JP5464706B2 - Portable terminal, program and method for determining direction of travel of pedestrian using acceleration sensor and geomagnetic sensor - Google Patents

Description

  The present invention relates to a technique 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 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 an accurate traveling direction and current position and driving route guidance to a destination on a display unit 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 determining a traveling direction based on a horizontal acceleration distribution (see, for example, Patent Documents 8 and 9). There is also a technique for determining the direction of travel of a pedestrian using the relationship between the acceleration in the vertical direction and the acceleration in the travel direction after determining the vertical direction in order to derive the posture of the terminal (see, for example, Patent Document 4). Furthermore, there is a technique for determining the traveling direction from the characteristics of a pedestrian's arm swing (see, for example, Non-Patent Document 2). Further, there is a technique for determining the traveling direction from the attitude of the terminal at a specific time (see, for example, Patent Document 5). Furthermore, when there are a plurality of roads through an intersection in the traveling direction, there is a technique for setting the intersection as the current position (see, for example, Patent Document 6).

  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 7). 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 2008-039619 A WO2006 / 104140 JP-A-3-099399 JP 63-011813 A Japanese Patent No. 4126388 JP 2008-116315 A JP 2009-229399 A

"Nike + iPod User's Guide", page 27, "online", [Search February 3, 2009], Internet <URL: http://manuals.info.apple.com/en/nikeipod_users_guide.pdf> Daisuke Uesaka, Kengo Iwamoto, Shigeki Muramatsu, Satoshi Nishiyama, “Position acquisition system using acceleration and geomagnetic sensors in mobile phones”, Multimedia, Distributed, Cooperation and Mobile Symposium, Proceedings, pp.761-767, July 2008 Moon

  According to the technique described in Patent Document 4, a direction in which acceleration exceeding a predetermined threshold is detected is set as a traveling direction candidate. However, when the acceleration distribution is not linear but has a width, it is necessary to evaluate a large number of candidates in the traveling direction, and the amount of calculation is enormous.

  Further, according to the techniques described in Patent Documents 5, 8, and 9, if the posture of the mobile terminal worn by the pedestrian is roughly constant, the horizontal acceleration detected during walking is Utilizing the distribution in the direction of travel. However, when moving with the terminal held in one hand, the horizontal acceleration may not be distributed in the traveling direction even if the terminal posture is roughly constant.

  FIG. 1 is an explanatory diagram illustrating an aspect of a mobile terminal held by a pedestrian.

  According to FIG. 1, the pedestrian is holding the mobile terminal and viewing the screen. For example, it is assumed that a map is displayed on the mobile terminal and the pedestrian is walking while browsing the display unit. This is the posture when the pedestrian wants to know the traveling direction most accurately. At this time, the posture of the mobile terminal while walking is approximately constant. If the attitude of the mobile terminal is roughly constant, the traveling direction can be estimated using an acceleration sensor and a geomagnetic sensor mounted on the mobile terminal.

  The sensor is fixedly built in the mobile terminal. Therefore, if the orientation of the mobile terminal is determined, the orientation of the x, y, and z axes (sensor coordinate system) of the sensor is also determined. For example, according to FIG. 1, the x-axis is assigned from the top to the bottom of the key surface, the y-axis is directed from the left to the right of the key surface, and the z-axis is assigned from the back of the key surface to the front. Yes. Of course, the assignment of the coordinate system of the sensor is not limited to this. Further, forward (backward), right (leftward), and vertical coordinate systems are determined for the direction of travel of the pedestrian.

  However, according to FIG. 1, although the attitude of the mobile terminal is almost constant, it swings in the horizontal direction and the vertical direction with walking. Further, the acceleration detected by the handheld portable terminal is absorbed by the arm. In such a state, when the technique described in Patent Document 4 is used, it is necessary to evaluate a large number of traveling direction candidates, and the amount of calculation is enormous.

  In addition, any of the conventional techniques requires processing for calculating the acceleration of the coordinate system in the traveling direction from the acceleration data of the sensor coordinate system detected by the sensor. That is, coordinate conversion processing is required for each piece of acceleration data detected by the sensor. This results in an increase in the amount of calculation.

