JP2010264174A - Surface myoelectric potential sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface myoelectric potential sensor, simply applied and used repeatedly by anyone. <P>SOLUTION: This surface myoelectric potential sensor 1 includes: a myoelectric potential detecting electrode 2 formed of a dry type passive electrode; and an amplifier circuit 3 for amplifying the myoelectric potential detected by the myoelectric potential detecting electrode 2. The myoelectric potential detecting electrode 2 and the amplifier circuit 3 are connected to each other by a coaxial cable 4, and an external conductor 5 of the coaxial cable 4 is a body earth wire 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface myoelectric sensor that detects a myoelectric potential generated when a muscle contracts from the skin surface, and more particularly to a surface myoelectric sensor with improved connection between a myoelectric potential detecting electrode and an amplifier circuit. is there.

  Muscle activity begins with α motor neurons 61 in the spinal cord 60, as shown in FIG. When the α motor neuron 61 is excited by a command from the brain or various reflexes via the spinal cord 60, the excitation impulse is transmitted to the muscle via the nerve axon 62. When the excitation impulse is transmitted to the muscle, the excitation impulse propagates from the neuromuscular connection portion 63 toward the end of the muscle fiber 64. It is known that when the excitement is transmitted to the muscle fibers 64, the muscle fibers 64 contract, and a voltage is generated in this process.

  Therefore, as shown in FIG. 6, by providing the electrode 65 on the propagation path of the excitation impulse of the muscle fiber 64, the myoelectric potential corresponding to the muscle activity state can be detected. However, the method of directly providing the electrode 65 on the muscle fiber 64 inevitably involves invasive measurement, and is therefore performed only when detailed data for each muscle is desired in the medical field.

  As another method, a method of detecting a myoelectric potential signal from the skin surface is also used. In this method, the measurement signal becomes an interference waveform of a myoelectric potential signal generated in various muscles and the SN ratio is deteriorated, but it is used as a simple measurement method.

  Myoelectric potential acquired from the skin surface is called surface myoelectric potential and can be measured non-invasively, so it is used for rough measurement of muscle movement during sports training and rehabilitation. Research has been conducted on methods for using myoelectric potential signals for control, such as control of a prosthetic hand and operation of a computer, and application products that are close to practical use, such as a power assist suit that supports the muscle strength of a person with weak muscle strength, are being made.

  Since the surface myoelectric potential is a very small signal of about several mV, the measurement is performed using an operation amplification circuit using an instrumentation amplifier 70 as shown in FIG. A method for removing irrelevant common-mode noise signals is employed.

The instrumentation amplifier 70 amplifies the difference between the myoelectric potentials input to the two input terminals from the two myoelectric potential detection electrodes 72 and 73 disposed on the skin surface 71, and outputs the difference centered on the reference potential _VREF. It is. The instrumentation amplifier 70 includes a gain adjustment circuit 74 that adjusts the gain (high-pass characteristics).

The body ground electrode 75 functions to suppress noise coupled to the human body through a space such as hum noise by setting the human body potential equal to the reference potential V _REF .

  As detection electrode methods, there are a wet electrode method using a conductive paste on the skin surface 71 and a dry electrode method using no conductive paste in order to reduce the contact impedance between the myoelectric potential detection electrodes 72 and 73 and the skin.

  When the dry electrode is used, the contact impedance is very large, so that the wiring between the myoelectric potential detection electrodes 72 and 73 and the input terminal of the instrumentation amplifier 70 becomes high impedance, weakens to noise, and increases the wiring length. I can't.

  For this reason, when a long wiring is desired, as shown in FIG. 8, a buffer amplifier 80 is inserted immediately after the myoelectric potential detection electrodes 72 and 73 to lower the impedance of the wiring (active electrode).

JP 2007-89676 A

  By the way, when considering application of the surface myoelectric potential sensor to the control of a subject that moves in a complicated manner such as a prosthetic hand, it is essential to simultaneously measure myoelectric potentials at a plurality of locations. Further, it is desirable that the surface myoelectric sensor be easily detachable. As shown in FIG. 9, a large number of myoelectric potential detection electrodes (or surface myoelectric potential sensors) 90 are installed on a garment-like one and worn as if worn. A possible multipoint myoelectric potential sensor (cloth-type surface myoelectric potential sensor) 91 has been studied.

