CN103134950B - 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of micromechanical accelerometer - Google Patents
5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of micromechanical accelerometer Download PDFInfo
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- CN103134950B CN103134950B CN201310021414.8A CN201310021414A CN103134950B CN 103134950 B CN103134950 B CN 103134950B CN 201310021414 A CN201310021414 A CN 201310021414A CN 103134950 B CN103134950 B CN 103134950B
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Abstract
The invention discloses a 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of a micromechanical accelerometer, and belongs to the field of acceleration signal measurement processing of the micromechanical accelerometer. A circuit is composed of a charge amplifier 5, a high-pass filter 6, a diode 7, a low-pass filter 8, a full differential amplifier 9, a phase compensation circuit 10, an integrating circuit I11, an integrating circuit II 12, an integrating circuit III 13, a repeater 14, a summator 15, a comparator 16, a D-trigger 17 and an analog switch 18. The 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of the micromechanical accelerometer has the advantages that local negative feedback is added to an integration link, so that a second integrator and a third integrator are equivalent to a 2-order resonance link equivalent, the resonance frequency fR of the equivalent 2-order resonance link is equal to a theoretical bandwidth frequency ft, the noise in the system theoretical bandwidth range [0 Hz, ft Hz] is effectively lowered, and the signal-to-noise ratio is improved.
Description
Technical field
The present invention relates to a kind of 5 rank continuous low pass resonance feed-forward type sigma-delta modulator closed control circuits for micro-mechanical accelerometer, belong to micro-mechanical accelerometer acceleration signal and measure process field.
Background technology
Micro-mechanical accelerometer is a kind of important MEMS (micro electro mechanical system) (MEMS) inertial sensor, is also one of MEMS device of early start research, has widely applied at present in dual-use field.Micro-mechanical accelerometer principle of work is: in the time that extraneous acceleration signal is loaded on micro-mechanical accelerometer, the centroplasm gauge block of accelerometer produces displacement in acceleration direction, cause Detection capacitance to change, by detecting this variable quantity, can calculate the size of acceleration.In order to realize high-precision micro-mechanical accelerometer, need to compensate error, what often adopt is closed loop control method, more generally adopting is at present the way of analog closed-loop control, but there are some shortcomings in analog closed-loop control system: larger acceleration signal easily causes the centroplasm gauge block of micro-mechanical accelerometer to be adsorbed onto on electrode, and systematic parameter is subject to extraneous factor impact, and be difficult to realize accurate control etc.And use the digital closed-loop control system of sigma-delta modulator (Σ Δ Μ) can effectively overcome above these shortcomings, and it has high-order noise shaping feature, effectively rejection of acceleration meter noise, therefore can obtain larger signal to noise ratio (S/N ratio) (SNR), so the digital closed-loop control system of Σ Δ Μ of micro-mechanical accelerometer is the focus and emphasis of research always.
Professor Boser of University of California Berkeley in 2005 has designed a kind of digital closed control circuit of 4 rank low pass feed-forward type Σ Δ Μ of micro-mechanical accelerometer, two integrators of cascade form closed loop configuration after micro-mechanical accelerometer, whole system possesses 4 rank noise shaping abilities; The 5 rank low passes that Southampton University of Southampton Michael professor Kraft in 2006 has designed a kind of micro-mechanical accelerometer are fed back the digital closed control circuit of Σ Δ Μ more, three integrators of cascade form closed loop configuration after micro-mechanical accelerometer, its theory diagram is with reference to Fig. 3, the extraction of signal adopts charge amplifier 5, then signal passes through fully-differential amplifier 9, phase compensating circuit 10, integrating circuit 19, digital conversion circuit 20 successively, and output pulse width density modulation digital signal b (t) control simulation switch 18 is by FEEDBACK CONTROL voltage V
fbbe loaded on FEEDBACK CONTROL electrode, whole closed-loop system possesses the noise shaping ability on 5 rank, greatly improved the signal to noise ratio (S/N ratio) of accelerometer detection signal, but this control system still exists certain drawback:
The open loop through path of system is to be composed in series by micro-mechanical accelerometer and 3 First-order Integral devices, in the time that the frequency of accelerometer signal is greater than the resonance frequency of accelerometer self, when signal process micro-mechanical accelerometer, gain declines with the slope of 40dB/dec, and during through each integrator, gain all declines with the slope of 20dB/dec, thereby system open-loop gain declines with the slope of 100dB/dec, cause the noise magnitude of system final output signal to increase with the slope of 100dB/dec, system noise shaping capability declines, thereby limit the effective bandwidth of system.
