CN105509770A - Method for online correction of barometer in GNSS and MEMS integrated navigation system - Google Patents

Abstract

The invention discloses a method for online correction of a barometer in a GNSS and MEMS integrated navigation system. Height estimation is conducted when the quality of a satellite signal is reliable, height error estimation is conducted by means of the steady position error estimation method based on satellite pseudo-range measurement value residual error, the MEMS barometer is corrected by correcting and updating the standard air pressure estimated value in real time according to the height estimated value of a GNSS, and the standard air pressure estimated value can be used for assisting the GNSS and MEMS integrated navigation system to improve the precision of the height estimated value. The satellite pseudo-range measurement value residual error is used to estimate the standard deviation of residual error steadily by means of the absolute mid-value deviation algorithm, so that the standard deviation of measured value error is estimated. The variance of GNSS receiver position error is estimated by means of the proportional relation between the standard deviation of measured value error and position error. The variance of the standard air pressure value and the variance of the standard air pressure error are estimated at the same time by means of the result of the GNSS. The error level of standard air pressure is updated in real time and compared with the latest GNSS height error level to obtain the standard air pressure estimated value with the highest precision.

Description

A kind of barometer on-line correction method in GNSS and MEMS integrated navigation system

Technical field

The present invention relates to the barometrical real-time correction method of a kind of MEMS, relate to a kind of barometer real-time correction method be applied in GNSS and MEMS integrated navigation system especially.

Background technology

GNSS satellite receiver is by catching, following the tracks of the signal of multiple satellite, the navigation message data such as demodulation of satellite orbit parameter, satellite atomic clock model from signal, calculate the satellite position in a certain moment, speed and time parameter, last hybrid satellite signal measurements estimates position and the speed of receiver (i.e. user).But satellite-signal is easily subject to environmental factor residing for receiver, as blocking of high building, valley, trees, tunnel etc., affect the availability of positioning result.

Because the characteristic of inertial navigation and satellite navigation have good complementarity, so the integrated navigation system of inertia device and GNSS is a kind of important navigation solution, the high development of MEMS technology, GNSS/MEMS sensor combinations navigational system is applied widely and is become possibility.Wherein MEMS barometer is an important sensor in integrated navigation system.

MEMS barometer can be used as barometric altimeter in GNSS/MEMS integrated navigation system, barometric altimeter principle is: in the low altitude area region of earth adjacent ground surface, air pressure in environment can diminish along with highly uprising, the rule of this change meets certain funtcional relationship, and this variation relation is a function:

$P=P_0{\[1-\frac{alt}{44330}\]}^{5.255}---\[1\]$

Wherein P ₀for sea-level pressure, also i.e. benchmark air pressure, so when reference gas press solidly determine, obtain the measured value P of a certain At The Height atmospheric pressure value, the estimated value that just can obtain sea level elevation is:

$alt=44330\[1-{\left(\frac{P}{P_0}\right)}^{\frac{1}{5.255}}\]---\[2\]$

But in practical situations both, air pressure has again different changes along with the weather conditions of locality, so directly utilize pressure model to calculate sea level elevation will produce larger error.Utilize outside correction means, the model error along with Changes in weather is summed up in the point that sea-level pressure value p ₀change on, can from the error to a certain degree reducing Height Estimation.But more barometrical performance characteristics cause again needing special Corrective control method in use.

General MEMS barometer is accurate to the precision comparison measuring relative barometric pressure change, can reach about 1Pa, and corresponding height change is 0.1m.The quiescent period relative barometric pressure change situation as shown in Figure 3.But iff starting initialization sea level benchmark atmospheric pressure value in time, so after several hours along with the accumulation of period drift itself and the change of local weather, the error meeting run-up of this air pressure estimated value, as shown in Figure 4, quiescent conditions lower 6 hours internal gas pressure altitude gauges obtain height change situation.The atmospheric pressure value that the combined effect of these two kinds of factors causes barometer in static to export changed 200Pa in short several hours, and corresponding height change is 20m.Therefore, those skilled in the art is devoted to a kind of barometer on-line correction method developed in GNSS and MEMS integrated navigation system, makes MEMS barometer indicate air pressure exactly in GNSS integrated navigation.

