Digital closed-loop detection system of micro-electro-mechanical gyroscope

Abstract

The invention discloses a digital closed-loop detection system of a micro-electro-mechanical gyroscope, which is used for realizing wide-range and high-resolution angular rate detection. A multi-channel feedback signal is formed through a distribution algorithm module, and the multi-channel feedback signal passes through different PI controllers and digital-to-analog converters with different ranges and resolutions to form a large alternating-current analog signal and a small alternating-current analog signal as feedback signals, so that the problem that the precision is influenced by digital closed-loop quantization noise is solved; therefore, the micro-electro-mechanical gyroscope can detect the angular rate in a wide-range and high-resolution manner.

Description

Technical Field

[0001] The invention belongs to the field of micro-electromechanical systems, and in particular to a digital closed-loop detection system for a micro-electromechanical system gyroscope. Background Art

[0002] A MEMS gyroscope is a sensor that detects angular velocity through the Coriolis effect. It is made of single-crystal silicon and is processed using mature MEMS technology. Compared with traditional gyroscopes, MEMS gyroscopes have the advantages of small size, light weight, low power consumption, low cost, and large-scale processing. Therefore, MEMS gyroscopes are the future direction of gyroscope development and occupy an important position in the field of gyroscopes.

[0003] MEMS gyroscopes are usually divided into two working modes: driving mode and sensitive mode. When the driving mode keeps oscillating at a stable frequency and amplitude and the MEMS gyroscope rotates in the sensitive direction, the Coriolis force generated by the Coriolis effect will excite the sensitive mode. Therefore, the displacement of the sensitive mode can be sensed and used for angular velocity detection. In practical applications, after an angular velocity input causes the detection mode to vibrate, it is necessary to wait for the vibration to decay to a stable state before continuing to measure the next angular velocity. The high-Q MEMS vibration gyroscope has a long decay time and a small bandwidth when working at a low frequency difference. Therefore, it is necessary to use closed-loop detection technology to control the amplitude of the sensitive mode to be constant at 0. This closed-loop detection technology that suppresses the displacement caused by the angular velocity through feedback force and keeps the amplitude of the sensitive mode at zero or a constant small amount is based on the size of the feedback signal to solve the angular velocity. In the digital closed-loop detection scheme, the signal generated by the digital PI controller needs to be converted into an analog signal by a digital-to-analog conversion circuit. When working with a large range, the angular velocity sensitivity accuracy is limited by the quantization noise of the digital-to-analog conversion circuit; when detecting with high precision, the gyroscope range is limited by the output voltage range of the digital-to-analog conversion circuit. Therefore, there is a problem of mutual restriction between the range and accuracy of the traditional MEMS gyroscope digital closed-loop detection method. Summary of the invention

[0004] The object of the present invention is to provide a digital closed-loop detection system for a micro-electro-mechanical system gyroscope, so as to simultaneously realize a large-range and high-precision detection angular rate of the micro-electro-mechanical system gyroscope.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A digital closed-loop detection system for a micro-electromechanical gyroscope, comprising:

[0007] A signal amplification module, used to amplify the displacement signal y(t) of the sensitive mode of the MEMS gyro resonator;

[0008] An analog-to-digital conversion module, used for converting the amplified displacement signal into a digital signal;

[0009] Signal demodulation module, used to demodulate the angular frequency ωx The carrier signal is used to obtain the in-phase amplitude signal cy and the orthogonal amplitude signal sy of the sensitive mode;

[0010] The allocation algorithm module is used to allocate the amplitude signal cy of the sensitive mode into two outputs: the larger digital signal is allocated to the first PI controller, and the smaller digital signal is allocated to the second PI controller;

[0011] The first PI controller and the second PI controller are used to convert the two digital quantity signals output by the distribution algorithm module into force balance feedback control voltages respectively;

[0012] A first signal modulation module and a second signal modulation module are used to modulate the balanced feedback control voltage converted by the first PI controller and the second PI controller into AC signals respectively;

