JP2005065789A - Magnetic balance type triaxial acceleration sensor and body movement detector using the sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic balance type triaxial acceleration sensor capable of dispensing with a power source for driving a sensor circuit capable of detecting the direction of body movement and acceleration and being miniaturized in terms of a mechanism, and a body movement detector using the sensor. <P>SOLUTION: The body movement detector is constituted of the magnetic balance type triaxial acceleration sensor, for which magnetic balance type acceleration sensors constituted of a movable magnet balanced so as to vibrate in an axial direction inside a cylinder and a coil wound around the outer surface of the cylinder are disposed in X axis, Y axis and Z axis directions so as to orthogonally cross each other, and an A/D converter for converting induced electromotive force outputted from the coil of the magnetic balance type triaxial acceleration sensor to a digital value. Also, a data output device for adding ID information for identifying data from the plurality of magnetic balance type triaxial acceleration sensors and interfacing with communication equipment is connected to the A/D converter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, a magnetic balance type 3 axis acceleration sensor composed of a combination of magnetic balance type acceleration sensors can detect a back-and-forth, right-and-left and up-and-down movement, that is, body movement of a measured object, particularly a human body. The present invention relates to an axial acceleration sensor and a body motion detection apparatus using the sensor.

  Conventionally, a body motion sensor has been used as a method for detecting body motion of a human body, detecting the number of steps of a pedometer, and the like. As the type of the body motion sensor, there is a photoelectric body motion sensor, a contact-type body motion sensor, or a pendulum body motion sensor, as described in “calorie measuring device” of JP-A-2000-041971. Further, as described in “Body Motion Detection Device” of Japanese Patent Application Laid-Open No. 2002-191580, there is an acceleration sensor using a piezoelectric element.

The photoelectric body motion sensor has a light emitting element and a light receiving element arranged at opposite corners in a substantially square container and accommodates a ball. Then, when the ball moves around in the container by body movement, light shielding and light reception between the light emitting element and the light receiving element are repeated and a pulse is output. Further, the contact type body motion sensor has four conductive pins arranged at the apex of the square and accommodates a large conductive ball inside the conductive pin. Then, the conductive ball comes into contact between the conductive pins due to body movement, and conducts to output a pulse. As another method, conductive electrodes are arranged on opposite surfaces in a spherical container and a plurality of small conductive balls are accommodated. When a plurality of conductive balls are collected on one side of the conductive electrode due to body movement, the conductive balls come into contact with each other and the conductive electrodes are connected to each other to output a pulse. The pendulum type body motion sensor houses a magnet in a cylindrical container and arranges a reed switch near the outside. Each time the magnet moves in the container due to body movement, the contact of the reed switch is turned ON / OFF to output a pulse. Further, in the case of the acceleration sensor, a piezoelectric element is disposed on the surface of a plate-like support and a weight is disposed at one end of the support. When the weight vibrates due to body movement, a voltage signal corresponding to the acceleration is output from the piezoelectric element.
Japanese Unexamined Patent Publication No. 2000-04-1971 JP 2002-191580 A

  However, the photoelectric body motion sensor, the contact body motion sensor, and the pendulum body motion sensor are suitable for performing body motion detection by periodic motion in a certain direction because the body motion is output as a pulse signal. There is a problem that the direction and acceleration of body movement cannot be detected. An acceleration sensor using a piezoelectric element outputs body movement as an electrical signal due to a change in voltage, so that not only the direction of body movement but also acceleration can be detected. However, in order to drive a sensor circuit using a piezoelectric element. However, there was a problem that a power source was necessary. Further, there is a problem that the size cannot be reduced due to the structure in which a weight is disposed at one end of the support.

  The present invention has been made to solve the above-described problems, and does not require a power source for driving a sensor circuit capable of detecting the direction of body movement or acceleration, and is mechanically small. It is an object of the present invention to provide a magnetically balanced three-axis acceleration sensor that can be realized and a body motion detection device using the sensor.

