CN103217176A - Method for eliminating null shift of micro-electromechanical system (MEMS) gyroscope - Google Patents

Abstract

The invention discloses a method for eliminating null shift of a micro-electromechanical system (MEMS) gyroscope. The method comprises the following steps of: (1) acquiring a zero-point value zero of an initial gyroscope; (2) arranging a tolerance range plus or minus allowance nearby the zero-point value zero of the initial gyroscope, and determining whether a difference value diff between a current output value of the gyroscope and the zero-point value zero of the initial gyroscope exceeds the minus or plus allowance or not; judging that the gyroscope is at a standstill if the difference value diff between the current output value of the gyroscope and the zero-point value zero of the initial gyroscope does not exceed the tolerance range, and enabling the current output value of the gyroscope to participate in the calculation of a zero point of the gyroscope; and judging that input is available outside if diff exceeds the tolerance range, and adopting the difference value as a magnitude of angular velocity of the gyroscope to be outputted normally and not to participate in the calculation of the zero point. Due to the adoption of the method, the null shift and temperature drift of the MEMS gyroscope can be effectively overcome, a precise and complex error compensation algorithm is not needed, and the zero point variation of the gyroscope can be tracked in real time.

Description

A kind of method of eliminating the drift of MEMS gyro

Technical field

The invention belongs to the micro mechanical sensor field, relate to a kind of MEMS gyro zero point correction method, relate in particular to that the drift of a kind of MEMS of elimination gyro, temperature are floated, the method for random walk.

Background technology

The gyrostatic structure of MEMS significantly reduces, and it is minimum that single encapsulation digital and analog interface accounts for the plate area, has only several square millimeters.The MEMS gyro is compared maximum advantage with traditional gyro be exactly that volume is little, and price advantage is obvious, and these advantages impel the MEMS gyro to be penetrated into portable equipment market.The MEMS gyro adds many amazing functions by portable set, for example improves the steady picture function that camera is taken performance, easy-to-use user interface and Entertainment function etc.

Simultaneously, the MEMS gyro need also will be used to the boat position of high sensitivity, low noise, low drift (use the measured deviation that takes place or be subjected to the deviation that ambient temperature effect produces because of long-time) to infer and the GPS assisting navigation.The MEMS gyro is compared with the other types gyro has many advantages, but himself also has some shortcomings, has brought some restrictions to its application.Because the special micro mechanical structure of MEMS gyro, its work mainly is subjected to the influence of resonance frequency, and the performance of the peripheral circuit of the elastic modulus of gyroscope material and gyro all can vary with temperature and change.The shortcoming of MEMS gyro maximum is exactly the random walk of gyro itself, and the influence that is subjected to external environment factors such as temperature easily.

Under the condition that guarantees measuring accuracy, the random walk and the zero point drift that how to overcome gyro just become most important.Now general way is that by experiment method finds the output valve of gyro and the accurate relation between angular velocity and the error, and then utilizes this relation to remove to revise the input angular velocity of gyro.For example a kind of high-accuracy compensation method (theory and method of micro-mechanical gyroscope error, 2012,31(8): utilize the gyrostatic noise figure of allan variance identification 18-20.), designed Kalman filter according to the error model of gyroscope and carried out dynamic simulation.The method needs be unfavorable for microprocessor processes such as single-chip microcomputer, and the output valve of gyro to be also with the zero-mean white Gaussian noise with the calculating that relates to matrix.The relational expression that this class methods differentiate simultaneously goes out is accurate, needs to determine the value of each parameter, and external environment condition all can change at any time, and the variation of any one parameter all can exert an influence to the output valve of gyro, and adaptability is poor in real time.

The present invention is directed to MEMS gyro characteristics and, designed and Implemented the method for a kind of real-time elimination MEMS gyro drift in conjunction with the practical engineering application requirement.This method have simplicity of design, operand little, be convenient to characteristics such as realization.The method can effectively suppress near the drift of MEMS gyro zero point, is satisfying under the situation of certain precision, brings very big easy for application.

Summary of the invention

The object of the present invention is to provide the method for a kind of MEMS of elimination gyro drift, by carried out long mean filter the zero point of gyro, make gyro when not adding the angular velocity input, the angular velocity of gyro is directly exported null value.

