CN103411594A - Micro-machine gyroscope detection modal 8th-order series band-pass sigma-delta closed control circuit - Google Patents

Abstract

The invention discloses a micro-machine gyroscope detection modal 8th-order series band-pass sigma-delta closed control circuit and belongs the technical field of guidance or control devices utilizing the Coriolis effect. The micro-machine gyroscope detection modal 8th-order series band-pass sigma-delta closed control circuit comprises a charge amplifier 5, a high pass filter 6, a diode 7, a low-pass filter 8, a fully differential amplifying circuit 9, a phase compensating circuit 10, a resonance circuit 11, a digital conversion circuit 12, an analog switch 13, a band-pass filter 14, a demodulator 15 and a low-pass filter 16. The micro-machine gyroscope detection modal 8th-order series band-pass sigma-delta closed control circuit provided by the invention has the following beneficial effects: 1, a resonator a 17, a resonator b 18 and a resonator c 19, together with a gyroscope detection modal, can achieve a 8th-order shaping effect on noise in the whole closed-loop circuit; 2, a simulation angular velocity signal ohm(t) is obtained through processing a pulse width density modulation digital signal b(t) by the band-pass filter 14, the demodulator and the low-pass filter 16.

Description

Micromechanical gyroscope detection mode 8th order continuous bandpass sigma-delta closed-loop control circuit

technical field

The invention relates to a closed-loop control circuit for micromechanical gyroscopes to detect modes, and belongs to the field of guidance or control devices utilizing the Coriolis effect.

Background technique

Micromechanical gyroscope is an important inertial sensor, which has the advantages of small size, light weight, low power consumption, and low cost. The inertial instrument realized by using micromechanical gyroscope is widely used in the attitude and position information detection of various moving objects. , especially in military fields such as precision-guided weapons and unmanned aerial vehicles, there is a clear demand for high-precision miniature inertial sensors. However, the precision of traditional micro-mechanical gyroscopes cannot reach the level of inertial navigation, and it is usually necessary to use an additional control system to control it or compensate for errors, so as to improve the accuracy. There are usually two types of closed-loop control systems for micromechanical gyro detection modes: analog closed-loop control systems and digital closed-loop control systems. The analog closed-loop control system has the disadvantages that the system parameters are easily affected by external factors, and the system is difficult to realize. The digital closed-loop control can effectively solve the problem that the central mass is easily adsorbed to the electrode, and the system has the advantages of simple implementation and good stability. Therefore, the digital closed-loop control system of the micromechanical gyro detection mode has always been a research focus and focus. In 2005, Dong Yunfeng, Michael Kraft and others from the University of Southampton in the United Kingdom proposed a 6-order continuous band-pass ΣΔΜ closed-loop control circuit for micro-mechanical gyroscope detection mode, which not only greatly reduces the sampling frequency, makes the system easier to implement, but also improves System signal-to-noise ratio (SNR) and bandwidth, etc. Refer to Figure 3 for its functional block diagram. The signal is extracted using a charge amplifier 5, and then the signal sequentially passes through a full differential amplifier circuit 9, a phase compensation circuit 10, a resonator a18, a resonator b19, and a digital conversion circuit 12 to output a pulse width density modulated digital signal b (t) Control the analog switch 13 to load the feedback control voltage V _fb onto the feedback control electrode. The entire closed-loop control system has a 6-order shaping capability for system noise, which improves the SNR. However, there are some problems in this control system:

(1) The SNR of the effective gyro signal extracted by the system is still not very high; (2) The pulse width density modulated digital signal b(t) output by the system is not the final angular velocity signal.

Contents of the invention

In order to overcome the problems existing in the prior art, the present invention proposes an 8-order continuous band-pass ΣΔ closed-loop control system for the micromechanical gyroscope detection mode, which can further improve the signal-to-noise ratio (SNR) of the detected gyroscope signal, and directly Output analog angular velocity signal Ω(t).

