JP2008295867A - Biological signal measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitively coupled biological signal measuring device, especially a myoelectric sensor, which is produced at low cost, has a degree of freedom in its shape and solves the problem of noises generated when sweating or the like. <P>SOLUTION: The biological signal measuring device measures a biological signal of a subject. The biological signal measuring signal is provided with an electric difference detection means having a detection electrode 42 for measuring an electric potential from a biological signal of a subject and a reference electrode for detecting a reference electric potential by contacting the subject, and a signal processing circuit for processing a signal output from the electric difference detection means. The detection electrode 42 consists of a two-layered structure including a conductor electrode 41a and a thin tape-like member made of an insulating material 41b layered on the surface of the conductor electrode 41a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a biological signal measuring apparatus that measures a biological signal of a subject person, in particular, a myoelectric potential by a capacitive coupling type.

  The biological signal observed during muscle contraction is called myoelectricity, and is measured in vivo or on the skin surface by a potential change of about 100 mV in each muscle fiber. The method of measuring invasively in a living body is suitable for seeing detailed muscle activity, and the method of measuring noninvasively on the skin surface is suitable for larger muscle activity.

  Myoelectric applications are used as signal sources for control and human interface in addition to diagnosing muscle diseases and ergonomic evaluation of muscle fatigue and motor function. In cases where a signal that faithfully reflects muscle activity, such as diagnosis of a muscular disease, is required, myoelectricity is measured invasively using a needle electrode or the like. On the other hand, in application to a human interface or the like, since it is important to be able to measure easily, measurement is often performed non-invasively on the skin surface.

  However, since myoelectrics are attenuated when transmitted through the living body, the signal observed on the skin surface is extremely weak, and the influence of noise mixed in from a commercial power source cannot be ignored. This disturbance noise is partly due to the contact resistance between the skin and the electrode. Conventionally, a method of reducing the influence of the disturbance noise by reducing the contact resistance by pretreatment such as using a conductive paste has been used. I came. However, in the method using the conductive paste, the time-dependent change of the conductive paste becomes a problem when measuring continuously for a long time. Also, the conductive paste is applied to the skin, peeled off, washed after the measurement, etc. The burden at the time of detachment was large, which hindered practical application. Furthermore, in application to human interfaces, etc., it is necessary for ordinary workers without specialized knowledge to attach myoelectric sensors, and since the frequency of attachment / detachment is large, complicated preprocessing at the time of attachment is avoided. There was a trend. Further, in actual use situations, there are cases where noise is mixed in by using without performing sufficient skin pretreatment, and the operation does not work as expected.

In order to solve this problem, a myoelectric sensor based on capacitive coupling using an insulator electrode has been developed as a myoelectric sensor that does not require skin pretreatment and can be easily handled. With this sensor, measurement that is not easily influenced by the state of the skin is possible, and myoelectricity can be measured through an insulator such as a cloth (for example, see Non-Patent Document 1).
Also, for example, as a myoelectric prosthetic hand, a myoelectric sensor is attached to the inside of the prosthetic limb socket, a stump portion of the human hand is inserted inside the prosthetic limb socket, and the myoelectricity is measured directly from above the skin at the stump portion. It is known to do (see, for example, Patent Document 1).
Isamu Isani Tetsuya Higuchi: "Development of myoelectric sensor using insulated electrode" IEICE technical report. WIT2006-13, p71-76 (2006) (The Institute of Electronics, Information and Communication Engineers / The Institute of Electronics, Information and Communication Engineers) Japanese Patent Laid-Open No. 11-113866

  In the non-patent document 1, a ceramic capacitor such as anodized aluminum, silicon oxide, barium titanate, silicon dioxide, or silicon nitride is processed and used as an electrical insulator used for capacitive coupling in the detection electrode portion. Therefore, it is difficult to freely change the size and shape of the electrode, and the degree of freedom in shape is insufficient. Moreover, there was a problem in durability during use.

  In the one disclosed in Patent Document 1, a substrate that can be freely deformed along the skin surface by providing a detection sensor on a flexible substrate is relatively supported by an elastically deformable support member with respect to the skin surface. It is designed to be pressed and to prevent poor contact between the skin and the detection sensor. However, in Patent Document 1, the substrate structure is devised to reduce the contact failure, but the problem due to the contact resistance is not solved.

  For this reason, a capacitively coupled myoelectric sensor using an electrode material that can be detected with high sensitivity regardless of the contact resistance of the skin and has a low degree of freedom in shape, that is, a capacitively coupled biological body. It is strongly desired to develop a signal measuring device.

