KR100674194B1 - Method of controlling magnetic sensor, control device therefor, and portable terminal - Google Patents

Abstract

 The control apparatus 200 calibrates the magnetic sensor 100 by calculation. The calculation unit 210 calculates the magnetic field strength from the outputs of the X, Y, and Z axes of the magnetic sensor 100. This is done for four or more other points. Among them, at least one or more points are performed at points not on the same plane. The calculating part 210 converts each output of the X, Y, Z-axis of the magnetic sensor 100 into three-dimensional space coordinates, and produces | generates the sphere which passes each coordinate with respect to the said four points or more. The coordinate of the center point of the created sphere becomes the offset magnetic field. Calibration is performed by subtracting the obtained magnetic field of the X, Y, and Z axes from the respective outputs of the X, Y, and Z axes of the magnetic sensor 100, respectively.

Description

Method of controlling magnetic sensor, control device therefor, and portable terminal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method, a control device, and a portable terminal device of a magnetic sensor for calibrating a magnetic sensor for detecting a geomagnetism.

In recent years, portable terminal apparatuses, such as a mobile telephone in which a magnetic sensor is mounted, have been put into practical use. Such a portable terminal device not only measures the orientation, but also has a function of displaying the current position or the like on a map of the screen according to the measured orientation based on the position information from the GPS (Globa1 Positioning System).

The magnetic sensor is affected not only by the geomagnetic field but also by the magnetic field of the electronic component embedded in the portable terminal device. The same is also true when moving to a place where a strong magnetic field occurs. For example, even in a building, since concrete, iron, etc. are magnetic, magnetic components other than geomagnetic components are magnetized in the magnetic sensor. For this reason, such a magnetic component causes an error in accurate orientation measurement and detection of a rotating magnetic field. Therefore, in order to extract only a geomagnetic component, calibration for removing other magnetic components from the detected magnetic component is necessary.

This invention is made | formed in view of such a situation, and the objective is to provide the technique which can carry out the calibration of a magnetic sensor easily.

One aspect of the present invention is a control method of a magnetic sensor. The method includes a control method of a magnetic sensor that detects three-axis components of a geomagnetic vector, the method comprising: maintaining reference coordinates in a predetermined coordinate space obtained by coordinate transformation of three-axis components of a reference geomagnetic vector; Acquiring the output of the triaxial component in at least four postures of the magnetic sensor; Coordinate-converting the obtained three-axis component output for each attitude, and acquiring coordinates in the same coordinate space as the reference coordinates; Generating a sphere passing through the acquired four or more coordinates, and calculating an offset magnetic field from the deviation between the center point and the reference coordinate; And calibrating the magnetic sensor with reference to the offset magnetic field. The "reference coordinates" may be the coordinates of the center point of the sphere whose radius is the total magnetic force of the geomagnetic field in the plurality of postures of the magnetic sensor. According to this aspect, it can be easily calibrated by finding the offset magnetic field at the center point of the sphere which passes 4 coordinates or more.

Another aspect of the present invention is a control method of a magnetic sensor. The method includes a control method of a magnetic sensor that detects two-axis components of a geomagnetic vector, the method comprising: maintaining reference coordinates in a predetermined coordinate plane obtained by coordinate-converting two-axis components of a reference geomagnetic vector; Acquiring the output of the biaxial component in three or more postures of the magnetic sensor; Coordinate-converting the output of the obtained biaxial components for each attitude, and obtaining coordinates in the same coordinate plane as the reference coordinates; Generating a circle passing through the acquired three-point or more coordinates, and obtaining an offset magnetic field from the deviation between the center point and the reference coordinate; And calibrating the magnetic sensor with reference to an offset magnetic field. According to this aspect, it can be easily calibrated by calculating the offset magnetic field at the center point of the circle passing through the coordinates of three or more points.

Another aspect of the present invention is a control device for a magnetic sensor. This apparatus is a control device for a magnetic sensor that detects three-axis components of a geomagnetic vector, comprising: a storage unit for holding reference coordinates in a predetermined coordinate space obtained by coordinate-converting three-axis components of a geomagnetic vector as a reference; And an arithmetic unit configured to coordinate-transform the output of the three-axis component in the four or more postures of the magnetic sensor for each posture to obtain coordinates in the same coordinate space as the reference coordinates, and to generate a sphere passing through the acquired four or more coordinates. The calculation unit calculates an offset magnetic field from the deviation between the generated sphere center point and the reference coordinates, and performs calibration of the magnetic sensor with reference thereto. According to this aspect, the calculating part can easily calibrate by calculating | requiring the offset magnetic field in the center point of the sphere which passes 4 coordinates or more.