Referring to Figure 2, the detection mode of the MEMS gyro structure 4 can be equivalent to a common electrode 1, a fixed electrode 2, and a fixed electrode 3. The capacitance change between the common electrode 1, the fixed electrode 2, and the fixed electrode 3 causes the change of the charge and discharge current , generating a changing current signal i(t).

使得整个闭环控制回路的相移不等于2n，因为根据闭环系统自激振荡的条件：如果满足闭环控制系统的相移等于2n，闭环增益大于1，整个闭环系统将会自激振荡；移相后得到信号V_i4(t)和V'_i4(t)进入谐振电路11，谐振电路11包括串联的完全相同的三个谐振器a17、谐振器b18和谐振器c19，谐振器a17、谐振器b18和谐振器c19的谐振中心频率f₂等于f_x，且谐振器a17、谐振器b18和谐振器c19在f₂处的增益为10-20dB，在其他频率范围内的增益均小于0dB；经过谐振电路11之后的信号V_i5(t)和V'_i5(t)进入数字转换电路12，其包括比较器20和D触发器21，比较器20对V_i5(t)和V'_i5(t)两路全差分信号进行比较，产生高低电平的数字比较信号b'(t)，D触发器21对b'(t)进行采样和量化，最终输出数字脉宽密度调制信号b(t)；b(t)一路用于控制模拟开关13将反馈电压V_fb加载到陀螺检测模态的反馈电极上；另一路经过带通滤波器14将[f_y-BW,f_y+BW]频率范围外的量化噪声去除，其中BW为陀螺的带宽；带通滤波之后的信号进入解调器15，与驱动信号V_d(t)进行解调，再通过低通滤波器16处理得到角速度信号Ω(t),低通滤波器16的截止频率f_c3满足：f_c3＞BW。Referring to Fig. 4, the MEMS gyroscope 8-order continuous band-pass ΣΔΜ closed-loop control circuit that the present invention proposes, by charge amplifier 5, high-pass filter 6, diode 7, low-pass filter 8, full differential amplifier circuit 9, phase compensation circuit 10, A resonant circuit 11, a digital conversion circuit 12, an analog switch 13, a band-pass filter 14, a demodulator 15 and a low-pass filter 16 are formed. The changing current signal i(t) is modulated to the high-frequency band by the high-frequency carrier V _c (t) of frequency f ₁ , and V _c (t) is loaded on the mass block of the MEMS gyro structure 4, which is the equivalent common On the electrode 1; after the modulation signal passes through the charge amplifier 5, the current signal is converted into a voltage signal V _i (t); the feedback capacitor of the charge amplifier 5 adopts a variable capacitor to adjust the two fully differential signals V _i (t) and V The matching of _i '(t) makes its amplitude equal and its phase opposite; V _i (t) and V _i '(t) pass through the high-pass filter 6 to filter out the driving mode coupling signal V _d '(t) to obtain V _i2 (t) and V' _i2 (t), the cut-off frequency f _c1 of the high-pass filter 6 satisfies: f _c1 > f _x , where f _x is the resonant frequency of the MEMS gyro drive mode, that is, the coupling signal V _d '( t) frequency; V _i2 (t) and V' _i2 (t) are demodulated and filtered through a demodulation circuit composed of diode 7 and low-pass filter 8, and the cut-off frequency f _c2 of low-pass filter 8 satisfies : f _y <f _c2 <f ₁ , where f _y is the resonant frequency of the gyro detection mode; the demodulated and filtered signal enters the full differential amplifier circuit 9 with a gain of G ₁ for further full differential amplification to obtain V _i3 (t) and V' _i3 (t); phase compensation circuit 10 carries out a certain phase shift to V _i3 (t) and V' _i3 (t)