Summary of the invention
In order to solve problems of the prior art, the present invention proposes a kind of 5 rank continuous low pass resonance feed-forward type Σ Δ Μ closed control circuits of micro-mechanical accelerometer, system not only possesses 5 rank noise shaping abilities, and can effectively suppress Systems Theory bandwidth [0Hz, f
thz] interior noise, improves signal to noise ratio (S/N ratio).
Consult Fig. 2, micro-mechanical accelerometer test section can be equivalent to public movable electrode 1, fixed electorde I 2, and fixed electorde II 3 forms.In the time having acceleration signal input, public movable electrode 1 moves along acceleration direction, causes Detection capacitance C1, C2 to change, and causes that charging and discharging currents changes, the current signal changing.
Consult Fig. 4,5 rank continuous low pass resonance feed-forward type Σ Δ Μ closed control circuits of the micro-mechanical accelerometer that the present invention proposes, by charge amplifier 5, Hi-pass filter 6, diode 7, low-pass filter 8, fully-differential amplifier 9, phase compensating circuit 10, integrating circuit I 11, integrating circuit II 12, integrating circuit III 13, multiplier (-icator) 14, totalizer 15, comparer 16, d type flip flop 17, analog switch 18 forms.In the time having extraneous acceleration signal a (t) input, cause Detection capacitance C1, C2 to change, cause that capacitor charge and discharge electric current changes, the current signal i changing
1and i (t)
2(t) the carrier wave V that, current signal is f through overfrequency
c(t) carry out high frequency modulated; Modulation signal, through charge amplifier 5, becomes voltage signal V by current signal conversion
1and V (t)
1' (t); Two-way voltage signal enters Hi-pass filter 6, filters out low-frequency interference signal, the cutoff frequency f of Hi-pass filter (6)
c1meet: f
c1< f; Filtered signal carries out demodulation through diode 7, and then signal carries out filtering through low-pass filter 8 and obtains V
2and V (t)
2' (t), the cutoff frequency f of low-pass filter (8)
c2meet: f
c2< f; Separate the filtered signal V of mediation
2and V (t)
2' (t) enter fully-differential amplifier 9 it is done to further differential amplification, obtain two paths of signals V
3and V (t)
3' (t); V afterwards
3and V (t)
3' (t) enter phase compensating circuit 10 and carry out phase shift and obtain V
4and V (t)
4' (t), phase compensating circuit makes system possess enough phase margins, thereby ensure the stability of closed-loop system; Signal V after phase shift
4and V (t)
4' (t) obtain V by integrating circuit I 11, integrating circuit II 12, integrating circuit III 13 successively
5and V (t)
5' (t); The signal V of integrating circuit III output terminal
5and V (t)
5' (t) through multiplier (-icator) 14 enter integrating circuit II input end form a LOCAL FEEDBACK, form a second order resonance link, its resonance frequency f
r=f
t, f
tfor the theoretical bandwidth frequency of system, theoretical bandwidth [0Hz, f like this
thz] in the overall gain of this second order link remain unchanged; Signal V after phase shift
4and V (t)
4' (t) all enter totalizer 15 with the signal of integrating circuit I (11), integrating circuit II (12), integrating circuit III (13) output terminal, obtain feed-forward signal V
6and V (t)
6' (t); Comparer 16 is to two-way feed-forward signal V
6and V (t)
6' (t) compare the digital comparison signal b'(t of output one road low and high level); Numeral comparison signal b'(t) through d type flip flop 17, sampling, (sample frequency is f
s) and quantize system output pulse width density modulation digital signal b (t); Pulsewidth density modulation digital signal b (t) control simulation switch 18 is by feedback voltage V
fbbe loaded on the feedback electrode of micro-mechanical accelerometer, form closed-loop control system.
The invention has the beneficial effects as follows: by add local negative feedback in integral element, make second, third integrator can be equivalent to a second order resonance link, the resonance frequency f of this equivalence second order resonance link
requal the theoretical bandwidth frequency f of system
t, can effectively reduce like this Systems Theory bandwidth range [0Hz, f
thz] interior noise, improves signal to noise ratio (S/N ratio).
