JP2018051099A - Living body skin resistance detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a skin resistance.SOLUTION: An electrode part D is formed by covering surfaces of a first electrode 1 and a second electrode 2 with an insulation 3. A high frequency power source 4 is connected to the first electrode 1 through a guide element 11 for forming a resonant circuit, and an ammeter 5 is connected to the second electrode 2. A relationship between a resonant frequency and a resonant ohmic value when a frequency from the high frequency power source 4 is swept and a current state indicating resonance is detected on the ammeter 5 is detected, is acquired. Based on the relationship, based on a minimum resonant ohmic value in a zone where the resonant frequency and the resonant ohmic value are reduced or increased together, a skin resistance is determined. The electrode part D is provided on a steering handle, and based on the determined skin resistance, a driver state (for example, strained state) can be determined.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a living body skin resistance detection apparatus.

  Recently, various sensors for detecting the relationship with a living body have been developed. Patent Literature 1 discloses a device that detects a heart rate and the like based on a change in distance between capacitance sensors. Japanese Patent Application Laid-Open No. 2004-133620 discloses a device that detects the presence or absence of an operation touch based on a change in capacitance. Patent Document 3 discloses a resonance circuit including an electrode portion having a structure in which the capacitance of the electrode portion is maximized, wherein the resistance value at the resonance point is the skin resistance of a living body.

JP, 2014-210127, A JP 2014-44225 A JP, 2015-110508, A

  As described in Patent Document 3, when the resistance value of the resonance point is determined as the skin resistance, it may be difficult to accurately detect the skin resistance. For example, when the skin resistance at that time is detected by bringing a fingertip of a living body into contact with the electrode part, the contact area is different depending on whether the fingertip is lightly contacting or strongly contacting the electrode part. Although it will be different, the detected skin resistance will be different if the contact area is different.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a living body skin resistance detection apparatus that can detect skin resistance of a living body with higher accuracy.

In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1,
The electrode part is configured by covering the surfaces of the first electrode and the second electrode with an insulating material,
A high frequency power source is connected to the first electrode part via an inductive element for constituting a resonance circuit, while a current measuring means is connected to the second electrode,
A correlation acquisition unit that obtains a correlation between a resonance frequency and a resonance resistance value when a current state indicating resonance is detected by the current measurement unit by sweeping a frequency from the high-frequency power source;
Skin resistance determination for determining the skin resistance of the living body based on the minimum resonance resistance value in a section in which both the resonance frequency and the resonance resistance value decrease or increase based on the correlation acquired by the correlation acquisition means Means,
It is supposed to be equipped with.

  According to the above solution, the skin resistance can be detected with high accuracy using the correlation between the resonance frequency and the resonance resistance value. That is, as the contact area of the living body with the electrode portion increases, the resonance frequency decreases while the resonance resistance value decreases. In other words, the resonance frequency and the resonance resistance value both have a section that decreases or increases, and the minimum resonance resistance value in such a section shows an accurate value corresponding to the skin resistance. .

A preferred mode based on the above solution is as described in claim 2 and the following. That is,
The skin resistance determining means determines the skin resistance on the condition that the reduction ratio of the resonance resistance value with respect to the decrease of the resonance frequency is less than a predetermined value (corresponding to claim 2). In this case, it is preferable to detect the skin resistance more accurately by determining the skin resistance on condition that the contact area of the living body with respect to the electrode portion is sufficiently large.

The living body is assumed to be the driver of the vehicle,
The electrode part is provided on a steering wheel of a vehicle,
(Corresponding to claim 3). In this case, the driver's skin resistance can be detected.

One of the first electrode and the second electrode is provided over the entire circumference of the annular portion of the steering handle that is gripped by the driver, while the first electrode and the second electrode The other of the second electrode is provided over the entire circumference on the outer peripheral side of the annular portion,
The first electrode and the second electrode cover the entire circumferential surface of the annular portion.
(Corresponding to claim 4). In this case, it is preferable to ensure a sufficient opportunity to detect the driver's skin resistance.