Make the phase shift of the entire closed-loop control loop not equal to 2n, because according to the condition of self-excited oscillation of the closed-loop system: if the phase shift of the closed-loop control system is equal to 2n, and the closed-loop gain is greater than 1, the entire closed-loop system will self-oscillate; after phase shift Obtained signals V _i4 (t) and V' _i4 (t) enter the resonant circuit 11, the resonant circuit 11 includes three identical resonators a17, resonator b18 and resonator c19 in series, resonator a17, resonator b18 and resonator c19 The resonant center frequency f ₂ of resonator c19 is equal to f _x , and the gains of resonator a17, resonator b18 and resonator c19 at f ₂ are 10-20dB, and the gains in other frequency ranges are all less than 0dB; after the resonant circuit The signals V _i5 (t) and V' _i5 (t) after 11 enter the digital conversion circuit 12, which includes a comparator 20 and a D flip-flop 21, and the comparator 20 pairs V _i5 (t) and V' _i5 (t) Comparing the fully differential signals of the two channels to generate a high-low level digital comparison signal b'(t), the D flip-flop 21 samples and quantizes b'(t), and finally outputs a digital pulse width density modulation signal b(t); b (t) One path is used to control the analog switch 13 to load the feedback voltage V _fb to the feedback electrode of the gyro detection _{mode ;} Quantization noise removal, where BW is the bandwidth of the gyroscope; the signal after bandpass filtering enters the demodulator 15, demodulates with the driving signal V _d (t), and then processes the angular velocity signal Ω (t) through the low-pass filter 16 , the cut-off frequency f _c3 of the low-pass filter 16 satisfies: f _c3 >BW.

The beneficial effects of the present invention are: first, the resonator a17, the resonator b18 and the resonator c19 together with the gyro detection mode have an 8-order shaping effect on the noise in the entire closed-loop circuit; third, the pulse width density modulated digital signal b (t), through the band-pass filter 14, the demodulator 15, and the processing of the low-pass filter 16 to obtain the analog angular velocity signal Ω(t).

Description of drawings

Fig. 1 is the electrical model schematic diagram of the MEMS gyroscope detection mode that the present invention is aimed at;

Fig. 2 is the MEMS gyroscope structure schematic diagram that the present invention is aimed at;

Fig. 3 is the schematic diagram of the 6-order continuous bandpass ΣΔΜ closed-loop control circuit proposed by people such as Dong Yunfeng in the prior art;

Fig. 4 is the schematic diagram of the 8-order continuous band-pass ΣΔΜ closed-loop control circuit that the present invention proposes;

Fig. 5 is a schematic diagram of an 8-order continuous band-pass ΣΔΜ closed-loop control circuit in an embodiment;

In the picture:

1-common electrode; 2-fixed electrode I; 3-fixed electrode II; 4-micromechanical gyro structure; 5-charge amplifier; 6-high-pass filter; 7-diode; 8-low-pass filter; 9-full differential Amplifying circuit; 10-phase compensation circuit; 11-resonant circuit; 12-digital conversion circuit; 13-analog switch; 14-bandpass filter; 15-demodulator; 16-low-pass filter; 17-resonator a ;18-resonator b; 19-resonator c; 20-comparator; 21-D trigger; 22-feedback electrode AI; 23-feedback electrode AII; 24-detection electrode AI; 25-detection electrode AII;

Detailed ways

Embodiment one:

The micromechanical gyroscope targeted in this embodiment is shown in Figure 2, the drive and detection mode comb center capacitance C _o =3.43e-13F, the resonant frequency f _x =4.30KHz of the drive mode is, and the detection mode Resonance frequency f _y =4.33KHz, bandwidth BW=50Hz, m _x = _my =2×10 ^-6 Kg.

的作用，陀螺的质量块在检测模态上产生位移y(t)，导致检测电极AI24和检测电极AII25电容变化，例如检测电极AI24电容增大，检测电极AII25电容减小，引起充放电电流变化，该变化电流信号i(t)被V_c(t)＝10sin(2πf₁t)调制到高频段，其中f₁＝2MHz，V_c(t)加载到陀螺的质量块上。该调制信号经过电荷放大器5，将电流信号转换为全差分电压信号V_i(t)和V_i'(t)；其中一路电荷放大器5上的反馈电容为可变电容C_f，调节C_f使得V_i(t)和V_i'(t)幅值相等；然后V_i(t)和V_i'(t)经过高通滤波器6将驱动耦合信号V_d'(t)＝a₂sin(ω_xt+φ)滤除，高通滤波器6的截止频率f_c1＝100KHz；滤除驱动耦合信号之后得到V_i2(t)和V'_i2(t)，V_i2(t)和V'_i2(t)经过由二极管7和低通滤波器8组成解调电路进行解调和滤波，其中低通滤波器8的截止频率f_c2＝10KHz;解调和滤波后的两路信号进入增益G₁＝200的全差分放大电路9对其做进一步的全差分放大得到V_i3(t)和V'_i3(t)；相位补偿电路10对V_i3(t)和V'_i3(t)进行