  However, when an active electrode is used as the myoelectric potential detection electrode, an active circuit element (buffer amplifier 80) is required for the myoelectric potential detection electrode. There was a problem of being lost. Since there are individual differences in the shape of the body, it is not preferable that flexibility is lost in order to fit the surface myoelectric potential sensor to anyone.

  In addition, the wet electrode has a problem that it is necessary to apply an adhesive conductive paste to the skin surface and is not suitable for repeated use.

  Therefore, an object of the present invention is to solve these problems and provide a surface myoelectric potential sensor that can be easily worn by anyone and can be used repeatedly.

  The present invention devised to achieve the above object is a surface myoelectric potential sensor having a myoelectric potential detection electrode comprising a dry passive electrode and an amplification circuit for amplifying myoelectric potential detected by the myoelectric potential detection electrode. In the surface myoelectric potential sensor, the myoelectric potential detection electrode and the amplifier circuit are connected by a coaxial cable, and an outer conductor of the coaxial cable is a body ground wiring.

  A plurality of units in which the myoelectric potential detection electrode and the body earth electrode are paired are connected by an elastic material, the myoelectric potential detection electrodes of each unit are connected to each amplifier circuit by the coaxial cable, and The body ground electrode of each unit may be connected to the outer conductor of each coaxial cable.

  The myoelectric potential detection electrode and the body ground electrode may be fixed to a cloth-like material, and at least a part of the coaxial cable may be sewn to the cloth-like material.

  According to the present invention, a surface myoelectric potential sensor that can be easily worn by anyone and can be used repeatedly can be provided.

It is the schematic of the surface myoelectric potential sensor which shows one embodiment of this invention. It is a figure which shows the myoelectric potential waveform acquired using a dry electrode as a passive electrode. It is a figure which shows the myoelectric potential waveform acquired by using a dry electrode as a passive electrode, and also wiring between the myoelectric potential detection electrode and the input terminal of an instrumentation amplifier with a coaxial cable. It is a figure which shows the example of a connection of a myoelectric potential detection electrode and an instrumentation amplifier. It is the schematic of the surface myoelectric potential sensor which shows other embodiment of this invention. It is a figure explaining the generation | occurrence | production mechanism of a myoelectric potential. It is the schematic which shows an example of a myoelectric potential detection circuit. It is the schematic which shows an example of the myoelectric potential detection circuit which used the dry type electrode as an active electrode. It is an image figure of a clothes type | mold surface myoelectric potential sensor.

  Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram of a surface myoelectric potential sensor according to a preferred embodiment of the present invention.

  As shown in FIG. 1, a surface myoelectric potential sensor 1 includes a myoelectric potential detection electrode 2 composed of a dry passive electrode, and an amplification circuit (hereinafter referred to as an instrumentation amplifier) that amplifies myoelectric potential detected by the myoelectric potential detection electrode 2. 3), the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 are connected by the coaxial cable 4, and the outer conductor 5 of the coaxial cable 4 is the body ground wiring 6.

  As the coaxial cable 4, it is preferable to use an ultrafine coaxial cable in which the outer periphery of the center conductor 7 is sequentially covered with an insulating coating layer 8, an outer conductor layer including the outer conductor 5, and a coating layer 9.

  The myoelectric potential detection electrode 2 and the body ground electrode 10 are fixed to the cloth-like material 11 to be attached to the human body, and a part of the coaxial cable 4 is sewn to the cloth-like material 11 to form a wearing part. ing.

  Since it is desirable that the body ground is connected to the human body with low impedance, the surface in contact with the human body is made of a conductive cloth, and this is used as the body ground electrode 10. On the body earth electrode 10, the myoelectric potential detection electrode 2 is disposed at a necessary position with the insulating layer 12 interposed therebetween.

Each myoelectric potential detection electrode 2 is electrically connected to the center conductor 7 of the coaxial cable 4, and the other end of the center conductor 7 of each coaxial cable 4 is connected to the input terminal of the instrumentation amplifier 3. The outer conductor 5 of each coaxial cable 4 is electrically connected to the body ground electrode 10, and the other end of the outer conductor 5 is electrically connected to the reference potential V _REF of the instrumentation amplifier 3 to be transmitted to the human body through a space such as hum noise. Noise to be combined is suppressed. Each coaxial cable 4 is bundled so as not to get in the way when measuring myoelectric potential.