[0013] A first digital-to-analog conversion module and a second digital-to-analog conversion module are used to convert the AC signals modulated by the first signal modulation module and the second signal modulation module into analog signals respectively;

[0014] The first signal gain module and the second signal gain module are used to amplify or reduce the analog signals converted by the first digital-to-analog conversion module and the second digital-to-analog conversion module, respectively; wherein the gain multiple of the first signal gain module is greater than the gain multiple of the second signal gain module.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] The present invention is a digital closed-loop detection system for a micro-electro-mechanical system gyroscope, which adopts two-way different feedback control to realize the stable amplitude control of the sensitive mode of the micro-electro-mechanical system gyroscope with high precision, wherein the first feedback control satisfies a large range and the second feedback control satisfies a high precision, and the large range and high precision are realized by combining the first feedback control and the second feedback control through a distribution algorithm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a block diagram of a specific embodiment of the closed-loop detection method system of the present invention.

[0018] Figure 2 It is a block diagram of a specific embodiment of the allocation algorithm in the closed-loop detection method system of the present invention.

[0019] Figure 3 It is a block diagram of another specific embodiment of the allocation algorithm in the closed-loop detection method system of the present invention.

[0020] Figure 4 It is a block diagram of another specific embodiment of the allocation algorithm in the closed-loop detection method system of the present invention.

[0021] Figure 5It is a block diagram of another specific embodiment of the closed-loop detection method system of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0023] The present invention discloses a digital closed-loop detection system for a micro-electromechanical gyroscope. The micro-electromechanical gyroscope has two electrode axes, namely an X-axis and a Y-axis. The electrode of the X-axis is used to excite and detect a driving mode, and the electrode of the Y-axis is used to excite and detect a sensitive mode. The modal displacements x(t) and y(t) of the two axes of the micro-electromechanical gyroscope satisfy the differential equation:

[0024]

[0025]

[0026] in, x(t) is the acceleration, velocity and displacement of the driving mode, t is the time variable, ω x is the angular frequency of the driving mode, Q x is the quality factor of the driving mode, ζ xy is the damping coupling coefficient, ω xy is the stiffness coupling coefficient, f x (t) is the driving force of the driving mode, f y (t) is the driving force of the sensitive mode, y(t) are the acceleration, velocity and displacement of the driving mode, ω y is the angular frequency of the sensitive mode, Q y is the quality factor of the sensitive mode, A g is the angular gain coefficient of the MEMS gyroscope, Ω z (t) is the input angular velocity along the Z axis, and the Z axis is defined as the axis perpendicular to the modal displacement directions x(t) and y(t).

[0027] When only the X axis is excited, f x (t), let f y (t) = 0, the displacement signal y(t) of the Y axis is:

[0028] y(t)=C1cos(ω x t)+C2sin(ω x t)

[0029] Among them, the in-phase signal amplitude coefficient C1 and the orthogonal signal amplitude coefficient C2 are:

[0030]

[0031]

[0032] Among them, ω x is the X-axis angular frequency, i.e. the driving modal angular frequency, ω y , Q y are the angular frequency and quality factor of the Y axis respectively. x is the amplitude of the X-axis driving mode, ω x , Q x are the angular frequency and quality factor of the X-axis respectively.

[0033] Resolution of angular velocity detected by MEMS gyroscope Y-axis open loop open for:

[0034]

[0035] Among them, V ad is the voltage range of the analog-to-digital converter, bit is the number of bits of the analog-to-digital converter, η vi is the rate-current conversion coefficient, K cv To detect the current-voltage amplification factor, π is the circumference of a circle.