Brief description of the drawings
Fig. 1 is the micro-mechanical accelerometer structural representation in embodiment
Fig. 2 is equivalent electrical model schematic diagram in micro-mechanical accelerometer test section in embodiment
Fig. 3 is that the 5 rank low passes that in prior art, Michael professor Kraft proposes are fed back Σ Δ Μ closed control circuit schematic diagram more;
Fig. 4 is 5 rank continuous low pass resonance feed-forward type Σ Δ Μ closed control circuit block schemes of the micro-mechanical accelerometer that proposes of the present invention;
Fig. 5 is 5 rank continuous low pass resonance feed-forward type Σ Δ Μ closed control circuit schematic diagram of micro-mechanical accelerometer in embodiment;
In figure, the public movable electrode of 1-, 2-fixed electorde I, 3-fixed electorde II, 4-micro-mechanical accelerometer, 5-charge amplifier, 6-Hi-pass filter, 7-diode, 8-low-pass filter, 9-fully-differential amplifier, 10-phase compensating circuit, 11-integrating circuit I, 12-integrating circuit II, 13-integrating circuit III, 14-multiplier (-icator), 15-totalizer, 16-comparer, 17-D trigger, 18-analog switch, 19-integrating circuit, 20-digital conversion circuit
Embodiment
In the present embodiment, the quality of the centroplasm gauge block of micro-mechanical accelerometer is m=1.4 × 10
-6kg, ratio of damping b=1.98 × 10
-4n × s/m, the rigidity of beam is k=1.24N/m, resonance frequency 150Hz, bandwidth 232Hz.The center electric capacity of micro-mechanical accelerometer detection comb is in pF magnitude, and capacitance change is in fF magnitude.
5 rank low pass resonance feed-forward type Σ Δ Μ closed control circuits of the micro-mechanical accelerometer proposing in the present embodiment are consulted Fig. 4, and whole Circuits System is by charge amplifier 5, Hi-pass filter 6, diode 7, low-pass filter 8, fully-differential amplifier 9, phase compensating circuit 10, integrating circuit I 11, integrating circuit II 12, integrating circuit III 13, multiplier (-icator) 14, totalizer 15, comparer 16, d type flip flop 17, analog switch 18 forms.When there being extraneous acceleration signal a (t) input, the centroplasm gauge block of micro-mechanical accelerometer produces displacement y (t) in acceleration signal direction, cause detecting electrode capacitor C 1, C2 to change, cause that capacitor charge and discharge electric current changes, the current signal i changing
1and i (t)
2(t); Current signal is f=1 × 10 through overfrequency
6after the high frequency carrier modulation of Hz, through charge amplifier 5, form two-way fully differential voltage signal V
1and V' (t)
1(t); Two-way voltage signal V
1and V' (t)
1(t) carry out filtering through Hi-pass filter 6, filter out low-frequency interference signal, wherein the cutoff frequency f of Hi-pass filter 6
c1=1 × 10
5hz; Filtered signal carries out demodulation through diode 7; Signal after demodulation carries out filtering through low-pass filter 8 and obtains two-way low frequency signal V
2and V (t)
2' (t), low pass filter cutoff frequency f
c2=2 × 10
4hz; Then V
2and V (t)
2' (t) enter fully-differential amplifier 9 and do further fully differential and amplify, obtain V
3and V (t)
3' (t), fully-differential amplifier gain G=100; Two-way fully differential signal V
3and V (t)
3' (t) carry out phase lead compensation and obtain V through phase compensator 10
4and V (t)
4' (t), the phase advance angle that phase compensator provides
; V
4and V (t)
4' (t) pass through successively integrating circuit I 11, integrating circuit II 12, integrating circuit III 13 obtains V
5and V (t)
5' (t), wherein integrating circuit I 11, integrating circuit II 12 and integrating circuit III 13 have identical structure, its integration constant τ=30000; The signal V of integrating circuit III output terminal
5and V (t)
5' (t) process multiplier (-icator) 14 (multiplier (-icator) gain g1=-0.001875) enters a LOCAL FEEDBACK of input end formation of integrating circuit II, forms a second order resonance link, its resonance frequency is f
r=234Hz; Signal after phase compensation and the signal of first, second and third grade of integrator output terminal all enter totalizer 15, obtain two-way feed-forward signal V
6and V (t)
6' (t); Two-way feed-forward signal V
6and V (t)
6' (t) enter comparer 16 and compare, form the digital comparison signal b'(t of a road low and high level); Numeral comparison signal b'(t) through d type flip flop 17, carry out sampling and Quantifying (sample frequency f
s=30000Hz), system output pulse width density modulation digital signal b (t); Pulse-width modulation digital signal b (t) control simulation switch 18 is by feedback voltage V
fbbe loaded on two feedback pole plates of micro-mechanical accelerometer, form closed-loop system.