The instrumentation amplifier 3 is a differential amplifier having two input terminals, and the myoelectric potential detection electrode 2 is connected to one input terminal via the coaxial cable 4 as described above. A reference myoelectric signal is input from another myoelectric potential detection electrode 2 to the other input terminal. Details of the connection method between the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 will be described later. The instrumentation amplifier 3 includes a gain adjustment circuit (not shown) that adjusts the gain (high-pass characteristics). The instrumentation amplifier 3 amplifies the difference between myoelectric potentials input to the respective input terminals and outputs the amplified signal with the reference potential V _REF as the center.

  A display unit (not shown) is connected to the instrumentation amplifier 3 so that the measurement result of the myoelectric potential can be output so that a person can sense it. The detection circuit units such as the instrumentation amplifier 3 and the display unit are provided separately from the wearing unit.

  The operation of the surface myoelectric potential sensor 1 of the present invention will be described.

When measuring the myoelectric potential using the surface myoelectric potential sensor 1, each myoelectric potential detection electrode 2 and each body ground electrode 10 are arranged on the skin surface of the human body. When a myoelectric potential is generated by the muscle activity, the difference between the myoelectric potential detected by each myoelectric potential detecting electrode 2 and the reference myoelectric potential is input to the instrumentation amplifier 3 and then amplified, and the reference potential V _{REF is} amplified. Is output as a center potential and displayed on a display unit or the like. The myoelectric potential can be detected by the above operation.

  In the surface myoelectric potential sensor 1 of the present invention, the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 are connected by a coaxial cable 4, and the outer conductor 5 of the coaxial cable 4 is a body ground wiring 6. The finest coaxial cable used for the coaxial cable 4 is commercially available up to 0.16 mm in diameter, and is flexible and can be sewn to a cloth using a sewing machine or the like. In addition, a passive electrode that does not require an active circuit element is used as the myoelectric potential detection electrode 2, and the flexibility of the surface myoelectric potential sensor 1 is not lost even when a large number of wires are sewn. The surface myoelectric potential sensor 1 uses a myoelectric potential detection electrode 2 made of a dry passive electrode suitable for repeated use.

  Therefore, according to the surface myoelectric potential sensor 1 of the present invention, even if a large number of wires are sewn, the surface myoelectric potential sensor 1 does not lose its flexibility and can be easily worn by anyone and can be used repeatedly. The potential sensor 1 can be provided.

  In order to measure myoelectric potential, a body earth electrode 10 is required in addition to the myoelectric potential detection electrode 2 for detecting myoelectric potential. In the surface myoelectric potential sensor 1 of the present invention, the outer conductor of the coaxial cable 4 is used. 5 is the body ground wiring 6, and if the central conductor 7 of the coaxial cable 4 is a wiring for a myoelectric potential signal (for myoelectric potential detection), the external conductor 5 blocks noise mixed from the outside into the myoelectric potential signal. Since the body ground wiring 6 can also be used, the wiring can be made compact.

  Further, for example, in a conventional surface myoelectric potential sensor in which a dry passive electrode is used as the myoelectric potential detection electrode 2 and the input terminals of the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 are connected by a normal single-core cable, FIG. As shown, the myoelectric potential signal is completely invisible due to the mixing of hum noise in the surrounding space. On the other hand, in the surface myoelectric potential sensor 1 of the present invention in which the myoelectric potential detecting electrode 2 and the input terminal of the instrumentation amplifier 3 are connected by the coaxial cable 4, as shown in FIG. Even when a dry passive electrode is used as the myoelectric potential detection electrode 2, the wiring between the myoelectric potential detection electrode 2 and the input terminal of the instrumentation amplifier 3 can be extended.

  That is, in the surface myoelectric potential sensor 1 of the present invention, the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 can be connected by the coaxial cable 4 to suppress the mixing of noise. The wiring between the input terminals can be extended.

  Next, a connection example of the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 will be described with reference to FIG.