Another aspect of the present invention is a control device for a magnetic sensor. This apparatus is a control device for a magnetic sensor that detects two-axis components of a geomagnetic vector, comprising: a storage unit for holding reference coordinates in a predetermined coordinate plane obtained by coordinate-converting two-axis components of a reference geomagnetic vector; And an arithmetic unit that coordinate-transforms outputs of biaxial components in three or more postures of the magnetic sensor for each posture to obtain coordinates in the same coordinate plane as the reference coordinates, and to generate a circle passing through the acquired three or more coordinates. Then, the calculating unit calculates an offset magnetic field from the deviation between the generated center point and the reference coordinate, and performs calibration of the magnetic sensor with reference thereto. According to this aspect, a portable terminal device such as a mobile phone equipped with a magnetic sensor that can be easily calibrated by calculating an offset magnetic field at a center point of a circle passing through coordinates of three or more points can be realized.

Another aspect of the present invention is a portable terminal device. This apparatus is provided with the control apparatus of the above-mentioned aspect of the magnetic sensor which detects the triaxial component of a geomagnetic vector, and the magnetic sensor which detects a triaxial component. According to this aspect, it can be easily calibrated by finding the offset magnetic field at the center point of the sphere which passes 4 coordinates or more.

Another aspect of the present invention is a portable terminal device. This apparatus is provided with the control apparatus of the above-mentioned aspect of the magnetic sensor which detects the biaxial component of a geomagnetic vector, and the magnetic sensor which detects a biaxial component. According to this aspect, a portable terminal device such as a mobile phone equipped with a magnetic sensor that can be easily calibrated by obtaining an offset magnetic field at a center point of a circle passing through three or more coordinates can be realized.

In addition, any combination of the above components and a conversion of the expression of the present invention between a method, a system, a recording medium, a computer program, and the like are also effective as aspects of the present invention.

1 is a diagram illustrating an example of a magnetic sensor.

It is a figure which shows the control apparatus and magnetic sensor in embodiment of this invention.

3 is a flowchart for calibrating a magnetic sensor by the control device in the embodiment.

4 is a diagram illustrating an example of a sphere generated by a calculation unit.

5 is a diagram illustrating a configuration of a portable terminal device in an embodiment.

6 is a flowchart for calculating a bearing based on detection results of a magnetic sensor and an inclination angle sensor.

<Short description of symbols>

100 magnetic sensors

102 first magnetic detection element

104 second magnetic detection element

106 third magnetic detection element

110 substrates

120 tilt angle sensor

200 control unit

210 calculator

220 memory

230 watchdog

300 mobile terminal devices.

First, before demonstrating the detail of the calibration method for removing magnetic components other than a geomagnetic component in this embodiment, the structure of the triaxial magnetic sensor used as the object is demonstrated. 1 is a diagram illustrating an example of the magnetic sensor 100. This magnetic sensor 100 has at least three magnetic detection elements 102, 104 and 106 which detect each of the three-axis components of X, Y and Z of the magnetic vector. The first magnetic detection element 102 detects the magnetic component in the X-axis direction, the second magnetic detection element 104 detects the magnetic component in the Y-axis direction, and the third magnetic detection element 106 is the Z-axis direction. Detect the magnetic component of

In the magnetic sensor 100, at least the first magnetic detection element 102 and the second magnetic detection element 104 are preferably MR (Magneto Resistance) elements, Hall elements, or MI (Magneto Impedance) elements. Similarly, the magnetic detection element 106 is preferably an MR element, a Hall element or an MI element. By forming all the magnetic detection elements as MR elements or Hall elements, this magnetic sensor 100 can be formed using a series of semiconductor manufacturing processes.