  Therefore, the inventor of the present application preferably uses a capacitively coupled myoelectric sensor as a sensor that can be detected with high sensitivity regardless of the contact resistance of the skin. Various researches have been made on electrode materials with low cost and flexibility in shape. In particular, research has been conducted on an alternative to a ceramic capacitor as an electrical insulator of the detection electrode section.

  As a result, the inventor of the present application cannot obtain what satisfies the requirements when sticking to a capacitive insulator such as a capacitor, and therefore, using a conductor electrode such as a silver electrode, An inversion idea was made as to whether a combined biological signal measuring device (for example, myoelectric sensor) could be created. However, if a conductive electrode body is used, the shape is flexible at a low cost, but an electrode potential is generated between the electrode and sweat (electrolyte) when sweating, etc., and noise caused by this may be mixed. It becomes a problem.

  It is an object of the present invention to provide a capacitively coupled biological signal measuring device having a degree of freedom in shape at a low cost while solving the above-described noise problem such as sweating.

  Specifically, in order to make a capacitively coupled electrode using a conductor electrode, an insulating member, particularly an insulating tape-like member having a high dielectric constant, such as titanium tape, is arranged on the surface of the conductor electrode, and pseudo capacitive coupling is performed. It is characterized by being a mold electrode.

  Specifically, the invention of claim 1 is a biological signal measuring apparatus that measures a biological signal of a specimen person, and contacts the specimen electrode with a detection electrode unit that measures a potential based on the biological signal from the specimen person. Differential detection means comprising a reference electrode section for detecting a reference potential and a signal processing circuit for processing a signal output from the differential detection means, the detection electrode section comprising a conductor electrode, It is characterized by a double structure in which an insulator made of a thin tape-like member is laminated on the surface of the conductor electrode.

  The invention of claim 2 is the biosignal measurement device according to claim 1, wherein the biosignal measurement device measures a myoelectric potential from the skin surface of the subject person, and the detection electrode unit is the skin The myoelectric potential from the surface is measured, and the reference electrode portion detects the reference potential of the skin surface.

  According to a third aspect of the present invention, in the biological signal measuring apparatus according to the first or second aspect, the conductor electrode is composed of any one of a silver electrode, a silver / silver chloride electrode, and a gold electrode.

  According to a fourth aspect of the present invention, in the biological signal measuring device according to any one of the first to third aspects, the two detection electrode portions of the differential detection means are provided, and the reference electrode portion is provided between the two detection electrode portions. It is characterized by being arranged at an equidistant position from both the detection electrode portions.

  According to the invention of claim 1, in addition to being able to detect a biological signal that is a fine electric potential with high accuracy and measuring a biological signal at the same level regardless of the detection site of the specimen person or the state of dryness, It is possible to obtain a capacitively coupled biological signal detection device with low shape and high degree of freedom. In addition, the insulator is a thin tape-like member that can be reliably insulated and can be easily replaced.

  According to the invention of claim 2, in addition to being able to detect a myoelectric signal, which is a fine potential, with high accuracy and measuring a myoelectric signal of the same level regardless of the dryness of the skin, the shape can be freely formed at low cost. A capacitively coupled myoelectric sensor having a high degree can be obtained.

  According to the invention of claim 3, a biological signal can be detected with higher accuracy at a lower cost.

  According to the invention of claim 4, a compact biological signal measuring device can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

  In this embodiment, a case where the biological signal detection device of the present invention is applied to an myoelectric sensor is shown. As shown in FIGS. 1 and 2, the detection electrode unit 2 of the myoelectric measurement device 1 is brought into contact from above the stapling bag F that covers the skin surface H of the step end D of the detection body K. The intention of movement of the detection body K is detected by a signal detected by the myoelectric measurement device 1 and used to help operate the prosthesis G. Specifically, as shown in FIGS. 3 and 4, the detection electrodes 41 and 42 of the myoelectric measurement device 1 have silver electrodes 42 a and 42 a attached to a case 44 made of an insulator such as plastic. On top of this, insulating tapes 41b and 42b having a high dielectric constant such as titanium tape are coated, and a pseudo capacitor circuit is formed to detect an alternating current signal of a living body. A reference electrode 43 is attached between the detection electrodes 41 and 42 at a position equidistant from the detection electrodes 41 and 42.

  Specifically, as shown in FIGS. 1 and 2, the detection electrode portions 41 and 42 and the reference electrode portion 43 of the myoelectric measurement device 1 are brought into contact with the skin surface H of the detection body K from above the stapling bag F. Let As a result, the detection potentials s1 and s2 are detected by the reference electrode portion 43 and the detection electrode portions 41 and 42, respectively, and the sums s1 + n1 and s1 + n2 of the disturbances n1 and n2 are detected as the detection potentials s1 and s2. 24. The differential amplifier 24 calculates (s1 + n1) − (s2 + n2) and amplifies and outputs the signal. The differential amplifier 24 includes a differential detection unit 24a and a preamplifier 24b.