  Therefore, the present invention provides a pedestrian with the least amount of computation using a acceleration sensor and a geomagnetic sensor mounted on a portable terminal held by the user so that the attitude of the terminal is approximately constant. It is an object of the present invention to provide a portable terminal, a program, and a method for determining the traveling direction of the mobile phone.

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
Vertical acceleration calculating means for calculating vertical acceleration from acceleration data;
Walking timing detection means for detecting the maximum point of vertical upward acceleration as walking timing;
Based on the walking timing, acceleration acquisition means for the specified number of steps for acquiring acceleration data for the specified number of steps,
Acceleration surface estimation means for estimating an acceleration surface generated by a walking motion of a pedestrian from acceleration data for a specified number of steps,
A longitudinal acceleration calculation means for calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
It has a traveling direction calculation means for calculating a traveling direction using a rightward unit vector, a gravity vector G, and a geomagnetic vector M in the normal vector.

According to another embodiment of the portable terminal of the present invention, the longitudinal acceleration calculating means is
Based on the acceleration for each axis output from the acceleration sensor, the gravity vector G is calculated,
From the acceleration surface normal vector V _LR and the gravity vector G, a forward or backward longitudinal vector V _FG is calculated,
Based on the longitudinal vector V _FG and the vertical acceleration, when the longitudinal vector V _FG is forward, the normal vector V _LR is directed to the right, and when the longitudinal vector V _FG is backward, the normal vector V _LR is It is also preferable to face left.

According to another embodiment of the portable terminal of the present invention, the traveling direction calculation means is
Using the gravity vector G and the geomagnetic vector M, the eastward unit vector e _East is calculated by G × M / | G × M |
Calculate the angle α between the normal vector e _Right and the east unit vector e _East in the normal vector,
Based on the angle β formed by the outer product (e _East × e _Right ) of the eastward unit vector e _East and the rightward unit vector e _Right and the gravity vector G, the direction angle θ with respect to the eastward unit vector e _East is calculated. Is also preferable.

According to another embodiment of the portable terminal of the present invention, the traveling direction calculation means,
The formed angle α is calculated by the following formula:
α = arccos ((e _East · e _Right ) / (| e _East || e _Right |))
The azimuth angle θ is derived by the following equation using the angle α formed and the angle β formed by the outer product vector and the gravity vector G: cos β ≧ 0: θ = α
cos β <0: θ = 360−α
It is also preferable.

  According to another embodiment of the portable terminal of the present invention, the acceleration surface estimation means calculates variances Vxx, Vyy and Vzz of each axis for the specified number of steps of acceleration, and uses the least square method for the axis with the smallest variance. It is also preferable to estimate the acceleration plane based on

  According to another embodiment of the portable terminal of the present invention, it is also preferable that the acceleration surface estimation means functions as a low-pass filter that blocks high frequency components for acceleration data.

According to the present invention, a computer mounted on a portable terminal having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data can be used as a pedestrian's progression from acceleration data and geomagnetic data. A program that functions as a traveling direction determination means for determining a direction,
The direction of travel determination means is
Vertical acceleration calculating means for calculating vertical acceleration from acceleration data;
Walking timing detection means for detecting the maximum point of vertical upward acceleration as walking timing;
Based on the walking timing, acceleration acquisition means for the specified number of steps for acquiring acceleration data for the specified number of steps,
Acceleration surface estimation means for estimating an acceleration surface generated by a walking motion of a pedestrian from acceleration data for a specified number of steps,
A longitudinal acceleration calculation means for calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
The computer is caused to function as a traveling direction calculation means for calculating a traveling direction using the rightward unit vector, the gravity vector G, and the geomagnetic vector M in the normal vector.

According to the present invention, a portable terminal having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data is used to determine a pedestrian's direction of travel from acceleration data and geomagnetic data. A direction determination method,
A first step of calculating vertical acceleration from acceleration data;
A second step of detecting a maximum point of vertical upward acceleration as a walking timing;
A third step of acquiring acceleration data for a specified number of steps based on the walking timing;
A fourth step of estimating an acceleration plane caused by a walking motion of a pedestrian from acceleration data for a specified number of steps;
A fifth step of calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
A sixth step of calculating a traveling direction using a rightward unit vector in the normal vector, a gravity vector G, and a geomagnetic vector M is provided.