Summary of the invention

Because the above-mentioned defect of prior art, technical matters to be solved by this invention is in GNSS and MEMS integrated navigation system, MEMS barometer how real time calibration error.

For achieving the above object, the invention provides a kind of barometer on-line correction method in GNSS and MEMS integrated navigation system, comprise the steps:

Step 1, utilize when satellite signal quality is reliable GNSS receiver estimate height alt _gNSS;

Step 2, utilize above-mentioned height results to correct MEMS barometer to obtain benchmark air pressure estimated value P _{0_EST};

Step 3, utilize formula

$alt=44330\[1-{\left(\frac{P}{P_0}\right)}^{\frac{1}{5.255}}\]$

Computed altitude estimated value.

Further, described step 2 comprises the following steps:

Step 2.1, utilize satellite pseudo-range measurements residual error, it is adopted to the standard deviation of the algorithm robust iterative residual error of absolute median deviation, estimate the standard deviation of measurement error;

Step 2.2, proportionate relationship between the standard deviation of measurement error and site error is utilized to estimate the variance of GNSS receiver site error;

Step 2.3, utilize the variance evaluation benchmark atmospheric pressure value of GNSS receiver site error and the variance of benchmark barometric error;

The error level of step 2.4, real-time update benchmark air pressure, and contrast with up-to-date GNSS height error level, obtain benchmark air pressure estimated value P _{0_EST}.

Further, described step 2.1 comprises the steps:

If the pseudorange residuals vector after step 2.11 receiver location calculates is

prResi＝[prResi1prResi2…prResin]；

Error variance and the corresponding site error variance of step 2.12, pseudo-range measurements are:

varPrRobust＝(median(abs(prResi–median(prResi))))

varAlt＝varPrRobust*HDOP

Wherein abs and median is respectively the function that subtend measures absolute value and median.

Further, described step 2.4 comprises following steps:

Step 2.41, upgrade during interval at each, GNSS receiver reads the air pressure sampled measurement near K receiver by MEMS barometer

Psample＝[Psample ₁Psample ₂...Psample _K]；

Step 2.42, the gas pressure measurement as this renewal epoch is averaged to sample sequence:

P _BARO＝mean(Psample)。

Further, if do not upgrade this epoch, then benchmark atmospheric pressure value continues to use history parameters, amplifies varP according to barometrical characteristic simultaneously ₀:

varP ₀＝varP ₀+varT。

Further, described varT span is 0.05 ~ 0.1.

Further, described step 2.4 also comprises:

Step 2.43, utilize the height alt of GNSS _gNSSwith the average gas pressure P that air pressure measures _bAROto benchmark air pressure P _{0_EST}upgrade, upgrade the error variance of its correspondence simultaneously:

$P_{0\_EST}=\frac{P_{BARO}}{{\[1-\frac{{\mathrm{alt}}_{GNSS}}{44330}\]}^{5.255}}.$

For the demand of MEMS barometer and integrated navigation system, the object of the invention is to provide a kind of barometric altimeter on-line correction method utilizing GNSS positioning result, also namely reference gas presses real-time estimation method, and the method is applied to the Height Estimation of GNSS/MEMS integrated navigation system.

The present invention is mainly divided into two parts: during reference gas compacting, update strategy and benchmark air pressure calculate.In integrated navigation system position fixing process; residing for receiver, the Satellite Tracking situation of environment, the information such as GNSS Height Estimation precision, buffer memory benchmark air pressure estimated value, buffer memory benchmark air pressure point estimated time of actual computation determine whether to upgrade, and accurately estimate when guaranteeing reference gas compacting.If the positioning result of GNSS satellite receiver meets the update condition of benchmark air pressure, then choose GNSS satellite Height Estimation value alt _gNSS, the average value P of another this location time internal gas pressure meter one second epoch of statistics _bARO, utilize formulae discovery benchmark atmospheric pressure value P ₀, its estimated value is designated as P _{0_EST}

$P_{0\_EST}=\frac{P_{BARO}}{{\[1-\frac{{\mathrm{alt}}_{GNSS}}{44330}\]}^{5.255}}$

Advantage of the present invention: combine GNSS receiver Height Estimation long-time without inclined and MEMS barometer short time metastable feature, utilize the benchmark air pressure P of the Height Estimation locality utilizing satellite receiver to estimate when satellite-signal situation is good ₀; Utilize relatively accurate barometer estimated value to estimate height when satellite-signal difference, thus the overall precision improving integrated navigation system Height Estimation.

