JP2011033489A - Marker for motion capture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a marker for motion captures, capable of eliminating the need for equipment enlargement and attaining high accuracy without restrictions regarding the motion of an object. <P>SOLUTION: The marker 1 for motion captures is used for motion captures which detects motions of an object and is attached to a plurality of portions of the object. The marker 1 includes a magnetic sensor 2 that detects respective components of a geomagnetic vector, in triaxial directions orthogonal to each other in a marker coordinate system fixed to the marker 1; an acceleration sensor 3 that detects respective components of a gravitational acceleration vector in triaxial directions; a signal processor 4 that processes detection signals detected by the magnetic sensor 2 and the acceleration sensor 3; a power supply portion 5 that supplies electric power to the signal processor 4; and wireless means 6 that radio-transmits the data of the geomagnetic vector and the gravitational acceleration vector processed by the signal processor 4 to an external receiver. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motion capture marker that is used in motion capture for detecting the motion of an object such as a human body and is attached to a plurality of parts of the object.

In motion capture, a marker is attached to each part such as a human body, the movement of the marker is detected, detection data is captured in a computer, and the movement of the human body or the like is captured.
In general, the motion capture is roughly classified into an optical type and a magnetic type.
In optical motion capture, a marker is photographed by a camera, the movement of the marker is read from the photographed image, and the movement of a human body or the like is captured (Patent Document 1).
In the magnetic motion capture, a magnetic field is generated by an exciting coil in an area where a human body or the like moves, and the movement of a magnetic sensor (marker) attached to the human body is detected in the magnetic field (Patent Document 2).
In addition to the above, motion capture using a gyro sensor as a marker attached to a human body or the like has been proposed (Patent Document 3).

JP 2005-256232 A JP 2000-146509 A JP 2005-337983 A

However, the conventional motion capture has the following problems.
That is, in the optical motion capture (Patent Document 1), since the marker is photographed by the camera, it cannot be read when the marker enters the blind spot. Moreover, since a camera is required, the whole system becomes large. Another problem is that real-time analysis is difficult.

  In addition, since the magnetic motion capture (Patent Document 2) requires an exciting coil for generating a magnetic field in a region where a human body or the like moves, there is a limit to an area where a sufficient magnetic field is generated. In addition, wiring for taking the detection signal of the magnetic sensor into the analysis device is required, and there are restrictions on the movement of the human body and the like.

As a motion capture that does not require a camera or an excitation coil as described above, there is one using a gyro sensor (Patent Document 3).
However, since the gyro sensor detects an angular velocity, it is necessary to time-integrate the detected angular velocity in order to obtain a motion (posture) of a human body or the like. For this reason, the error in the relative position and the relative posture of each part becomes larger with time as the detection error of acceleration accumulates. For this reason, the time during which the movement of the human body or the like can be analyzed accurately is limited to a short time.

Further, not only the initial position of the gyro sensor but also the initial posture (yaw, roll, pitch) needs to be stored, and there is an error between the actual initial position and initial posture and the stored initial position and initial posture. The movement of the human body cannot be accurately captured.
In addition, it is not possible to wirelessly transmit signals directly from a plurality of gyro sensors to an external analyzer, and it is necessary to connect each gyro sensor to a transmitter and fix the transmitter to the human body. Restrictions arise.

  The present invention has been made in view of such conventional problems, and does not restrict the operation of an object, does not require an increase in equipment size, and provides a highly accurate marker for motion capture. Is.

The present invention is a motion capture marker used in motion capture for detecting the motion of an object and attached to a plurality of parts of the object,
The marker includes a magnetic sensor that detects each component of a geomagnetic vector in three axis directions orthogonal to each other in a marker coordinate system fixed to the marker,
An acceleration sensor for detecting each component of the gravitational acceleration vector in the three-axis directions;
A signal processing unit for processing detection signals detected by the magnetic sensor and the acceleration sensor;
A power supply for supplying power to the signal processor;
A motion capture marker comprising: wireless means for wirelessly transmitting data of the geomagnetic vector and the gravitational acceleration vector processed by the signal processing unit to an external receiving device (claim 1). ).

  The motion capture marker includes the magnetic sensor and the acceleration sensor. Thereby, it is possible to detect the geomagnetic vector and the acceleration vector in the three-axis coordinate system (marker coordinate system) orthogonal to each other fixed to the marker, and based on these, the earth coordinate system based on the marker coordinate system Can be requested. Based on the relationship between the earth coordinate system and the marker coordinate system, the posture (azimuth and inclination) of the marker can be obtained.