的相位移动，使得整个闭环控制回路的相移总和不等于2nπ，防止闭环回路自激振荡，提高系统的稳定性；移相后的信号V_i4(t)和V'_i4(t)进入谐振电路11，谐振电路11包括谐振器a17、谐振器b18和谐振器c19；谐振器a17、谐振器b18和谐振器c19具有相同的结构，均包括串联的两个全差分运算放大器，谐振器a17的第一个全差分运算放大器A₁的反向输入端一路经过电阻R₁连到第二个全差分运算放大器A₂的反向输出端，另一路依次串联连接一个电容C₁、电阻R₂和电容C₂，连到A₂的正向输出端；谐振器a17的A₁的正向输入端一路经过电阻R₁'连到A₂的正向输出端，另一路依次串联连接一个电容C₁'、电阻R'₂和电容C'₂，连到A₂的反向输出端；谐振器a17的A₁的正向输出端，连入谐振器b18的第一个全差分运算放大器A₁'的负向输入端，谐振器a17的A₁的负向输出端，连入谐振器b18的A₁'的正向输入端；谐振器b18的A₁'的正向输出端，连入谐振器c19的第一个全差分运算放大器A''₁的负向输入端，谐振器b18的A₁'的负向输出端，连入谐振器c19的A₁''的正向输入端；其中R₁＝R₂＝R₁'＝R'₂＝1.68kΩ，C₁＝C₂＝C₁'＝C'₂＝22nF，谐振器a17、谐振器b18和谐振器c19的谐振中心频率 $f_2=\frac{1}{2\mathrm{\&pi;}\&CenterDot;(1.68\&times;{10}^3)\&CenterDot;(22\&times;{10}^{-9})}\&ap;4.30\mathrm{KHz},$ 谐振器c19的A'₁的正向和负向输出端输出信号为V_i5(t)和V'_i5(t)作为比较器20的两路输入信号；比较器20对V_i5(t)和V'_i5(t)进行比较，输出高电平为5V，低电平为0V的数字比较信号b'(t)，D触发器21对b'(t)进行采样和量化，采样频率为32KHz，最终输出1bit的数字脉宽密度调制数字信号b(t)，高电平为3.3V，低电平为0V；b(t)一路用于控制模拟开关从而将反馈电压V_fb＝1V加载到陀螺检测模态的反馈电极AI22和AII23上；b(t)另一路经过带通滤波器14将[4330-50,4330+50]频率范围外的量化噪声去除，然后进入解调器15，与驱动信号V_d(t)进行第二次解调，再通过截止频率f_c3＝100Hz的低通滤波器16处理得到陀螺的角速度信号Ω(t)。The 6-order continuous band-pass ΣΔΜ closed-loop control circuit of its detection mode is referring to Fig. 5, and the whole circuit system is composed of a fully differential charge amplifier 5, a high-pass filter 6, a diode 7, a low-pass filter 8, a fully differential amplifier circuit 9, and a phase compensation Circuit 10, resonant circuit 11, digital conversion circuit 12, analog switch 13, band-pass filter 14, demodulator 15, low-pass filter 16 are composed; first, external driving voltage makes the gyroscope resonate in the driving mode, and the resonance displacement is x(t)＝a ₁ sin(ω _x t+φ), where ω _x ＝2πf _x ＝2π·4300, when there is angular velocity Ω(t) input, due to the Coriolis force

