JP4111211B2 - Direction data generation method, direction sensor unit, storage medium, and portable electronic device - Google Patents

Description

  The present invention relates to a technique for performing calibration (offset correction) for azimuth measurement using azimuth measurement data using a geomagnetic sensor, and in particular, data obtained from a three-axis geomagnetic sensor is limited to a specific plane. Even in such a case, the present invention relates to a direction data generation method, a direction sensor unit, a storage medium, and a portable electronic device that perform proper calibration and measure a correct direction.

A portable terminal such as a mobile phone that includes a magnetic sensor that detects geomagnetism and performs azimuth measurement based on the geomagnetism detected by the magnetic sensor is known. The azimuth | direction measured here is utilized for the display of a map, for example, for example, recently GPS (Global) which performs position detection is used.
Mobile terminals having a function of (Positioning System) and having a function of displaying a map based on the current position in accordance with the orientation (direction) of the mobile terminal have appeared.

  However, since a mobile terminal has magnetism leaking from a speaker and a microphone mounted on the mobile terminal and a metal package of a magnetized electronic component, the magnetic sensor mounted on the mobile terminal is an electronic component inside the mobile terminal. Thus, a magnetic field generated by combining the magnetic field generated from the magnetic field and the geomagnetism is detected. Therefore, a calibration process for correcting an error (offset) due to a magnetic field generated from an electronic component or the like inside the portable terminal is necessary. Therefore, in a conventional portable terminal equipped with a biaxial geomagnetic sensor, a user rotates the portable terminal, for example, 180 degrees to perform calibration processing, and during this operation, the portable terminal collects measurement data from the magnetic sensor, The offset was estimated based on the measurement data.

Regarding the calibration of such a magnetic sensor mounted on a portable terminal, there is a technique disclosed in Patent Document 1, for example. In this technology, the portable terminal is rotated by a predetermined angle, and the offset is estimated based on data measured by the magnetic sensor at each angle, so that calibration can be performed without depending on the rotation speed. .
JP 2004-12416 A

  However, even in the method described in Patent Document 1, the user must consciously rotate the portable device on which the magnetic sensor is mounted and perform the calibration process. Since the operation for processing is forced, it is still troublesome for the user. In particular, in the case of a three-axis geomagnetic sensor, three-axis data is required for calibration, which further complicates the user.

  On the other hand, in the case of a three-axis geomagnetic sensor, in order to perform an accurate calibration, it is preferable that data acquired by the geomagnetic sensor exist uniformly in the azimuth sphere, and the data is concentrated in a specific plane. In this case, there is a problem that calibration cannot be executed.

  The present invention has been made in view of the above points. Even when data obtained from a three-axis geomagnetic sensor is limited to a specific plane in a three-dimensional azimuth space, proper calibration is performed to correct the data. An azimuth data generation method for measuring an azimuth, an azimuth sensor unit, a storage medium, and a portable electronic device are provided.

  In order to solve the above-mentioned problem, the invention according to claim 1 inputs magnetic data output from a geomagnetic sensor that detects a magnetic field in the axial direction of three axes and measures magnetic field data based on the input data. A measurement step, a magnetic field data storage step for sequentially storing the measured magnetic field data, a determination step for determining whether or not the plurality of stored magnetic field data exist in the same plane in a three-dimensional orientation space; An arc calculation step for calculating center coordinates and a radius of an arc in which the magnetic field data exists based on the plurality of stored magnetic field data according to a predetermined algorithm when the determination step determines that the magnetic field data exists in the same plane A standard deviation calculating step for calculating a standard deviation of the magnetic field data using the magnetic field data and the center coordinates and radius of the arc; Whether or not the center coordinates of the arc are valid as a temporary offset value is determined based on the calculated standard deviation, and if it is determined to be valid, the center coordinates of the arc are determined as a temporary offset value. A temporary offset value determining step, and a step of correcting the magnetic field data measured after the temporary offset value is determined with the temporary offset value, and performing an operation for obtaining azimuth data based on the corrected magnetic field data The azimuth | direction data generation method which comprises these is proposed.

  According to a second aspect of the present invention, in the azimuth data calculation method according to the first aspect, the provisional offset value determination step determines that the diameter of the arc is effective if the arc diameter is equal to or greater than a certain value, and An azimuth data calculation method has been proposed in which center coordinates are determined as a temporary offset value.

According to a third aspect of the present invention, there is proposed an azimuth data calculation method characterized in that the standard deviation is obtained by using the mathematical formula 1 in the azimuth data calculation method according to the first aspect. In Equation 1, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

  The invention according to claim 4 is an algorithm different from the predetermined algorithm when it is determined that the direction data calculation method according to claim 1 does not exist in the same plane in the determination step. An offset value calculation step for calculating an offset value based on the plurality of stored magnetic field data, and the magnetic field data measured after the offset value is calculated are corrected with the offset value, and the corrected magnetic field And a step of calculating azimuth data based on the data.

  According to a fifth aspect of the present invention, in the azimuth data calculation method according to the first aspect, the magnetic field data measurement step measures a plurality of the magnetic field data while moving the geomagnetic sensor and changing its direction with respect to the geomagnetism. We have proposed a azimuth data calculation method characterized by:

  According to a sixth aspect of the present invention, in the azimuth data calculation method according to the first aspect, the magnetic field data measuring step is configured such that the geomagnetic sensor is parallel to the ground surface while being tilted within a predetermined range with respect to the ground surface. An azimuth data calculation method is proposed which measures a plurality of the magnetic field data based on data from the geomagnetic sensor for different azimuths while rotating in a plane.