The position of each part relative to the reference position can be obtained based on the posture data of the markers arranged in each part of the object thus obtained and the skeleton data of the object prepared in advance.
As a result, the position and orientation relative to the reference position can be obtained for each part of the target object to which the marker is attached. By capturing the position and orientation data of each part continuously every moment, motion capture can accurately grasp the movement of the entire object.

Here, the marker detects its posture using the magnetic sensor and the acceleration sensor. That is, by using geomagnetism and gravitational acceleration existing in the natural world, the posture of the marker can be detected, and based on this, the relative position of the marker at each part can also be obtained.
Therefore, it is not necessary to artificially form a magnetic field over the entire motion region of the target object, and it is not necessary to use a large-scale device such as an excitation coil, thereby preventing an increase in size of the facility. In other words, the motion area of the object can be greatly increased.

Further, the marker detects a geomagnetic vector and a gravitational acceleration vector by a magnetic sensor and an acceleration sensor built in itself, and does not require a camera for imaging the marker as in optical motion capture. From this viewpoint, the equipment can be reduced in size and simplified.
Furthermore, unlike the case of the marker imaged by the camera, the marker does not become a blind spot of the object and the state where the movement cannot be detected does not occur. Therefore, there is no restriction on the posture of the object that can be detected.

Further, since the position and relative position of each part can be detected using geomagnetism and gravitational acceleration, detection errors are unlikely to occur, and highly accurate detection can be achieved.
That is, unlike the case of the gyro sensor, the posture of the marker can be accurately derived from the obtained geomagnetic vector and gravity acceleration vector without the need for time integration of the detected angular velocity, and the skeleton data The position of the marker can also be accurately derived from the superposition of. Therefore, accurate measurement over a long time is possible.
Further, since the posture of each marker is obtained from the obtained geomagnetic vector and gravitational acceleration vector, it is not necessary to store the initial posture.

  Further, since the marker includes the wireless unit, the data of the geomagnetic vector and the gravitational acceleration vector can be wirelessly transmitted from each marker to an external receiving device. Thereby, it is not necessary to connect between each marker, or to connect each marker and the receiving device, and it is possible to reduce restrictions on the movement of the object.

  As described above, according to the present invention, it is possible to provide a highly accurate motion capture marker without restricting the operation of an object and without requiring an increase in size of equipment.

The perspective view of the marker for motion capture in an Example. Explanatory drawing of the state which attached the marker to the target object (human body) in an Example. The image figure of the data transmission / reception between a marker, a receiver, and a personal computer in an Example.

In the present invention (Claim 1), examples of the object include a human body and other animals.
In addition to the geomagnetic vector and the gravitational acceleration vector data themselves, the data wirelessly transmitted by the wireless means to the receiving device may be the attitude data of the marker calculated based on these.
Further, the motion data of the object captured by the motion capture can be used for various purposes such as medicine, sports, animation, and advertisement.

Preferably, the magnetic sensor includes three magneto-impedance sensor elements that detect the geomagnetic components in the three axial directions, respectively.
In this case, the detection accuracy of the magnetic sensor can be easily improved and downsized, and a small motion capture marker with excellent detection accuracy can be obtained. Thereby, it is possible to smoothly capture fine and delicate movements of the object. Furthermore, it is possible to accurately capture the detailed movement of the object, such as the movement of the finger.

A motion capture marker according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 2, the motion capture marker 1 of this example is used in motion capture for detecting the operation of a target (human body) and is attached to a plurality of parts of the target (human body).

As shown in FIG. 1, the marker 1 includes the following magnetic sensor 2, acceleration sensor 3, signal processing unit 4, power supply unit 5, and wireless unit 6.
The magnetic sensor 2 detects each component of the geomagnetic vector in the three axis directions orthogonal to each other in the marker coordinate system fixed to the marker 1.
The acceleration sensor 3 detects each component of the gravitational acceleration vector in the three axis directions.
The signal processing unit 4 processes the detection signals detected by the magnetic sensor 2 and the acceleration sensor 3.
The power supply unit 5 supplies power to the signal processing unit 4.
The wireless means 6 wirelessly transmits the geomagnetic vector and gravity acceleration vector data processed by the signal processing unit 4 to an external receiving device 81 (see FIGS. 2 and 3).

As shown in FIG. 1, the marker 1 has a magnetic sensor 2, an acceleration sensor 3, a signal processing unit 4, and a power supply on one surface (component mounting surface 51) of a power supply unit 5 made of a disk-shaped coin-type battery. The unit 5 and the wireless means 6 are mounted.
The magnetic sensor 2 includes three magneto-impedance sensor elements 21x, 21y, and 21z that respectively detect the geomagnetic components in the three axial directions. The magneto-impedance sensor elements 21x, 21y, and 21z perform magnetic sensing using an MI (Magneto-impedance) phenomenon, and are disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-113993.
Further, as the acceleration sensor 3, a capacitive acceleration sensor can be used.