The mass block of the gyroscope produces a displacement y(t) in the detection mode, which causes the capacitance change of the detection electrode AI24 and the detection electrode AII25, for example, the capacitance of the detection electrode AI24 increases, and the capacitance of the detection electrode AII25 decreases, causing the change of the charge and discharge current , the changing current signal i(t) is modulated to the high frequency band by V _c (t)=10sin(2πf ₁ t), where f ₁ =2MHz, and V _c (t) is loaded on the quality block of the gyroscope. The modulation signal passes through the charge amplifier 5 to convert the current signal into fully differential voltage signals V _i (t) and V _i '(t); wherein the feedback capacitance on one charge amplifier 5 is a variable capacitance C _f , and adjusting C _f makes V _i (t) and V _i '(t) are equal in amplitude; then V _i (t) and V _i '(t) will drive coupling signal V _d '(t)=a ₂ sin(ω _x t+φ) filtering, the cut-off frequency f _c1 of the high-pass filter 6 =100KHz; get V _i2 (t) and V' _i2 (t), V _i2 (t) and V' _i2 ( t) Demodulate and filter through a demodulation circuit composed of a diode 7 and a low-pass filter 8, wherein the cut-off frequency _fc2 of the low-pass filter 8=10KHz; the two-way signals after demodulation and filtering enter the gain G ₁ = The full differential amplifier circuit 9 of 200 performs further full differential amplification to obtain V _i3 (t) and V' _i3 (t); the phase compensation circuit 10 performs V _i3 (t) and V' _i3 (t)

The phase shift of the entire closed-loop control loop makes the sum of the phase shifts of the entire closed-loop control loop not equal to 2nπ, which prevents the self-excited oscillation of the closed-loop loop and improves the stability of the system; the phase-shifted signals V _i4 (t) and V' _i4 (t) enter the resonant circuit 11. The resonant circuit 11 includes a resonator a17, a resonator b18 and a resonator c19; the resonator a17, the resonator b18 and the resonator c19 have the same structure, all of which include two fully differential operational amplifiers connected in series, the first of the resonator a17 The inverting input terminal of a fully differential operational amplifier A ₁ is connected to the inverting output terminal of the second fully differential operational amplifier A ₂ through a resistor R ₁ , and the other channel is connected in series with a capacitor C ₁ , a resistor R ₂ and a capacitor C ₂ , connected to the positive output terminal of A ₂ ; the positive input terminal of A ₁ of the resonator a17 is connected to the positive output terminal of A ₂ through the resistor R ₁ ′, and the other path is connected in series with a capacitor C ₁ ′ , resistor R' ₂ and capacitor C' ₂ are connected to the inverting output of A ₂ ; the positive output of A ₁ of resonator a17 is connected to the first fully differential operational amplifier A ₁ ' of resonator b18 The negative input terminal, the negative output terminal of A ₁ of resonator a17, is connected to the positive input terminal of A ₁ ' of resonator b18; the positive output terminal of A ₁ ' of resonator b18 is connected to resonator c19 The negative input terminal of the first fully differential operational amplifier A'' ₁ , the negative output terminal of A ₁ ' of resonator b18, is connected to the positive input terminal of A ₁ '' of resonator c19; where R ₁ =R ₂ =R ₁ '=R' ₂ =1.68kΩ, C ₁ =C ₂ =C ₁ '=C' ₂ =22nF, the resonance center frequencies of the resonator a17, the resonator b18 and the resonator c19 $f_{}$${}_2=\frac{1}{2\mathrm{\&pi;}\&CenterDot;(1.68\&times;{10}^3)\&CenterDot;(\mathrm{twenty\; two}\&times;{10}^{-9})}\&ap;4.30\mathrm{KHz},$ The positive and negative output signals of the A' ₁ of the resonator c19 are V _i5 (t) and V' _i5 (t) as two input signals of the comparator 20; the comparator 20 is V _i5 (t) and V' _i5 (t) is compared, and the digital comparison signal b'(t) with a high level of 5V and a low level of 0V is output, and the D flip-flop 21 samples and quantizes b'(t), and the sampling frequency is 32KHz , and finally output a 1-bit digital pulse width density modulated digital signal b(t), the high level is 3.3V, and the low level is 0V; b(t) is used to control the analog switch so as to load the feedback voltage V _fb =1V to On the feedback electrodes AI22 and AII23 of the gyro detection mode; the other way of b(t) passes through the bandpass filter 14 to remove the quantization noise outside the [4330-50,4330+50] frequency range, then enters the demodulator 15, and The driving signal V _d (t) is demodulated for the second time, and then processed by a low-pass filter 16 with a cut-off frequency f _c3 =100 Hz to obtain the angular velocity signal Ω(t) of the gyroscope.

