JP2009156660A - Portable terminal, program and method for determining traveling direction of pedestrian by using acceleration sensor and geomagnetic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a portable terminal, a program and a method for accurately determining the traveling direction of a pedestrian by using only a geomagnetic sensor mounted to the portable terminal even if the pedestrian walks while he/she carries the portable terminal. <P>SOLUTION: A travel direction determining means of the portable terminal includes: a reference vector deriving means for deriving a gravity vector in the gravity direction from acceleration data, and selecting a geomagnetic vector corresponding to the gravity vector; a coordinate system conversion matrix calculating means for calculating a coordinate system conversion matrix as a combination of rotation matrices along x, y and z axes so as to convert the gravity vector and the geomagnetic vector of a sensor coordinate system into a world coordinate system; a coordinate system converting means for converting the gravity vector and the geomagnetic vector into the world coordinate system by using the coordinate system conversion matrix; and a direction angle calculating means for calculating an angle between an axis for indicating the north orientation and an approximation line for indicating a positive projection of a trajectory of an acceleration vector group in the world coordinate system to the ground as a direction angle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a portable terminal, a program, and a method for determining a traveling direction of a pedestrian using an acceleration sensor and a geomagnetic sensor. In particular, the present invention relates to an autonomous navigation technique for deriving a traveling direction and a current position in real time.

  Conventionally, there is an autonomous navigation technique that derives a traveling direction and a current position in real time using an acceleration sensor and a direction sensor. Autonomous navigation technology is combined with GPS (Global Positioning System) technology and is mainly used for a car navigation system. The car navigation system displays, on a display, an accurate traveling direction and current position, and a travel route guide to a destination for a driver of a car.

  The car navigation system corrects the current position information measured by the GPS by an autonomous navigation technique such as a vehicle speed pulse or a gyro. Further, the road map information is read out as necessary, and the traveling direction and the current position are corrected so that the current travel route coincides with the road (refer to map matching technology based on a projection method, for example, Patent Document 1). As a result, it is possible to prevent the current position from being a position not on the road due to a sensor error.

  On the other hand, there is a system in which such navigation technology is applied to a portable terminal possessed by a pedestrian. Specifically, a cumulative current position from the starting point is derived using the detected “number of steps” of the pedestrian and the “step length” of the pedestrian (see, for example, Patent Document 2). When the autonomous navigation technology is applied to a pedestrian, acceleration components other than horizontal movement are also detected. Thus, the measured distance is derived from the number of steps and the step length, rather than simply integrating the output of the acceleration sensor.

The “number of steps” is detected by taking the acceleration for each axis detected by the acceleration sensor in the mobile terminal as the square root of the sum of squares (√ (x ² + y ² + z ² )) and taking the peak-to-peak as one step (for example, (See Patent Document 3). The “step length” is preset by the user or estimated from the height of the user. Alternatively, according to another technique, there is a technique of calibrating the stride by causing a pedestrian to walk a specified distance (see, for example, Non-Patent Document 1).

  The “traveling direction” is detected by the “direction sensor”. As the direction sensor, a geomagnetic sensor is generally used. There is also a technique for three-dimensionally displaying the orientation and direction of a terminal detected using a geomagnetic sensor on a display (see, for example, Patent Document 4). In addition, when there are a plurality of roads through an intersection in the traveling direction, there is a technique in which the intersection is the current position (see, for example, Patent Document 5).

  A technology to determine the current position using autonomous navigation technology, in order to prevent the influence of the cumulative error of sensor data, when the right turn or left turn at the intersection is detected, the intersection is the starting point for specifying the current position (See, for example, Patent Document 6). That is, every time a turn is detected, the cumulative error of the sensor data is reset, and the previous cumulative error does not affect the subsequent specification of the current position.

JP-A-5-061408 Japanese Patent Laid-Open No. 9-089584 Japanese Patent Laying-Open No. 2005-038018 JP 2004-046006 A JP-A-3-099399 JP 63-011813 A "Nike + iPod User's Guide", page 27, "online", [searched August 31, 2007], Internet <URL: http://manuals.info.apple.com/en/nikeipod_users_guide.pdf>

  According to the technique described in Patent Literature 4, it is possible to derive the azimuth in a stationary state using an acceleration sensor and a geomagnetic sensor. In the stationary state, the acceleration vector detected by the acceleration sensor represents only gravity. Therefore, the direction can be derived from the world coordinate system derived using the gravity vector and the geomagnetic vector.

  However, when the azimuth is derived by a portable terminal carried by a pedestrian, the waveform detected by the sensor is disturbed due to the handheld state, and the correct azimuth cannot be derived. In particular, the acceleration vector generated during walking is a combination of motion acceleration, centrifugal force due to arm swing motion, and the like in addition to gravity. Therefore, since the direction of gravity cannot be determined, the world coordinate system cannot be derived, and eventually the azimuth cannot be derived. Moreover, it is difficult to use a gyro sensor mounted on a car navigation system for a portable terminal held by a pedestrian due to size and cost constraints.