The signal processing unit 4 includes a microcomputer including a CPU, a ROM, a RAM, an I / O, and a connection line that connects them, and the magnetic sensor 2, the acceleration sensor 3, and the wireless unit 6 are connected to the signal processing unit 4. Then, detection signals of the geomagnetic vector and the gravitational acceleration vector are input to the signal processing unit 4 from the magnetic sensor 2 and the acceleration sensor 3.
The wireless unit 6 includes a wireless IC 61 and an antenna 62. The antenna 62 is formed on the entire circumference of the component mounting surface 51 in the power supply unit 5.

As shown in FIG. 2, the marker 1 (1a to 1p) in this example includes a head, left and right shoulders, left and right elbows, left and right wrists, left and right hands, waist, left and right knees, left and right heels, and left and right toes. It attaches to each site | part in the human body 7 of a to-be-measured person. About the attachment site | part of the marker 1, it changes suitably according to the objective and application of motion capture.
Further, skeleton data of the human body 7 to which the marker 1 is attached is prepared. This skeleton data is stored in a personal computer 82 that is separate from the marker 1 and is not attached to the human body 7. Further, the data of the attachment position of the marker 1 on the human body 7 is stored in the personal computer 82 in association with the skeleton data.

  Then, the basic posture (for example, an upright posture) is maintained before the movement of the human body 7 is started. The position (initial position) of each part to which the marker 1 is attached in this initial state is set in advance based on the skeleton data. That is, before starting the exercise, the basic posture is taken in order to adjust each part to the initial position.

  In this state, the detection of the geomagnetic vector and the gravitational acceleration vector is started in each marker 1, and then the motion of the human body 7 is started. And each marker 1 (1a-1p) detects a geomagnetic vector and a gravitational acceleration vector moment by moment, and as shown in FIG. 3, the data of a geomagnetic vector and a gravitational acceleration vector are sent from each marker 1 to the receiving apparatus 81. Sequential wireless transmission. The data of the geomagnetic vector and the gravitational acceleration vector received by the receiving device 81 is analyzed by the personal computer 82 to determine the movement of the human body 7. Thereby, the movement of the human body 7 is captured.

  In the data analysis of the geomagnetic vector and the gravitational acceleration vector by the personal computer 82, the earth coordinate system fixed to the earth with respect to the marker coordinate system fixed to the marker 1 in each marker 1 is determined from the data of the geomagnetic vector and the gravitational acceleration vector. Obtain the orientation and orientation of the marker 1 from these relationships. That is, the azimuth | direction and attitude | position (yaw, roll, pitch) which each part of the human body 7 faces are calculated | required.

For example, the posture of each marker 1 is defined as the yaw angle η with respect to the true north in the horizontal direction, the roll angle φ around the Y axis of the marker coordinate system fixed to the marker 1, and the pitch around the X axis of the marker coordinate system. Obtained as the angle θ. The yaw angle η, roll angle φ, and pitch angle θ can be derived from the following calculation formula (Formula 2) using the components (Formula 1) of the geomagnetic vector M and the gravitational acceleration vector G. This posture calculation method is disclosed in, for example, “Robot Manipulator <Mathematical Foundations, Programming, and Control>” (Corona, RP Paul, Tsuneo Yoshikawa, P.46). This is a well-known method.
Note that Mx, My, and Mz in [Equation 1] and [Equation 2] are the components of the geomagnetic vectors in the X-axis direction, the Y-axis direction, and the Z-axis direction, which are three axis directions orthogonal to each other in the marker coordinate system. Gx, Gy, and Gz are components of gravity acceleration vectors in the X-axis direction, the Y-axis direction, and the Z-axis direction, which are three axis directions orthogonal to each other in the marker coordinate system.

Further, the relative position of each part is obtained from the obtained posture data of each part and the skeleton data. That is, for example, the positions of the head, hands, feet, etc. with respect to the waist are obtained.
Thereby, the posture and position of each part of the human body 7 are obtained, and the movement of the human body 7 is obtained. Then, the obtained motion of the human body 7 is displayed or recorded in real time on an image display device connected to the personal computer 82.

  In detecting the gravitational acceleration by the acceleration sensor 3, it is necessary to remove accelerations other than the gravitational acceleration as noise. In other words, since the movement of each part of the human body 7 is accompanied by an acceleration, the marker 1 also acts on the marker 1 with an acceleration other than the gravitational acceleration. Therefore, the signal processing unit 4 in each marker 1 is provided with a filter for removing acceleration components other than the gravitational acceleration component from the obtained acceleration component. Only the data remains. For example, a digital filter such as an IIR filter can be used as a filter for realizing this.

