A digital closed-loop detection system for a micro-electromechanical gyroscope

Abstract

This invention discloses a digital closed-loop detection system for a microelectromechanical gyroscope (MEMS) to achieve large-range, high-resolution angular rate detection. A multi-channel feedback signal is generated through an allocation algorithm module. These signals are then processed by different PI controllers and digital-to-analog converters of varying ranges and resolutions to form large and small AC analog signals as feedback signals. This improves the accuracy of the digital closed-loop quantization by mitigating noise, enabling the MEMS to detect angular rates over a large range and at high resolution.

Description

Technical Field

[0001] This invention belongs to the field of microelectromechanical systems (MEMS), and specifically relates to a digital closed-loop detection system for a microelectromechanical gyroscope. Background Technology

[0002] A microelectromechanical gyroscope (MEMS) is a sensor that detects angular velocity through the Coriolis effect. It is made of single-crystal silicon and fabricated using mature MEMS technology. Compared to traditional gyroscopes, MEMS gyroscopes offer advantages such as small size, light weight, low power consumption, low cost, and the ability to be mass-produced. Therefore, MEMS gyroscopes represent the future direction of gyroscope development and occupy an important position in the field.

[0003] Microelectromechanical gyroscopes (MEMS) are typically divided into two operating modes: a driving mode and a sensing mode. When the driving mode oscillates at a stable frequency and amplitude, and the MEMS gyroscope rotates in the sensing direction, the Coriolis effect generates a Coriolis force that excites the sensing mode. Therefore, the displacement of the sensing mode can be sensed and used for angular velocity detection. In practical applications, after an angular rate input causes vibration in the sensing mode, it is necessary to wait for the vibration to decay to a stable state before measuring the next angular rate. High-Q MEMS gyroscopes have long decay times and very small bandwidths when operating at low frequency differences. Therefore, closed-loop detection technology is required to control the amplitude of the sensing mode to remain constant at zero. This closed-loop detection technology, which uses feedback force to suppress displacement caused by angular rate and keep the amplitude of the sensing mode at zero or a constant small amount, calculates the angular rate based on the magnitude of the feedback signal. In digital closed-loop detection schemes, the signal generated by the digital PI controller needs to be converted into an analog signal by a digital-to-analog converter (DAC). When operating with a large range, the angular rate sensitivity is limited by the quantization noise of the DAC; when detecting with high precision, the gyroscope range is limited by the output voltage range of the DAC. Therefore, the range and accuracy of traditional microelectromechanical gyroscope digital closed-loop detection methods are mutually constrained. Summary of the Invention

[0004] The purpose of this invention is to provide a digital closed-loop detection system for microelectromechanical gyroscopes (MEMS) to simultaneously achieve large range and high precision detection of angular rate for MEMS gyroscopes.

[0005] The technical solution to achieve the purpose of this invention is as follows:

[0006] A digital closed-loop detection system for a microelectromechanical gyroscope includes:

[0007] The signal amplification module is used to amplify the displacement signal y(t) of the sensitive mode of the microelectromechanical gyroscope resonator;

[0008] The analog-to-digital converter module is used to convert the amplified displacement signal into a digital signal;

[0009] The signal demodulation module is used to demodulate signals with an angular frequency of ω.x From the carrier signal, the in-phase amplitude signal cy and the quadrature amplitude signal sy of the sensitive mode are obtained;

[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 signals output by the distribution algorithm module into force balance feedback control voltages, respectively.

[0012] The first signal modulation module and the 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] The first digital-to-analog converter module and the second digital-to-analog converter 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 converter module and the second digital-to-analog converter module, respectively; wherein the gain factor of the first signal gain module is greater than the gain factor of the second signal gain module.

[0015] The significant advantages of this invention compared to existing technologies are:

[0016] This invention is a digital closed-loop detection system for microelectromechanical gyroscopes (MEMS). It employs dual-path feedback control to achieve high-precision amplitude stabilization control of the sensitive modes of the MEMS. The first feedback control satisfies a large range, while the second feedback control satisfies high precision. A distribution algorithm is used to combine the first and second feedback controls to achieve both a large range and high precision. Attached Figure Description

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

[0018] Figure 2 This 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 This 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 This 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 5This is a block diagram of another specific embodiment of the closed-loop detection method system of the present invention. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

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

[0024]

[0025]

[0026] in, x(t) represents the acceleration, velocity, and displacement of the driving mode, respectively, where t is the time variable and ω is the displacement. x For the angular frequency of the driving mode, Q x The quality factor for driving the mode, ζ xy ω is the damping coupling coefficient. xy f is the stiffness coupling coefficient. x (t) represents the driving force of the driving mode, f y (t) represents the driving force of the sensitive mode. y(t) represents the acceleration, velocity, and displacement of the driving mode, respectively, and ω represents the displacement. y For the angular frequency of the sensitive mode, Q y A is the quality factor for the sensitive mode. g It is the angular gain coefficient of the microelectromechanical gyroscope, Ω. z (t) is the Z-axis input angular velocity, and the Z-axis is defined as an axis perpendicular to the modal displacements x(t) and y(t).