  Therefore, the present invention uses the acceleration sensor and the geomagnetic sensor mounted on the mobile terminal as accurately as possible even when the pedestrian is walking with the mobile terminal handheld. It is an object of the present invention to provide a portable terminal, a program, and a method that are determined.

According to the present invention, the acceleration sensor that outputs the triaxial acceleration data, the geomagnetic sensor that outputs the triaxial geomagnetic data, and the traveling direction determination means that determines the traveling direction of the pedestrian from the acceleration data and the geomagnetic data. A portable terminal possessed by a pedestrian,
The direction of travel determination means is
A reference vector deriving means for deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
A coordinate system conversion matrix calculating means for calculating a coordinate system conversion matrix combining a rotation matrix for each of the x axis, the y axis, and the z axis in order to convert the gravity vector and the geomagnetic vector of the sensor coordinate system into the world coordinate system;
Coordinate system conversion means for converting a plurality of acceleration vectors and geomagnetic vectors into a world coordinate system using a coordinate system conversion matrix;
A direction angle calculation means for calculating an angle formed by an approximate straight line representing an orthogonal projection of the locus of acceleration vector groups mapped in the world coordinate system on the ground surface and an axis representing the north direction as a direction angle; Features.

According to another embodiment of the portable terminal of the present invention, the coordinate system transformation matrix calculation means is
Calculating a first transformation matrix component for rotating the gravity vector vertically downward in the world coordinate system;
Next, a second transformation matrix component for rotating the geomagnetic vector in the north direction in the world coordinate system is calculated,
It is also preferable to synthesize the first transformation matrix component and the second transformation matrix component to calculate a coordinate system transformation matrix for transforming the sensor coordinate system to the world coordinate system.

According to another embodiment of the mobile terminal of the present invention,
The first transformation matrix component is a rotation matrix Ax that rotates the yz component of the gravity vector in the negative z-axis direction, and a rotation matrix Ay that rotates the xz component of the gravity vector in the negative z-axis direction. Based on
It is also preferable that the second transformation matrix component is calculated as a rotation matrix Az that rotates the xy component of the geomagnetic vector to the positive direction of the x axis.

According to another embodiment of the mobile terminal of the present invention,
Gait timing determination means for classifying the acceleration data input from the acceleration sensor for each number of steps or for each time unit based on the number of steps, and outputting to the traveling direction determination means;
It is also preferable to further include a direction change determination unit that determines whether or not the direction change has been made for each step number or the traveling direction for each time unit based on the step number output from the traveling direction determination unit.

According to another embodiment of the mobile terminal of the present invention,
It further has a forward determining means for determining the direction of walking of the pedestrian, that is, the front of the acceleration surface,
Preferably, the forward determining means determines the larger one of the continuous peak points of the composite acceleration in the acceleration data string output from the acceleration sensor as the front of the acceleration surface, and notifies the direction change determining means to that effect.

  According to another embodiment of the portable terminal of the present invention, the acceleration data and the geomagnetic data input to the reference vector deriving means are memorized in a predetermined time range, and a predetermined ratio of data is removed from the maximum value and the minimum value. It is also preferable to further have a filter means.

  According to another embodiment of the portable terminal of the present invention, the direction angle θ output from the direction angle calculation means is memorized for the direction angle θ in a predetermined time range, and the change before and after the direction angle θ is a predetermined angle threshold value. It is also preferable to further have a correction means for removing the directional angle θ as described above.

According to the present invention, an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data, and a computer mounted on a portable terminal carried by a pedestrian, the acceleration data And a program for a mobile terminal that functions as a traveling direction determining means for determining a traveling direction of a pedestrian from geomagnetic data,
The direction of travel determination means is
A reference vector deriving means for deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
A coordinate system conversion matrix calculating means for calculating a coordinate system conversion matrix combining a rotation matrix for each of the x axis, the y axis, and the z axis in order to convert the gravity vector and the geomagnetic vector of the sensor coordinate system into the world coordinate system;
Coordinate system conversion means for converting a plurality of acceleration vectors and geomagnetic vectors into a world coordinate system using a coordinate system conversion matrix;
Causes the computer to function as a direction angle calculation means for calculating an angle formed by an approximate straight line representing an orthogonal projection of the locus of acceleration vector groups mapped in the world coordinate system to the ground surface and an axis representing the north direction as a direction angle It is characterized by that.