  A driver state determining unit that determines a driver state based on the skin resistance determined by the skin resistance determining unit is further provided (corresponding to claim 5). In this case, the driver's condition can be determined using skin resistance.

  According to the present invention, skin resistance can be accurately detected.

The figure which shows the state which the fingertip has touched the electrode part in which the resonance circuit was incorporated. The characteristic view which shows the correlation of a resonance resistance value and a resonance frequency. The figure which shows the example which has arrange | positioned the electrode part with respect to the steering handle. The figure which shows the example of a control system of this invention. The figure which shows the example of control of the controller in FIG.

  In FIG. 1, 1 is a first electrode (transmission side electrode) and 2 is a second electrode (reception side electrode). The electrodes 1 and 2 are arranged in parallel in the embodiment, and the surface thereof is covered with an insulating material 3. The insulating material 3 is disposed across the electrodes 1 and 2. Although the insulating material 3 is shown in a thick state in FIG. 1, it is actually a thin film. The electrodes 1 and 2 and the insulating material 3 constitute an electrode part D.

  The first electrode 1 is connected to a high frequency power source 4. The high-frequency power supply 4 is configured such that the frequency can be changed (swept) in the range of 500 KHz to 4 MHz, for example. The second electrode 2 is connected to an ammeter 5 as current measuring means. In order to form a resonance circuit for the electrode part D, an induction element 11 (whose inductance is shown as L) is interposed between the first electrode 1 and the high-frequency power source 4.

  In FIG. 1, a human body as a living body (a driver of a car in the embodiment) is indicated by a symbol M, and a fingertip thereof is indicated by a symbol M1. FIG. 1 shows an equivalent circuit when the fingertip M1 is in contact with the electrode D (the insulating material 3). That is, R1 is a leakage resistance value between both electrodes 1 and 2, and Cm is a mutual capacitance between both electrodes 1 and 2. Cf is a capacitance between the fingertip M1 and the electrode 1 or 2 (the capacitance for the first electrode 1 and the capacitance for the second electrode 2 are shown as the same value Cf), Rf is skin resistance. In addition, skin resistance changes with contact areas.

  Furthermore, in the state where the fingertip M1 is in contact with the electrode D, a human body ground path that flows through the driver's body as the living body M is configured. That is, the living body M that is a driver of the automobile is in a state of being grounded to the vehicle body by sitting on the driver's seat. In this human body ground path, Rb is a human body resistance, and Cp is a human body capacitance.

  When the fingertip M1 is greatly separated from the insulating material 3 (for example, when separated by 30 cm or more), the skin resistance Rf and the human body ground are ignored. For this reason, the path through which the current from the high-frequency power source 4 flows is a path from the induction element 11 through the first electrode 1 to the second electrode 2 through the leakage resistor R1 and the mutual capacitance Cm. Such a current flow is indicated by a solid line in the figure.

  When the fingertip M1 is in contact with the insulating material 3, two circuit systems resulting from the living body M are generated. The first circuit system resulting from the living body M is a path involving the skin resistance Rf, and the current from the high-frequency power source 4 is the inductive element 11, the first electrode 1, the electrostatic capacitance Cf on the left side in the figure, and the skin resistance Rf. , A path to the second electrode 2 through the capacitance Cf on the right side in the figure. Such a current flow is indicated by a one-dot chain line in the figure.

  The second circuit system resulting from the living body M is a human body ground path, and the current from the high frequency power source 4 is the inductive element 11, the first electrode 1, the left side capacitance Cf, the human body resistance Rb, the human body static. This is a path through the capacitance Cb. Such a current flow is indicated by a broken line in the figure (a path that does not pass through the ammeter 5).

