KR101576424B1

KR101576424B1 - Automatic calibration method of magnetometer for indoor positioning

Info

Publication number: KR101576424B1
Application number: KR1020150084955A
Authority: KR
Inventors: 이효영
Original assignee: 코디스페이스 주식회사
Priority date: 2015-06-16
Filing date: 2015-06-16
Publication date: 2015-12-10

Abstract

Disclosed in the present invention is a method for an automatic calibration of a terrestrial magnetic sensor for indoor positioning comprising: (a) a step of determining whether conditions for automatic calibration of a terrestrial magnetic sensor are satisfied; (b) a step of generating reference value sets of estimated terrestrial magnetism by collecting a plurality of number (Nr) of reference values of estimated terrestrial magnetism of body coordinates when conditions for automatic calibration of a terrestrial magnetic sensor are satisfied; (c) a step of generating a plurality of number (Nm) of measured value sets of terrestrial magnetism which can be matched with the reference value sets of estimated terrestrial magnetism by collecting measured values of terrestrial magnetism at a certain period; (d) a step of calculating a bias error having minimal residual (J) by comparing all of the reference value sets of the estimated terrestrial magnetism and the measured values sets of terrestrial magnetism, and then estimating the result as the bias error; and (e) a step of calibrating an error of the terrestrial magnetic sensor using the estimated bias error. According to the present invention, estimated values of the terrestrial magnetism of a body coordinate system can be obtained using reference values of terrestrial magnetism of a navigation coordinate system, a bias error having minimal residual can be estimated by comparing the reference value sets of estimated terrestrial magnetism and the measured values sets of terrestrial magnetism, and an error of a terrestrial magnetic sensor can be calibrated using the bias error; thus improving a reliability of measurement by enhancing the accuracy for an indoor positioning and detection of direction.

Description

[0001] The present invention relates to an automatic calibration method of a magnetometer for indoor positioning,

The present invention relates to a geomagnetic sensor automatic correction method, and more particularly, to a geomagnetic sensor automatic correction method for indoor positioning that estimates a bias error of a geomagnetic sensor in an indoor positioning and erases the same.

As the demand and interest of indoor location information is increasing, various technologies for an indoor positioning system are being developed. Typical technologies include positioning system using WiFi, positioning system using inertial navigation, positioning system using image data processing, positioning system using RFID, positioning system using geomagnetic sensor, positioning system using LED map matching and LED And a positioning system using optical communication.

On the other hand, techniques for indoor positioning using a portable mobile communication terminal (for example, a smart phone or the like), which has become a necessity for modern people, are gradually developed.

In the indoor positioning technology, the magnetometer information plays an important role in the detection of the traveling direction and the positioning. However, a low-cost geomagnetic sensor mounted on a smart phone or the like has a large variation in bias error depending on the change in the current amount of the internal electronic circuit and environmental characteristics.

Therefore, it is necessary to estimate the deviation error and erase the bias error component from the measured value for accurate indoor positioning and direction detection.

Korean Patent Publication No. 10-2009-0092055 (published on August 31, 2009) Korean Patent Publication No. 10-2015-0055423 (published on May 21, 2015)

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a geomagnetism sensor that estimates a geomagnetism estimation reference value, compares the geomagnetism estimation reference value with a geomagnetism measurement reference value, And an object of the present invention is to provide an automatic correction method of a geomagnetic sensor for an indoor positioning for correcting an error.

According to another aspect of the present invention, there is provided a method of automatically calibrating a geomagnetic sensor for indoor positioning, comprising the steps of: a) determining whether a geomagnetic sensor automatic correction condition is satisfied; b) generating a set of estimated geomagnetic reference values by collecting a plurality of geomagnetism estimation reference values of the body coordinates (Nr) at predetermined intervals when the geomagnetic sensor automatic correction condition is satisfied; c) collecting the geomagnetism measurement values of the body coordinates at regular intervals to generate a plurality of geomagnetism measurement values sets that can be matched with the geomagnetism estimation reference value set; d) comparing both the geomagnetism estimation reference value set and the measured value set to calculate a deviation error which is the minimum value of the residula J and estimating the deviation error with a deviation error; And e) correcting the geomagnetism sensor error using the estimated deflection error.