[0027] When only the X-axis is excited, i.e., f is applied x (t), let f y When (t) = 0, the displacement signal y(t) along the Y-axis is:

[0028] y(t)=C1cos(ω x t)+C2sin(ω x t)

[0029] The amplitude coefficients C1 and C2 for the in-phase and quadrature signals are as follows:

[0030]

[0031]

[0032] Where, ω x The X-axis angular frequency, i.e., the driving mode angular frequency, ω y Q y These are the angular frequency and quality factor along the Y-axis, respectively. A x It is the amplitude of the X-axis driven mode, ω x Q x These are the angular frequency and quality factor along the X-axis, respectively.

[0033] Resolution of Y-axis open-loop angular rate detection in microelectromechanical gyroscopes open for:

[0034]

[0035] Among them, V ad The voltage range of the analog-to-digital converter (ADC), bit represents the number of bits in the ADC, and η vi K is the rate-to-current conversion factor. cv To measure the current-voltage amplification factor, π is the mathematical constant pi.

[0036] In open-loop detection mode, the microelectromechanical gyroscope reduces the angular frequency ω. x ω y While high resolution can be achieved through small frequency differences, bandwidth is lost when the difference is very small. Therefore, microelectromechanical gyroscopes with small frequency differences often employ closed-loop detection to improve bandwidth. The closed-loop detection mode uses a feedback force f applied to the sensitive mode. y (t) is used to control the amplitude of the sensitive mode to zero, and then the feedback force f is used. y The magnitude of (t) is used to calculate the angular velocity. Therefore, the digital-to-analog converter module generates AC f. y The resolution of (t) determines the closed-loop detection resolution of the microelectromechanical gyroscope. The analog-to-digital converter module generates AC f. y The range of (t) determines the measurement range of the closed-loop detection of the microelectromechanical gyroscope.

[0037] Resolution in closed-loop mode close for:

[0038]

[0039] The voltage-to-force conversion coefficient η of the parameter-sensitive mode excitation electrode in the formula vf The gain factor K of the signal gain module fb Voltage range V of the digital-to-analog converter module da The equivalent mass m and angular gain coefficient A of the driving mode g , amplitude A x angular frequency ω x This enables closed-loop resolution. closeThe smaller the value, the higher the resolution, meaning the higher the accuracy of the microelectromechanical gyroscope in detecting angular rate, thus achieving high precision.

[0040] Through closed-loop resolution Resolution close As can be seen from the expression, the resolution of the microelectromechanical gyroscope in closed-loop detection mode cannot be improved by reducing the frequency difference. This is because the voltage-to-force conversion coefficient η of the sensitive mode excitation electrode... vf As the value increases, the resolution decreases. Since the analog signal output from the digital-to-analog converter module is typically not amplified or attenuated, it can be considered as the gain factor K of the signal gain module. fb In this embodiment, 'bit' represents the number of bits in the digital-to-analog converter (DAC), which is limited by the DAC chip. V da The voltage of the digital-to-analog converter is typically between 3V and 1V. In closed-loop mode, the range of the microelectromechanical gyroscope is... close for:

[0041]

[0042] It can be seen that V da η vf K fb Increasing the range reduces resolution and increases the measurement range. This contradiction between resolution and measurement range limits the detection rate of microelectromechanical gyroscopes with high precision and large measurement range.

[0043] Example 1

[0044] Combination Figure 1 This embodiment of a digital closed-loop detection system for a microelectromechanical gyroscope includes a signal amplification module 300, an analog-to-digital conversion module 200, a signal demodulation module 100, a distribution 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 microelectromechanical gyroscope is working, the sensitive mode closed-loop control stabilizes the vibration amplitude of the sensitive mode to zero. The angular rate input will cause the sensitive mode to vibrate. After the closed loop stabilizes 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 calculating the angular rate.

[0046] The signal amplification module 300 is connected to the detection electrode of the sensitive mode of the microelectromechanical gyroscope 400, and is used to amplify the displacement signal y(t) of the sensitive mode of the microelectromechanical 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 y is the amplification gain during the conversion of the displacement signal y(t) into the digital signal y(t)'.

[0050] The signal demodulation module 100 is connected to the analog-to-digital converter module 200 and is used to demodulate signals with an angular frequency of ω. x From the carrier signal, the in-phase amplitude signal cy and the quadrature amplitude signal sy of the sensitive mode are obtained;

[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 quadrature reference signal, LPF represents low-pass filtering; φ is the phase of the reference signal.