  Here, since the capacitance Cf is generated even in a state where the fingertip M1 is slightly separated from the insulating material 3 (a hover touch state where the fingertip M1 is not in contact but at a short distance), in addition to the flow shown by the solid line, A flow indicated by a broken line is generated. That is, when the fingertip M1 is gradually approached from the state of being largely separated from the electrode part D (the insulating material 3 thereof) and finally brought into contact with the electrode part D (the insulating material 3), "," State of solid line in FIG. 1 + state of broken line in FIG. 1 "," state of solid line in FIG. 1 + state of broken line in FIG. 1 + state of dashed line in FIG.

  Now, it is assumed that the fingertip M1 is gradually separated from the insulating material 3 and gradually brought closer to the insulating material 3 and finally strongly pressed against the insulating material 3. In this process of changing the position of the fingertip M1, the frequency of the high-frequency power source 4 is changed (swept), and the correlation between the resonance frequency and the resonance resistance value at that time is shown together in FIG. 2. The resonance is detected when the ammeter 5 detects the extreme value, the frequency at the time of resonance is the resonance frequency, and the resistance value at that time is the resonance resistance value (resonance resistance value is (Calculated based on the voltage generated by the high frequency power source 4 and the detected current by the ammeter 5)

  In FIG. 2, when the fingertip M1 is greatly separated from the insulating material 3, the initial resistance value at the time of resonance is the leak resistance R1, and the resonance frequency at this time is the initial resonance frequency. The point in time when the initial resistance value (= R1) is reached is indicated by symbol α in FIG.

  When the fingertip M1 is further moved closer to the insulating material 3 from the state in which the initial resistance value R1 is detected, a current flow indicated by a broken line in FIG. 1 is generated, and as a result, the current value detected by the ammeter 5 decreases accordingly. Thus, the resonance resistance value increases while the resonance frequency decreases. As described above, in a state where the resonance resistance value increases from the initial resistance value and the resonance frequency decreases from the initial frequency, the fingertip M1 is in the hover touch state located near the insulating material 3.

  When the fingertip M1 contacts the insulating material 3, a current flow indicated by a one-dot chain line in FIG. 1 is also generated, and the resonance resistance value is changed from the increased state to the decreased state. That is, as the fingertip M1 is strongly pressed against the insulating material 3 (as the contact area of the fingertip M1 with the insulating material 3 is increased), the skin resistance Rf decreases, so that the resonance resistance value Is changed to a decreasing state. As the resonance resistance value decreases, the resonance frequency decreases. The end point of the hover touch is when the resonance resistance value reaches an extreme value (maximum value) that shifts from increase to decrease. The end point of the hover touch is indicated by a symbol β in FIG. Note that the maximum distance (the distance between the electrode D and the fingertip M1) that can be detected as being in the hover touch state can be 6 cm or more.

  As described above, when the resonance resistance value is larger than the initial resistance value (range α to β in FIG. 2), the increase or decrease of the resonance frequency is opposite to the increase or decrease of the resonance resistance value (that is, When the resonance resistance value increases as the resonance frequency decreases, in other words, the resonance resistance value decreases as the resonance frequency increases), the living body is in a hover touch state with respect to the electrode unit. It can be determined that

  In the final state in which the fingertip M1 is strongly pressed against the electrode part D, the resonance resistance value becomes the minimum value, and the point in time when the resonance resistance value becomes the minimum value is indicated by the symbol γ in FIG. Note that the minimum resonance resistance value when the resonance resistance value is minimized can be determined as the skin resistance value. When the skin resistance value (minimum resonance resistance value) changes in a direction that decreases by a predetermined value or more even though the resonance frequency has hardly changed, it can be determined that the living body M is sweating.

  The posture state of the living body M can be determined based on the resonance resistance value in the range of β to γ, and the posture change can be detected from the change in the resonance resistance value. That is, for example, when the living body M is seated in the driver's seat, for example, when leaning on the seat back, when the back is separated from the seat back, or when the hip is lifted from the driver seat, etc. Since the ground position with respect to the vehicle body changes, the resonance resistance value changes. Therefore, by creating a correlation between the posture state of the living body M and the resonance resistance value in advance as a database, it is possible to determine the posture state of the living body M by comparing the acquired resonance resistance value with the database. Become.