According to the present invention, the step a) includes: a1) detecting a step using the acceleration and the angular velocity, and calculating a walking speed, and a2) estimating the current position.

In the step a), if the geomagnetic sensor automatic correction condition is satisfied when at least one of whether linear movement during a certain step, movement in the same layer, and standard deviation of the step rate is below a threshold value .

According to the present invention, in the step b), the geomagnetism estimation reference value of the body coordinate system is estimated as a geomagnetism reference value in the navigation coordinates measured by the existing geomagnetism sensor stored in the database.

The step b) includes: b1) collecting the geomagnetism measurement values of the body coordinate system at regular intervals; b2) extracting a plurality of geomagnetic reference values of the navigation coordinate system at a predetermined distance from the database based on the current position; And b3) transforming the geomagnetism reference value in the extracted navigation coordinate system to the geomagnetism estimation reference value in the body coordinate system.

According to the present invention, in the step c), the geomagnetism estimation reference values of the plurality of extracted (Nr) geomagnetism reference values among the geomagnetic measurement values collected in the step b1) are matched with the geomagnetism estimation reference values (Nm) that can be extracted.

According to the present invention, in the step d), the deviation error is calculated by calculating a deviation error that minimizes the sum of the squares of the residues using the least square method, Is estimated as a bias error.

According to the present invention, after the step (e), the step (f) further includes the step of: (f) updating the current deviation error to the final deviation error when the estimated deviation is smaller than the current deviation of the estimated deviation error of the previous step.

According to the present invention, the geomagnetism estimation value of the body coordinate system is obtained by using the geomagnetism reference value of the navigation coordinate system, the deviation error of the tram is minimized by comparing the geomagnetism estimation reference value set and the geomagnetism measurement reference value set, The error can be corrected. Therefore, the accuracy of the indoor positioning and the direction detection can be improved and the reliability of the measurement can be improved.

1 is a flowchart of a method of automatically calibrating a geomagnetic sensor for indoor positioning according to an embodiment of the present invention;
2 is a diagram for explaining generation of a set of Nr geomagnetism estimation reference values,
3 is a diagram for explaining generation of Nm geomagnetic measurement values.

These and other objects, features and other advantages of the present invention will become more apparent by describing in detail preferred embodiments of the present invention with reference to the accompanying drawings. Hereinafter, a method of automatically calibrating a geomagnetic sensor for indoor positioning according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Meanwhile, the present invention is not necessarily limited to this, but is preferably applied to a technique of performing indoor positioning using a portable mobile communication terminal (for example, a smart phone, a tablet PC, a notebook computer, a PDA, or the like).

Geomagnetic sensor error model

To estimate the geomagnetic sensor bias error, the geomagnetism measurement model is expressed by Equation 1 below. Here, only the largest deviation error of the geomagnetism sensor error factors is taken into consideration, and other errors such as a scale factor error and a soft-ion error are not considered.

here,

: The geomagnetism measurement vector of x, y, z components in the body coordinates measured by the geomagnetic sensor,

: True in body coordinates (geodetic) real vector of x, y, z components,

: Geomagnetism error vector of x, y, z components in body coordinates by geomagnetic sensor,

Is the geomagnetism error vector of the true x, y, z components in the body coordinates.

Basic data collection

Referring to FIG. 1, first, a step is detected using an acceleration and an angular velocity, a step velocity is calculated (S101), and a current position is estimated (S102). Basic data will be collected. This basic data collection is used to determine if the geomagnetic sensor calibration conditions described below are met.

The step detection and speed calculation can be performed by using an accelerometer provided in a portable mobile communication terminal and an angular velocity sensor (gyrometer) for measuring an angular velocity. The current position can be detected by wireless communication signals such as Wi-Fi and mobile communication network And can be obtained by using a wireless communication device for measurement and a magnetometer or the like.