According to the present invention, a mobile terminal possessed by an pedestrian having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data walks from acceleration data and geomagnetic data. A method of determining the direction of travel of a person,
Deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
A second step of calculating a coordinate system transformation matrix that combines rotation matrices for the x-axis, y-axis, and z-axis to transform the gravity vector and geomagnetic vector of the sensor coordinate system into the world coordinate system;
A third step of converting a plurality of acceleration vectors and geomagnetic vectors into a world coordinate system using a coordinate system conversion matrix;
And a fourth step of calculating an angle formed by an approximate straight line representing an orthogonal projection of the trajectory of the acceleration vector group mapped in the world coordinate system onto the ground surface and an axis representing the north direction as a direction angle. Features.

  According to the portable terminal, the program, and the method of the present invention, the direction angle between the locus of the acceleration data group (approximate straight line) and the north direction can be calculated by converting the sensor coordinate system to the world coordinate system. Even when a pedestrian is walking with a portable terminal handheld, the traveling direction of the pedestrian can be determined as accurately as possible using the acceleration sensor and the geomagnetic sensor mounted on the portable terminal. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram illustrating a walking mode of a pedestrian, an acceleration variation direction, and a geomagnetic variation direction.

  According to FIG. 1, a pedestrian is walking while holding a portable terminal and shaking his / her hand back and forth. If such a general walking mode is seen from the lateral direction, the position of the mobile terminal fluctuates back and forth in a pendulum shape while drawing an arc. Further, when viewed from the traveling direction, the position of the mobile terminal fluctuates up and down.

  The shoulder portion of the arm holding the mobile terminal serves as a rotation axis of an arc drawn by the position change of the mobile terminal. This curve variation is detected by an acceleration sensor or a geomagnetic sensor mounted on the portable terminal. That is, a plane (fan shape) composed of the rotation axis and the arc is represented as an acceleration surface (a surface formed by an acceleration vector group). As long as the mobile terminal is shaken by hand, this acceleration plane is parallel to the traveling direction.

Further, by obtaining the square root of the sum of squares (√ (x ² + y ² + z ² )) from the acceleration data output from the acceleration sensor, a combined acceleration can be obtained. According to FIG. 1, the position A, the position B, and the position C are represented as the position of the mobile terminal held by the pedestrian. The position B is when the hand of the pedestrian is directly below (the lowest point), and the combined acceleration of the handheld portable terminal becomes a maximum (maximum). Conversely, position A and position C are when the pedestrian's hand is at the highest position (top point), and the resultant acceleration is minimal (minimum). Therefore, the position of the mobile terminal when the combined acceleration becomes maximum represents the direction of gravity. Thus, the acceleration plane based on the arm swing direction and the gravity direction can be derived from the acceleration data.

  Furthermore, geomagnetism has arrived for pedestrians and mobile terminals. As long as the pedestrian holds the terminal in a constant posture and travels straight in one direction, the arrival direction in the geomagnetic sensor coordinate system is the same. However, in order for a pedestrian to swing his / her portable terminal back and forth, the direction of arrival of geomagnetism varies in a curved manner according to his arm swing. This curve variation is detected by a geomagnetic sensor mounted on the portable terminal. That is, the surface formed by the axis and the curve is represented as a geomagnetic surface (a surface formed by a geomagnetic vector group).

  FIG. 2 is an image diagram converted from the sensor coordinate system to the world coordinate system.

  According to FIG. 2, the sensor coordinate system is represented in the upper stage, and the subsequent world coordinate system is represented by the coordinate system conversion. The “sensor coordinate system” is a plot of triaxial acceleration data (x, y, z) obtained from the acceleration sensor and triaxial geomagnetic data (x, y, z) obtained from the geomagnetic sensor. An orthogonal coordinate system fixed to the mobile terminal. Geomagnetic data can be detected on the side opposite to the direction of arrival of geomagnetism. In addition, the geomagnetism and acceleration when the mobile terminal is at position A, position B, and position C shown in FIG. 1 are also shown. The geomagnetic surface and the acceleration surface can be detected by connecting the geomagnetism and acceleration plots at positions A, B, and C according to the arm swinging motion of a pedestrian holding the mobile terminal.

  The “world coordinate system” refers to an orthogonal coordinate system in which the direction indicating gravity and the direction indicating north are fixed to a specific direction (positive or negative) of a specific axis (x axis, y axis or z axis). According to FIG. 2, an orthogonal coordinate system in which the negative direction of the z axis is fixed in the direction of gravity and the positive direction of the x axis is fixed in the north direction is defined as a world coordinate system. “Coordinate system conversion” refers to converting (rotating and moving) certain vector data having three-axis values in the sensor coordinate system into vector data having three-axis values in the world coordinate system.

  According to FIG. 2, an approximate straight line (traveling direction) representing an orthogonal projection of the trajectory of the acceleration vector group on the ground surface is represented around the gravity vector in the world coordinate system. The x axis in the world coordinate system represents the north direction. Therefore, the direction angle in the traveling direction of the pedestrian holding the mobile terminal is represented by an angle θ between the pedestrian and the approximate straight line representing the locus of the acceleration vector group as seen from the x-axis.