  In FIG. 2, the range between β and γ means an increase in the contact area of the fingertip M1 with the insulating material 3, and therefore the insulating material 3 of the fingertip M1 is calculated from the capacitance calculated from the resonance frequency in this range. It becomes possible to acquire the contact area with respect to.

  In the case where the current is a flow indicated by a one-dot chain line in FIG. 1, the circuit resistance Z at the time of resonance is calculated by the following equation (1). In the equation, f is a resonance frequency, and the resonance frequency f can be known by looking at the output state of the high-frequency power source 4. At resonance, L and Cf cancel each other, so that the circuit resistance Z becomes the skin resistance Rf.

  Further, the capacitance value Cf is calculated by the following equation (2).

  Since the resonance frequency f and the inductance L of the induction element 11 are known, the capacitance value Cf can be calculated from the equation (2). The contact area of the fingertip M1 can be obtained from the obtained capacitance value Cf. For example, the contact area can be determined by creating a database of the relationship between the capacitance value Cf and the contact area in advance and comparing the calculated Cf with the database.

  Note that the circuit resistance and the capacitance value can be calculated in the same manner as in the equations (1) and (2) when the current flow is indicated by a solid line in FIG. In this case, when the current is a flow indicated by a solid line, R1 may be used instead of Rf, and Cm may be used instead of Cf. When the current is a flow indicated by a broken line in FIG. 1, Rb may be used instead of Rf, and “Cf + Cp” may be used instead of Cf.

  FIG. 3 shows a case where the steering handle 41 is provided with a pair of electrode portions D. That is, FIG. 3 shows a state in which the steering handle 41 is in a neutral position. In FIG. 3, the first electrode 1 and the first electrode 1 are arranged so as to cover the entire peripheral surface of the annular portion of the steering handle 41 that is the object of the gripping operation. Two electrodes 2 are provided. Specifically, one of the first electrode 1 and the second electrode 2 is disposed on the inner peripheral side of the steering handle 41 (of the annular portion), and the other is disposed on the outer peripheral side of the steering handle 41. . The electrodes 1 and 2 are arranged so as to extend over the entire circumference of the steering handle 1, and the electrodes 1 and 2 cover the entire circumferential surface of the steering handle 1 (annular portion thereof). . As a result, the skin resistance can be detected regardless of which part of the steering handle 41 (the annular portion thereof) is held by the driver (ensures sufficient detection opportunity).

Note that the smaller the value obtained by dividing the area of the first electrode 1 by the area of the second electrode 2, the sensor sensitivity is improved (the change in the resonance resistance value accompanying the change in the resonance frequency is large). It is preferable to increase the area of the second electrode 2 as compared to the one electrode 1.
FIG. 4 shows an example of a control system in the present invention. In the figure, U is a controller (control unit) configured using a microcomputer. The controller U receives the current detected by the ammeter 5. Further, the controller U controls the high frequency power supply 4 and the display 42. For example, when the driver state determined according to the detected skin resistance is tense or anxious, the display 42 performs a warning warning such as prompting for rest.

  Next, an example of control by the controller U, particularly detection of skin resistance, will be described with reference to the flowchart of FIG. In the following description, Q indicates a step. First, in Q1, the high frequency power supply 4 is controlled to change (sweep) the frequency within a specific frequency band range.

  After Q1, an initial resistance value (= R1) and a resonance frequency f1 at that time are determined at Q2. Thereafter, in Q3, a correlation between the resonance resistance value and the resonance frequency is acquired (characteristics as shown in FIG. 2 are acquired, but characteristics in the entire frequency range from the α point to the γ point are obtained. Not necessarily).

  After Q3, at Q4, it is determined whether or not the resonance resistance value is smaller than the initial resonance resistance value R1 (whether or not there is a reduction range). When the determination in Q4 is YES, it is determined in Q5 whether or not the resonance frequency is decreasing (whether or not there is a decrease range).