  According to the portable terminal, the program, and the method of the present invention, it is possible to use the acceleration sensor and the geomagnetic sensor mounted on the portable terminal with respect to the portable terminal held by the user so that the attitude of the terminal is approximately constant. The traveling direction of the pedestrian can be determined with as little calculation amount as possible. This is based on determining the traveling direction using geomagnetic data after calculating the longitudinal acceleration from the acceleration data of the sensor coordinate system.

It is explanatory drawing showing the aspect of the portable terminal hand-held by the pedestrian. It is a graph showing the change of acceleration. It is a functional block diagram of the portable terminal in this invention. It is a graph of the acceleration for every axis | shaft according to elapsed time. It is a graph of the vertical direction acceleration according to elapsed time. It is explanatory drawing showing the change of a horizontal direction acceleration. It is explanatory drawing showing the response | compatibility of the change of a horizontal direction acceleration and a vertical direction acceleration. It is a figure showing the acceleration surface and normal vector which actually generate | occur | produce. It is explanatory drawing showing the relationship of the direction with respect to gravity G and geomagnetism M. It is explanatory drawing showing the relationship between the angle | corner formed and an azimuth angle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a graph showing a change in acceleration.

  FIG. 2A shows a change in acceleration in the sensor coordinate system based on the terminal posture. FIG. 2B shows a change in acceleration in the coordinate system based on the traveling direction. The conversion between FIG. 2A and FIG. 2B is an inner product operation based on a unit vector. It is clear that this conversion only changes the direction of the axis and does not affect the magnitude of acceleration or the relationship with other axes. Therefore, it is also clear that the plane that bisects the angle formed by the planes of acceleration distribution in the odd-numbered steps and even-numbered steps in FIG. 2A is the plane including the traveling direction. That is, it is possible to calculate the traveling direction by calculating a plane including the traveling direction from the acceleration for each axis and then executing coordinate transformation.

  FIG. 3 is a functional configuration diagram of the mobile terminal according to the present invention.

  According to FIG. 3, the mobile terminal 1 is a terminal that can be held by a user, for example, a mobile phone. The mobile terminal 1 includes a traveling direction determination unit 10, an acceleration sensor 11, a geomagnetic sensor 12, a positioning unit 13, a map information storage unit 14, a display control unit 15, and a display unit 16. The traveling direction determination unit 10, the map information storage unit 14, and the display control unit 15 are realized by executing a program that causes a computer mounted on the portable terminal to function.

  The acceleration sensor 11 detects acceleration (sensor coordinate system) for each of the x-axis, y-axis, and z-axis. In the case of existing general mobile phones, there are many cases in which an acceleration sensor is mounted in advance. The detected acceleration data is output to the traveling direction determination unit 10.

  FIG. 4 is a graph of acceleration for each axis according to elapsed time.

  According to FIG. 4, acceleration data for each axis obtained by an acceleration sensor is shown when a pedestrian holds a mobile terminal and walks while visually checking the display unit.

  The geomagnetic sensor 12 detects geomagnetism, which is the magnetic field lines of the earth from south to north. The direction of the orthogonal projection of the detected geomagnetism with respect to the horizontal plane is “north”. In the case of a triaxial geomagnetic sensor, the orientation can be detected by detecting the tilt even if it is not horizontal. The detected geomagnetic data is output to the traveling direction determination unit 10.

  The positioning unit 13 receives a positioning radio wave from a GPS (Global Positioning System) satellite and acquires latitude and longitude data of the current position. The latitude / longitude data is output to the display control unit 15.

  The map information storage unit 14 accumulates map information. Based on the current position instructed from the display control unit 15, the map information is output to the display control unit 15.

  The display control unit 15 receives the traveling direction data from the traveling direction determination unit 10 and the current position information from the positioning unit 13. Further, the display control unit 15 outputs the current position information to the map information storage unit 14 and acquires the map information of the current position. And the display control part 15 produces | generates the image which displayed the present position on the map, and displayed the advancing direction with the arrow. The image is output to the display unit 16. For example, it is used for a navigation system for pedestrians.

