JP2000292111A - Apparatus and method for measuring attitude and position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable fast detection by simultaneously detecting attitude and position to simplify data processing. SOLUTION: A sensor 1 as 3-axis magnetic field sensor is arranged in a measuring area within an attitude/position measuring device 50. Two kinds of uniform magnetic fields h and h parallel in direction with the Z and X axes are generated by two of first and second coils 10 and 20 separately in the measuring area. With the uniform magnetic fields, a magnetic field measured by a local coordinate system (U, V, W) of the sensor 1 is converted to a global coordinate system (X, Y, Z) to measure an attitude. Currents opposite in direction are made to flow through a third coil 30 as a pair of coils wound at both ends thereof to generate a linear gradient magnetic field to measure a position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a posture position measuring apparatus and a measuring method, and more particularly to a posture position measuring apparatus capable of measuring a three-dimensional position and posture using a uniform magnetic field and a linear gradient magnetic field at a high speed. And a measuring method.

[0002]

2. Description of the Related Art Non-contact measurement of the coordinates and posture of an object in a three-dimensional space is a technology that is the basis of a man-machine interface such as capturing human body motion, and is becoming increasingly important. The technology for simultaneous detection of the posture and position of an object includes an optical system that processes data from images captured by multiple cameras and a magnetic system that measures the magnetic field from a dipole magnetic field generator using a magnetic sensor attached to the object And is used for motion capture and the like.

[0003] In the optical system, a marker is attached to each part of the human body to be measured, this is photographed by a plurality of cameras, and a three-dimensional position is measured from the obtained data. There are several methods of measurement using magnetic methods, but most of them require complex calculations to detect position and orientation using dipole magnetic fields (FHRaab, EBBlood, TOSteiner, HRJ
ones: Magnetic Position Tracker.IEEE.Trans., Vol.AE
S-15, NO.5, pp.709-717 (1979), and Atoda, Nakamura, Tomizawa, Yokoyama, Imada: Transactions of the Society of Instrument and Control Engineers, Vol. 34, N
O.5, pp.445-453 (1998), etc.).

[0004]

In the conventional optical measuring method, it is difficult to obtain accurate data when the reference points overlap or are hidden behind. On the other hand, in the magnetic type,
Although there is no problem with the concealment of the sensor as in the case of the optical system, there is a problem that it takes time to perform data processing because a complicated nonlinear equation for calculating the distance is required. In the case of optical measurement, similarly, data processing took time.

In view of the above, the present invention uses a uniform magnetic field and a linear gradient magnetic field in a magnetic system, and uses a uniform magnetic field for posture detection and a linear gradient magnetic field for position detection.
An object of the present invention is to detect attitude and position using a simple linear equation relating to the magnitude of a magnetic field, thereby simplifying data processing and enabling high-speed detection.

Further, the present invention makes it possible to greatly simplify the calculation algorithm as compared with the method using a dipole magnetic field, to shorten the time for producing three-dimensional computer graphics by motion capture and the like, and to produce sports medicine and entertainment software. It is intended to be used for such purposes.

[0007]

According to a first aspect of the present invention, there is provided an attitude and position measuring apparatus for measuring an attitude and a position of a sensor, the first and the second means generating a uniform magnetic field in a first axial direction. , A second coil that generates a uniform magnetic field in a second axial direction orthogonal to the first axial direction, and a third coil that generates a linear gradient magnetic field in three orthogonal axial directions, Provided is a posture position measuring device that measures a posture of a sensor by a magnetic field generated by the first and second coils and measures a position of the sensor by a magnetic field generated by the third coil.

According to a second solution of the present invention,
A posture and position measuring method for measuring a posture and a position of a magnetic field sensor, wherein a uniform magnetic field is generated in a first axial direction and a second axial direction orthogonal to the first axial direction. The method of measuring the attitude of the magnetic field sensor by each uniform magnetic field, generating a linear gradient magnetic field in three orthogonal axes, and measuring the position of the magnetic field sensor by the generated linear gradient magnetic field. provide.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a coordinate system and a uniform magnetic field. FIG. 1A shows a global coordinate system, and FIG.
(B) illustrates a local coordinate system.

In the coordinate system of FIG. 1A, the global coordinate system is an (X, Y, Z) coordinate system. In FIG. 1B, the local coordinate system of the sensor 1 itself is (U, V, W). Coordinate system is defined. FIG. 1B shows a local coordinate system (U, V, W), which is a local coordinate system representing a sensitivity axis, in which a sensor 1 that is a three-axis magnetic field sensor is arranged at an arbitrary position in a measurement area. I have.

First, the attitude measurement will be described. Departure
In the light, the X-axis and Z-axis
Parallel uniform magnetic fields h_X, H_ZUse This uniform magnet
World _X, H_ZIs a Helmholtz coil type coil, etc.
Can be generated.