  If the determination in Q5 is YES, it is determined in Q6 whether or not the decrease ratio of the resonance resistance value with respect to the decrease in the resonance frequency is less than a predetermined value. In other words, the determination of Q6 is a determination as to whether or not there is a range in which the resonance resistance value hardly changes regardless of the change in the resonance frequency. In FIG. 2, whether or not there is a region indicated as the skin resistance detection range. It becomes the judgment.

  When the determination in Q6 is YES, in Q7, the skin resistance is determined based on the minimum resonance resistance value (in the embodiment, the minimum resonance resistance value is determined as the skin resistance value). If NO in Q4, NO in Q5, or NO in Q6, the process ends without determining skin resistance.

  Here, based on the skin resistance determined as described above, the driver state (particularly, the driver's emotional state) can also be determined. For example, since the skin resistance decreases when sweating, the presence or absence of sweating (or the degree of sweating) can be determined according to the skin resistance. Since sweating is presumed that the driver is nervous or anxious, attention information such as prompting for rest can be displayed on the display 42 when the sweating level is high.

  Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. In addition to detection of skin resistance, any one or more of detection of hover touch, detection of posture state (change in posture), and detection of contact area can be performed together. The part to be detected for skin resistance is not limited to the fingertip, but may be an appropriate part of the living body such as a foot tip or an elbow. The present invention can be applied to an appropriate thing that a living body may come into contact with, for example, a ship other than a vehicle (particularly an automobile), an aircraft, etc. A stationary object other than a moving object can also be a detection target. The determined skin resistance can be determined by a continuously variable value, or can be determined in multiple stages, for example, large, medium and small. Each step or step group shown in the flowchart indicates the function of the controller U, and the name indicating the function can be attached to the name of the means so as to be grasped as a constituent requirement of the controller U. Of course, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage.

  The present invention can accurately detect skin resistance.

U: Controller M: Living body M1: Fingertip D: Electrode unit 1: First electrode 2: Second electrode 3: Insulating material 4: High frequency power supply 5: Ammeter R1: Leakage resistance Cm: Mutual capacitance Cf: Capacitance (fingertip) Between)
Rf: Skin resistance Cp: Human body capacitance Rb: Human body resistance 41: Steering handle α: Indicates initial resistance value β: Indicates extreme value (when hover touch ends)
γ: Indicates the minimum resonance resistance value (shows skin resistance)

Claims (5)

The electrode part is configured by covering the surfaces of the first electrode and the second electrode with an insulating material,
A high frequency power source is connected to the first electrode part via an inductive element for constituting a resonance circuit, while a current measuring means is connected to the second electrode,
A correlation acquisition unit that obtains a correlation between a resonance frequency and a resonance resistance value when a current state indicating resonance is detected by the current measurement unit by sweeping a frequency from the high-frequency power source;
Skin resistance determination for determining the skin resistance of the living body based on the minimum resonance resistance value in a section in which both the resonance frequency and the resonance resistance value decrease or increase based on the correlation acquired by the correlation acquisition means Means,
An apparatus for detecting skin resistance of a living body, comprising: In claim 1,
The skin resistance detecting device according to claim 1, wherein the skin resistance determining means determines skin resistance on condition that a reduction ratio of a resonance resistance value with respect to a decrease in resonance frequency is less than a predetermined value. In claim 1 or claim 2,
The living body is assumed to be the driver of the vehicle,
The electrode part is provided on a steering wheel of a vehicle,
A living body skin resistance detection device characterized by the above. In claim 3,
One of the first electrode and the second electrode is provided over the entire circumference of the annular portion of the steering handle that is gripped by the driver, while the first electrode and the second electrode The other of the second electrode is provided over the entire circumference on the outer peripheral side of the annular portion,
The first electrode and the second electrode cover the entire circumferential surface of the annular portion.
A living body skin resistance detection device characterized by the above. In claim 3 or claim 4,
A living body skin resistance detection apparatus, further comprising: a driver state determination unit that determines a driver state based on the skin resistance determined by the skin resistance determination unit.

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