The invention according to claim 7 is a geomagnetic sensor that detects the axial direction of three axes, a magnetic field data measurement unit that inputs data output from the geomagnetic sensor, and calculates magnetic field data based on the input data; A storage unit that sequentially stores the measured magnetic field data, a determination unit that determines whether or not the plurality of stored magnetic field data exist in the same plane in a three-dimensional orientation space, and the same plane in the determination unit An arc calculation unit that calculates a center coordinate and a radius of an arc in which the magnetic field data exists, based on the magnetic field data, and the magnetic field data and the center coordinates of the arc when determined to exist within And a standard deviation calculation unit that calculates a standard deviation of the magnetic field data using the radius, and whether the center coordinates of the arc are valid as a temporary offset value are calculated. Determined on the basis of the quasi-deviation, if it is judged to be valid, the temporary offset value determination unit for determining the arc center coordinates as the temporary offset value,
An azimuth data calculation unit that corrects the magnetic field data measured after the temporary offset value is determined with the temporary offset value and performs calculation for obtaining azimuth data based on the corrected magnetic field data. We have proposed an orientation sensor unit.

  According to an eighth aspect of the present invention, in the azimuth sensor unit according to the seventh aspect, the temporary offset value determining unit determines that the diameter of the circular arc is equal to or greater than a predetermined value, and determines that the center of the circular arc is effective. An azimuth sensor unit has been proposed in which coordinates are determined as temporary offset values.

The invention according to claim 9 proposes an orientation sensor unit characterized in that the standard deviation of the orientation sensor unit according to claim 7 is obtained using a mathematical expression of Formula 2. In Equation 2, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

  According to a tenth aspect of the present invention, in the azimuth sensor unit according to the seventh aspect, when the determination unit determines that the azimuth sensor unit does not exist in the same plane, the storage is performed using an algorithm different from the predetermined algorithm. An offset value calculation unit that calculates an offset value based on the plurality of magnetic field data, and the azimuth data calculation unit uses the offset value to calculate the magnetic field data measured after the offset value is calculated. An azimuth sensor unit is proposed that corrects and calculates azimuth data based on the corrected magnetic field data.

  The invention according to claim 11 is a computer-readable storage medium containing a group of instructions for causing a computer to execute an azimuth data calculation process based on data output from a geomagnetic sensor that detects magnetic fields in three axial directions. In the azimuth data calculation process, data output from the geomagnetic sensor is input, magnetic field data measuring step for measuring magnetic field data based on the input data, and magnetic field data for sequentially storing the measured magnetic field data A storage step, a determination step of determining whether or not the plurality of stored magnetic field data exist in the same plane in a three-dimensional orientation space, and a determination in the determination step that it is present in the same plane, Based on the plurality of stored magnetic field data, according to a predetermined algorithm, the inside of the arc in which the magnetic field data exists. An arc calculation step for calculating coordinates and a radius; a standard deviation calculation step for calculating a standard deviation of the magnetic field data using the magnetic field data and the center coordinates and radius of the arc; and A provisional offset value determining step for determining whether the value is valid based on the calculated standard deviation, and if it is determined to be valid, the center coordinates of the arc are determined as a temporary offset value; Correcting the magnetic field data measured after the provisional offset value is determined with the provisional offset value, and performing an operation for obtaining azimuth data based on the corrected magnetic field data. A storage medium is proposed.

The invention according to a twelfth aspect proposes a storage medium according to the eleventh aspect, wherein the standard deviation is obtained using a mathematical expression of Formula 3. In Equation 3, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

  According to a thirteenth aspect of the present invention, the storage medium according to the eleventh aspect is stored in an algorithm different from the predetermined algorithm when it is determined in the determining step that the storage medium does not exist in the same plane. An offset value calculating step for calculating an offset value based on the plurality of magnetic field data, and correcting the magnetic field data measured after the offset value is calculated with the offset value, and based on the corrected magnetic field data And a step of calculating azimuth data.

  The invention according to claim 14 proposes a portable electronic device comprising the direction sensor unit according to claim 7.

  According to a fifteenth aspect of the present invention, in the portable electronic device according to the fourteenth aspect, the magnetic field data measurement unit of the azimuth sensor unit is input from the geomagnetic sensor in response to a azimuth data request generated inside itself. A portable electronic device characterized in that magnetic field data is measured based on the recorded data is proposed.

According to the present invention, when it is determined that a plurality of magnetic field data sequentially measured exist in the same plane in the three-dimensional azimuth space, the center of the arc in which the plurality of magnetic field data exist is determined according to a predetermined algorithm. Since the coordinates are calculated as a temporary offset value, and the magnetic field data measured thereafter is corrected (calibrated) with the calculated temporary offset value, the triaxial geomagnetic sensor is calibrated in the calibration of the triaxial geomagnetic sensor. Calibration can be executed even when the output data from is concentrated on a specific plane.
Also, even if valid three-axis data cannot be obtained during calibration, the calibration process can be performed with the temporary offset value, so that the user does not have to move the portable electronic device with care to acquire the orientation data. Therefore, calibration can be executed without imposing an excessive burden on the user.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which the user rotates 360 degrees, for example, with a portable terminal equipped with a triaxial geomagnetic sensor in his hand. Conventionally, in such a case, since the posture of the mobile terminal itself is not changed, the calibration cannot be executed because the output from the triaxial geomagnetic sensor is concentrated on a specific plane. The present invention provides a method for performing calibration even in such a case.