  In order to solve the above-described problems, a magnetically balanced three-axis acceleration sensor and a body motion detection device using the sensor of the present invention are wound around a movable magnet and an outer surface of the cylinder that are balanced in an axially vibrated manner. A magnetic balance type triaxial acceleration sensor constituted by arranging magnetic balance type acceleration sensors constituted by coils so as to be orthogonal to each other in the X-axis, Y-axis and Z-axis directions, and a coil of the magnetic balance type three-axis acceleration sensor The A / D conversion device for converting the induced electromotive force output from the digital value into a digital value. A data output device for adding ID information for identifying data from a plurality of magnetic balance type triaxial acceleration sensors and for interfacing with a communication device is connected to the A / D conversion device.

  If the body movement in the measurement object, particularly the human body, is detected by the magnetic balance type triaxial acceleration sensor of the present invention and the body movement detection device using the sensor, the inside of the coil of the magnetic balance type triaxial acceleration sensor vibrates. Since the induced electromotive force proportional to the frequency and acceleration is obtained by the magnet that performs, the sensor circuit and the power source are unnecessary. Furthermore, there is an effect that the sensitivity is increased by adjusting the output voltage by the number of turns of the coil and the magnetic strength of the magnet and by scaling in the A / D converter. Furthermore, since the vibration direction of the magnet is the axial direction inside the cylinder, there is an effect that it is possible to reduce the size mechanically.

  A best mode for carrying out a magnetic balance type triaxial acceleration sensor of the present invention and a body motion detection apparatus using the sensor will be described with reference to the drawings. FIG. 1 is a front sectional view of a magnetic balance type acceleration sensor of the present invention, and FIG. 2 is a configuration layout diagram of a magnetic balance type three-axis acceleration sensor configured by combining the magnetic balance type acceleration sensors of the present invention.

  As shown in FIG. 1, a magnetic balance type acceleration sensor 1 constituting a magnetic balance type triaxial acceleration sensor 7 of the present invention has a movable magnet 3 housed in a cylinder 2 and movable magnets at both ends of the cylinder 2. The fixed magnets 5 and 5 are fixed so that the same polarity as the polarity of 3 is opposed, and the movable magnet 3 is arranged in a balanced manner so as to vibrate in the axial direction inside the cylinder 2. Further, a coil for generating an induced electromotive force is wound around the outer surface of the cylinder 2 at the tip of the movable magnet 3. In FIG. 1, the coils 6 and 6 are wound around the two ends of the movable magnet. However, either one of the upper coil 6 and the lower coil 6 may be used. The magnetic strength of the fixed magnets 5 and 5 and the number of turns of the coils 6 and 6 for placing the movable magnet 3 in a balanced manner are arbitrarily designed depending on the system used.

  In FIG. 1 (a), steel balls 4 and 4 are disposed at both ends of the movable magnet 3. This is because the inner surface of the cylinder 2 and the steel ball are moved when the movable magnet 3 vibrates inside the cylinder 2. FIG. This is to reduce the influence of sliding friction when 4 and 4 are in point contact. Further, in (b), since both end portions of the movable magnet 3 'are formed in a spherical shape in advance, the same effect as in (a) can be obtained. In this case, the steel balls 4 and 4 are unnecessary.

  Next, as shown in FIG. 2, the magnetic balance type acceleration sensor 1 is arranged so as to be orthogonal to each other in the X-axis, Y-axis, and Z-axis directions to form a magnetic balance type three-axis acceleration sensor 7. Here, an induced electromotive force is generated from the coils 6a, 6a of the magnetic balance type acceleration sensor 1a arranged in the X axis direction when the magnetic balance type acceleration sensor 1a vibrates in the X axis direction, and is arranged in the Y axis direction. An induced electromotive force is generated from the coils 6b and 6b of the magnetic balance type acceleration sensor 1b provided when the magnetic balance type acceleration sensor 1b vibrates in the Y axis direction, and the magnetic balance type acceleration sensor 1c arranged in the Z axis direction. From the coils 6c and 6c, an induced electromotive force is generated when the magnetic balanced acceleration sensor 1c vibrates in the Z-axis direction.