[0012] First, to generate a parallel uniform magnetic field _{h Z} in the Z-axis. Then, the sensor 1 located at any position of the measurement region of this time, the magnetic field S _{Z =} in the local coordinate system at the location of the sensor _{1 (h uz, h vz,} h wz) measured. From this, the Z component (a _uz , a _vz , a _wz ) of the basis vector associated with each of the U, V, and W axes can be obtained by the following equation. Similarly to generate a uniform magnetic field h _X parallel to the X axis, like the calculation, U, V, X component of the basis vectors associated with each axis of the _{W (a ux, a vx,} a
_wx ) is determined by the following equation.

[0013]

(Equation 1)

A matrix A representing the attitude of the sensor 1 is determined as follows.

[0015]

(Equation 2)

When the determinant | A | = 1 of the attitude matrix A, each column vector equation (a _ux , a _vx , a _{w x} ), (a _uz , a
_vz , a _wz ) and to be determined (a _ui , a _vy ,
a _wy ) have a size of 1 and have properties orthogonal to each other.
Therefore, the Y component (a _uuy ) is obtained from the orthogonal relationship between the base vectors by using the X component and the Z component obtained by the formulas (1) and (2) by the actual measurement according to the following equation (3) of the cross product of the vectors. , a _vy , a _wy ).

[0017]

(Equation 3)

By using the attitude matrix A, the magnetic field measured in the local coordinate system (U, V, W) as shown in equation (4) can be converted into the global coordinate system (X,
(Y, Z) coordinate system.

[0019]

(Equation 4)

Next, the position measurement will be described. A global linear gradient magnetic field is used to determine the position of the sensor 1.
That is, a magnetic field whose intensity linearly changes in the X-axis direction, the Y-component in the Y-axis direction, and the Z-component in the Z-axis direction is used for the position.

[0021] FIG 2 shows a distribution diagram of a linear gradient field gh _X with a gradient in the X direction. This distribution is the same for linear gradient magnetic fields gh _Y and gh _Z having gradients in the Y direction and the Z direction, respectively. Such a linear gradient magnetic field can be generated in the intermediate region and the internal region by a pair of magnetic dipoles having the same polarity and opposite polarities on a straight line. If the point of symmetry of the linear gradient magnetic field obtained in this manner is set as the origin of the global coordinate system (X, Y, Z), the relationship between the linear gradient magnetic field gh _X and the position X is gh _X = kX. if Motomare linear gradient field gh _X, it is possible to easily calculate the X component of the position of the sensor 1. Note that k is a proportional constant determined by the coil constant and the sensor sensitivity. The Y component of the position,
The Z component can be calculated similarly. That is, the sensor position can be easily obtained from the linear gradient magnetic fields gh _Y and gh _Z and the proportional relationship between the obtained magnetic field vector component and each component of the position coordinates.

FIG. 3 is an explanatory diagram of each coil provided in the posture and position measuring device according to the present invention. FIG. 3A shows the first coil 10 for generating a uniform magnetic field on the Z axis, as shown in FIG.
Represents a second coil 20 for generating a uniform magnetic field on the X axis,
FIG. 3C illustrates a third coil 30 that generates a linear gradient magnetic field.

2 (A) and 3 (B).
Set of coils (first coil 10, second coil 20)
Also in the center is arranged a coil, it is intended to generate two kinds of uniform magnetic field h _X and h _Z having parallel orientation to the Z axis and the X-axis in the measurement region. As described later in experiments and calculations, the coils at both ends of the first coil 10 and the second coil 20 are, for example, 50 turns, and the coil at the center is
For example, the current can flow in the same direction as 31 turns (0.62 times).

The third coil 30 for generating a linear gradient magnetic field shown in FIG. 3C generates a linear gradient magnetic field by applying currents in opposite directions to a pair of coils wound at both ends. Things. With such a pair of rectangular coils, a linear gradient magnetic field can be generated in the directions of the X, Y, and Z axes. In experiments and calculations to be described later, the coils at both ends have, for example, 20 turns, and currents flow in opposite directions. The current flowing through the coil is, for example, a sine wave alternating current with a frequency of 50 Hz, and the current flowing through the two sets of uniform magnetic field generating coils is, for example, 78 mA.
The current flowing through the gradient magnetic field generating coil is, for example, 950
mA. The generated magnetic field is applied to a flux gate (eg,
The sensitivity was measured at 10 V / G, the resolution was 2 × 10 ⁻⁵ G, dc to 1 kHz). Note that the direction of the sensor 1 itself is (U, V, W) = (0,
0,1), that is, the W direction is defined as the direction of the sensor 1.