  The display unit 16 displays the image from the display control unit 15 so that the walking user can visually recognize the image.

  The traveling direction determination unit 10 includes a vertical acceleration calculation unit 101, a walking timing detection unit 102, an acceleration acquisition unit 103 for a specified number of steps, an acceleration surface estimation unit 104, a longitudinal acceleration calculation unit 105, and a traveling direction calculation unit. 106. Hereinafter, these functional components will be described in detail.

[Vertical acceleration calculation unit]
The vertical acceleration calculation unit 101 calculates vertical acceleration using acceleration data. The vertical acceleration and the horizontal acceleration are orthogonal to each other.

  FIG. 5 is a graph of vertical acceleration according to elapsed time.

  According to FIG. 5, the upper side of the vertical acceleration represents a vertically downward direction, and the lower side represents a vertically upward direction. In addition, the change in vertical acceleration has a periodicity that coincides with walking. Here, the maximum point of vertical downward acceleration represents the time when the body falls, that is, the time when the foot that has left the ground touches the ground. On the other hand, the maximum point of vertical upward acceleration represents the time when the body is raised, that is, the time when the foot is raised. The interval between the minimum points of vertical downward acceleration, that is, the maximum point of vertical upward acceleration, represents one step of the pedestrian.

[Walking timing detector]
The walking timing detection unit 102 detects the walking timing generated by the walking motion of the pedestrian from the vertical acceleration output from the vertical acceleration calculation unit 101. The walking timing detects the maximum point of vertical upward acceleration as the walking timing. Note that, according to FIG. 5, every time the vertical downward acceleration becomes a minimum point, the walking timing is output to the acceleration acquisition unit 103 for the specified number of steps.

[Acceleration unit for specified number of steps]
The acceleration acquisition unit 103 for the specified number of steps acquires acceleration data for the specified number of steps based on the walking timing. Each piece of acceleration data corresponding to the specified number of steps is output to the acceleration surface estimation unit 104.

  FIG. 6 is an explanatory diagram showing changes in horizontal acceleration.

  According to FIG. 6, the horizontal acceleration actually obtained by the pedestrian gripping the portable terminal with the right hand and walking in the manner as shown in FIG. 1 is plotted. As described above, the forward acceleration repeats acceleration / deceleration, and at the same time, repeats forward / backward / up / down. The point that became clear here is that the distribution of horizontal acceleration does not coincide with the traveling direction. According to FIG. 5, odd-numbered steps and even-numbered steps (right foot and left foot) are distributed in different directions. In addition, as a clear point, the directions of the bisectors in the directions of the odd and even steps correspond to the traveling direction. Thereby, the traveling direction can be calculated.

Furthermore, the acceleration of a one-step walking cycle is observed in the following order.
Vertical maxima-> Maximum backward direction->
Vertical downward maximum-> travel direction forward maximum This makes it possible to sort forward in the travel direction according to the direction of acceleration distribution.

  FIG. 7 is an explanatory diagram showing the correspondence between changes in horizontal acceleration and vertical acceleration.

According to FIG. 7, the locus of acceleration for two steps is represented. The vertical acceleration and the horizontal acceleration are orthogonal to each other.
[t0] For the first step, when the vertical downward acceleration is a maximum, the horizontal acceleration has shifted to the left in the traveling direction.
[t1] For the first step, when the vertical upward acceleration is maximum, the horizontal acceleration has shifted to the right in the traveling direction.
[t2] Regarding the second step, when the vertical downward acceleration is at a maximum, the horizontal acceleration has shifted to the right in the traveling direction.
[t3] With respect to the second step, when the vertical upward acceleration is at a maximum, the horizontal acceleration is shifted to the left in the traveling direction.

[Acceleration surface estimation unit]
The acceleration surface estimation unit 104 estimates an acceleration surface generated by a walking motion of a pedestrian from acceleration data for a specified number of steps.