[0036] In the open-loop detection mode, the MEMS gyro reduces the angular frequency ω x ,ω y The difference can obtain very high resolution, but the difference is too small to lose bandwidth. Therefore, MEMS gyroscopes with small frequency difference often use closed-loop detection to improve bandwidth. The closed-loop detection mode applies a feedback force f to the sensitive mode. y (t) to control the amplitude of the sensitive mode to zero, and then through the feedback force f y (t) to calculate the angular velocity. Therefore, the digital-to-analog conversion module generates an AC f y The resolution of (t) determines the resolution of the closed-loop detection of the MEMS gyroscope. The digital-to-analog conversion module generates an AC f y The range of (t) determines the range of the MEMS gyroscope closed-loop detection.

[0037] Resolution in closed loop mode close for:

[0038]

[0039] The parameter in the formula is the voltage-force conversion coefficient η of the sensitive modal excitation electrode vf , the gain multiple K of the signal gain module fb , the voltage range of the digital-to-analog conversion module is V da and the equivalent mass m of the driving mode, the angular gain coefficient A g , amplitude A x , angular frequency ω x Make the closed loop resolution closeThe smaller the value, the higher the resolution, that is, the higher the detection accuracy of the angular rate of the MEMS gyroscope, thus having high precision.

[0040] Through closed-loop resolution close It can be seen from the expression that the resolution of the MEMS gyroscope in the closed-loop detection mode cannot be improved by reducing the frequency difference. When the voltage-force conversion coefficient η of the sensitive mode excitation electrode is vf When it increases, the resolution will decrease. The analog signal output by the digital-to-analog conversion module is usually not amplified or reduced, so it is regarded as the gain multiple K of the signal gain module. fb is 1. In this embodiment, bit is the number of bits of the digital-to-analog converter. Due to the limitation of the digital-to-analog converter chip, V da The voltage of the digital-to-analog converter is usually between 3V and 1V. In closed-loop mode, the range of the MEMS gyroscope is close for:

[0041]

[0042] It can be seen that V da , η vf , K fb Increasing the value will reduce the resolution and increase the range. The contradiction between the resolution and the range limits the detection rate of the MEMS gyroscope with high precision and large range.

[0043] Example 1

[0044] Combination Figure 1 , a digital closed-loop detection system of a micro-electromechanical gyroscope of the present embodiment includes a signal amplification module 300, an analog-to-digital conversion module 200, a signal demodulation module 100, an allocation algorithm module 600, a first PI controller 500, a second PI controller 501, a first signal modulation module 101, a second signal modulation module 102, a first digital-to-analog conversion module 201, a second digital-to-analog conversion module 202, a first signal gain module 301, and a second signal gain module 302;

[0045] In this embodiment, when the MEMS gyroscope is working, the sensitive mode closed-loop control stabilizes the vibration amplitude of the sensitive mode to zero, and the angular rate input causes the sensitive mode to vibrate. After the closed-loop loop is stabilized again, the sensitive vibration amplitude stabilizes to zero. At this time, the feedback voltage amplitude of the loop is used as the signal quantity for solving the angular rate.

[0046] The signal amplification module 300 is connected to the detection electrode of the sensitive mode of the MEMS gyroscope 400, and is used to amplify the displacement signal y(t) of the sensitive mode of the MEMS gyroscope resonator;

[0047] The analog-to-digital conversion module 200 is connected to the signal amplification module 300 and is used to convert the amplified analog signal into a digital signal y(t)';

[0048] y(t)'=y(t)*gain y

[0049] Among them, gain y It is the amplification gain in the process of converting the displacement signal y(t) into the digital signal y(t)'.

[0050] The signal demodulation module 100 is connected to the analog-to-digital conversion module 200 and is used to demodulate the angular frequency ω x The carrier signal is used to obtain the in-phase amplitude signal cy and the orthogonal amplitude signal sy of the sensitive mode;

[0051] cy=LPF(y′(t)*cos(ω x t+φ))

[0052] sy=LPF(y′(t)*sin(ω x t+φ))

[0053] cos(ω x t+φ) is the in-phase reference signal used for demodulation, sin(ω x t+φ) is the orthogonal reference signal, LPF represents low-pass filtering; φ is the phase of the reference signal.