FIG. 2 is a configuration diagram of an embodiment of a portable electronic device according to the present invention, and is an electrical diagram of a portable communication terminal (hereinafter referred to as a portable terminal) using a CDMA (Code Division Multiple Access) communication method. The configuration is shown as a block diagram.
In the following description, the same reference numerals are given to portions common to the respective drawings to be referred to.

  As shown in FIG. 2, the mobile terminal 1 according to the present embodiment includes antennas 101 and 106, an RF unit 102, a modem unit 103, a CDMA unit 104, an audio processing unit 105, a GPS receiving unit 107, Main control unit 108, ROM 109, RAM 110, notification unit 111, clock unit 112, main operation unit 113, SW 114, magnetic sensor chip (magnetic sensor unit) 300, electronic imaging unit 202, and display unit 203, a touch panel 204, and a sub operation unit 205.

  As shown in FIG. 2, the antenna 101 transmits and receives radio waves to and from a radio base station (not shown). The RF unit 102 performs processing related to signal transmission / reception. This RF unit 102 includes a local oscillator and the like, and converts a received signal into a received IF signal of an intermediate frequency (IF) by mixing a locally transmitted signal of a predetermined frequency with a received signal output from the antenna 101 during reception. And output to the modem 103. Further, the RF unit 102 mixes a local transmission signal having a predetermined frequency with a transmission IF signal having an intermediate frequency during transmission, thereby converting the transmission IF signal into a transmission signal having a transmission frequency and outputting the signal to the antenna 101.

  The modem 103 performs demodulation processing on the received signal and modulation processing on the transmitted signal. The modulation / demodulation unit 103 includes a local oscillator and the like, converts the received IF signal output from the RF unit 102 into a baseband signal having a predetermined frequency, converts the baseband signal into a digital signal, and outputs the digital signal to the CDMA unit 104. . Further, the modem unit 103 converts the digital baseband signal for transmission output from the CDMA unit 104 into an analog signal, converts it into a transmission IF signal having a predetermined frequency, and outputs the signal to the RF unit 102.

  The CDMA unit 104 performs encoding processing of a transmitted signal and decoding processing of a received signal. The CDMA unit 104 decodes the baseband signal output from the modem unit 103. The CDMA unit 104 encodes a transmission signal and outputs the encoded baseband signal to the modem unit 103.

  The voice processing unit 105 performs processing related to voice during a call. The voice processing unit 105 converts an analog voice signal output from a microphone (MIC) during a call into a digital signal and outputs the digital signal to the CDMA unit 104 as a transmission signal. Also, the voice processing unit 105 generates an analog drive signal for driving the speaker (SP) based on a signal indicating the voice data decoded by the CDMA unit 104 during a call, and sends the analog drive signal to the speaker (SP). Output. The microphone (MIC) generates an audio signal based on the audio input by the user and outputs the audio signal to the audio processing unit 105. The speaker (SP) emits the other party's voice based on the signal output from the voice processing unit 105.

  The GPS antenna 106 receives a radio wave transmitted from a GPS satellite (not shown) and outputs a reception signal based on this radio wave to the GPS receiving unit 107. The GPS receiver 107 demodulates the received signal, and acquires accurate time information of GPS satellites and information such as radio wave propagation time based on the received signal. The GPS receiving unit 107 calculates a distance to three or more GPS satellites based on the acquired information, and calculates a position (latitude, longitude, altitude, etc.) in a three-dimensional space based on the principle of triangulation.

  The main control unit 108 includes a CPU (Central Processing Unit) and the like, and controls each unit inside the mobile terminal 1. The main control unit 108 includes an RF unit 102, a modem unit 103, a CDMA unit 104, an audio processing unit 105, a GPS reception unit 107, an orientation sensor unit 201, a ROM 109, and a RAM 110 described below. Perform input / output. The ROM 109 stores various programs executed by the main control unit 108, initial characteristic values of the temperature sensor and the tilt sensor measured at the time of shipping inspection, and the like. The RAM 110 temporarily stores data processed by the main control unit 108.

  The notification unit 111 includes, for example, a speaker, a vibrator, a light emitting diode, or the like, and notifies the user of an incoming call or mail reception by sound, vibration, light, or the like. The clock unit 112 has a clocking function, and generates clocking information such as year, month, day, day of the week, and time. The main operation unit 113 includes an input key for character input operated by the user, a conversion key for conversion of kanji and numbers, a cursor key for cursor operation, a power on / off key, a call key, a redial key, and the like. And outputs a signal indicating the operation result of the user to the main control unit 108. The open / close switch (SW) 114 is a switch for detecting the opening start and the closing end in the case of a foldable portable terminal.

  The magnetic sensor chip (magnetic sensor unit) 300 includes magnetic sensors (1) to (3) that detect magnetism (magnetic field) in the axial directions of the X axis, the Y axis, and the Z axis that are orthogonal to each other, and the detection results of each sensor. The block (sensor control part) which processes is provided. Details will be described later with reference to FIG.

  The electronic imaging unit 202 includes an optical lens and an imaging device such as a CCD (Charge Coupled Device), converts an image of a subject formed on the imaging surface of the imaging device by the optical lens into an analog signal, and converts the analog signal to the analog signal. The signal is converted into a digital signal and output to the main control unit 108. The display unit 203 includes a liquid crystal display or the like, and displays images, characters, and the like based on display signals output from the main control unit 108. The touch panel 204 is incorporated on the surface of the liquid crystal display included in the display unit 203 and outputs a signal corresponding to the operation content by the user to the main control unit 108. The sub-operation unit 205 includes a push switch used for display switching.