The first magnetic detection element 102 and the second magnetic detection element 104 are configured at a predetermined angle with respect to the surface of the substrate 110 and are arranged in a direction parallel to the surface of the substrate, that is, in the X-axis direction and the Y-axis direction. Two magnetic components are detected respectively. Here, it is preferable that the first magnetic detection element 102 and the second magnetic detection element 104 are formed so as to be almost upright on the surface of the substrate 110. In the surface of the substrate 110, the first magnetic detection element 102 and the second magnetic detection element 104 are preferably arranged such that the direction parallel to the respective surfaces is 90 °. The third magnetic detection element 106 is formed on the surface of the substrate 110 to detect magnetic components in a direction perpendicular to the substrate surface, that is, in the Z-axis direction.

Each magnetic detection element has a magnetoresistive film of a thin film structure represented by general formula (Co1-aFea) 100x-y-zLxMyOz. The magnetic film may have a magnetic permeability of 1,000,000 or more, and may be formed using rare earth and magnetic metal powder of nano order capable of detecting a magnetic field of 1 µT or more.

In the magnetic sensor 100 shown in FIG. 1, two magnetic detection elements 102 and 104 are formed upright. In another example, two magnetic detection elements are formed on the plane of the substrate 110. One magnetism detecting element may be formed upright on the substrate 110. At this time, the two magnetic detection elements formed on the plane of the substrate 110 detect the vertical magnetic field and the horizontal magnetic field of the magnetic vector, and the magnetic detection element constituted upright may detect a component perpendicular to such magnetic field.

In addition, the magnetic sensor may be a flux gate type magnetic sensor. Since the flux gate type magnetic sensor requires the core of the coil, the flux gate type magnetic sensor is slightly larger in configuration. Therefore, there is no problem when the flux gate type magnetic sensor is mounted in a vehicle having a sufficient placement space. However, when the flux gate type magnetic sensor is embedded in a small terminal device such as a cellular phone, the arrangement design in the case is studied from the relationship with other internal elements. Needs to be. On the other hand, magneto-resistive effect elements such as MR elements and magnetic sensitive elements such as hall elements can be formed smaller than flux gate type magnetic sensors, and are suitable for mounting in portable terminal devices.

2 is a block diagram showing the control device 200 and the magnetic sensor 100 in the embodiment of the present invention. The control apparatus 200 is realized by a magnetic field removal program loaded on a CPU, RAM, ROM, ROM of an arbitrary computer, etc., but here, the functional block is realized by their linkage. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms only by hardware, only by software, or by a combination thereof.

The control device 200 includes a calculation unit 210, a storage unit 220, and a monitoring unit 230. The calculating part 210 performs the calculation process mentioned later, and calibrates the magnetic sensor 100. FIG. The storage unit 220 registers basic data and the like which are references to the actual output of the magnetic sensor 100. In a state where there is no magnetizing component other than the geomagnetic component, the output of the magnetic sensor 100 from the X, Y, and Z axes is such that the component of the geomagnetic magnetic force is detected. The attitude | position of the magnetic sensor 100 is changed and in 4 or more attitude | positions, an output is acquired from an X-axis, a Y-axis, and a Z-axis, respectively. Then, the acquired output of the three-axis component is coordinate-converted for each posture to generate a sphere passing through four or more coordinates, and the coordinates of the center point are taken as reference coordinates. This reference coordinate can be set as the basic data. This reference coordinate can be obtained by simulation or experiment, and the obtained value is set in the storage unit 220. Moreover, you may draw the sphere which used the magnetomagnetic force for the radius from the coordinate of the center point, and may register the coordinate of the point which passes through the sphere as basic data.

The monitoring unit 230 monitors each output of the X, Y, and Z axes of the magnetic sensor 100. The output of the X axis from the first magnetic detection element 102 of the magnetic sensor 100, the output of the Y axis from the second magnetic detection element 104, and the output of the Z axis from the third magnetic detection element 106 are controlled, respectively. Is input to the device 200.

The output of each X, Y, Z can be expressed by the following formula.