  FIG. 8 is a diagram showing acceleration surfaces and normal vectors that are actually generated.

  For the sake of simplicity, the gravity direction is set as the downward direction in the figure, but gravity itself cannot be detected. In addition, in which direction the geomagnetism is actually detected with respect to the sensor coordinate system depends on the attitude of the terminal. However, the relationship between the acceleration plane and the normal vector does not depend on the attitude of the terminal.

  According to FIG. 8, the three-axis acceleration data (x, y, z) obtained from the acceleration sensor and the three-axis geomagnetic data (x, y, z) obtained from the geomagnetic sensor are expressed in three-dimensional coordinates. Plotted in the system. An acceleration plane can be detected from plots of acceleration data measured at different times. In addition, a normal vector with respect to the acceleration surface can be detected.

  According to FIG. 8, the pedestrian is walking in the direction of the direction angle θ with respect to the geomagnetism coming from the south. At this time, the acceleration plane can be detected in parallel with the traveling direction in accordance with the motion of the pedestrian holding the mobile terminal, and the normal vector is specified.

  According to the present invention, a normal vector can be calculated by approximating a plurality of acceleration data to a plane.

As a method for approximately calculating the acceleration surface, for example, there is a least square method. The least square method is a method of determining each coefficient of the prediction function f (x) for the phenomenon so that the sum of the squares of the residuals is minimized. The residual, and the i-th data _{n i} with respect to the predicted function values f _{(n i),} which is the difference between the measured data _{m i,} i.e. _m i -f _{(n i).}

In general, a plane passing through the origin is represented by the following equation (1).
ax + by + cz = 0 Formula (1)
At this time, (a, b, c) is a normal vector with respect to the plane.

Here, in order to simplify the calculation, Equation (1) is transformed into Equation (2).
z = αx + βy Equation (2)
Since (a, b, c) is a normal vector, there is no problem when c = -1.

When n point groups x _i , y _i , and z _i (i = 1 to n) are given, α and β that minimize the following expression (3) may be calculated.
S = Σ _{i = 1} ⁿ (z _i −αx _i −βy _i ) Equation ² (3)

Here, it is assumed that it is defined as follows.
A = Σ _{i = 1} ⁿ (x _i ² )
B = Σ _{i = 1} ⁿ (y _i ² )
C = Σ _{i = 1} ⁿ (z _i ² )
D = Σ _{i = 1} ⁿ (x _i × y _i )
E = Σ _{i = 1} ⁿ (x _i × z _i )
F = Σ _{i = 1} ⁿ (y _i × z _i )

At this time, the expression (3) becomes the following expression (4).
S = Aα ² + Bβ ² + C + 2αβD-2αE-2βF Formula (4)

When Expression (4) is regarded as a function of α, it becomes a concave quadratic function, and the minimum value is minimized. The same applies to β. That is, S is partially differentiated with respect to α and β, and a point that becomes 0 is obtained.

When the equations (5) and (6) are solved, they can be calculated as the following equations (7) and (8).
α = (BE-DF) / (AB-D ² ) Formula (7)
β = (AF−DE) / (AB−D ² ) Formula (8)
As described above, the normal vector is (α, β, −1).

As another embodiment for estimating the acceleration plane, variances Vxx, Vyy, and Vzz of each axis are calculated for the specified number of steps of acceleration, and the acceleration plane is calculated based on the least square method for the axis that minimizes the variance. presume.
_{Vxx = 1 / n · Σ i} = 1 n (x i -x¯) 2
_{Vyy = 1 / n · Σ i} = 1 n (y i -y¯) 2
Vzz = 1 / n · Σ _{i = 1} ⁿ (z _i −z￣) ²
n: number of data x￣: average value of x Note that, according to the above-described equation (2), the acceleration plane is calculated so that the residual in the z-axis direction is minimized.

  The acceleration surface estimation unit 104 also preferably functions as a low-pass filter that blocks high-frequency components with respect to acceleration data. As a result, acceleration data as an abnormal value can be removed, and an accurate traveling direction can be calculated.

[Front-back direction acceleration calculation unit]
The longitudinal acceleration calculation unit 105 calculates the normal vector and the longitudinal acceleration on the acceleration surface from the acceleration surface and the vertical acceleration.