Determine whether the geomagnetic sensor is automatically calibrated

The collected basic data is used to determine whether the geomagnetic sensor automatic correction condition is satisfied (S103).

For example, when the portable mobile communication terminal (or the user having the portable mobile communication terminal) performs a linear movement for a certain step (for example, five steps), it is determined that the geomagnetic sensor automatic correction condition is satisfied. That is, in the case of turning or turning without moving linearly, the condition of automatic correction of the geomagnetic sensor does not correspond to the condition.

As another example, when moving in the same layer, it is determined that the geomagnetic sensor automatic correction condition is satisfied. That is, when moving a layer using a staircase or an escalator, the condition for automatic correction of the geomagnetic sensor does not correspond to the condition.

As another example, when the standard deviation of the walking speed is below the threshold value, it is determined that the geomagnetic sensor automatic correction condition is satisfied. That is, when the step speed is fast or slow, and the speed deviation is large, if it is not continuous, it does not correspond to the automatic correction condition of the geomagnetic sensor.

If at least one of these conditions is satisfied or all of the conditions are satisfied, it is determined that the geomagnetic sensor automatic correction condition is satisfied and the following process is performed.

Geomagnetism estimation Reference value Collection and Estimation Reference value Create Set

If the geomagnetic sensor automatic correction condition is satisfied, the geomagnetism measurement values of the body coordinates by measurement of the geomagnetism sensor are collected at regular intervals (S104).

Then, a plurality of geomagnetic reference values are extracted from the database at a predetermined distance based on the current position (S105), and the estimated geomagnetic reference values of the extracted navigation coordinates are converted into coordinate values based on the estimated geomagnetic reference values of the body coordinate system S106).

The actual values of the true geomagnetism in the Body Coordinates of each location (

) Is unknown. However, it can be estimated as a geomagnetic reference value in Navigation Coordinates previously measured for indoor positioning. The posture change matrix can be obtained by using the posture of the sensor generated during the posture calculation, that is, Roll, Φ, Pitch, θ, Yaw, and ψ.

Here, the navigation coordinate system is a coordinate system in which the north direction is the X axis direction, the east direction is the Y axis direction, and the earth center direction is the Z axis direction. The body coordinate system is a coordinate system in which the X, Y, and Z axes are fixed to the portable terminal to which the current is attached, and the coordinate axis direction is defined according to the application of the technology. In order to correct the error of the geomagnetic sensor, the same coordinate system should be compared. In the present invention, the measured value is compared with the reference value in the body coordinate system. Therefore, the reference value of the navigation coordinate system is

To be used in the body coordinate system.

Therefore, the geomagnetism actual value (

) Can be expressed by the following equation (2).

here,

: Geomagnetism estimation reference value in body coordinate system,

: Coordinate transformation matrix from navigation coordinate system to body coordinate system,

: This is the geomagnetic reference value in the navigation coordinate system measured with the previously calibrated geomagnetic sensor.

On the other hand, in order to estimate the bias error, the data set to be compared is made up of several sets of geomagnetism estimation reference values due to the uncertainty of the current position, so that the accuracy of the bias error estimation becomes high. Therefore, as shown in FIG. 2, Nr pieces of Nr estimated reference values are generated by extracting Nr pieces of geomagnetism estimation reference values of the body coordinate system to be compared with the current position reference from the database (S107). In other words, the reference value is extracted within the positioning error range based on the current position and compared with the measured value.

Create geomagnetic measurement set

As shown in FIG. 3, a plurality of geomagnetism measurement values that can be matched with the generated geomagnetism estimation reference value set in the geomagnetism data collected in step S104 are calculated using the step velocity calculated in step S101 Nm number of measurement values are extracted to produce Nm sets of measurement values (S108). Here, an error occurs in the average speed and direction calculated using the accelerometer and each speedometer. At this time, the calculated average speed is changed in the error range, and a set of measurement values that can be matched with the reference value sets is made.

Geomagnetic sensor Bias error Estimation and error correction

The generated geomagnetic reference value set is compared with the geomagnetic measurement value set to estimate the bias error and calculate the tram (S109).