[0054] The distribution algorithm module 600 is connected to the demodulation module 101 and is used to distribute the amplitude signal cy of the sensitive mode; in this embodiment, the distribution is two-way output: the larger digital signal is distributed to the first PI controller 500, and the smaller digital signal is distributed to the second PI controller 501;

[0055] The first PI controller 500 and the second PI controller 501 are connected to the allocation algorithm module 600, and are used to convert the two digital signals output by the allocation algorithm module 600 into force balance feedback control voltages V1 and V2 respectively;

[0056] The digital discrete transfer function G of the first PI controller 500 c1 (k) and the digital discrete transfer function G of the second PI controller 501 c2 (k) are:

[0057]

[0058]

[0059] Among them, K p1 , K p2are the proportional adjustment coefficients of the first PI controller 500 and the second PI controller 501, respectively, i1 , K i2 are the integral adjustment coefficients of the first PI controller 500 and the second PI controller 501 respectively, T is the control period, e(k) is the error at time k, and e(j) is the error at time j.

[0060] The first signal modulation module 101 and the second signal modulation module 102 are connected to the first PI controller 500 and the second PI controller 50, respectively, and are used to modulate the balanced feedback control voltages V1 and V2 converted by the first PI controller 500 and the second PI controller 501 into digital AC signals v1(t) and v2(t), respectively:

[0061] v1(t)=V1cos(ω x t+φ)

[0062] v2(t)=V2cos(ω x t+φ)

[0063] The first digital-to-analog conversion module 201 and the second digital-to-analog conversion module 202 are connected to the first signal modulation module 101 and the second signal modulation module 102, respectively, and are used to convert the digital AC signals v1(t) and v2(t) modulated by the first signal modulation module 101 and the second signal modulation module 102 into analog AC signals v1′(t) and v2′(t), respectively;

[0064] The first signal gain module 301 and the second signal gain module 302 are connected to the first digital-to-analog conversion module 201 and the second digital-to-analog conversion module 202, respectively, and are used to amplify or reduce the analog AC signals v1′(t) and v2′(t) converted by the first digital-to-analog conversion module 201 and the second digital-to-analog conversion module 202, respectively. The gain multiples of the first signal gain module 301 and the second signal gain module 302 are K fb1 , K fb2 .

[0065] In this embodiment, K is designed fb1 The first digital-to-analog conversion module 201 is large, so that it can generate a large AC force feedback signal, suppress the vibration of sensitive modes caused by large angular rate input, and achieve a large range; design K fb2 Small, so that the second digital-to-analog conversion module 202 can generate a fine small AC force feedback signal, suppress the weak vibration of the sensitive mode caused by the small angular rate input, and achieve high precision.

[0066] The allocation algorithm module 600 has a calculation flow of one embodiment as follows: Figure 2As shown, when the amplitude signal cy of the sensitive mode is greater than the set value d, the amplitude signal flows to the first PI controller 500, and when the amplitude signal cy of the sensitive mode is less than d, the signal flows to the second PI controller 501;

[0067] The allocation algorithm module 600, the operation flow of another embodiment is as follows Figure 3 As shown, when the digital amplitude signal cy[K:0] of the sensitive mode is K bits, the signal is intercepted from the Nth bit in 0 to K, so that the high-order signal cy[K:N] flows to the first PI controller 500, and the low-order signal cy[N:0] flows to the second PI controller 501.

[0068] The allocation algorithm module 600, the operation flow of another embodiment is as follows Figure 4 As shown, the amplitude signal cy of the sensitive mode is modulo the divisor M, the product signal of the quotient and the divisor M flows to the first PI controller 500, and the remainder signal flows to the second PI controller 501;

[0069] In this embodiment, a dual closed-loop feedback is adopted, wherein the gain multiple K of the first signal gain module 301 in the first feedback closed loop is fb1 must be greater than the gain multiple K of the second signal gain module 302 in the second feedback closed loop fb2 , K fb2 If it is small, the resolution is small, that is, the detection accuracy of the gyroscope is high, K fb1 The larger the value, the larger the range; the larger the resolution, the lower the accuracy.