Next, the function and effect of this example will be described.
The motion capture marker 1 includes a magnetic sensor 2 and an acceleration sensor 3. Thereby, it is possible to detect the geomagnetic vector and the acceleration vector in a three-axis coordinate system (marker coordinate system) orthogonal to each other fixed to the marker 1, and based on these, the earth coordinates based on the marker coordinate system A system can be obtained. Based on the relationship between the earth coordinate system and the marker coordinate system, the posture (azimuth and inclination) of the marker 1 can be obtained.

The position of each part relative to the reference position can be obtained based on the posture data of the marker 1 arranged at each part of the human body 7 and the skeleton data of the human body 7 prepared in advance.
As a result, the position and posture relative to the reference position can be obtained for each part of the human body 7 to which the marker 1 is attached. By capturing the position and posture data of each part continuously and momentarily, the motion capture can accurately grasp the movement of the entire human body 7.

Here, the marker 1 detects its own posture using the magnetic sensor 2 and the acceleration sensor 3. That is, it is possible to detect the posture of the marker 1 by using the geomagnetism and the gravitational acceleration existing in the natural world, and to obtain the relative position of the marker 1 at each part based on this.
For this reason, it is not necessary to artificially form a magnetic field in the entire motion region of the human body 7, and it is not necessary to use a large-scale device such as an excitation coil, thereby preventing an increase in size of the facility. In other words, the motion area of the human body 7 can be significantly widened.

In addition, the marker 1 detects the geomagnetic vector and the gravitational acceleration vector by the magnetic sensor 2 and the acceleration sensor 3 incorporated in the marker 1 and does not require a camera or the like for imaging the marker as in the optical motion capture. . From this point of view, the facility can be reduced in size and simplified.
Furthermore, unlike the case of the marker imaged by the camera, the marker 1 does not become a blind spot of the human body 7 so that the movement cannot be detected. Therefore, there is no restriction on the posture of the human body 7 that can be detected.

Further, since the position and relative position of each part can be detected using geomagnetism and gravitational acceleration, detection errors are unlikely to occur, and highly accurate detection can be achieved.
That is, unlike the case of the gyro sensor, the posture of the marker 1 can be accurately derived from the obtained geomagnetic vector and the gravitational acceleration vector without the need for time integration of the detected angular velocity. From the overlay with the data, the position of the marker 1 can also be accurately derived. Therefore, accurate measurement over a long time is possible.
Further, since the posture of each marker 1 is obtained from the obtained geomagnetic vector and the gravitational acceleration vector, it is not necessary to store the initial posture.

  In addition, since the marker 1 includes the wireless unit 6, the data of the geomagnetic vector and the gravitational acceleration vector can be wirelessly transmitted from each marker 1 to the external receiving device 81. Thereby, it is not necessary to connect between the markers 1 or connect the markers 1 and the receiving device 81, and the restriction of the movement of the human body 7 can be reduced.

  The magnetic sensor 2 includes three magneto-impedance sensor elements 21x, 21y, and 21z. Therefore, the detection accuracy of the magnetic sensor 2 can be easily improved and downsized, and the small motion capture marker 1 with excellent detection accuracy can be obtained. Thereby, the fine delicate movement of the human body 7 can be captured smoothly. Furthermore, it is possible to accurately capture the movement of details in the human body 7, such as the movement of a finger.

  As described above, according to this example, it is possible to provide a highly accurate motion capture marker without restricting the movement of the human body, without requiring an increase in size of equipment.

DESCRIPTION OF SYMBOLS 1 Marker 2 Magnetic sensor 3 Acceleration sensor 4 Signal processing part 5 Power supply part 6 Wireless means 81 Receiver

Claims (2)

A motion capture marker that is used in motion capture to detect the motion of an object and is attached to a plurality of parts of the object,
The marker includes a magnetic sensor that detects each component of a geomagnetic vector in three axis directions orthogonal to each other in a marker coordinate system fixed to the marker,
An acceleration sensor for detecting each component of the gravitational acceleration vector in the three-axis directions;
A signal processing unit for processing detection signals detected by the magnetic sensor and the acceleration sensor;
A power supply for supplying power to the signal processor;
A motion capture marker, comprising: wireless means for wirelessly transmitting data of the geomagnetic vector and the gravitational acceleration vector processed by the signal processing unit to an external receiving device.   2. The motion capture marker according to claim 1, wherein the magnetic sensor includes three magneto-impedance sensor elements that respectively detect the geomagnetic components in the three axial directions.

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