The geomagnetism sensor deflection error is calculated by comparing at least three data of the measured value and the estimated reference value with a deviation error that minimizes the estimation error. In this case, the Least Square method is used to estimate the deviation error that minimizes the sum of squares of residual (J). The tram can be expressed as shown in Equation 3 below.

The equation (3) can be expressed as the following equation (4).

Equation (4) can be summarized as Equation (5), and Equation (5) can be rearranged into Equation (6).

In this way, both the geomagnetism reference value set Nr and the geomagnetism measurement value set Nm are compared to obtain a deviation error that minimizes the residual (J), and the deviation error is estimated.

In this way, the deviation error having the smallest value is set as the estimated error, and the error of the geomagnetism sensor is corrected by using the error (S110).

In step S111, the current error value is compared with the error value of the estimated error value in the previous step, and the current error value is updated to the final error value if the current error value is small. Here, the tram of the previous step estimation error refers to the calculated tram that most recently calculates the deviation error.

Although the preferred embodiments of the present invention have been described, the present invention is not limited to the specific embodiments described above. It will be apparent to those skilled in the art that numerous modifications and variations can be made in the present invention without departing from the spirit or scope of the appended claims. And equivalents should also be considered to be within the scope of the present invention.

Claims

a) determining whether the geomagnetic sensor automatic correction condition is satisfied;
b) generating a set of estimated geomagnetic reference values by collecting a plurality of geomagnetism estimation reference values of the body coordinates (Nr) at predetermined intervals when the geomagnetic sensor automatic correction condition is satisfied;
c) collecting the geomagnetism measurement values of the body coordinates at regular intervals to generate a plurality of geomagnetism measurement values sets that can be matched with the geomagnetism estimation reference value set;
d) comparing both the geomagnetism estimation reference value set and the measured value set to calculate a deviation error which is the minimum value of the residula J and estimating the deviation error with a deviation error; And
and e) correcting the geomagnetism sensor error using the estimated deflection error. < RTI ID = 0.0 > 11. < / RTI >

The method according to claim 1, wherein before step a)
a1) detecting a step using an acceleration and an angular velocity and calculating a walking speed, and a2) estimating a current position, wherein the basic data collecting step includes automatic geomagnetism sensor calibration for indoor positioning Way.

3. The method of claim 2, wherein step a)
The automatic correction condition is satisfied if at least one of whether a linear movement is performed for a certain period of time, whether the robot moves in the same layer, and whether a standard deviation of a stepping velocity is not more than a threshold value is satisfied. Automatic calibration method of geomagnetic sensor for indoor positioning.

3. The method of claim 2, wherein in step b)
Wherein the geomagnetism estimation reference value of the body coordinate system is estimated as a geomagnetism reference value in a navigation coordinate system measured by an existing corrected geomagnetic sensor stored in a database.

5. The method of claim 4, wherein step b)
b1) collecting the geomagnetic measurement values of the body coordinate system at regular intervals;
b2) extracting a plurality of geomagnetic reference values of the navigation coordinate system at a predetermined distance from the database based on the current position;
and b3) transforming the geomagnetism reference value in the extracted navigation coordinate system to the geomagnetism estimation reference value in the body coordinate system.

6. The method of claim 5, wherein step c)
(Nm) that can be matched with the geomagnetism estimation reference values of the extracted plurality (Nr) of the geomagnetic measurement values collected in step b1) using the step rate calculated in step a1) Wherein the method comprises the steps of:

2. The method of claim 1, wherein step d)
The deviation error is calculated by calculating a deviation error that minimizes the sum of squares of residues (J) using Least Square Method, and estimates a deviation error that minimizes the sum of squares of the trains by a deviation error A method of automatically calibrating a geomagnetic sensor using indoor positioning.

8. The method of claim 7, wherein after step e)
f) comparing the estimated error with a tilt of the estimated error of the previous step, and if the current tare is small, updating the current deviation error to a final deviation error. Automatic calibration method.