X = W {cos (f) cos (p) cos (d) -sin (f) sin (p)} + A

Y = W {-cos (f) cos (r) sin (d) -cos (f) sin (p) sin (r) cos (d) -sin (f) cos (p) sin (r)} + B

Z = W {-cos (f) sin (r) sin (d) + cos (f) sin (p) cos (r) cos (d) + sin (f) cos (p) cos (r)} + C

W = magnetic field strength, f = dip, d = rotation angle, p = pitch angle, r = roll angle, A = magnetization magnetic field on X axis, B = magnetism magnetic field on Y axis, C = magnetism magnetic field on Z axis. Therefore, the magnetic field strength W of each axis here represents the component of the geomagnetic magnetic force and the magnetizing magnetic field of each axis.

In the case of not considering magnetizing magnetic fields other than the geomagnetism, in the magnetic sensor 100 equipped with three-axis characteristics, three-dimensional coordinate spaces appearing in the outputs X, Y, and Z of each magnetic detection element when rotated in all directions among the geomagnetisms. A collection of points of can draw a sphere whose origin is the geomagnetic field with a radius around the zero magnetic field.

On the other hand, when a magnetizing magnetic field, i.e., an offset magnetic field, exists in the magnetic sensor 100, the collection of points when rotated as described above may draw a sphere in which only the center point of the sphere is displaced and the radius does not change.

Hereinafter, the calibration operation of the control device 200 will be described on the premise of this. 3 is a flowchart showing a calibration operation of the magnetic sensor 100 by the control device 200 according to the present embodiment. First, when a terminal or the like on which the magnetic sensor 100 is mounted is activated, the monitoring unit 230 monitors the output of the magnetic sensor 100 (S10). Then, the output is converted into spatial coordinates, and the coordinates are compared with the coordinate group which is the basic data set in advance in the storage unit 220 (S12).

As a result of the comparison, when the difference exceeds a predetermined threshold (Y in S12), a calibration process described later is performed. Here, the difference may be a difference between the input coordinates and the registration coordinates closest to the difference. If the predetermined threshold is not exceeded (N in S12), monitoring continues (S10). Here, the predetermined threshold is for detecting that the magnetic component other than the geomagnetic component is magnetized, and may be obtained experimentally. It also depends on the design of how far the tolerance is allowed.

The calculating part 210 calculates a magnetic field intensity from each output of the X, Y, Z-axis of the magnetic sensor 100 (S14). This is done for four or more other points. Among them, at least one or more points are points that do not exist on the same plane. The formula for calculating the magnetic field strength of another four points is shown below.

W ₁ ² = X ₁ ² + Y ₁ ² + Z ₁ ²

W ₂ ² = X ₂ ² + Y ₂ ² + Z ₂ ²

W ₃ ² = X ₃ ² + Y ₃ ² + Z ₃ ²

W ₄ ² = X ₄ ² + Y ₄ ² + Z ₄ ²

Next, the calculating part 210 produces | generates a sphere from these four or more points (S16). In other words, each output of the X, Y, and Z axes of the magnetic sensor 100 is used as coordinates in a three-dimensional space, and a sphere passing each coordinate is generated for four or more points. In other words, a sphere is created with the center point at the same radius of each coordinate. This radius represents the geomagnetic force. 4 is a diagram illustrating an example of a sphere generated by the calculator 210. The lengths from points 1, 2, 3, and 4 are all equal, and the center of the sphere is 0. Of course, four or more points may be sufficient.

The calculator 210 calculates coordinates of the center point of the generated sphere. The coordinate becomes the offset magnetic field (S18). Hereinafter, the calculation formula for calculating the center coordinate of a sphere is shown. This formula can be derived from the formula for calculating the output of each of the above-described X, Y, and Z.

The calculation unit 210 performs calibration by subtracting the calculated magnetic fields A, B, and C on the X, Y, and Z axes from the outputs of the X, Y, and Z axes of the magnetic sensor 100 (S20).

As described above, according to the present embodiment, a magnetic sphere other than the geomagnetic component can be easily and automatically removed by generating a sphere based on the output of the magnetic sensor in four or more postures, and detecting an offset magnetic field from the center point. Can be. It is not necessary to perform a process such as making the user rotate one horizontally and finding the middle of the maximum value and the minimum value of the output data in the meantime. Therefore, the user does not have to make a cumbersome rotation, so there is no need to consider the magnetization component. In addition, even when manufacturing a magnetic sensor, it is possible to determine the arrangement of parts without considering the magnetizing magnetic field, which facilitates development.