[0054] The allocation algorithm module 600 is connected to the demodulation module 101 and is used to allocate the amplitude signal cy of the sensitive mode. In this embodiment, the allocation is divided into two outputs: the larger digital signal is allocated to the first PI controller 500 and the smaller digital signal is allocated 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 respectively:

[0057]

[0058]

[0059] Among them, K p1 K p2K represents the proportional adjustment coefficient of the first PI controller 500 and the second PI controller 501, respectively. i1 K i2 These 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 respectively connected to the first PI controller 500 and the second PI controller 50, 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):

[0061] v1(t)=V1cos(ω x t+φ)

[0062] v2(t)=V2cos(ω x t+φ)

[0063] The first digital-to-analog converter module 201 and the second digital-to-analog converter module 202 are respectively connected to the first signal modulation module 101 and the second signal modulation module 102, 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 respectively connected to the first digital-to-analog converter module 201 and the second digital-to-analog converter module 202, and are used to amplify or reduce the analog AC signals v1′(t) and v2′(t) converted by the first digital-to-analog converter module 201 and the second digital-to-analog converter module 202, respectively. The gain factors of the first signal gain module 301 and the second signal gain module 302 are K and K, respectively. fb1 K fb2 .

[0065] In this embodiment, K is designed. fb1 The larger value allows the first digital-to-analog converter module 201 to generate a large AC force feedback signal, suppressing the vibration of sensitive modes caused by large angular rate input and achieving a large range; the design of K... fb2 The smaller size allows the second digital-to-analog converter module 202 to generate a fine small AC force feedback signal, suppressing the weak vibrations of the sensitive mode caused by small angular rate input, and achieving high precision.

[0066] The operation flow of the allocation algorithm module 600 in one embodiment is 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; when the amplitude signal cy of the sensitive mode is less than d, the signal flows to the second PI controller 501.

[0067] The operation flow of the allocation algorithm module 600 in 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 extracted from the Nth bit in the range of 0 to K, so that the high bit signal cy[K:N] flows to the first PI controller 500 and the low bit signal cy[N:0] flows to the second PI controller 501.

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

[0069] This embodiment employs a dual-loop feedback, wherein the gain factor K of the first signal gain module 301 in the first feedback loop is... fb1 It must be greater than the gain multiple K of the second signal gain module 302 in the second feedback closed loop. fb2 K fb2 A smaller K value results in lower resolution, meaning the gyroscope has higher detection accuracy. fb1 Larger resolution means larger measurement range, but higher resolution means lower accuracy.

[0070] The first feedback closed-loop control signal and the second feedback closed-loop control signal are superimposed. Therefore, the closed-loop resolution of the entire digital closed-loop detection system is the smaller of the resolutions of the first and second feedback loops, i.e., the resolution of the second feedback loop.

[0071]

[0072] Therefore, the entire digital closed-loop detection system features low resolution and high precision, and the measurement 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 microelectromechanical 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. The adder 700 is connected to the first signal gain module 301 and the second signal gain module 302. It is used to superimpose the two feedback signals and input them to the sensitive mode excitation electrode of the microelectromechanical gyroscope 400, so that the microelectromechanical 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 microelectromechanical gyroscope, characterized in that, include: The signal amplification module is used to amplify the displacement signals of the sensitive modes of the microelectromechanical gyroscope resonator. y ( t ) to magnify; The analog-to-digital converter module is used to convert the amplified displacement signal into a digital signal; The signal demodulation module is used to demodulate carrier signals with an angular frequency of 0. The in-phase amplitude signal of the sensitive mode is obtained. cy and orthogonal amplitude signals sy ; The allocation algorithm module is used to allocate the in-phase amplitude signal of the sensitive mode. cy The signal is allocated to 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 signals output by the distribution algorithm module into force balance feedback control voltages, respectively. The first signal modulation module and the 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. The first digital-to-analog converter module and the second digital-to-analog converter 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. 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 factor of the first signal gain module is greater than the gain factor of the second signal gain module.

2. The digital closed-loop detection system for a microelectromechanical gyroscope according to claim 1, characterized in that, Also includes: The adder is used to superimpose the two feedback signals and input them to the sensitive mode excitation electrode of the microelectromechanical gyroscope.

3. A digital closed-loop detection system for a microelectromechanical gyroscope according to claim 1 or 2, characterized in that, The allocation algorithm module will assign the in-phase amplitude signal of the sensitive mode. cy The allocation process is as follows: When the in-phase amplitude signal of the sensitive mode cy Greater than the set value d At that time, the amplitude signal flows to the first PI controller; when the in-phase amplitude signal of the sensitive mode... cy Less than the set value d At that time, the amplitude signal flows to the second PI controller.

4. A digital closed-loop detection system for a microelectromechanical gyroscope according to claim 1 or 2, characterized in that, In-phase amplitude signal for sensitive modes cy Regarding the remainder of the divisor M, 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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