Be described further below with reference to the technique effect of accompanying drawing to design of the present invention, concrete structure and generation, to understand object of the present invention, characteristic sum effect fully.

Accompanying drawing explanation

Fig. 1 is the GNSS/MEMS integrated navigation system schematic diagram of a preferred embodiment of the present invention;

Fig. 2 is the benchmark air pressure update strategy figure that the GNSS/MEMS combined altitudes of a preferred embodiment of the present invention is estimated;

Fig. 3 is the situation map of quiescent period relative barometric pressure change;

Fig. 4 is that under quiescent conditions, barometric altimeter obtains height change situation map.

Embodiment

As shown in Figure 1, GNSS/BAROMETER integrated navigation system schematic diagram.GNSS satellite receiver, by GNSS aerial receiver satellite-signal, receives the barometrical real-time gas pressure measurement in MEMS sensor by general-purpose interface simultaneously.GNSS receiver, by conjunction with the information of satnav and gas pressure measurement, by real time correction benchmark air pressure, improves the positioning precision of receiver height.

As shown in Figure 2, GNSS/MEMS combined altitudes drawing for estimate.The present invention is intended to real-time update benchmark air pressure estimated value P _{0_EST}, estimate for GNSS/MEMS combined altitudes.Combine satellite receiver GNSS Height Estimation (101) and the barometrical gas pressure measurement of MEMS (102) in real-time update process, utilize the height results of GNSS to correct the barometrical result of MEMS and obtain benchmark air pressure estimated value P _{0_EST}, recycling formula [2] computed altitude estimated value (108).

Wherein the renewal of GNSS comprises Height Estimation value alt _gNSSwith height error estimate of variance varAlt (101).Locate epoch at each, receiver extracts satellite orbit point position by tracking satellite-signal, in conjunction with the position of the pseudo-range measurements calculating receiver that tracking channel obtains.Specific mathematical relation is there is between pseudo-range measurements and location status, namely equation is measured, so in computation process, the variance of pseudo-range measurements error can be reflected in by certain scale factor in site error variance, this scale factor is called dilution of precision (DOP), DOP is relevant with the space geometric relationship participating in satellite and the receiver of locating, and the scale factor that wherein height error is corresponding is HDOP.If be varPr by the error variance calculating pseudo-range measurements someway, so corresponding height error variance is

varAlt＝varPr*HDOP。

Especially, wherein a kind of positional precision computing method are listed here: based on the positional precision Robust Estimate Method of pseudorange residuals.If the pseudorange residuals vector after receiver location calculates is

prResi＝[prResi ₁prResi ₂…prResi _n]

So the error variance of pseudo-range measurements and corresponding site error variance are:

varPrRobust＝(median(abs(prResi–median(prResi))))

varAlt＝varPrRobust*HDOP

Wherein abs and median is respectively the function that subtend measures absolute value and median.The method can utilize the Robust Estimate Method of median effectively can to eliminate in pseudo-range measurements a small amount of singular value for the impact of error variance.

During each upgrades interval, receiver reads the air pressure sampled measurement Psample=[Psample near K receiver by MEMS barometer ₁psample ₂... Psample _k], the gas pressure measurement as this renewal epoch is averaged to sample sequence: P _bARO=mean (Psample)

The trimming process of benchmark air pressure.If receiver continues first time correction and position does not upgrade (103), to P ₀estimated value carry out initialization, default value P is composed to it _{0_EST}=101235Pa, thinks that benchmark barometric error variance is 4e ⁴pa ²(107), corresponding height error variance is 400m ², note benchmark air pressure variance of estimaion error is varP ₀, especially in order to represent that facilitating its identity transformation is m ²; Otherwise, if judge receiver more new high degree and the height-precision upgraded is less than benchmark air pressure precision (104), also i.e. varAlt<varP ₀, then think that the Height Estimation value of receiver is more reliable, then utilize the height alt of GNSS _gNSSwith the average gas pressure P that air pressure measures _bAROto benchmark air pressure P _0ESTcarry out upgrading (105), upgrade the error variance of its correspondence simultaneously.