5 shows a configuration of a portable terminal device 300 according to an embodiment of the present invention. The portable terminal device 300 is a portable small electronic device such as a cellular phone, a personal handyphone system (PHS) and a personal data assistant (PDA). Fig. 5 shows a configuration for realizing orientation measurement and an application to be described later. It will be understood by those skilled in the art that the portable terminal device 300 may have other configurations according to the use.

The portable terminal device 300 includes a control device 200, a detection unit 20, an imaging unit 30, a communication unit 32, a GPS information acquisition unit 34, and a display unit 36. The detector 20 includes a magnetic sensor 100, an inclination angle sensor 120, an air pressure sensor 140, and a temperature sensor 160, and has a function of detecting a position, azimuth, attitude, altitude, and the like. The imaging unit 30 includes a photoelectric conversion element such as a CCD, and acquires an image and passes it to the control device 200. The communication unit 32 has a function of communicating with an external server through a wireless line. This communication may be performed by a wired line. The GPS information acquisition unit 34 receives location information from the GPS satellites. The control apparatus 200 calculates a current position, ie, the current latitude and longitude, according to this positional information. In addition, by making the position information correctable by the orientation information from the magnetic sensor 100, the accurate current position and orientation can be obtained. The control device 200 may be used to complement the position information and the orientation information. In addition, the control apparatus 200 may obtain the current position and orientation using only the detection result from the detection unit 20 without using the position information from the GPS satellites. The display unit 36 has a display and outputs information processed by the control apparatus 200 according to an application. In addition, a speaker (not shown) may be provided to output a variety of information to the user.

The magnetic sensor 100 can use the above-mentioned thing. The azimuth angle, ie yaw angles, which are rotation angles from the magnetic north, is detected based on the geomagnetic vectors of the X and Y axes, except that the geomagnetic vector is almost horizontal near the equator but inclined elsewhere. . In addition, the posture of the portable terminal device 300 is not always horizontal. Therefore, using the relative angles to the direction of gravity, that is, the pitch angle and the roll angle, the geomagnetic vector must be corrected. This pitch angle and the roll angle are detected by the inclination angle sensor 120. The control apparatus 200 corrects the detection result of the X-axis and Y-axis using the said pitch angle and the roll angle so that the detection result of a Z-axis will always be equivalent to the state maintained as the detection result at the time of horizontal Z-axis. Thus, by making the magnetic sensor 100 into three axes and using the Z-axis detection result for correction, the accuracy of an azimuth angle can be maintained even when a posture changes large.

The inclination angle sensor 120 is an acceleration sensor for detecting acceleration components in the three axis direction, and includes a resistance value change method, a capacitance change method, a piezoelectric change method, and the like. In the inclination angle sensor 120, the X-axis and the Y-axis are arranged so as to go straight in the horizontal plane, and the Z-axis is arranged in the direction of gravity. When the posture of the portable terminal device 300 is inclined, the gravity acceleration is changed, and the pitch angle and the roll angle are detected by detecting the gravity acceleration. In the state in which the portable terminal device 300 is stopped, the attitude | position of the portable terminal device 300 can also be detected correctly even with two axes. When the user who holds the portable terminal device 300 is walking or riding in a vehicle such as a car or a bicycle, since the acceleration component is added to the inclination angle sensor 120, the posture cannot be detected accurately. . By setting it as 3 axes, gravity acceleration and movement acceleration can be isolate | separated, and an accurate posture can be detected. Accurate pitch angle and roll angle can be calculated by integrating the output value of each axis to obtain the assumed angle, comparing the acceleration component with that, and performing a predetermined calculation.

The atmospheric pressure sensor 140 detects the pressure of the outside air, and the temperature sensor 160 detects the temperature. The detected temperature is used to correct misalignment of the outputs of the magnetic sensor 100, the inclination angle sensor 120, and the barometric pressure sensor 140 due to the temperature drift.