The technical solution that realizes the object of the invention is: a kind of method of eliminating the drift of MEMS gyro, and concrete steps are as follows:

1) be worth zero the zero point of the initial gyro of acquisition:

A, sample, the output signal when the record gyro is static is worth digital quantity the zero point that obtains gyro after the Chip Microcomputer A conversion;

B, with it by wave filter, to its carry out length be the pipeline filtering of N to reduce the noise of sampling, obtain the output valve of gyro, the output valve of gyro is carried out x*y time on average, be worth zero the zero point that obtains initial gyro.The span of above-mentioned N is 20-200, and the x span is 80-120, and the y span is 80-120.

2) near being worth zero the zero point of initial gyro, a marginal range ± allowance is set, determines whether the current output valve of gyro and the difference diff that is worth zero zero point of initial gyro surpass ± allowance:

If the difference diff that is worth zero zero point of the current output valve of gyro and initial gyro does not surpass this marginal range, then judge that the state of gyro is static this moment, the current output valve of gyro will participate in the resolving of zero point of gyro simultaneously; Think that there is input in the external world if diff exceeds marginal range, then will be worth as the magnitude of angular velocity of gyro and normally export and do not participate in resolving of zero point.

The calculation method at the zero point of gyro is as follows:

A, the current output valve of gyro is sent into array ZERO[x];

B, judge array ZERO[x] whether be filled, if array ZERO[x] be filled, determine array ZERO[x] mean value, again with ZERO[x] mean value bring array ZERO[y into], Wherein n is array ZERO[x] length; Otherwise do not handle;

C, to array ZERO[y] average, the mean value that obtains is to be worth zero the zero point of current gyro;

D, repeating step a-c are worth zero the zero point of calculating current gyro in real time.

In gyro static state, promptly extraneous not input is carried out long-term sampling monitoring to the current output valve of gyro, and it is real-time calculating this zero point simultaneously, promptly as long as gyro is in static state in a certain period, just can follow the tracks of the zero point of gyro.

Table 1

The present invention compared with prior art, its remarkable advantage:

1. MEMS gyro and the MCU combination that will simulate output are packaged together, and have effectively reduced the output noise of gyro, have realized the numeral output of simulation gyro simultaneously.

2. the drift and the temperature that have effectively overcome the MEMS gyro are floated, and do not need accurate and complicated Error Compensation Algorithm, and change the zero point of tracking gyro that can be real-time.

3. the introducing of noise margin greatly facilitates follow-up work of treatment though sacrificed some sensitivity near zero point, does not have the phase mutual interference between zero point correction and the normal output simultaneously.

Description of drawings

Fig. 1 is the present invention program's square frame principle synoptic diagram.

Fig. 2 is a system handles process flow diagram of the present invention.

Fig. 3 is for following synoptic diagram zero point of the present invention.

Fig. 4 is gyro output valve synoptic diagram before handling.

Fig. 5 is for handling back gyro output valve synoptic diagram.

Embodiment

Below in conjunction with accompanying drawing the present invention is described in further detail.

System principle of the present invention as shown in Figure 1.What at first MEMS gyro and single-chip microcomputer (MCU) were compact is installed on the circuit board, the output signal of gyro is short as much as possible to the AD sampling of MCU, guarantee that impedance is as much as possible little, simultaneously digital signal and simulating signal are separately reduced the interference of digital signal to simulating signal.

The noise ratio of the gyro output valve of Direct Sampling is bigger, ADI646 gyro, pipeline mean filter, C8051F061 single-chip microcomputer with AD company are example, when the frequency band of ADIXRS646 gyro is arranged on 400Hz, noise level is about ± unit of 110(16 bit AD sample, down with), as shown in Figure 4,20 values of continuous sampling are placed on formation AD ₂₀In [], sample the value that a new value is just put into tail of the queue and thrown away original head of the queue at every turn, to this formation average that averages,

This value is exactly the output valve of gyro.This method has good inhibition effect to PERIODIC INTERFERENCE, and the smoothness height can effectively overcome the random walk of gyro.Noise after the process Filtering Processing is in ± 35, as shown in Figure 5.

