of the gas medium (5) is: ξ =0.481 SQR ( P e η o ) / ( af ) 2 In the above formula, ξ is the amplitude of the gas medium (5), SQR is the square root function, P e is the power driving the sound source (4), η o is the conversion efficiency, a is the sound source radius of the driving sound source (4), f is the frequency of the driving sound source (4).

4. The gas medium driven MEMS gyroscope according to claim 1, characterized in that: The driving force F generated by the driving sound source (4) on the mass block (1) is 90° out of phase with the displacement of the mass block (1) in the X-axis direction.

5. The gas medium driven MEMS gyroscope according to claim 1, characterized in that: It also includes a phase compensation driving circuit (6) for compensating for the air breath phase delay generated by the gap between the driving sound source (4) and the mass block (1), and the phase compensation driving circuit (6) is respectively connected to the vibration amplitude detection plate (3) and the driving sound source (4).

6. The gas medium driven MEMS gyroscope according to claim 5, characterized in that: The calculation function expression of the air break phase delay is: P = Df 360 / 330， In the above formula, P is the air break phase delay, D To drive the gap between the sound source (4) and the mass block (1), f is the frequency of the driving sound source (4).

7. The gas medium driven MEMS gyroscope according to claim 6, characterized in that: The phase compensation driving circuit (6) comprises a capacitor voltage amplifier circuit (61), an amplitude phase detection circuit (62), a phase shift amplitude adjustment amplifier (63) and a driving module (64); the vibration amplitude detection plate (3) is connected to the input end of the capacitor voltage amplifier circuit (61); the capacitor voltage amplifier circuit (61), the amplitude phase detection circuit (62), the phase shift amplitude adjustment amplifier (63) and the driving module (64) are connected in sequence; the driving module (64) is a moving coil or piezoelectric generator used to drive the driving sound source (4) to produce sound.

8. The gas medium driven MEMS gyroscope according to claim 7, characterized in that: The amplitude phase detection circuit (62) comprises a digital-to-analog conversion circuit ADC, a phase-locked loop PLL and a multiplication switch; the output end of the capacitor voltage amplifier circuit (61) is connected to the input end of the digital-to-analog conversion circuit ADC; the output end of the digital-to-analog conversion circuit ADC is respectively connected to the phase-locked loop PLL and the multiplication switch to output a phase signal through the phase-locked loop PLL and output an amplitude signal through the multiplication switch.

9. The gas medium driven MEMS gyroscope according to claim 8, characterized in that: The phase-shift amplitude adjustment amplifier (63) comprises a multiplication module, a delay module, a digital-to-analog conversion circuit DAC and an amplifier; the output end of the multiplication switch of the amplitude phase detection circuit (62) is connected to an input end of the delay module via the multiplication module; the other input end of the delay module is connected to the output end of the phase-locked loop PLL of the amplitude phase detection circuit (62); the output end of the delay module, the digital-to-analog conversion circuit DAC and the amplifier are connected in sequence.

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