  FIG. 3 is a flowchart of the coordinate system conversion in the present invention.

According to FIG. 3, four basic steps are represented.
(S1) [Derivation of reference vector]
A gravity vector in the direction of gravity is derived from the acceleration data, and a geomagnetic vector corresponding to the gravity vector is selected.
(S2) [Calculation of coordinate system conversion matrix]
In order to convert the gravity vector and the geomagnetic vector of the sensor coordinate system into the world coordinate system, a coordinate system conversion matrix A that combines rotation matrices for the x-axis, y-axis, and z-axis is calculated.
(S3) [Coordinate system conversion]
Using the coordinate system conversion matrix A, the acceleration vector and the geomagnetic vector in the unit section are converted into the world coordinate system.
(S4) [Calculation of direction angle]
The angle formed by the approximate straight line representing the orthogonal projection of the locus of the acceleration vector group mapped in the world coordinate system onto the ground surface and the x axis representing the north direction is calculated as the direction angle θ.

  Each step will be described in detail.

(S1) [Derivation of reference vector]
A plurality of acceleration observation data and geomagnetism observation data in a unit section are input from the acceleration sensor and the geomagnetic sensor. For example, it is expressed as follows. At least three or more combinations of these data are input for the unit section.
Acceleration observation data: (x _a , y _a , z _a )
Geomagnetic observation data: (x _m , y _m , z _m )

  The portable terminal is hand-held by a pedestrian and exposed to an arm swinging motion. At this time, an acceleration plane composed of a plurality of acceleration vectors is detected in parallel with the traveling direction. In addition to gravity, acceleration of arm swing motion, acceleration of arm motion, centrifugal force, and the like are combined, and the direction indicated by the vector does not necessarily match the direction of gravity (vertically downward). However, the combined acceleration detected at the moment when the arm of the pedestrian reaches the lowest point is approximately equal to the sum of gravity and the centrifugal force in the same direction as the gravity. Therefore, the acceleration vector at the lowest point among the plurality of acceleration vectors can be regarded as a gravity vector except for its magnitude. The lowest point is equal to the walking timing. Furthermore, a geomagnetic vector corresponding to the gravity vector can be selected from among a plurality of geomagnetic vectors. Using the derived gravity vector and geomagnetic vector as a reference vector, the sensor coordinate system is converted to the world coordinate system by the following S2 and S3.

(S2) [Calculation of coordinate system conversion matrix]
(S21) A first transformation matrix component for rotating the gravity vector in the negative z-axis direction, a rotation matrix AyAx, is calculated.
(S211) A rotation matrix Ax for rotating the yz component of the gravity vector to the negative direction of the z axis is calculated.

  FIG. 4 is an image diagram showing the coordinate system conversion in S211.

(S211-1) A yz component vector excluding the x component is extracted from the gravity vector. This vector is an orthogonal projection of the gravity vector onto the yz plane.
V ₁₁ = (0, y _a , z _a )
(S211-2) Rotate around the x axis until the yz component vector matches the negative direction of the z axis.
V ₁₂ = (0, 0, − | V ₁₁ |)
_(S211-3) for calculating the angle formed between the _{V 11} and _{V 12.}
Angle formed (rad) = arccos ((V ₁₁ · V ₁₂ ) / (| V ₁₁ | · | V ₁₂ |))
(S211-4) The rotation in the rotation matrix turns clockwise in the positive direction of the rotation axis. Therefore, the calculated angle is converted into a clockwise rotation angle.
y ≦ 0: rotation angle βx (rad) = angle formed y> 0: rotation angle βx (rad) = 2π−angle formed

(S211-5) A rotation matrix Ax is calculated.

(S211-6) The calculated x-axis rotation is applied to the observation data.

(S212) Next, a rotation matrix Ay for rotating the xz component of the gravity vector to the negative direction of the z-axis is calculated.

  FIG. 5 is an image diagram showing the coordinate system conversion in S212.

(S212-1) An xz component vector excluding the y component is extracted from the vector after applying rotation around the x-axis in S212 (orthographic projection of the vector onto the xz plane).
V ₂₁ = (x _a ′, 0, z _a ′)
(S212-2) Rotate around the y-axis until the xz component vector coincides with the negative direction of the z-axis.
V ₂₂ = (0, 0, − | V ₂₁ |)
_(S212-3) to calculate the angle between _{V 21} and _{V 22.}
Angle formed (rad) = arccos ((V ₂₁ · V ₂₂ ) / (| V ₂₁ | · | V ₂₂ |))
(S212-4) The rotation in the rotation matrix is clockwise in the positive direction of the rotation axis. Therefore, the calculated angle is converted into a clockwise rotation angle.
x ≧ 0: rotation angle βy (rad) = angle formed x <0: rotation angle βy (rad) = 2π−angle formed

(S212-5) A rotation matrix Ay is calculated.