The output valve of filtered gyro averaged to calculate be worth zero the zero point of obtaining gyro.In gyro static state, promptly extraneous not input is carried out long-term sampling monitoring to the output valve of gyro, and the value that collects is stored in ZERO[x] and ZERO[y] in these two numerical value, x and y are made as 100.Wherein

$\mathrm{ZERO}\left[x\right]=\frac{{\mathrm{\&Sigma;}}_1^{100}\mathrm{<figure-callout\; id="100"\; label="average"\; filenames="130503142240.png,130503142243.png"\; state="\{\{state\}\}">average</figure-callout>}}{100},x=\mathrm{1,2,3}......100,$

$\mathrm{ZERO}\left[y\right]=\frac{{\mathrm{\&Sigma;}}_1^{100}\mathrm{ZERO}\left[x\right]}{100},y=\mathrm{1,2,3}......100.$ Being worth zero the zero point of gyro is exactly array ZERO[y] mean value $\mathrm{zero}=\frac{{\mathrm{\&Sigma;}}_1^{100}\mathrm{ZERO}\left[y\right]}{100}.$

Be worth zero the zero point of gyro just as the initial zero of gyro, setting a noise margin ± allowance on this basis is ± 40, this value can be set flexibly according to gyro output band, noise scope, as long as the output valve of gyro filtering and the difference at zero point are in this noise scope, this value all will participate in the gyro correction and the tracking at zero point, and can revise in advance according to the variation tendency at gyro zero point, Fig. 3 follows synoptic diagram in real time for zero point.When the filtered output valve of gyro exceeds marginal range, will be worth and the magnitude of angular velocity of the corresponding gyro of the difference at zero point, it will be carried out the angle value that integration can wait until that gyro turns over.

By above analysis as can be known, adopt this method that the output valve of MEMS gyro is handled, can effectively solve the MEMS gyro because drift and temperature that oneself factor causes are floated.Owing to MEMS self, expect the relation of accurate gyro output valve and each error, need advance complicated algorithm and handle and experimental demonstration.And the method most important character among the present invention is exactly simple, direct, effective.Not to start with, but, simplified calculating greatly directly to following the tracks of the zero point of gyro from the exact relationship formula of seeking gyro zero point and each factor.Method of the present invention has broad application prospects after can extending to other fields that need determine zero point.

Claims (5)

1. method of eliminating the drift of MEMS gyro is characterized in that step is as follows:

1) is worth zero the zero point of the initial gyro of acquisition;

2) near being worth zero the zero point of initial gyro a marginal range being set is ± allowance, determines whether the current output valve of gyro and the difference diff that is worth zero zero point of initial gyro surpass ± allowance:

If the difference diff that is worth zero zero point of the current output valve of gyro and initial gyro does not surpass this marginal range, then judge that the state of gyro is static this moment, the current output valve of gyro will participate in the resolving of zero point of gyro simultaneously; Think that there is input in the external world if diff exceeds marginal range, then will be worth as the magnitude of angular velocity of gyro and normally export and do not participate in resolving of zero point.

2. the method for elimination MEMS gyro according to claim 1 drift, it is characterized in that: marginal range is as shown in the table:

3. the method for elimination according to claim 1 MEMS gyro drift is characterized in that: in the step 1), it is as follows to be worth the zero method zero point that obtains initial gyro:

A, sample, the output signal when the record gyro is static is worth digital quantity the zero point that obtains gyro after the Chip Microcomputer A conversion;

B, with it by wave filter, to its carry out length be the pipeline filtering of N to reduce the noise of sampling, obtain the output valve of gyro, the output valve of gyro is carried out x*y time on average, be worth zero the zero point that obtains initial gyro.

4. the method for elimination MEMS gyro according to claim 3 drift, it is characterized in that: the span of N is 20-200, and the x span is 80-120, and the y span is 80-120.

5. the method for elimination MEMS gyro according to claim 1 drift is characterized in that: step 2) in, the calculation method at the zero point of gyro is as follows:

A, the current output valve of gyro is sent into array ZERO[x];

B, judge array ZERO[x] whether be filled, if array ZERO[x] be filled, determine array ZERO[x] mean value, again with ZERO[x] mean value bring array ZERO[y into],

Wherein n is array ZERO[x] length; Otherwise do not handle;

C, to array ZERO[y] average, the mean value that obtains is to be worth zero the zero point of current gyro;

D, repeating step a-c are worth zero the zero point of calculating current gyro in real time.

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