Next, functional blocks for azimuth measurement will be described in detail with reference to FIG.
As shown in FIG. 3, the functional block for azimuth measurement includes a magnetic sensor chip (magnetic sensor unit) 300 and an azimuth data calculation unit 400. The azimuth data calculation unit 400 is shown in FIG. The main control unit 108 corresponds. The azimuth data calculation unit 400 includes a three-dimensional magnetic field measurement unit 302, a measurement data storage determination unit 303, a measurement data storage unit 304, a mode determination unit 305, a temporary offset calculation unit 306, and an offset calculation unit 307. , Offset validity determination means 308, azimuth measurement means 309, and offset calculation trigger means (not shown).

  The magnetic sensor unit 300 includes magnetic sensors (1) to (3) and sensor initialization means (1) to (3) (not shown) for initializing each magnetic sensor after the power is turned on. When the strong magnetic field is applied to the sensor initialization means (1) to (3), the direction of magnetization of the magnetic bodies of the magnetic sensors (1) to (3) is out of order. This is provided to reset (3) to the initial state.

  The three-dimensional magnetic field measuring means 302 measures X-axis, Y-axis, and Z-axis magnetic field data from input data input as a digital signal from the rising magnetic sensor unit 300 together with a trigger for measurement, and the measured third order The original magnetic field data is supplied to the measurement data storage discriminating means 303 and the azimuth measuring means 309. Note that the three-dimensional magnetic field measurement unit 302 starts the measurement operation of the three-dimensional magnetic field data at the timing of a measurement trigger from an application program that requires azimuth measurement described later.

  The measurement data storage discriminating unit 303 performs processing related to data storage such as determination as to whether or not the three-dimensional magnetic field data measured from the input data from the magnetic sensor should be stored in the measurement data storage unit 304 at the time of calibration. If the measurement data storage determining unit 303 determines that the measured three-dimensional magnetic field data should be stored in the measurement data storage unit 304, the measurement data storage determining unit 303 outputs the three-dimensional magnetic field data to the measurement data storage unit 304. The measurement data storage unit 304 receives the three-dimensional magnetic field data output from the measurement data storage determination unit 303, and stores the three-dimensional magnetic field data according to a predetermined storage method.

  The offset calculation trigger means (not shown) sends the measurement data storage means 304 to output the three-dimensional magnetic field data stored in the measurement data storage means 304 to the subsequent stage when the trigger generation condition for performing the offset calculation is satisfied. Instructed as a trigger for offset calculation. The mode determination unit 305 determines whether or not the three-dimensional magnetic field data stored in the measurement data storage unit 304 is on the same plane in the three-dimensional orientation space, and if the three-dimensional magnetic field data exists on the same plane. When it is determined, this three-dimensional magnetic field data is output to the temporary offset calculation means 306. When it is determined that the three-dimensional magnetic field data does not exist on the same plane, this three-dimensional magnetic field data is output to the offset calculation means 307.

  The temporary offset calculation unit 306 estimates a temporary offset value from the three-dimensional magnetic field data input from the mode determination unit 305 by a predetermined algorithm described later (details will be described later), and outputs it to the offset validity determination unit 308. The offset calculation unit 307 calculates an offset value based on the measured three-dimensional magnetic field data acquired at the time of calibration (details will be described later), and outputs the offset value to the offset validity determination unit 308. Further, the offset validity determination unit 308 determines the validity of the offset value calculated by the offset calculation unit 307 or the temporary offset value estimated by the temporary offset calculation unit 306 (details will be described later), and is determined to be valid. The offset value is output to the direction measuring means 309. The azimuth measuring unit 309 removes the offset using the offset value validated by the offset validity determining unit 308 and outputs the three-dimensional magnetic field data of the X, Y, and Z axes output from the three-dimensional magnetic field measuring unit 302. The direction measurement is performed based on (details will be described later).

Next, a specific processing operation will be described using the flowchart of FIG.
As shown in FIG. 4, when an application program that requires azimuth measurement (an application program that uses azimuth data for navigation software, games, etc.) or the like is started, a trigger is repeatedly generated at a timing when the application program requires azimuth data. This takes place (step S101).
As specific triggers, 1) a method of triggering at regular intervals, and 2) monitoring the output of another device (for example, the electronic video unit 202) provided in the mobile terminal, which is different from the magnetic sensor unit 300 Then, a method of triggering when the direction is estimated to be changed based on the output (for example, a timing when the image data captured by the electronic imaging unit 202 is slid (moved) by a predetermined amount) can be considered.

  Here, the method in which a trigger is applied by an application program has an advantage that unnecessary power can be reduced since the number of times of measurement is minimized. Further, in the above-described method 1), that is, the method of triggering at regular intervals, the data is measured regularly. Therefore, when the application program requests the azimuth measurement, the azimuth measurement request is issued. Since it is sufficient to output the three-dimensional magnetic field data measured immediately before, there is an advantage that a response in a short time is possible. In addition, in the method 2) described above, for example, it is a condition that another device different from the magnetic sensor unit 300 provided in the mobile terminal is operating. This has the advantage that wasteful power can be reduced, and that it can respond in a short time. Therefore, what method should be selected may be appropriately determined depending on the feature of the apparatus.

  When the measurement trigger is applied, the three-dimensional magnetic field measurement unit 302 measures the three-dimensional magnetic field data from the data input from the magnetic sensor, and outputs the three-dimensional magnetic field data to the measurement data storage determination unit 303 and the direction measurement unit 309. (Step S102). The measurement data storage discriminating unit 303 performs processing relating to the determination as to whether or not the three-dimensional magnetic field data should be stored in the measurement data storage unit 304 (step S103).