(S22) Next, a second transformation matrix component, a rotation matrix Az, for rotating the geomagnetic vector calculated in S21 in the positive x-axis direction (north direction in the positive x-axis direction) is calculated. Specifically, the rotation matrix Az is a rotation matrix that rotates the xy component of the geomagnetic vector about the z axis to the positive direction of the x axis.

  FIG. 6 is an image diagram showing the coordinate system conversion in S22.

(S22-1) The x-axis rotation calculated in S211 is applied to the geomagnetic observation data.

(S22-2) Next, the y-axis rotation calculated in S212 is applied to the geomagnetic vector calculated in S601.

(S22-3) Next, an xy component (ground surface component) vector excluding the z component (vertical component) is extracted from the geomagnetic vector calculated in S602 (orthographic projection of the vector onto the xy plane).
_{V 31 = (x m ''} , y m '', 0)
(S22-4) Then, a rotation destination vector is derived so as to coincide with the positive direction of the x-axis.
V ₃₂ = (| V ₃₁ |, 0, 0)
_(S22-5) to calculate the angle of the _{V 31} and _{V 32.}
Angle formed (rad) = arccos ((V ₃₁ · V ₃₂ ) / (| V ₃₁ | · | V ₃₂ |))
(S22-6) The rotation in the rotation matrix is clockwise in the positive direction of the rotation axis. Therefore, the calculated angle is converted into a clockwise rotation angle.
y ≧ 0: rotation angle βz (rad) = angle formed y <0: rotation angle βz (rad) = 2π−angle formed

(S22-7) A rotation matrix Az is calculated.

(S23) A coordinate system conversion matrix A for converting the sensor coordinate system to the world coordinate system is calculated based on the rotation matrix AyAx and the rotation matrix Az.
Rotation matrix A = AzAyAx

(S3) [Coordinate system conversion]
Each acceleration observation data (x _a , y _a , z _a ) in the unit section is multiplied by the coordinate system conversion matrix described above.
Acceleration observation data in the sensor coordinate system S = (x _a , y _a , z _a )
Acceleration S _g of the world coordinate system _{= (xg a, yg a,} zg a)
S _g = A · S

(S4) [Calculation of direction angle]
The angle formed by the approximate straight line calculated from the orthogonal projection of the trajectory of the acceleration vector group mapped in the world coordinate system onto the ground surface and the x axis representing the north direction is calculated as the direction angle.

  Here, specific numerical values are substituted into the flowchart of FIG. 3 described above.

(S1) [Derivation of reference vector]
Assume that the following observation data is selected as a reference vector.

(S2) [Calculation of coordinate system conversion matrix]
(S211) A rotation matrix Ax is calculated.

(S212) A rotation matrix Ay is calculated.

(S22) A rotation matrix Az is calculated.

(S23) A coordinate system rotation matrix A is calculated.

(S3) [Coordinate system conversion]
By converting arbitrary acceleration observation data in the sensor coordinate system with the coordinate system conversion matrix A, the following ground surface component (xy component) in the world coordinate system is calculated.

この近似直線は、ｙ＝ａｘとすると、ａは、最小二乗法により、以下のように求められる。
ａ＝０．５８ (S4) [Calculation of direction angle]
An approximate straight line representing the locus of the acceleration vector group is derived from the above-described ground surface component. FIG. 7 is a graph showing the following approximate straight line.

Assuming that y = ax, this approximate straight line is obtained as follows by the least square method.
a = 0.58

In general, the angle θ formed by the straight line y = ax with respect to the x-axis is
From tan θ = a, θ = arctan (a)
It is expressed.
Here, in order to obtain a direction angle from north (positive direction of the x-axis) with a clockwise angle as a positive angle and a counterclockwise direction as a negative angle, θ is positive when the slope a of the approximate line is negative. Like,
θ = arctan (−a)
And The direction angle is −90 ° to + 90 ° (+ 90 ° and −90 ° are the same as the direction angle).
θ = arctan (−0.58) = − 30 (deg)

The direction angle θ is an angle formed by the approximate straight line indicating the traveling direction with respect to the north-south direction. The traveling direction is an undirected straight line, and there is no distinction between front and rear. At this time, in order to derive a clockwise azimuth angle (0 to 360 °) with 0 degrees north, it is necessary to determine the front (or rear) of the approximate line (this determination will be described later). 8 forward determination unit 107).
The azimuth angle can be determined as follows depending on which “quadrant” is in front of the approximate straight line indicating the traveling direction on the ground surface (xy plane) of the world coordinate system.
(A) When the front of the approximate straight line is in the first quadrant, the azimuth angle = θ + 360.
(B) When the front of the approximate line is in the second or third quadrant, the azimuth angle = θ + 180.
(C) When the front of the approximate straight line is in the fourth quadrant, the azimuth angle = θ.