Claims (1)
1. 5 rank continuous low pass resonance feed-forward type Σ Δ Μ closed control circuits of micro-mechanical accelerometer, mainly comprise charge amplifier (5), Hi-pass filter (6), diode (7), low-pass filter (8), fully-differential amplifier (9), phase compensating circuit (10), integrating circuit I (11), integrating circuit II (12), integrating circuit III (13), multiplier (-icator) (14), totalizer (15), comparer (16), d type flip flop (17), analog switch (18); In the time having extraneous acceleration signal a (t) input, cause Detection capacitance C1, C2 to change, cause that capacitor charge and discharge electric current changes, the current signal i changing
1and i (t)
2(t) the carrier wave V that, current signal is f through overfrequency
c(t) carry out high frequency modulated; Modulation signal, through charge amplifier (5), becomes voltage signal V by current signal conversion
1and V (t)
1' (t); Two-way voltage signal enters Hi-pass filter (6), filters out low-frequency interference signal, the cutoff frequency f of Hi-pass filter (6)
c1meet: f
c1< f; Filtered signal carries out demodulation through diode (7), and then signal carries out filtering through low-pass filter (8) and obtains V
2and V (t)
2' (t), the cutoff frequency f of low-pass filter (8)
c2meet: f
c2< f; Separate the filtered signal V of mediation
2and V (t)
2' (t) enter fully-differential amplifier (9) it is done to further differential amplification, obtain two paths of signals V
3and V (t)
3' (t); V afterwards
3and V (t)
3' (t) enter phase compensating circuit (10) and carry out phase shift and obtain V
4and V (t)
4' (t); Signal V after phase shift
4and V (t)
4' (t) obtain V by integrating circuit I (11), integrating circuit II (12), integrating circuit III (13) successively
5and V (t)
5' (t); The signal V of integrating circuit III output terminal
5and V (t)
5' (t) through multiplier (-icator) (14) enter integrating circuit II input end form a LOCAL FEEDBACK, form a second order resonance link, its resonance frequency f
r=f
t, f
tfor the theoretical bandwidth frequency of system; Signal V after phase shift
4and V (t)
4' (t) all enter totalizer (15) with the signal of integrating circuit I (11), integrating circuit II (12), integrating circuit III (13) output terminal, obtain feed-forward signal V
6and V (t)
6' (t); Comparer (16) is to two-way feed-forward signal V
6and V (t)
6' (t) compare the digital comparison signal b'(t of output one road low and high level); Numeral comparison signal b'(t) through d type flip flop 17), carrying out sample frequency is f
ssampling and Quantifying, system output pulse width density modulation digital signal b (t); Pulsewidth density modulation digital signal b (t) control simulation switch (18) is by feedback voltage V
fbbe loaded on the feedback electrode of micro-mechanical accelerometer, form closed-loop control system.
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|---|---|---|---|
| CN201310021414.8A CN103134950B (en) | 2013-01-21 | 2013-01-21 | 5-order continuous low-pass resonance feedforward type sigma-delta modulator closed-loop control circuit of micromechanical accelerometer |
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| CN103134950B true CN103134950B (en) | 2014-07-16 |
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Cited By (1)
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| RU2808728C1 (en) * | 2023-07-13 | 2023-12-04 | Акционерное общество "Инерциальные технологии "Технокомплекса" (АО "ИТТ") | Acceleration measuring device |
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| DE102013217102B4 (en) * | 2013-08-28 | 2023-03-16 | Robert Bosch Gmbh | Controller for controlling a micromechanical actuator, control system for controlling a micromechanical actuator, micromirror system and method for controlling a micromechanical actuator |
| CN105699694B (en) * | 2016-04-21 | 2019-02-22 | 中国科学院上海微系统与信息技术研究所 | Micro electronmechanical mixing Σ Δ M accelerometer closed-loop detection circuit system based on FPGA |
| RU2730423C1 (en) * | 2019-11-27 | 2020-08-21 | Федеральное государственное автономное образовательное учреждение высшего образования "Санкт-Петербургский государственный электротехнический университет "ЛЭТИ" им. В.И. Ульянова (Ленина)" (СПбГЭТУ "ЛЭТИ") | Accelerometer for measuring linear accelerations |
| CN111323189A (en) * | 2020-04-08 | 2020-06-23 | 北京融智世纪节能技术服务有限公司 | Non-contact vibration measuring device for blade of aircraft engine |
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| WO2003006103A2 (en) * | 2001-07-12 | 2003-01-23 | Merck & Co., Inc. | Electrical field stimulation of eukaryotic cells |
| CN102621884B (en) * | 2012-01-12 | 2013-10-09 | 西北工业大学 | Six-order continuous band-pass sigma-delta closed-loop control circuit for MEMS (micro-electromechanical system) gyroscope |
| CN102707088B (en) * | 2012-05-28 | 2013-10-16 | 西北工业大学 | High-order continuous low-pass sigma-delta closed-loop control circuit of micro-mechanical accelerometer |
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