  The myoelectricity from the skin can be detected with high accuracy by the difference detection unit 24a. By providing the preamplifier 24b, a necessary signal can be reliably detected by amplifying a fine myoelectric potential from the skin surface by the preamplifier. In addition, because of the high impedance, it is possible to minimize the influence of noise by connecting the wiring between the electrode and the amplification section that are most susceptible to noise at the shortest distance.

  As shown in FIG. 5, the signal S <b> 11 from the differential amplifier 24 is sent to the signal processor 30. In the signal processing unit 30, for example, a first high-pass filter 32 having a cut-off frequency of 1.6 Hz is provided to reduce a frequency component of 1.6 Hz or less, and a low-pass filter 31 having a cut-off frequency of 1327 Hz is provided. The above frequency components are reduced, and the frequency band of the region that is a normal disturbance frequency region is removed. In addition, in this embodiment, a second high-pass filter 33 having a cutoff frequency of 300 Hz is provided as a frequency domain removal filter including a frequency domain that is not normally removed, and frequency components of 300 Hz or less are reduced. The second high-pass filter 33 removes a commercial frequency region, which is one of large disturbances, and removes frequency components in the vicinity of this frequency region as disturbance factors. In addition, in the present embodiment, the signal of the skin surface H of the detection body K is detected via the stapling bag F, but the contact pressure between the stapling bag 8 (F) and the detection electrode portions 41 and 42. Since the baseline fluctuation that occurs when the value changes is large, this influence is removed before amplification by the second high-pass filter.

  In this way, the signal S12 after boldly removing the frequency region below the predetermined frequency is sent to the amplification unit 34 and amplified by the amplifier 34. After amplification, the notch filter 35 again removes the commercial frequency of 50 Hz or 60 Hz, reliably eliminates the influence of the commercial frequency, and outputs the signal S13. As a result, the myoelectric potential necessary for the myoelectric measurement device 1 can be detected effectively.

  As a function required for the insulator used in the detection electrode portions 41 and 42, it is preferable that a noise signal is hardly generated against perspiration in addition to being able to be insulated. In particular, it is preferable that it can be easily attached / detached and exchanged, and further, it is preferable that it can be obtained at low cost without causing damage to the skin. As the insulator, for example, adhesive bandages, earthquake-resistant tape, double-sided tape, cellophane tape (trademark), seal tape, and the like can be applied. In particular, titanium tape is preferable because it can be insulated, hardly generates a noise signal against perspiration, and can be easily attached and detached.

  If the thickness of this insulator is too thick, it is difficult to generate an electric potential, and if insulation can be obtained, the thinner the better, the better the thickness of the tape that is generally used, and capacitive coupling. It is a thickness that can be maintained, and the thickness itself is different depending on the material, and it is difficult to specify it numerically.

  The electrode preferably has a low contact potential difference, and a silver electrode, a gold electrode, a silver / silver chloride electrode, or the like is used. In particular, it is a silver / silver chloride electrode that has a low electrode potential difference and is unlikely to cause a potential difference between sweat and an electrode, but has a high processing cost and a problem in durability. The gold electrode is expensive. Silver electrodes are slightly inferior in terms of electrode potential compared to myoelectric stations and silver / silver chloride electrodes, but are easy to process and advantageous in terms of material cost.

Example 1
As shown in FIG. 4, a 0.2 mm thick titanium tape was pasted on the silver electrodes 41 and 42, and the reference electrode 43 was mounted in the center. As specifications, the gain (preamplifier 24b) was 13.821 times, the input impedance was 1000 TΩ, and the CMR (divided valve ratio) was 78 dB.

(Comparative Example 1)
A capacitively coupled myoelectric sensor shown in Non-Patent Document 1 was used, and a reduced re-oxidation type barium titanate semiconductor magnetic capacitor was processed as an electrode for measurement and used instead of the detection electrodes 41 and 42. The specifications are the same as in Example 1.

  Next, an example of measuring myoelectricity using the embodiment and Comparative Example 1 will be described.

  The myoelectric measurement device of the embodiment and the myoelectric measurement device of Comparative Example 1 were arranged on the skin surface in the vicinity of the muscle abdomen of the forearm flexor muscle group and fixed with a wristband. In the embodiment, the reference electrode 43 is embedded integrally, but in order to align the experimental conditions with Comparative Example 1, the measurement was performed by bringing the common reference electrode into contact with the skin surface on the extensor side of the forearm.