[S1] The longitudinal acceleration calculation unit 105 first calculates a gravity vector G based on the acceleration for each axis output from the acceleration sensor.

  FIG. 9 is an explanatory diagram showing the orientation relationship with respect to gravity G and geomagnetism M. FIG.

The gravity vector G and the geomagnetic vector M are expressed as follows for each of the x-axis, the y-axis, and the z-axis. In addition, since the posture of the portable terminal while walking is roughly constant, the geomagnetic data observed in a short time is almost constant.
Gravity vector G: G = (g _x , g _y , g _z )
Geomagnetic vector _{M: M = (m x,} m y, m z)

  First, the gravity vector G is calculated. It is difficult to accurately determine the gravitational direction of the mobile terminal during walking even when using acceleration data. Therefore, the direction of the vector of the sum of the accelerations of each axis is regarded as the direction of gravity using a large number of x-axis, y-axis and z-axis acceleration data detected in a predetermined time range.

The acceleration of each i-th axis is expressed as follows.
x-axis acceleration: ACC _x [i]
y-axis acceleration: ACC _y [i]
z-axis acceleration: ACC _z [i]
The sum of n pieces of acceleration data is expressed as follows.
ACCS _x = Σ _{i = 1} ^N ACC _x [i]
ACCS _y = Σ _{i = 1} ^N ACC _y [i]
ACCS _z = Σ _{i = 1} ^N ACC _z [i]
The gravity vector G is expressed as follows.
G = (g _x , g _y , g _z ) = (ACCS _x , ACCS _y , ACCS _z )

[S2] Next, the longitudinal acceleration calculation unit 105 calculates a forward or backward longitudinal vector V _FG from the normal vector V _LR and the gravity vector G of the acceleration plane. Here, the normal vector V _LR and the gravity vector G of the acceleration surface and the longitudinal vector V _FG are expressed by the following relational expressions.
V _FG = V _LR × G ×: Cross product

A unit vector in the front-rear direction vector V _FG is expressed as follows.
e _FB = (e _FBx , e _FBy , e _FBz )
At this time, the longitudinal acceleration A _FG is expressed as follows.
A _FG = e _FGx × A _x + e _FGy × A _z + e _FGz × A _z
A _FG is a forward or backward acceleration.

[S3] Next, the longitudinal acceleration calculating unit 105, on the basis of the front-rear direction vector V _FG and vertical acceleration, based on the longitudinal direction vector V _FG and vertical acceleration, when the longitudinal direction vector V _FG is positive When the normal vector V _LR is directed to the right (+) and the front-rear direction vector V _FG is backward, the normal vector V _{LR is set} to the left (−).

  Either forward or backward can be determined because the acceleration is observed in the order of vertical upward peak-> backward peak-> downward peak-> forward peak for a one-step walking cycle.

[Advancing direction calculation unit]
The traveling direction calculation unit 106 calculates the traveling direction using the rightward unit vector in the normal vector, the gravity vector G, and the geomagnetic vector M. The calculated traveling direction is output to the display control unit 15.

[S1] First, the traveling direction calculation unit 106 calculates the eastward unit vector e _East by G × M / | G × M | using the gravity vector G and the geomagnetic vector M.

  Refer to FIG. 9 again.

Next, assuming that the x-axis, y-axis, and z-axis are right-handed as in FIG. 1, the unit vectors in each direction are expressed as follows.
North-facing unit vector e _North : e _North = (e _Nx , e _Ny , e _Nz )
Eastward unit vector e _East : e _East = (e _Ex , e _Ey , e _Ez )
Downward unit vector e _Down : e _Down = (e _Dx , e _Dy , e _Dz )
Further, the acceleration data is expressed as follows.
A = (A _x , A _y , A _z )

According to FIG. 9, when the gravity vector G and the geomagnetic vector M are used, each unit vector is expressed as follows.
North-facing unit vector e _North : e _North = G × M × G / | G × M × G |
East unit vector e _East : e _East = G × M / | G × M |
Downward unit vector e _Down : e _Down = G / | G |
×: Cross product (vector product, outer product)

  “G × M” (outer product) creates a vector in a direction perpendicular to the plane formed by the gravity vector G and the geomagnetic vector M. When viewed in the direction of the gravity vector G, G × M extends in a clockwise direction as viewed from the geomagnetic vector M. Since the geomagnetic vector M is directed from the south to the north, the direction of 90 degrees clockwise from the axis, that is, G × M is directed to the “east” direction.