The determination method refers to the three-dimensional magnetic field data stored in the measurement data storage unit 304, and based on the determination method described later, the three-dimensional magnetic field data input from the three-dimensional magnetic field measurement unit 302 is used as the measurement data storage unit 304. It is determined whether or not to store, and if it is determined to store, the three-dimensional magnetic field data is stored in the measurement data storage unit 304 (step S103a).
Next, it is determined whether or not the number of three-dimensional magnetic field data stored in the measurement data storage unit 304 has reached a predetermined number (step S103b). If NO is determined in step S103b, the process returns to step S102, and the three-dimensional magnetic field data is measured again in step S102. If YES is determined in the step S103b, the process proceeds to a step S104 described later.

As a method for determining whether or not to store the three-dimensional magnetic field data in step S103, 1) a method for storing all data,
2) If no 3D magnetic field data is stored in the measurement data storage means 304, it is stored. If 3D magnetic field data already exists, the 3D data stored in the measurement data storage means 304 immediately before is stored. A method of storing only when the relationship of the following mathematical expression 4 is satisfied in comparison with the magnetic field data (the most recently stored three-dimensional magnetic field data stored in the measurement data storage means 304) (note that In the formula, (Hx0, Hy0, Hz0) is the three-dimensional magnetic field data measured this time, and (Hx1, Hy1, Hz1) is the three-dimensional magnetic field data stored in the measurement data storage means 304 immediately before. D is preferably about 0.05 Oe).
3) If there is no 3D magnetic field data stored in the measurement data storage means 304, it is stored. If 3D magnetic field data already exists, all the 3D data stored in the measurement data storage means 304 are stored. A method of storing only when each of the magnetic field data and the three-dimensional magnetic field data measured this time satisfies the relationship of the following mathematical formula 5 (in the mathematical formula of formula 5, (Hx0, Hy0, Hz0) is measured this time. (Hx ⁱ , Hy ⁱ , Hz) (i = 1,..., N) are the three-dimensional magnetic field data already stored in the measurement data storage means 304. In this case, d is also preferably about 0.05 Oe).
Can be considered.

In the method 1), a large amount of three-dimensional magnetic field data can be collected, and a large amount of data can be collected in the shortest time. Therefore, the frequency of calibration processing increases, and even if offset fluctuation occurs, the offset can be offset within a short period. There is an advantage that can be corrected. The method 2) has an advantage that the three-dimensional magnetic field data can be prevented from being concentrated on a part of the azimuth sphere. Here, the azimuth sphere is a space (the output of each axis component of the 3-axis magnetic sensor is plotted) when the 3-axis magnetic sensor is rotated in constant geomagnetism. This is a sphere formed by a locus when plotted in a space (also referred to as a three-dimensional azimuth space). The center of the sphere corresponds to the offset of the azimuth sensor, and the radius of the sphere corresponds to the strength of the geomagnetism.
The method 3) has the highest uniformity of the three-dimensional magnetic field data, but has a problem that it takes a long time to accumulate the three-dimensional magnetic field data. Therefore, in consideration of the above contents, which method should be selected may be appropriately determined depending on the feature of the apparatus.

  As described above, the measurement data storage unit 304 receives the three-dimensional magnetic field data from the measurement data storage determination unit 303 when it is determined that the data should be stored, and stores the three-dimensional magnetic field data according to a storage method described later. Then, the measurement data storage means 304 inquires of an offset calculation trigger means (not shown) whether or not the stored three-dimensional magnetic field data should be output to the subsequent stage (the offset calculation means 307 or the temporary offset calculation means 306). The offset calculation trigger means outputs the three-dimensional magnetic field data stored in the measurement data storage means 304 to the subsequent stage (offset calculation means 307 or provisional offset calculation means 306) when an offset calculation trigger generation condition described later is satisfied. The measurement data storage means 304 is instructed as an offset calculation trigger. The measurement data storage unit 304 outputs the stored three-dimensional magnetic field data to the offset calculation unit 307 when there is an instruction to output the three-dimensional magnetic field data to the offset calculation unit 307 from the mode determination unit 305 described later. When the mode determining unit 305 instructs to output the three-dimensional magnetic field data to the temporary offset calculating unit 306, the stored three-dimensional magnetic field data is output to the temporary offset calculating unit 306.

  Here, the storage method of the three-dimensional magnetic field data is as follows: 1) When the three-dimensional magnetic field data is stored in the order of acquisition, and when the offset calculation trigger means is triggered and the offset calculation processing is completed, all the three-dimensional magnetic field data is stored. Erasing and storing 3D magnetic field data from the beginning again 2) When 3D magnetic field data is stored in the order of acquisition, and a certain amount of 3D magnetic field data is collected, when acquiring new 3D magnetic field data 3) Method to delete the oldest 3D magnetic field data and always keep a certain amount of new 3D magnetic field data 3) Accumulate the 3D magnetic field data in the order of acquisition and trigger the offset calculation trigger means to perform offset calculation When processing is complete, deleting some 3D magnetic field data from the old 3D magnetic field data and starting to accumulate 3D magnetic field data 4) Method of accumulating 3D magnetic field data in order of values, and when a certain amount of 3D magnetic field data is accumulated, there is a method of replacing the 3D magnetic field data with the direction closest to the new 3D magnetic field data. .

  The method 1) has an advantage that the processing load is light, and the method 2) has an advantage that the frequency of the calibration process can be easily increased and the offset can be corrected in the shortest time. Further, in the method 3), the offset can be corrected in a shorter time than the method 1), but there is also a problem that the calculation load of the calibration process becomes large. However, as compared with the method 2), the calculation frequency of the offset becomes lower, and the calculation processing load can be reduced. Furthermore, the method 4) has an advantage that the three-dimensional magnetic field data density can be maintained uniformly compared with the method 2) when the magnitude of the offset variation is small, but the offset variation is larger than the radius of the azimuth sphere. In some cases, there is a risk that unnecessary three-dimensional magnetic field data may remain. Therefore, what method should be selected may be appropriately determined depending on the feature of the apparatus.