  Three types of measurements were performed. First, (1) the noise signal mixed during weakness was measured, and then (2) the signal observed during maximum contraction was measured. In addition, (3) measurement was repeated while repeating weakness and maximum contraction every second according to the electronic metronome. 6 to 11 show graphs of the measured signal waveforms, FIGS. 6, 8 and 10 show Comparative Example 1, and FIGS. 7, 9 and 11 show the measurement results of the embodiment. The upper row is the voltage obtained by AD conversion of the EMG signal output from the amplifier, and the lower row is the signal power spectrum.

Comparing the power spectrum at the time of weakness in FIG. 6 and FIG. 7, the embodiment is larger in comparison with the first comparative example, but it is seen from the graphs at the time of the maximum contraction in FIG. 8 and FIG. It can be seen that both can measure myoelectric signals exceeding the noise level of 50 Hz. Further, it can be seen from the graphs at the time of muscle contraction in accordance with the metronome shown in FIGS. 10 and 11 that a signal capable of clearly separating muscle contraction and weakness can be measured in both Comparative Example 1 and the embodiment.
Further, it can be seen from the graph of the power spectrum that when the silver electrode 41a (42a) is insulated by the titanium tape 41b (42b), both the low frequency component and the high frequency component are attenuated. The combination of the titanium tape 41b (42b) and the silver electrode 41a (42a) is considered to function as a band pass filter. From these graphs, it can be seen that in Comparative Example 1 and the embodiment, the muscle contraction and weakness can be clearly separated. That is, it is shown that the myoelectric sensor of the embodiment can detect myoelectricity at the same level as the capacitively coupled myoelectric sensor as a pseudo capacitively coupled myoelectric sensor.

  In addition, although embodiment is a myoelectric sensor, this invention is applicable not only to this myoelectric sensor but to the myoelectric sensor of other structures, Furthermore, it can apply also to another biological signal measuring device. .

  As described above, the biological signal measuring apparatus according to the present invention can be applied to detection of various biological signals, for example, myoelectric sensors such as myoelectric prosthetic hands and myoelectric prostheses.

The present invention relates to an embodiment in which the present invention is applied to a myoelectric sensor, and schematically shows a differential electric power detection means. The state which uses the myoelectric sensor concerning embodiment for a myoelectric prosthetic hand is shown. The AA cross section of FIG. 4 is shown. The perspective view explaining the external appearance of the electromyogram measuring device concerning an embodiment is shown. The block diagram of the signal processing circuit of the myoelectric measurement apparatus concerning embodiment is shown. 5 is a graph showing measured values at the time of weakness in Comparative Example 1. It is a graph which shows the measured value at the time of weakness in embodiment. 6 is a graph showing measured values at maximum contraction in Comparative Example 1. It is a graph which shows the measured value at the time of maximum contraction in an embodiment. It is a graph which shows a measured value when weak force / shrinkage is repeated in Comparative Example 1. It is a graph which shows a measured value when repeating weak force / shrinkage in an embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Myoelectric measurement apparatus 2 Differential electric power detection means 41 Detection electrode part 41a Silver electrode 41b Insulator 42 Detection electrode part 42a Silver electrode 42b Insulator 22 Differential electric current detection part 23 Reference electrode part 24 Differential amplification part 30 Signal processing circuit 31 Low pass Filter 32 First high-pass filter 33 Second high-pass filter 34 Amplifying unit 35 Notch filter

Claims (4)

A biological signal measuring device for measuring a biological signal of a specimen person,
A difference detection unit comprising a detection electrode unit for measuring a potential based on a biological signal from the sample person and a reference electrode unit for contacting the sample person to detect a reference potential;
A signal processing circuit for processing a signal output from the differential detection means,
The biological signal measuring device, wherein the detection electrode section has a double structure in which a conductor electrode and an insulator made of a thin tape-like member are laminated on the surface of the conductor electrode. The biological signal measuring apparatus according to claim 1,
The biosignal measuring device is a myoelectric measuring device that measures myoelectric potential from the skin surface of the subject person, wherein the detection electrode unit measures myoelectric potential from the skin surface, and the reference electrode unit is a reference potential of the skin surface A biological signal measuring device characterized in that the signal is detected. In the biological signal measuring device according to claim 1 or 2,
The biological signal measuring device, wherein the conductor electrode is one of a silver electrode, a silver / silver chloride electrode, and a gold electrode. In the biological signal measuring device according to any one of claims 1 to 3,
Two detection electrode portions of the differential detection means are provided,
A biological signal measuring device, wherein the reference electrode unit is arranged at a position equidistant from the two detection electrode units between the two detection electrode units.

Images