  Further, “(G × M) × G” creates a vector in a direction perpendicular to a plane formed by the eastward unit vector G × M and the gravity vector G. When looking toward the eastward unit vector G × M, (G × M) × G extends in the clockwise direction as viewed from the gravity vector. Since the gravity vector is directed from the top to the bottom, the direction of 90 degrees clockwise from the axis, that is, (G × M) × G is directed to the “north” direction.

The acceleration vector in each direction is calculated by taking the inner product of the acceleration vector A with respect to the unit vector e in each direction.
Northward acceleration: A _N = e _Nx × A _x + e _Ny × A _y + e _Nz × A _z
East acceleration: A _E = e _Ex × A _x + e _Ey × A _y + e _Ez × A _z
Vertical downward acceleration: A _D = e _Dx × A _x + e _Dy × A _y + e _Dz × A _z

[S2] Next, the traveling direction calculation unit 106 calculates an angle α formed by the rightward unit vector e _Right and the eastward unit vector e _East in the normal vector. The angle formed by the two vectors can be calculated from the inner product and the norm (vector magnitude) product. From the eastward unit vector e _East and the rightward unit vector e _Right , the angle α formed by both vectors is expressed by the following equation.
α = arccos ((e _East · e _Right ) / (| e _East || e _Right |)) Equation (9)

[S3] Then, the traveling direction calculation unit 106 obtains the azimuth angle θ.

  Here, the formed angle α is an inferior angle (0 to 180 degrees). On the other hand, the azimuth angle θ to be obtained is 0 to 360 degrees (clockwise angle with the north azimuth being 0 degrees) and includes a dominant angle. Therefore, the formed angle is converted into an azimuth angle.

  FIG. 10 is an explanatory diagram showing the relationship between the formed angle and the azimuth angle.

According to FIG. 10, according to the outer product vector e _East × e _Right of the eastward unit vector e _East and the rightward unit vector e _Right , the same as the gravity vector when the direction angle θ with respect to the eastward unit vector e _East is less than 180. Indicates direction. At this time, θ = α. On the other hand, when θ should be 180 degrees or more, e _East × e _Right indicates a direction opposite to the gravity vector. At this time, θ = 360−α. Therefore, an angle formed by e _East × e _Right and the gravity vector G is obtained (cosine instead of angle), and α is converted to θ based on the result.

The direction angle θ with respect to the eastward unit vector e _East is derived by the following equation using β as the angle formed by e _East × e _Right and the gravity vector G.
cos β ≧ 0: θ = α
cos β <0: θ = 360−α

  As described above in detail, according to the mobile terminal, the program, and the method of the present invention, the acceleration mounted on the mobile terminal held by the user so that the attitude of the terminal is approximately constant. Using the sensor and the geomagnetic sensor, the direction of travel of the pedestrian can be determined as accurately as possible.

  Various changes, modifications, and omissions of the above-described various embodiments of the present invention can be easily made by those skilled in the art. 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.

DESCRIPTION OF SYMBOLS 1 Mobile terminal 10 Travel direction determination part 101 Vertical direction acceleration calculation part 102 Walking timing detection part 103 Acceleration acquisition part for designated steps 104 Acceleration surface estimation part 105 Front-rear direction acceleration calculation part 106 Travel direction calculation part 11 Acceleration sensor 12 Geomagnetic sensor 13 Positioning Unit 14 map information storage unit 15 display control unit 16 display unit

Claims (8)