  The front of the approximate straight line can be specified as the larger one of the continuous peak points of the combined acceleration. Although the magnitude of acceleration generated by walking is symmetric on the left and right sides of the body, the mobile terminal is detected asymmetrically because it is held with one hand (a position biased to the left or right from the center of the body). For example, when a pedestrian is holding a mobile terminal with his right hand, the magnitude of acceleration when kicking the ground with the right foot and the magnitude of acceleration when kicking the ground with the left foot are detected differently. . In this case, the acceleration when kicking the ground with the right foot is larger than the acceleration when kicking the ground with the left foot. Usually, in human walking, a hand and a foot are interlocked. For example, when the right hand is in front, the right foot kicks out the ground. Therefore, if it can be determined that the ground has been kicked with the foot on the side holding the mobile terminal, it can be determined that the mobile terminal at that time is positioned forward.

  FIG. 8 is a functional configuration diagram of the mobile terminal according to the present invention.

  According to FIG. 8, the mobile terminal 1 includes a microprocessor unit 10, a geomagnetic sensor 11, an acceleration sensor 12, a GPS unit 13, a map information storage unit 14, and a display unit 15.

  The geomagnetic sensor 11 measures the direction of geomagnetism in three axial directions (front-rear direction, left-right direction, and up-down direction). The geomagnetic sensor 11 separates the detection coils and outputs values detected from the separated detection coils.

  The acceleration sensor 12 detects acceleration, that is, a change in speed per unit time. In the case of the three-axis type that can detect the tilt of the mobile terminal, three-dimensional acceleration can be detected, and measurement of the gravity (static acceleration) of the earth can be supported.

  The GPS unit 13 measures latitude and longitude information that is the current position of the reference. Using the measured current position as a reference point, the current position of the pedestrian can be integrated according to the number of steps, the step length, and the traveling direction.

  The map information storage unit 14 stores map information representing a travel route such as a road map. The display unit 15 displays the traveling direction and the current position output from the microprocessor unit 10 together with the map information. This provides a navigation function for pedestrians.

  The microprocessor unit 10 includes a walking timing determination unit 101, a traveling direction determination unit 102, a direction change determination unit 103, a stride determination unit 104, a movement amount integration unit 105, a current position determination unit 106, and a front determination unit. A program that functions as 107 is executed.

  The walking timing determination unit 101 divides the acceleration data string output from the acceleration sensor 12 into acceleration data for each unit section, for example, for each number of steps, or for each time unit based on the number of steps. Here, the unit section is a section having an arbitrary width that includes the walking timing determined by the walking timing determination unit and does not include the previous walking timing and the first walking timing. The unit section includes at least three sets of acceleration data including walking timing. For example, the number of steps can be calculated from the change in the combined acceleration, that is, the degree of shaking during movement.

  The traveling direction determination unit 102 determines the traveling direction from the geomagnetic data from the geomagnetic sensor 11 and the acceleration data from the walking timing determination unit 101 at predetermined time intervals. The present invention is based on the method of specifying the traveling direction in the traveling direction determination unit 102.

  The forward determination unit 107 determines the direction of walking of the pedestrian, that is, the front of the acceleration plane, from the acceleration data string output from the acceleration sensor 12. The front of the acceleration surface can be specified by the magnitude of the combined acceleration. For example, when the ground is kicked with the foot on the side holding the mobile terminal, the acceleration increases, and it can be determined that the mobile terminal is positioned forward.

  The direction change determination unit 103 receives data on the traveling direction from the traveling direction determination unit 102 and receives data on the forward direction from the front determination unit 107. The direction change determination unit 103 has a memory and stores data on the direction of travel and the direction as time passes. And the direction change determination part 103 determines whether the direction change was made about the advancing direction of the fixed time range memorize | stored in memory.

  The stride determination unit 104 receives acceleration data for one step from the walking timing determination unit 101, and determines the stride for each step. The determined stride length is output to the movement amount accumulating unit 105. The stride length determination unit 104 also outputs the stride information to the direction change determination unit 103.

  The movement amount accumulating unit 105 receives the traveling direction information from the traveling direction determining unit 102 and the stride information from the stride determining unit 104. Then, the movement amount accumulation unit 105 accumulates the traveling direction and the stride for one step. The current position determination unit 106 acquires map information from the map information storage unit 14 and identifies the current position from the accumulated movement amount. If the current position determination unit 106 determines that the direction change determination unit 103 has changed direction, the current position determination unit 106 determines the position of a nearby intersection in the map information as the current position. If it is determined that the direction has not changed (if it is determined that the vehicle has moved straight), the position projected by map matching is determined as the current position.