  The instrumentation amplifiers 3 are prepared as many as the myoelectric potential detection electrodes 2, and the myoelectric potential detection electrodes 2 are connected to one input terminal of the instrumentation amplifier 3. A signal COM from any other myoelectric potential detection electrode 2 is connected to the other input terminal using a multiplexer 40.

  Further, a buffer amplifier 41 is provided immediately before the instrumentation amplifier 3. The buffer amplifier 81 is provided to lower the impedance between the myoelectric potential detection electrodes 72 and 73 and the input terminal of the instrumentation amplifier 70 and to be strong against noise. The buffer amplifier 41 is input to the detection circuit by the multiplexer 40. Since there is a possibility that the impedance becomes small, the detection circuit is inserted in order to obtain a high input impedance and is provided immediately before the instrumentation amplifier 3.

  With such a connection, a myoelectric potential waveform based on an arbitrary myoelectric potential detection electrode 2 can be acquired. Moreover, a weak myoelectric potential can be amplified, and detection accuracy can be improved.

  Next, a surface myoelectric potential sensor according to another embodiment of the present invention will be described.

  FIG. 5 is a schematic view of a surface myoelectric potential sensor showing another embodiment of the present invention.

  In order to fit the surface myoelectric potential sensor to the human body, it is desirable that there is not only flexibility but also elasticity. In the embodiment described above, the entire surface that contacts the human body is a conductive cloth, but the conductive cloth is generally not very stretchable.

  Therefore, as shown in FIG. 5, in the surface myoelectric potential sensor 50, the conductive cloth is divided into small pieces for each myoelectric potential detection electrode 2, and a pair of the body ground electrode 10 and the myoelectric potential detection electrode 2 made of the divided conductive cloth are paired. The plurality of units are connected by the elastic material 51.

  Although not shown, the myoelectric potential detection electrode 2 of each unit is connected to each instrumentation amplifier 3 by the central conductor 7 of the coaxial cable 4, and the body ground electrode 10 of each unit is connected to each coaxial cable. 4 external conductors 5. The connection method of the myoelectric potential detection electrode 2 and the instrumentation amplifier 3 is the same as the connection example described in FIG.

  With such a configuration, the surface myoelectric potential sensor can have elasticity. Further, since all the outer conductors 5 of the coaxial cable 4 are connected to the reference potential, all the finely divided conductive cloths have the same potential and work as a body ground. Therefore, although the contact area between the human body and the body ground electrode 10 is small individually, since the body ground is distributed at multiple points, a large contact area can be obtained in total.

  In short, according to the surface myoelectric potential sensor 50 of the present invention, a plurality of units in which the body ground electrode 10 and the myoelectric potential detecting electrode 2 are paired are connected by an elastic material, and the myoelectric potential detecting electrode of each unit is connected. 2 is connected to each instrumentation amplifier 3 by a coaxial cable 4 and the body ground electrode 10 of each unit is connected to the outer conductor 5 of each coaxial cable 4. A surface myoelectric potential sensor that can be easily mounted and can be used repeatedly can be provided.

1 Surface Myoelectric Potential Sensor 2 Myoelectric Potential Detection Electrode 3 Amplification Circuit (Instrumentation Amplifier)
4 Coaxial cable 5 Outer conductor 6 Body ground wiring

Claims (3)

A surface myoelectric potential sensor having a myoelectric potential detection electrode comprising a dry passive electrode and an amplification circuit for amplifying myoelectric potential detected by the myoelectric potential detection electrode,
A surface myoelectric potential sensor, wherein the myoelectric potential detection electrode and the amplifier circuit are connected by a coaxial cable, and an outer conductor of the coaxial cable is a body ground wiring.   A plurality of units in which the myoelectric potential detection electrode and the body earth electrode are paired are connected by an elastic material, the myoelectric potential detection electrodes of each unit are connected to each amplifier circuit by the coaxial cable, and The surface myoelectric potential sensor according to claim 1, wherein the body ground electrode of each unit is connected to an outer conductor of each coaxial cable.   The surface myoelectric potential sensor according to claim 1 or 2, wherein the myoelectric potential detection electrode and the body ground electrode are fixed to a cloth-like material, and at least a part of the coaxial cable is sewn to the cloth-like material.

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