[0070] The first feedback closed-loop control signal and the second feedback closed-loop control signal are in a superposition relationship, so the closed-loop resolution of the entire digital closed-loop detection system is the smaller of the first feedback loop resolution and the second feedback loop resolution, that is, the resolution of the second feedback loop:

[0071]

[0072] Therefore, the entire digital closed-loop detection system has the characteristics of small resolution and high precision, and the range of the entire digital closed-loop detection system is the superposition of the large range of the first feedback loop and the small range of the second feedback loop:

[0073]

[0074] Therefore, this embodiment enables the micro-electromechanical gyroscope to have a large range and high precision.

[0075] Example 2

[0076] Combination Figure 5The difference between this embodiment and embodiment 1 is that it also includes an adder 700, which is connected to the first signal gain module 301 and the second signal gain module 302, and is used to superimpose the two feedback signals and input them into the sensitive mode excitation electrode of the micro-electro-mechanical gyroscope 400, so that the micro-electro-mechanical gyroscope with only one sensitive mode excitation electrode can achieve a large range and high precision.

Claims

1. A digital closed-loop detection system for a micro-electromechanical gyroscope, characterized in that: include: A signal amplification module, used to amplify the displacement signal y(t) of the sensitive mode of the MEMS gyro resonator; An analog-to-digital conversion module, used for converting the amplified displacement signal into a digital signal; Signal demodulation module, used to demodulate the angular frequency ω x The carrier signal is used to obtain the in-phase amplitude signal cy and the orthogonal amplitude signal sy of the sensitive mode; The allocation algorithm module is used to allocate the amplitude signal cy of the sensitive mode into two outputs: the larger digital signal is allocated to the first PI controller, and the smaller digital signal is allocated to the second PI controller; The first PI controller and the second PI controller are used to convert the two digital quantity signals output by the distribution algorithm module into force balance feedback control voltages respectively; A first signal modulation module and a second signal modulation module, used for modulating the balanced feedback control voltage converted by the first PI controller and the second PI controller into AC signals respectively; A first digital-to-analog conversion module and a second digital-to-analog conversion module, used to convert the AC signals modulated by the first signal modulation module and the second signal modulation module into analog signals respectively; The first signal gain module and the second signal gain module are used to amplify or reduce the analog signals converted by the first digital-to-analog conversion module and the second digital-to-analog conversion module, respectively; wherein the gain multiple of the first signal gain module is greater than the gain multiple of the second signal gain module.

2. A digital closed-loop detection system for a micro-electromechanical gyroscope according to claim 1, characterized in that: Also includes: The adder is used for adding two feedback signals and inputting the superimposed signals into the sensitive mode excitation electrode of the micro-electro-mechanical gyroscope.

3. A digital closed-loop detection system for a micro-electromechanical gyroscope according to claim 1 or 2, characterized in that: The process of allocating the amplitude signal cy of the sensitive mode by the allocation algorithm module is as follows: When the amplitude signal cy of the sensitive mode is greater than the set value d, the amplitude signal flows to the first PI controller; when the amplitude signal cy of the sensitive mode is less than the set value d, the amplitude signal flows to the second PI controller.

4. A digital closed-loop detection system for a micro-electromechanical gyroscope according to claim 1 or 2, characterized in that: The process of allocating the amplitude signal cy of the sensitive mode by the allocation algorithm module is as follows: When the amplitude signal cy of the sensitive mode is K bits, the signal is intercepted from N bits, the amplitude signal of [K:N] bits flows to the first PI controller, and the amplitude signal of [N:0] bits flows to the second PI controller; 0<N<K.

5. A digital closed-loop detection system for a micro-electromechanical gyroscope according to claim 1 or 2, characterized in that: The amplitude signal cy of the sensitive mode is modulo the divisor M, and the product signal of the quotient and the divisor M flows to the first PI controller, and the remainder signal flows to the second PI controller.

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