  The traveling direction determination unit 102, which is a feature of the present invention, includes a filter unit 1021, a reference vector derivation unit 1022, a coordinate system conversion matrix calculation unit 1023, a coordinate system conversion unit 1024, a direction angle calculation unit 1025, and a correction unit. 1026. The filter unit 1021 and the correction unit 1026 are not essential functions of the present invention, but can improve the accuracy of the traveling direction.

  The reference vector deriving unit 1022 derives a gravity vector in the direction of gravity from a plurality of acceleration data, and selects a geomagnetic vector corresponding to the gravity vector.

  The coordinate system conversion matrix calculation unit 1023 generates a coordinate system conversion matrix A that combines rotation matrices for the x-axis, y-axis, and z-axis to convert the gravity vector and geomagnetic vector of the sensor coordinate system into the world coordinate system. calculate. Specifically, the coordinate system conversion matrix calculation unit 1023 calculates a rotation matrix AyAx that is a first conversion matrix component for rotating the gravity vector in the negative z-axis direction. The rotation matrix AyAx is based on a rotation matrix Ax that rotates the yz component of the gravity vector to the negative direction of the z axis and a rotation matrix Ay that rotates the xz component of the gravity vector to the negative direction of the z axis. Calculated.

  Next, the coordinate system conversion matrix calculation unit 1023 calculates a rotation matrix Az that is a second conversion matrix component for rotating the geomagnetic vector in the positive x-axis direction. The rotation matrix Az is calculated as a rotation matrix for rotating the xy component of the geomagnetic vector after applying the rotation matrix AyAx to the positive direction of the x axis.

  Then, the coordinate system conversion matrix calculation unit 1023 calculates a coordinate system conversion matrix A = AzAyAx for converting the sensor coordinate system to the world coordinate system based on the rotation matrix AyAx and the rotation matrix Az.

  The coordinate system conversion unit 1024 converts the acceleration vector and the geomagnetic vector in the unit section into the world coordinate system using the coordinate system conversion matrix.

  The direction angle calculation unit 1025 calculates, as a direction angle, an angle formed by an approximate straight line obtained by projecting the locus of the acceleration vector group mapped in the world coordinate system onto the ground surface and the x axis representing the north direction. For example, a linear method is approximated using a known method such as a least square method.

  The filter unit 1021 stores data in a predetermined time range for acceleration data and geomagnetic data input to the reference vector deriving unit 1022, and removes a predetermined ratio of data from the maximum value and the minimum value. In other words, unexpected data can be removed.

  The correction unit 1026 stores the direction angle θ in a predetermined time range for the direction angle θ output from the direction angle calculation unit 1025, and the direction angle θ in which a change before and after the direction angle θ is equal to or greater than a predetermined angle threshold value. Remove.

For example, as shown in Table 7 below, when only one data is swung more than a previous value, such as 60 ° (predetermined angle threshold), the data is removed.

Further, the correction unit 1026 preferably supplements the removed data with an average of the direction angles θ of the unit sections calculated before and after in time as shown in Table 8 below.

Further, the correction unit 1026 preferably averages the accumulated changes in the plurality of direction angles θ. According to Table 9 below, the values are averaged for each direction angle θ within a certain range.

  As described above in detail, according to the mobile terminal, the program, and the method of the present invention, the trajectory (approximate straight line) of the acceleration data group and the north direction are obtained by performing the coordinate system conversion from the sensor coordinate system to the world coordinate system. The direction angle of the pedestrian can be calculated by using the acceleration sensor and the geomagnetic sensor mounted on the portable terminal even when the pedestrian is walking with the portable terminal held by hand. It can be determined as accurately as possible.

  According to the various embodiments of the present invention described above, those skilled in the art can easily make various changes, modifications and omissions within the scope of the technical idea and the viewpoint of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is explanatory drawing showing the walk mode of a pedestrian, an acceleration fluctuation direction, and a geomagnetic fluctuation direction. It is the image figure converted from the sensor coordinate system to the world coordinate system. It is a flowchart of coordinate system conversion in the present invention. It is an image figure showing the coordinate system conversion in S211. It is an image figure showing the coordinate system conversion in S212. It is an image figure showing the coordinate system conversion in S22. It is a graph showing the example of an approximate line. It is a functional block diagram in the portable terminal of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Portable terminal 10 Microprocessor part 101 Walking timing determination part 102 Travel direction determination part 1021 Filter part 1022 Reference vector derivation part 1023 Coordinate system conversion matrix calculation part 1024 Coordinate system conversion part 1025 Direction angle calculation part 1025 Correction part 103 Direction change determination part 104 Step Determining Unit 105 Travel Amount Accumulating Unit 106 Current Position Determining Unit 107 Forward Determining Unit 11 Geomagnetic Sensor 12 Acceleration Sensor 13 GPS Unit 14 Map Information Storage Unit 15 Display Unit

Claims (9)