The coil 10 for generating a uniform magnetic field on the Z-axis and the coil 30 for generating a linear gradient magnetic field may be shared or separated, and may be appropriately designed. Also, in the measurement, the current flowing through each of the coils 10, 20 and 30 can be separately supplied instead of flowing all at once. However, the uniform magnetic field and the linear gradient magnetic field are the first, second and third magnetic fields. By operating any or all of the coils 10, 20, and 30 by time division or frequency division, a magnetic field is generated, and the attitude and / or position of the magnetic field sensor can be appropriately measured. Further, a current may be applied to only one of the first and second coils 10 or 20 to generate one uniform magnetic field, and the uniform magnetic field for the other one may be replaced by geomagnetism.

FIG. 4 shows a configuration diagram of a posture and position measuring apparatus according to the present invention. Here, the posture position measuring device 50 of FIG.
Is based on a frame in the shape of a cube. The posture position measuring device 50 includes first and second coils 10 and 20 for generating uniform magnetic fields on the Z axis and X axis, a third coil 30 for generating a linear gradient magnetic field, and the sensor 1.
The posture and position measurement device 50 includes the coils 10, 20, and 3
It is connected to an oscillator OSC, such as a sine wave oscillator, which supplies a current to 0, and a power amplifier. The sensor 1 is placed in the posture and position measuring device 50, and its signal is amplified by a flux gate magnetic flux amplifier and measured by a multimeter. Three sets of coils as shown in FIGS. 3A, 3B and 3C are attached to this frame. In principle,
3 defining the direction of the axis to which the uniform magnetic field is directed and the linear gradient magnetic field
The two axial directions may or may not be shared.

Next, experimental results and calculation results of the posture and position measuring apparatus according to the present invention will be described. First, the uniform magnetic field will be described.

FIG. 5 is an explanatory diagram of a calculation result of a magnetic field distribution of a uniform magnetic field. In order to measure the attitude of the sensor 1, the direction vector of the magnetic field must be uniform over the entire measurement area, and it is necessary to confirm this. Therefore, a rail for moving the sensor 1 is formed by a frame, and the X, Y, and Z components of the magnetic field when a uniform magnetic field parallel to the X-axis and the Z-axis are respectively generated are measured in a range of −20 ≦ X, Y , Z ≦ 20 every 5 cm.

FIG. 6 shows a characteristic diagram of the uniformity of the X-axis uniform magnetic field. This figure shows the X component of the magnetic field when a uniform magnetic field parallel to the X axis is generated. It can be seen that the movement on the X-axis and the movement on the diagonal line are almost constant, and the error is less than 1%.

FIG. 7 shows a characteristic diagram of the uniformity of the Z-axis uniform magnetic field. This figure shows the normalized Z component of the magnetic field when a uniform magnetic field parallel to the Z axis is generated, but the same result as in FIG. 7 was obtained. It can be seen that the direction vector of the magnetic field is substantially uniform over the entire measurement area, and that the uniformity is sufficient for posture measurement.

Next, the linear gradient magnetic field will be described.
Figure 8 is a diagram for explaining the calculation results of the relationship between X and the magnetic field gh _X.

This figure shows the result of calculation on the relationship between the X coordinate and the X component gh _X when a linear gradient magnetic field is generated by arranging two pairs of 1 m square coils facing each other at a distance of 1 m. When the position of the X coordinate is -20 ≦ X ≦ 20 and 0
It can be seen that when ≤Z≤20, X and gh _X are in a proportional relationship. Further, even if Z changes in the same range, the gradients of the graph match. This is the same even if Y changes. This shows that gh _X is a function of X only.
The calculation results also show the same tendency in the relationship between Y and gh _Y and between Z and gh _Z.

FIG. 9 is an explanatory diagram of the calculation result of the magnetic field distribution of the gradient magnetic field. In FIG. 10, the X component of the linear gradient magnetic field and gh
The relationship illustration of _X, FIG. 11 shows the relationship explanatory view of the Z component and gh _Z linear gradient fields. These figures show that the X, Y, and Z components of the gradient magnetic field are 5c in the measurement range -20 ≦ X, Y, Z ≦ 20.
The values measured for each m and their linearity are verified. As can be seen from FIG. 10, the X coordinate and gh _X are in a proportional relationship, and even when Y and Z are changed, the slopes of the graphs are almost the same, indicating that gh _X is a function dependent only on X. From the symmetry of the rectangular coil, the same can be said for the Y component gh _Y as for gh _X. Further, as can be seen from FIG. 11, the Z coordinate and gh _Z are also in a proportional relationship, and gh _Z
Is a function of only Z. This allows
It can be confirmed that the relationship of the expression (4) is sufficiently satisfied in the range of −20 ≦ X, Y, Z ≦ 20.