  The trigger conditions for the offset calculation are 1) a method of triggering when the three-dimensional magnetic field data stored in the measurement data storage means 304 reaches a certain amount in step S103b, and 2) in the measurement data storage means 304. A method of triggering when the stored 3D magnetic field data reaches a certain amount, or when the 3D magnetic field data reaches a certain amount and a certain amount of time has elapsed since the previous calibration process. 3) Measurement data storage There is a method of triggering at regular intervals when there are four or more three-dimensional magnetic field data stored in the means 304.

  In the method 1), since the number of three-dimensional magnetic field data is constant, the accuracy based on the number of three-dimensional magnetic field data is stable, and there is an advantage that the effectiveness can be easily judged. The method 2) has an advantage that the calibration operation can be performed in a shorter time than the method 1), and the offset fluctuation can be corrected in a shorter time. The method 3) has an advantage that it is possible to avoid a situation where the calibration operation is not entered indefinitely. Therefore, in consideration of the above contents, which method should be selected may be appropriately determined depending on the feature of the apparatus.

  Next, the mode determination unit 305 determines whether or not the three-dimensional magnetic field data stored in the measurement data storage unit 304 exists on the same plane in the three-dimensional azimuth space (step S104). When the mode determination unit 305 determines that the three-dimensional magnetic field data does not exist on the same plane, the stored three-dimensional magnetic field data is output to the offset calculation unit 307 (step S105), and the offset value is Calculated (step S106).

Here, when it is determined that the three-dimensional magnetic field data stored in the measurement data storage unit 304 does not exist on the same plane in the three-dimensional azimuth space, the offset calculation executed by the offset calculation unit 307 in step S106. The algorithm will be described.
Assuming that the measurement data (three-dimensional magnetic field data) is (x _i , y _i , z _i ) (i = 1,..., N), the offset is (X0, Y0, Z0), and the azimuth radius is R, The following relational expression holds.
(x _i −X 0) ² + (y _i −Y 0) ² + (z _i −Z 0) ² = R ² At this time, the least square error ε is defined as follows.

here,
a _i = x _i ² + y _i ² + z _i ²
b _i = -2x _i
c _i = -2y _i
d _i = −2z _i
When D = (X0 ² + Y0 ² + Z0 ² ) −R ² (1), ε is represented by the following equation.

  At this time, the condition for minimizing the least square error ε is as follows by differentiating ε by X0, Y0, Z0, D with X0, Y0, Z0, D as independent variables.

  Therefore, the following equation holds.

However,

It is. By solving the simultaneous equations, X0, Y0, Z0, and D, which are offset values that minimize the least square error ε, are obtained. Moreover, R which is an azimuth | direction sphere radius can also be calculated | required by (1) Formula.

  On the other hand, when the mode determination unit 305 determines in step S104 that the three-dimensional magnetic field data exists on the same plane, the stored three-dimensional magnetic field data is output to the temporary offset calculation unit 306 (step S107). The temporary offset calculation means 306 calculates a temporary offset value (step S108).

Here, the determination as to whether or not the 3D magnetic field data performed in step S104 is on the same plane in the 3D orientation space is performed by performing the fitting process on the assumption that the 3D magnetic field data is on the same plane. Executed. Now, the measurement data point (three-dimensional magnetic field data) is (X _i , Y _i , Z _i ) (i = 1,..., N), the plane is by + cz + 1 = 0, and b and c are expressed as follows: It is calculated | required by the least squares method using the numerical formula of. Here, ε0 is a least square error.

  Then, b and c are obtained by solving the simultaneous equations. Next, Equation 12 is calculated using the obtained b and c.

  When ε1 is 10% or less of the geomagnetic intensity, it is determined that the data points are substantially on the same plane. In this case, the plane on which the data point exists is assumed to be by + cz + 1 = 0.

Next, the offset value when the three-dimensional magnetic field data exists on the same plane is calculated by a temporary offset calculation algorithm described below. This temporary offset calculation algorithm is executed by the temporary offset calculation means 306 in step S108.
That is, when the three-dimensional magnetic field data exists on the same plane by + cz + 1 = 0, these data exist on a certain arc. Therefore, in the temporary offset calculation processing in step S108, the center coordinates (X0, Y0, Z0) of the arc, which are temporary offset values, and the radius R thereof are obtained from the following mathematical formulas 13, 14, and 15.

  The offset value obtained in step S106 and the temporary offset value obtained in step S108 are output to the offset validity determination means 308, and the validity is determined by different methods (step S109).

  First, for the offset obtained in step S106, the following values are calculated from the calculated offset value and azimuth sphere radius and the three-dimensional magnetic field data stored in the measurement data storage means 304.

However, Max (x _i ) represents the maximum value among measurement data (three-dimensional magnetic field data) x ₁ ,..., X _N , and Min (x _i ) represents measurement data (three-dimensional magnetic field data) x _1, ..., represent the minimum value of the _{x N.} Σ is a standard deviation. It is determined whether or not the following determination criterion is satisfied with respect to the above value, and when the determination criterion is satisfied, it is determined that the estimated offset value is valid.
σ <F
w _x > G
w _y > G
w _z > G
Here, F is preferably about 0.1, and G is preferably about 1.