Claims (1)

1. MEMS gyroscope 8-order continuous band-pass sigma-delta closed-loop control circuit, characterized in that it consists of a charge amplifier (5), a high-pass filter (6), a diode (7), a low-pass filter (8), and a full differential amplifier Circuit (9), phase compensation circuit (10), resonant circuit (11), digital conversion circuit (12), analog switch (13), band-pass filter (14), demodulator (15), low-pass filter (16) composition; the changing current signal i(t) is modulated to the high-frequency band by the high-frequency carrier V _c (t) with frequency f ₁ , and V _c (t) is loaded on the mass block of the MEMS gyro structure (4), That is, on the equivalent common electrode (1); after the modulation signal passes through the charge amplifier (5), the current signal is converted into a voltage signal V _i (t); the feedback capacitor of the charge amplifier (5) uses a variable capacitor for Adjust the matching of the two fully differential signals V _i (t) and V _i '(t) so that their amplitudes are equal and their phases are opposite; V _i (t) and V _i '(t) pass through a high-pass filter (6) Filter out the driving mode coupling signal V _d '(t) to obtain V _i2 (t) and V' _i2 (t). The cut-off frequency f _c1 of the high-pass filter (6) satisfies: f _c1 > f _x , where f _x is the resonant frequency of the MEMS gyroscope drive mode, that is, the frequency of the coupled signal V _d '(t); V _i2 (t) and V' _i2 (t) are then resolved by a diode 7 and a low-pass filter (8) demodulation and filtering by the modulation circuit, the cut-off frequency f _c2 of the low-pass filter (8) satisfies: f _y <f _c2 <f ₁ , where f _y is the resonant frequency of the gyro detection mode; after demodulation and filtering The signal enters the fully differential amplifier circuit (9) with a gain of G ₁ to further fully differentially amplify it to obtain V _i3 (t) and V' _i3 (t); the phase compensation circuit (10) pairs V _i3 (t) and V ' _i3 (t) performs a certain phase shift

The phase shift of the entire closed-loop control loop is not equal to 2n; after the phase shift, the signals V _i4 (t) and V' _i4 (t) enter the resonant circuit (11), and the resonant circuit (11) includes three identical resonant circuits in series Resonator a (17), resonator b (18) and resonator c (19), the resonant center frequency f ₂ of resonator a (17), resonator b (18) and resonator c (19) is equal to f _x , And the gains of resonator a (17), resonator b (18) and resonator c (19) at _f2 are 10-20dB, and the gains in other frequency ranges are all less than 0dB; after passing through the resonant circuit (11) The signals V _i5 (t) and V' _i5 (t) enter the digital conversion circuit (12), which includes a comparator (20) and a D flip-flop (21), and the comparator (20) has a pair of V _i5 (t) and V ' _i5 (t) compares two fully differential signals to generate a high-low level digital comparison signal b'(t), D flip-flop (21) samples and quantizes b'(t), and finally outputs a digital pulse width density The modulation signal b(t); one way of b(t) is used to control the analog switch (13) to load the feedback voltage V _fb to the feedback electrode of the gyro detection mode; the other way passes through the band-pass filter (14) to [f _y -BW, f _y +BW] frequency range to remove quantization noise, where BW is the bandwidth of the gyroscope; the signal after bandpass filtering enters the demodulator (15), demodulates with the driving signal V _d (t), and then The angular velocity signal Ω(t) is obtained by processing the low-pass filter (16), and the cut-off frequency f _c3 of the low-pass filter (16) satisfies: f _c3 > BW.

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