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
Vertical acceleration calculation means for calculating vertical acceleration from the acceleration data;
Walking timing detection means for detecting the maximum point of vertical upward acceleration as walking timing;
Based on the walking timing, an acceleration acquisition unit for the specified number of steps for acquiring acceleration data for the specified number of steps,
Acceleration surface estimation means for estimating an acceleration surface generated by a walking motion of a pedestrian from acceleration data for the specified number of steps,
A longitudinal acceleration calculation means for calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
A mobile terminal, comprising: a traveling direction calculation unit configured to calculate a traveling direction using a rightward unit vector in the normal vector, the gravity vector G, and the geomagnetic vector M. The longitudinal acceleration calculation means includes:
Based on the acceleration for each axis output from the acceleration sensor, the gravity vector G is calculated,
From the normal vector V _{LR of the} acceleration surface and the gravity vector G, a forward or backward longitudinal vector V _FG is calculated,
Based on the front-rear direction vector V _FG and the vertical acceleration, when the front-rear direction vector V _FG is forward, the normal vector V _LR is rightward, and when the front-rear direction vector V _FG is rearward, 2. The mobile terminal according to claim 1, wherein the normal vector _VLR is leftward. The traveling direction calculation means includes
Using the gravity vector G and the geomagnetic vector M, an eastward unit vector e _East is calculated by G × M / | G × M |
An angle α formed by a rightward unit vector e _Right in the normal vector and the eastward unit vector e _East is calculated;
Based on the angle β formed by the outer product (e _East × e _Right ) of the eastward unit vector e _East and the rightward unit vector e _Right and the gravity vector G, the direction angle θ with respect to the eastward unit vector e _East is determined. The mobile terminal according to claim 1, wherein the mobile terminal is calculated. About the traveling direction calculation means,
The formed angle α is calculated by the following equation:
α = arccos ((e _East · e _Right ) / (| e _East || e _Right |))
The azimuth angle θ is derived by the following equation using the angle α formed and the angle β formed by the outer product vector and the gravity vector G: cos β ≧ 0: θ = α
cos β <0: θ = 360−α
The mobile terminal according to claim 3. The acceleration surface estimation means includes
Calculate the variances Vxx, Vyy and Vzz of each axis for the specified number of steps of acceleration.
The mobile terminal according to any one of claims 1 to 4, wherein an acceleration plane is estimated based on a least-squares method for an axis having a minimum variance.   The mobile terminal according to any one of claims 1 to 5, wherein the acceleration surface estimation unit functions as a low-pass filter that blocks high frequency components with respect to the acceleration data. A computer mounted on a portable terminal having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data is used to determine the direction of travel of a pedestrian from the acceleration data and the geomagnetic data. A program that functions as a direction of travel determination means,
The traveling direction determination means includes
Vertical acceleration calculation means for calculating vertical acceleration from the acceleration data;
Walking timing detection means for detecting the maximum point of vertical upward acceleration as walking timing;
Based on the walking timing, an acceleration acquisition unit for the specified number of steps for acquiring acceleration data for the specified number of steps,
Acceleration surface estimation means for estimating an acceleration surface generated by a walking motion of a pedestrian from acceleration data for the specified number of steps,
A longitudinal acceleration calculation means for calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
A program for a portable terminal, which causes a computer to function as a traveling direction calculation unit that calculates a traveling direction using a rightward unit vector in the normal vector, the gravity vector G, and the geomagnetic vector M. A traveling direction determining method for determining a traveling direction of a pedestrian from the acceleration data and the geomagnetic data by a portable terminal having an acceleration sensor that outputs triaxial acceleration data and a geomagnetic sensor that outputs triaxial geomagnetic data. There,
A first step of calculating vertical acceleration from the acceleration data;
A second step of detecting a maximum point of vertical upward acceleration as a walking timing;
A third step of acquiring acceleration data for a specified number of steps based on the walking timing;
A fourth step of estimating an acceleration plane generated by the walking motion of the pedestrian from the acceleration data for the specified number of steps;
A fifth step of calculating a normal vector on the acceleration surface and a longitudinal acceleration from the acceleration surface and the vertical acceleration;
A mobile terminal traveling direction determination method, comprising: a sixth step of calculating a traveling direction using a rightward unit vector in the normal vector, the gravity vector G, and the geomagnetic vector M.