Next, the effectiveness of the temporary offset value obtained in step S108 is determined by, for example, the following two methods.
1) If the diameter of the arc obtained when obtaining the temporary offset value is greater than or equal to a certain value, it is determined to be valid.
2) When the radius of the circular arc obtained when obtaining the temporary offset value is R, and the data stored at this time is Hx ⁱ , Hy ⁱ , Hz ^i, and σ obtained in Equation 20 is less than a certain value Is determined to be valid.
When it is determined that both of 1) and 2) are valid, it is determined that the temporary offset value obtained in step S108 is valid. Alternatively, when it is determined that either one of 1) or 2) is effective, the temporary offset value obtained in step S108 may be determined to be effective.

  When it is determined that the offset value is valid, the valid offset value is output to the azimuth measuring unit 309, and the offset value stored in the storage unit (not shown) in the azimuth measuring unit 309 is updated. (Step S110).

  Subsequently, when the offset stored in the azimuth measuring unit 309 is not a temporary offset value, the azimuth measuring unit 309 removes the offset from the measurement data (three-dimensional magnetic field data) input from the three-dimensional magnetic field measuring unit 302. (Three-dimensional magnetic field data is corrected with an offset value), and then the azimuth is calculated by one of the following methods (step S111).

1) For example, when it is assumed that the mobile terminal is horizontal, the azimuth is calculated based on the mathematical formula 21. Note that the inclination a may be obtained by providing an inclination sensor on the mobile terminal 1 and may be used in the mathematical formula 22 or an appropriate angle assumed when the user has the mobile terminal 1 is determined in advance. , And may be used in the mathematical expression of Equation 22.
2) For example, when it is assumed that the mobile terminal is inclined a (rad) with respect to the horizontal plane, the azimuth is calculated based on Equation 22.
Here, Hx, Hy, and Hz are the outputs of the magnetic sensor, and the azimuth indicates the azimuth of the Y axis of the magnetic sensor, and magnetic north is 0 degree.

  In the method 1), it is relatively easy for the user to level the mobile terminal, and the orientation accuracy is easily obtained. In addition, in the method 2), since the user normally has an angle with the mobile terminal, the user can obtain an approximately correct orientation, but on the other hand, it may be difficult to adjust the mobile terminal to a fixed angle. Therefore, there is a problem that accuracy cannot be expected so much.

  On the other hand, when the offset stored in the storage unit in the azimuth measuring unit 309 is a temporary offset value, the azimuth measuring unit 309 performs measurement input from the three-dimensional magnetic field measuring unit 302 after the offset value is calculated. The offset value (temporary offset value) is removed from the data (three-dimensional magnetic field data) (the three-dimensional magnetic field data is corrected with the temporary offset value), and then the azimuth is calculated by the following method (step S111). That is, the data obtained from the magnetic sensor is (Sx, Sy, Sz), the temporary offset values are (X0, Y0, Z0), and Hx1 and Hy1 are obtained by calculating the following equation (23). The direction is calculated by substituting Hx1 into Hx and Hy1 into Hy in the mathematical formula 21. The orientation obtained in this way is displayed on a display (not shown) of the mobile terminal (step S112).

  Therefore, according to the present embodiment, even when the three-dimensional magnetic field data obtained from the three-axis geomagnetic sensor is limited within a specific plane, it is possible to perform proper calibration and measure the correct orientation. For example, the calibration can be performed only by an operation that is most easily taken when the user looks at a map, that is, an operation that changes the direction while viewing the screen of the mobile terminal, and correct orientation information can be provided.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes a configuration and the like that do not depart from the gist of the present invention. Needless to say. For example, in the present embodiment, an example in which calculation of azimuth data is performed by a main control unit such as a portable terminal is shown, but the present invention is not limited thereto, and as a azimuth sensor unit having a magnetic sensor chip and a calculation function of azimuth data Also good.

It is the figure which showed the aspect by which this invention is implemented. It is a block diagram of the portable electronic device (mobile terminal) which concerns on this embodiment. It is a block diagram of the direction sensor unit which concerns on this embodiment. It is a processing flow regarding the azimuth | direction output which concerns on this embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Portable terminal, 101, 106 ... Antenna, 102 ... RF part, 103 ... Modulation / demodulation part, 104 ... CDMA part, 105 ... Voice processing part, 107 ... GPS reception , 108... Main control unit, 109... ROM, 110... RAM, 111. 202: Electronic imaging unit, 203: Display unit, 204: Touch panel, 205: Sub-operation unit, 302: Three-dimensional magnetic field measuring means, 303: Measurement data storage determining means, 304 ... Measurement data storage means, 305 ... Mode judgment means, 306 ... Temporary offset calculation means, 307 ... Offset calculation means, 308 ... Offset validity judgment means, 309 ... Direction measurement means , 400 ・And direction data calculation unit

Claims (15)

A magnetic field data measurement step of inputting data output from a geomagnetic sensor that detects magnetic fields in the axial direction of three axes, and measuring magnetic field data based on the input data;
A magnetic field data storage step for sequentially storing the measured magnetic field data;
A discriminating step for discriminating whether or not the plurality of stored magnetic field data exist in the same plane in the three-dimensional orientation space;
An arc calculation step for calculating center coordinates and a radius of an arc in which the magnetic field data exists based on the plurality of stored magnetic field data according to a predetermined algorithm when the determination step determines that the magnetic field data exists in the same plane When,
A standard deviation calculating step of calculating a standard deviation of the magnetic field data using the magnetic field data and a center coordinate and a radius of the arc;
Whether or not the center coordinates of the arc are valid as a temporary offset value is determined based on the calculated standard deviation, and if it is determined to be valid, the center coordinates of the arc are determined as a temporary offset value. A temporary offset value determination step to be performed;
Correcting the magnetic field data measured after the provisional offset value is determined with the provisional offset value, and performing an operation for obtaining azimuth data based on the corrected magnetic field data;
A direction data generation method comprising:   2. The azimuth according to claim 1, wherein the temporary offset value determining step determines that the diameter of the circular arc is valid if the diameter is equal to or larger than a predetermined value, and determines the center coordinates of the circular arc as a temporary offset value. Data generation method. The azimuth data generation method according to claim 1, wherein the standard deviation is obtained by using a mathematical expression of Formula 1.
In Equation 1, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