$P_{0\_EST}=\frac{P_{BARO}}{{\&lsqb;1-\frac{{\mathrm{alt}}_{GNSS}}{44330}\&rsqb;}^{5.255}}$

varP ₀＝varAlt

Upgrade (106) if do not carry out this epoch, then benchmark atmospheric pressure value continues to use history parameters, then needs suitably to amplify varP according to barometrical characteristic simultaneously ₀, consider that benchmark air pressure drifts about the impact brought in the meantime.

varP ₀＝varP ₀+varT

Wherein varT span is generally 0.05 ~ 0.1.

After correcting, then utilize formula [2] in conjunction with gas pressure measurement P _bAROcalculate the sea level elevation estimated value (108) of receiver.

The most application scenarios of present GNSS receiver is in urban environment, when signal is severe, the tracking quality of signal significantly reduces, the position utilizing satellite-signal to estimate is caused to have significantly error, in conjunction with in barometrical method, the precision of Height Estimation can be significantly improved, improve location availability.

More than describe preferred embodiment of the present invention in detail.Should be appreciated that the ordinary skill of this area just design according to the present invention can make many modifications and variations without the need to creative work.Therefore, all technician in the art, all should by the determined protection domain of claims under this invention's idea on the basis of existing technology by the available technical scheme of logical analysis, reasoning, or a limited experiment.

Claims (7)

1. the barometer on-line correction method in GNSS and MEMS integrated navigation system, is characterized in that, comprise the steps:

Step 1, utilize when satellite signal quality is reliable GNSS receiver estimate height alt _gNSS;

Step 2, utilize above-mentioned height results to correct MEMS barometer to obtain benchmark air pressure estimated value P _{0_EST};

Step 3, utilize formula

$alt=44330\&lsqb;1-{\left(\frac{P}{P_0}\right)}^{\frac{1}{5.255}}\&rsqb;$

Computed altitude estimated value.

2. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 1, it is characterized in that, described step 2 comprises the following steps:

Step 2.1, utilize satellite pseudo-range measurements residual error, it is adopted to the standard deviation of the algorithm robust iterative residual error of absolute median deviation, estimate the standard deviation of measurement error;

Step 2.2, proportionate relationship between the standard deviation of measurement error and site error is utilized to estimate the variance of GNSS receiver site error;

Step 2.3, utilize the variance evaluation benchmark atmospheric pressure value of GNSS receiver site error and the variance of benchmark barometric error;

The error level of step 2.4, real-time update benchmark air pressure, and contrast with up-to-date GNSS height error level, obtain benchmark air pressure estimated value P _{0_EST}.

3. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 2, it is characterized in that, described step 2.1 comprises the steps:

If the pseudorange residuals vector after step 2.11 receiver location calculates is

prResi＝[prResi1prResi2…prResin]；

Error variance and the corresponding site error variance of step 2.12, pseudo-range measurements are:

varPrRobust＝(median(abs(prResi–median(prResi))))

varAlt＝varPrRobust*HDOP

Wherein abs and median is respectively the function that subtend measures absolute value and median.

4. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 2, it is characterized in that, described step 2.4 comprises following steps:

Step 2.41, upgrade during interval at each, GNSS receiver reads the air pressure sampled measurement near K receiver by MEMS barometer

Psample＝[Psample ₁Psample ₂...Psample _K]；

Step 2.42, the gas pressure measurement as this renewal epoch is averaged to sample sequence:

P _BARO＝mean(Psample)。

5. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 4, it is characterized in that, if do not upgrade this epoch, then benchmark atmospheric pressure value continues to use history parameters, amplifies varP according to barometrical characteristic simultaneously ₀:

varP ₀＝varP ₀+varT。

6. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 5, it is characterized in that, described varT span is 0.05 ~ 0.1.

7. the barometer on-line correction method in GNSS and MEMS integrated navigation system as claimed in claim 2, it is characterized in that, described step 2.4 also comprises:

Step 2.43, utilize the height alt of GNSS _gNSSwith the average gas pressure P that air pressure measures _bAROto benchmark air pressure P _{0_EST}upgrade, upgrade the error variance of its correspondence simultaneously:

$P_{0\_EST}=\frac{P_{BARO}}{{\&lsqb;1-\frac{{\mathrm{alt}}_{GNSS}}{44330}\&rsqb;}^{5.255}}.$