An acceleration sensor that outputs triaxial acceleration data; a geomagnetic sensor that outputs triaxial geomagnetic data; and a traveling direction determination means that determines a traveling direction of a pedestrian from the acceleration data and the geomagnetic data. A portable terminal owned by a person,
The traveling direction determination means includes
A reference vector deriving means for deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
Coordinate system conversion matrix calculation means for calculating a coordinate system conversion matrix that combines rotation matrices for the x-axis, y-axis, and z-axis to convert the gravity vector and the geomagnetic vector of the sensor coordinate system into the world coordinate system When,
Coordinate system conversion means for converting the plurality of acceleration vectors and the geomagnetic vector into the world coordinate system using the coordinate system conversion matrix;
Direction angle calculating means for calculating an angle formed by an approximate straight line representing an orthogonal projection of the trajectory of the acceleration vector group mapped in the world coordinate system onto the ground surface and an axis representing the north direction as a direction angle; A mobile terminal characterized by. The coordinate system conversion matrix calculation means includes:
Calculating a first transformation matrix component for rotationally moving the gravity vector vertically downward in the world coordinate system;
Next, a second transformation matrix component for rotating the geomagnetic vector in the north direction in the world coordinate system is calculated,
2. The coordinate system conversion matrix for converting the sensor coordinate system into the world coordinate system is calculated by combining the first conversion matrix component and the second conversion matrix component. Mobile devices. The first transformation matrix component includes a rotation matrix Ax that rotates the yz component of the gravity vector in the negative z-axis direction, and a rotation matrix Ay that rotates the xz component of the gravity vector in the negative z-axis direction. And based on
3. The mobile terminal according to claim 1, wherein the second transformation matrix component is calculated as a rotation matrix Az that rotates the xy component of the geomagnetic vector to a positive direction of the x-axis. The acceleration data input from the acceleration sensor is divided for each number of steps, or for each time unit based on the number of steps, and the walking timing determining means for outputting to the traveling direction determining means,
The apparatus further comprises direction change determination means for determining whether or not the direction change has been made for each of the number of steps output from the direction of travel determination means or for each time unit based on the number of steps. Item 4. The mobile terminal according to any one of Items 1 to 3. It further has a forward determining means for determining the direction of walking of the pedestrian, that is, the front of the acceleration surface,
The forward determination means determines the larger one of the continuous peak points of the composite acceleration in the acceleration data string output from the acceleration sensor as the front of the acceleration surface, and notifies the direction change determination means to that effect. The mobile terminal according to claim 4. About the acceleration data and the geomagnetic data input to the reference vector deriving means,
6. The portable terminal according to claim 1, further comprising a filter unit that stores data in a predetermined time range and removes a predetermined ratio of data from a maximum value and a minimum value. For the direction angle θ output from the direction angle calculation means,
7. The apparatus according to claim 1, further comprising correction means for storing a direction angle θ in a predetermined time range and removing the direction angle θ in which a change before and after the direction angle θ is equal to or greater than a predetermined angle threshold. The portable terminal of any one of Claims. A computer having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data, and is mounted on a portable terminal carried by a pedestrian is obtained from the acceleration data and the geomagnetic data. A program for a portable terminal that functions as a traveling direction determining means for determining a traveling direction of the pedestrian,
The traveling direction determination means includes
A reference vector deriving means for deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
Coordinate system conversion matrix calculation means for calculating a coordinate system conversion matrix that combines rotation matrices for the x-axis, y-axis, and z-axis to convert the gravity vector and the geomagnetic vector of the sensor coordinate system into the world coordinate system When,
Coordinate system conversion means for converting the plurality of acceleration vectors and the geomagnetic vector into the world coordinate system using the coordinate system conversion matrix;
The computer functions as a direction angle calculation means for calculating an angle formed by an approximate straight line representing an orthogonal projection of the trajectory of the acceleration vector group mapped in the world coordinate system to the ground surface and an axis representing the north direction as a direction angle. A program for a portable terminal characterized by causing the program to be executed. A portable terminal having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data, and the progress of the pedestrian based on the acceleration data and the geomagnetic data. A traveling direction determination method for determining a direction,
Deriving a gravity vector in the direction of gravity from a plurality of acceleration vectors and selecting a geomagnetic vector corresponding to the gravity vector;
A second step of calculating a coordinate system transformation matrix combining a rotation matrix for each of the x-axis, y-axis, and z-axis to transform the gravity vector and the geomagnetic vector of the sensor coordinate system into a world coordinate system;
A third step of converting the plurality of acceleration vectors and the geomagnetic vector into the world coordinate system using the coordinate system conversion matrix;
And a fourth step of calculating an angle formed by an approximate straight line representing an orthogonal projection of the locus of the acceleration vector group mapped in the world coordinate system onto the ground surface and an axis representing the north direction as a direction angle. A method for determining a traveling direction of a mobile terminal.

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