  Next, FIG. 3 is a configuration diagram of a body motion detection apparatus using the magnetic balance type triaxial acceleration sensor of the present invention, and induced electromotive force generated from the coils 6a and 6a of the magnetic balance type acceleration sensor 1a in the X-axis direction. The induced electromotive force generated from the coils 6b and 6b of the magnetic balance type acceleration sensor 1b in the Y axis direction and the induced electromotive force generated from the coils 6c and 6c of the magnetic balance type acceleration sensor 1c in the Z axis direction are A / D. Connect to the converter 8. The A / D converter 8 performs analog arithmetic processing and A / D conversion on the induced electromotive force generated from the coils 6 and 6 of each magnetic balance type acceleration sensor 1 of the magnetic balance type triaxial acceleration sensor 7 accompanying body movement. It is converted into a digital value in each axial direction by processing. Further, in order to identify data from a plurality of magnetic balance type three-axis acceleration sensors 7, ID information is added to the data, and an interface with a communication device such as a wireless receiver or LAN for processing the data is performed. The data output device 14 is connected to the A / D conversion device 8.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 4 shows voltage waveforms output from the magnetic balance type acceleration sensor of the present invention. The movable magnet 3 of each magnetic balance type acceleration sensor 1 of the magnetic balance type triaxial acceleration sensor 7 described in FIGS. 1 and 2 vibrates. It shows the waveform of the induced electromotive force generated at the time. Here, when the magnetic balance type acceleration sensor 1 vibrates once in the direction of the arrow A in the figure, one cycle AC voltage indicated by V1 is generated from the coils 6 and 6 of the movable magnet 3. Further, when one vibration is made in the direction of arrow B in the figure, one cycle of AC voltage indicated by V2 is generated from the coils 6 and 6 of the movable magnet 3. Since the alternating voltages of V1 and V2 have opposite polarities, the body movement direction can be detected by determining the polarity. Further, since the voltage value of the induced electromotive force changes depending on the strength of body motion, that is, the strength of acceleration, the body motion acceleration can be detected by measuring the voltage value and the fluctuation period.

  Next, FIG. 5 is a schematic block circuit diagram of the A / D converter in FIG. As shown in the figure, the A / D converter 8 is output from a magnetic balance type acceleration sensor 1a in the X axis direction, a magnetic balance type acceleration sensor 1b in the Y axis direction, and a magnetic balance type acceleration sensor 1c in the Z axis direction. An analog arithmetic unit 9 for inputting the induced electromotive force, and the input voltage of the three channels of the X axis, the Y axis, and the Z axis scaled by the analog arithmetic unit 9 are selectively switched to the A / D converter 11 at the subsequent stage. An analog multiplexer 10 for outputting, an A / D converter 11 for converting a voltage input output from the analog multiplexer 10 into a digital value, and clock generation and timing control of the analog multiplexer 10 and the A / D converter 11 The clock control unit 12 and the like for performing the above.

  In the above description, since the coils 6 are arranged above and below the cylinder 2 in each magnetic balance type acceleration sensor 1, the induced electromotive force generated from each of the coils 6 and 6 is matched in polarity, and the analog calculation unit 10 are added by the preceding addition circuit and are scaled by the subsequent OP amplifier. In each magnetic balance type acceleration sensor 1, when only one coil 6 is provided, an adding circuit is not necessary. Note that the analog operation unit 9 in FIG. 5 is only a component, and is not limited to the illustrated circuit.