6 shows a flow for calculating the orientation based on the detection results of the magnetic sensor 100 and the inclination angle sensor 120. First, the inclination angle of the magnetic sensor 100 is calculated based on the acceleration component in the three axis direction detected by the inclination angle sensor 120 (S30). Here, the pitch angle and the roll angle are calculated. The magnetic sensor 100 detects three-axis components of the geomagnetic vector (S32). The control apparatus 200 performs the above-described calibration and removes the magnetizing magnetic field (S34). Thereafter, the components of the geomagnetic vector are coordinate-converted by the pitch angle and the roll angle (S36) to obtain an accurate orientation (S38). At this time, temperature correction may be performed using the detection result of the temperature sensor 160. As described above, the detection result of the inclination angle sensor 120 is used to calculate the orientation, and various applications can be realized by using the detection result more effectively.

As described above, according to the present embodiment, calibration of the magnetizing magnetic field and the inclination angle can be easily realized, and the output of the highly accurate magnetic sensor can be obtained.

In the above, this invention was demonstrated with reference to embodiment. Embodiment is an illustration, It is understood by those skilled in the art that various modifications are possible for each component of them and the combination of each processing process, and such a modification is in the scope of the present invention.

In the embodiment, a method of calibrating a magnetizing magnetic field of a three-axis magnetic sensor has been described. In contrast, a two-axis magnetic sensor can also be calibrated by the same method. In the case of two axes, the calculating part 210 makes each output of the X and Y axes of the magnetic sensor 100 into the coordinates of a two-dimensional plane, and produces | generates the circle which passes each coordinate with respect to another three or more points. That is, a circle is created with the center point as the radius of each coordinate being the same. The offset magnetic field values of the X and Y axes of the magnetic sensor 100 are obtained from the coordinates of the center point, and the calibration is performed.

In the embodiment, instead of outputting four points from the magnetic sensor 100, the center point may be obtained by selecting a point at which the error is minimum from the output of five or more points, that is, four points that are separated from each other as much as possible. In addition, this selection may be repeated several times to obtain a center point. Thereby, the error by the subtle change of the output precision, the output resolution, and the geomagnetism electromagnetic force of the magnetic sensor 100 can be reduced, and a higher precision calibration can be performed.

In addition, when detecting geomagnetism, a declination is caused by a place on earth. Therefore, the declination measured in advance for each place may be registered in the storage unit 220, and the declination may be calibrated according to the current position of the magnetic sensor 100. The current position can be specified by latitude and longitude information based on time information from a GPS satellite or by user input.

According to the present invention, the magnetic sensor can be easily calibrated.

The present invention can be applied to the field of calibrating a magnetic sensor.

Claims (6)

 In the control method of the magnetic sensor for detecting the three-axis component of the geomagnetic vector, Maintaining reference coordinates in a predetermined coordinate space obtained by coordinate transformation of three-axis components of the geomagnetic vector as a reference; Acquiring the output of the triaxial component in four or more postures of the magnetic sensor; Coordinate-converting the output of the obtained three-axis component for each attitude, and acquiring coordinates in the same coordinate space as the reference coordinates; Selecting four points from the acquired four or more coordinates, generating a sphere passing through the four coordinates, and obtaining an offset magnetic field from the deviation between the center point and the reference coordinates; And calibrating the magnetic sensor with reference to the offset magnetic field. The method for controlling a magnetic sensor according to claim 1, wherein the step of calculating the offset magnetic field is selected from four acquired coordinates of which positional distances are as far as possible from each other.  In the control device of the magnetic sensor for detecting the three-axis component of the geomagnetic vector, A storage unit which holds reference coordinates in a predetermined coordinate space obtained by coordinate-converting three-axis components of the geomagnetic vector as reference; Coordinate-transform the output of three-axis components in four or more postures of the magnetic sensor for each posture, obtain coordinates in the same coordinate space as the reference coordinates, and select four points from the acquired four or more coordinates, And a calculation unit for generating a sphere passing through the coordinates of the four points, And said calculating section calculates an offset magnetic field from a deviation between the generated sphere center point and said reference coordinate, and performs calibration of said magnetic sensor with reference thereto. 4. The control apparatus for a magnetic sensor according to claim 3, wherein the calculation unit selects four points that are in a positional relationship where the mutual distance is as far as possible from the acquired coordinates of five or more points.  A magnetic sensor for detecting triaxial components of the geomagnetic vector, The control device of Claim 3 is provided, The portable terminal device characterized by the above-mentioned.  A magnetic sensor for detecting triaxial components of the geomagnetic vector, The control device of Claim 4 is provided, The portable terminal device characterized by the above-mentioned.

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