An offset value calculating step of calculating an offset value based on the plurality of stored magnetic field data using an algorithm different from the predetermined algorithm when it is determined in the determining step that they do not exist in the same plane; ,
Correcting the magnetic field data measured after the offset value is calculated with the offset value, and calculating azimuth data based on the corrected magnetic field data;
The direction data generation method according to claim 1, further comprising:   2. The direction data generation method according to claim 1, wherein the magnetic field data measurement step measures a plurality of the magnetic field data while moving the geomagnetic sensor to change its direction with respect to the geomagnetism.   The magnetic field data measurement step is based on data from the geomagnetic sensor for different orientations while the geomagnetic sensor is rotated in a plane parallel to the ground surface while being tilted within a predetermined range with respect to the ground surface. The direction data generation method according to claim 1, wherein a plurality of the magnetic field data are measured. A geomagnetic sensor for detecting the axial direction of three axes;
A magnetic field data measurement unit that inputs data output from the geomagnetic sensor and calculates magnetic field data based on the input data;
A storage unit for sequentially storing the measured magnetic field data;
A discriminator for discriminating whether or not the plurality of stored magnetic field data exist in the same plane in the three-dimensional orientation space;
An arc calculation unit that calculates the center coordinates and radius of an arc in which the magnetic field data exists, based on the magnetic field data, when the determination unit determines that the magnetic field data exists in the same plane;
A standard deviation calculating unit that calculates the standard deviation of the magnetic field data using the magnetic field data and the center coordinates and radius of the arc;
Whether or not the center coordinates of the arc are valid as a temporary offset value is determined based on the calculated standard deviation, and if it is determined to be valid, the center coordinates of the arc are determined as a temporary offset value. A provisional offset value determination unit to
An azimuth data calculation unit that corrects the magnetic field data measured after the provisional offset value is determined with the temporary offset value and performs calculation for obtaining azimuth data based on the corrected magnetic field data;
An azimuth sensor unit comprising:   The azimuth according to claim 7, wherein the temporary offset value determination unit determines that the diameter of the arc is valid if the diameter is equal to or greater than a predetermined value, and determines the center coordinates of the arc as a temporary offset value. Sensor unit. The azimuth sensor unit according to claim 7, wherein the standard deviation is obtained by using a mathematical expression of Formula 2.
In Equation 2, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

An offset value calculation unit that calculates an offset value based on the plurality of stored magnetic field data using an algorithm different from the predetermined algorithm when the determination unit determines that they do not exist in the same plane. In addition,
The azimuth data calculator corrects the magnetic field data measured after the offset value is calculated with the offset value, and calculates the azimuth data based on the corrected magnetic field data. The direction sensor unit according to 7. A computer-readable storage medium having a group of instructions for causing a computer to execute an azimuth data calculation process based on data output from a geomagnetic sensor that detects a magnetic field in three axial directions. The azimuth data calculation process includes:
A magnetic field data measurement step of inputting data output from the geomagnetic sensor and measuring magnetic field data based on the input data;
A magnetic field data storage step for sequentially storing the measured magnetic field data;
A discriminating step for discriminating whether or not the plurality of stored magnetic field data exist in the same plane in the three-dimensional orientation space;
An arc calculation step for calculating center coordinates and a radius of an arc in which the magnetic field data exists based on the plurality of stored magnetic field data according to a predetermined algorithm when the determination step determines that the magnetic field data exists in the same plane When,
A standard deviation calculating step of calculating a standard deviation of the magnetic field data using the magnetic field data and a center coordinate and a radius of the arc;
Whether or not the center coordinates of the arc are valid as a temporary offset value is determined based on the calculated standard deviation, and if it is determined to be valid, the center coordinates of the arc are determined as a temporary offset value. A temporary offset value determination step to be performed;
Correcting the magnetic field data measured after the provisional offset value is determined with the provisional offset value, and performing an operation for obtaining azimuth data based on the corrected magnetic field data;
A storage medium comprising: The storage medium according to claim 11, wherein the standard deviation is obtained by using a mathematical expression of Formula 3.
In Equation 3, Hx ⁱ , Hy ⁱ , and Hz ⁱ are the three-axis components of the stored magnetic field data, X0, Y0, and Z0 are the center coordinates of the arc, R is the radius of the arc, and N is the storage Represents the number of magnetic field data obtained.

An offset value calculating step of calculating an offset value based on the plurality of stored magnetic field data using an algorithm different from the predetermined algorithm when it is determined in the determining step that they do not exist in the same plane; ,
Correcting the magnetic field data measured after the offset value is calculated with the offset value, and calculating azimuth data based on the corrected magnetic field data;
The storage medium according to claim 11, further comprising:   A portable electronic device comprising the orientation sensor unit according to claim 7.   15. The magnetic field data measurement unit of the orientation sensor unit measures magnetic field data based on data input from the geomagnetic sensor in response to a request for orientation data generated inside the device. The portable electronic device as described in.

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