  When the magnetic balance type triaxial acceleration sensor 7 is attached to a measurement object such as a human body and the person moves back and forth, right and left and up and down, the induced electromotive force is generated from each magnetic balance type acceleration sensor 1 of the magnetic balance type triaxial acceleration sensor 7. Will be generated. Since the speed of body movement of the human body is at most several Hz, the induced electromotive force is sampled by the analog multiplexer 10 with a period of about several tens Hz and converted into a digital value by the A / D converter 11. As the digital value, a polarity of 1 bit and a data resolution of 7 bits, that is, a resolution of about −127 to +127 are sufficient, and a serial output is preferable as the data output form, but it is not limited to this.

  FIG. 6 is a schematic block circuit diagram of the data output device in FIG. As shown in the figure, the data output device 13 stores an input interface unit 14 for inputting a serial output from the A / D converter 8 and an ID uniquely given to the data output device 13. A memory unit 15 for storing, a logic control unit 16 for controlling a subsequent-stage RF output unit 18 in the case of wireless output, and a subsequent-stage serial data output unit 19 in the case of wired output, and the memory The clock control unit 17 and the like for performing clock generation and timing control of the unit 15 and the logic control unit 16 are configured.

  FIG. 7 is an example of a data format of serial data output from the body motion detection device using the magnetically balanced three-axis acceleration sensor of the present invention. A header indicating the start of data, X-axis data, and Y-axis Data, Z-axis data, and an ID uniquely assigned to the data output device 13. When the output of the data output device 13 is a wireless output, data in the format is output from the RF output unit 18 and the antenna 20 to the wireless receiver. In the case of wired output, data in the format is output from the serial data output unit 19 to the LAN or the like.

  Since the X-axis data, Y-axis data, and Z-axis data include polarity data and electromotive force data, it is possible to detect the direction and acceleration of body movement by analyzing the data in vector. Become.

It is front sectional drawing of the magnetic balance type | mold acceleration sensor of this invention. It is a block diagram of a magnetic balance type triaxial acceleration sensor configured by combining the magnetic balance type acceleration sensors of the present invention. It is a block diagram of the body motion detection apparatus using the magnetic balance type | mold triaxial acceleration sensor of this invention. It is a voltage waveform output from the magnetic balance type | mold acceleration sensor of this invention. FIG. 4 is a schematic block circuit diagram of the A / D conversion device in FIG. 3. FIG. 4 is a schematic block circuit diagram of the data output device in FIG. 3. It is an example of the data format of the serial data output from the body motion detection apparatus which uses the magnetic balance type | mold triaxial acceleration sensor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic balance type acceleration sensor 2 Cylinder 3 Movable magnet 4 Steel ball 5 Fixed magnet 6 Coil 7 Magnetic balance type 3 axis acceleration sensor 8 A / D converter 9 Analog operation part 10 Analog multiplexer 11 A / D converter 12 Clock control part 13 Data output device 14 Input interface unit 15 Memory unit 16 Logic control unit 17 Clock control unit 18 RF output unit 19 Serial data output unit 20 Antenna

Claims (2)

  A magnetic balance type acceleration sensor (1) composed of a movable magnet (3) balanced inside the cylinder (2) so as to vibrate in the axial direction and a coil (6) wound on the outer surface of the cylinder (2) is connected to the X axis, Y Magnetic balance type triaxial acceleration sensor (7) arranged so as to be orthogonal to each other in the direction of the axis and the Z axis, and induction output from the coil (6) of the magnetic balance type triaxial acceleration sensor (7) A magnetic balance type triaxial acceleration sensor and a body motion detection apparatus using the sensor, characterized by comprising an A / D converter (8) for converting an electromotive force into a digital value.   A data output device (14) for adding ID information for identifying data from a plurality of magnetic balance type three-axis acceleration sensors (7) and interfacing with communication equipment is the A / D converter (8). 2. A magnetic balance type triaxial acceleration sensor according to claim 1, and a body motion detection apparatus using the sensor.

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