The following is a result of arranging the sensor 1 at an arbitrary position in an arbitrary posture and comparing the measured value with the actual position and posture. Experiment 1 setpoint sensor position (X, Y, Z) = (13,8, -5) sensor attitude _{(a X, a Y, a} Z) = (1,0,0) ( sensor facing the X positive direction State) Measurement value Sensor position (X, Y, Z) = (12.9, 7.7, −5.
3) Sensor position _{(a X, a Y, a} Z) = (0.99,0.01,
0.05) Experiment 2 Measurement value sensor position (X, Y, Z) = (2.2, -6.7,0.6) sensor attitude _{(a X, a Y, a} Z) = (- 0.01 , 0.9
7, -0.23) setpoint sensor position (X, Y, Z) = (1.5, -6,1) sensor attitude _{(a X, a Y, a} Z) = (0,0.97, - 0.
25)

From the above results, it can be seen that the set value and the measured value of the attitude of the sensor 1 substantially match. On the other hand, an error of less than 1 cm was observed in the position of the sensor 1, but this was because the sensors of each axis of the three-axis fluxgate used in this experiment were not at the same point in space, and were treated as the same point. Things seem to be the main cause. If the position of the sensor 1 is located, more accurate measurement can be performed.

[0036]

According to the present invention, a uniform magnetic field and a linear gradient magnetic field are used in a magnetic system, and a uniform magnetic field is used for posture detection.
By using a linear gradient magnetic field for position detection, the attitude and position can be simultaneously detected by a simple linear equation relating to the magnitude of the magnetic field, thereby simplifying data processing and enabling high-speed detection. .

Further, according to the present invention, the calculation algorithm is extremely easy as compared with the method using a dipole magnetic field, so that the time required for producing three-dimensional computer graphics by motion capture or the like can be shortened, and sports medicine and recreation can be used. It can be used for software production.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a coordinate system and a uniform magnetic field.

[Figure 2] distribution diagram of a linear gradient field gh _X with a gradient in the X direction.

FIG. 3 is an explanatory diagram of each coil provided in the posture and position measuring device according to the present invention.

FIG. 4 is a configuration diagram of a posture and position measurement device according to the present invention.

FIG. 5 is an explanatory diagram of a calculation result of a magnetic field distribution of a uniform magnetic field.

FIG. 6 is a characteristic diagram of uniformity of an X-axis uniform magnetic field.

FIG. 7 is a characteristic diagram of uniformity of a Z-axis uniform magnetic field.

Figure 8 is an explanatory diagram of a calculation result of the relationship between X and the magnetic field gh _X.

FIG. 9 is an explanatory diagram of a magnetic field distribution calculation result of a gradient magnetic field.

[10] relationship diagram of the X component and gh _X linear gradient fields.

[11] related illustration of the Z component and gh _Z linear gradient fields.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor 10 1st coil 20 2nd coil 30 3rd coil 50 Posture position measuring device

Claims (8)

[Claims] An attitude and position measuring device for measuring an attitude and a position of a sensor, comprising: a first coil for generating a uniform magnetic field in a first axial direction; and a second coil orthogonal to the first axial direction. A second coil for generating a uniform magnetic field in the axial direction; and a third coil for generating a linear gradient magnetic field in the three orthogonal axes, wherein a sensor is provided by the magnetic field generated by the first and second coils. A posture and position measuring device for measuring a posture of the sensor and measuring a position of the sensor by a magnetic field generated by the third coil. 2. The posture position measuring device according to claim 1, wherein said sensor is a three-axis magnetic field sensor. 3. The third coil has a pair of rectangular coils, and generates a gradient magnetic field in three orthogonal axes by applying currents to the respective rectangular coils in opposite directions. The posture position measuring device according to claim 1 or 2, wherein: 4. The posture position measurement according to claim 1, wherein the third coil is shared by a part or all of the first or second coil. apparatus. 5. A posture and position measuring method for measuring a posture and a position of a magnetic field sensor, wherein a uniform magnetic field is generated in a first axial direction and a second axial direction orthogonal to the first axial direction. The attitude of the magnetic field sensor is measured by the generated uniform magnetic fields, linear gradient magnetic fields are generated in three orthogonal axes, and the position of the magnetic field sensor is measured by the generated linear gradient magnetic fields. Posture position measurement method. 6. A method for generating a magnetic field by operating any or all of the first, second and third coils by time division or frequency division to measure the attitude and / or position of a magnetic field sensor. The posture position measuring method according to claim 5, wherein: 7. The method according to claim 5, wherein terrestrial magnetism is used as a uniform magnetic field in either the first or second axial direction. 8. The orthogonal three-axis directions are a first axial direction, a second axial direction, and a third axial direction orthogonal to the first and second axial directions, respectively. The posture position measuring method according to any one of claims 5 to 7.