Identification device

An identification device measures a potential difference signal between two contact electrodes contacted by a driver out of a plurality of electrodes installed in a handling unit or a potential difference signal between one contact electrode installed in the handling unit and a contact electrode different from the electrodes installed in the handling unit. The device identifies a contact electrode contacted by driver's hand out of the plurality of electrodes installed in the handling unit. The device determines whether the driver's hand in contact with the identified contact electrode is the right hand or the left hand on the basis of a rotational state of the handling unit and a position of the contact electrode in the handling unit. The device identifies the heart beat from the potential difference signal amplified by an amplification factor determined on the basis of a result of determination.

FIELD

The embodiments discussed herein are directed to an identification device.

BACKGROUND

Detecting a physiological state of a driver contributes to the deterrence of an accident due to the deterioration of the physiological state. Therefore, there is a detection method to detect a driver's physiological state using a state of driver's pulse or heartbeat. For example, a device that implements the detection method measures a potential difference signal between two electrodes in contact with a driver, and identifies a heart rate signal indicating driver's pulse or heartbeat from the measured potential difference signal. Then, the device detects the sleepiness or alertness, etc. as a physiological state of the driver using the identified heart rate signal.

A potential difference signal measured by the device that implements the detection method includes noise generated from other electronic devices installed in a vehicle and noise generated around the vehicle, and a heart rate signal included in the potential difference signal is weak. Therefore, the device that implements the detection method amplifies a potential difference signal by a predetermined amplification factor, and then identifies a heart rate signal.

To identify a weak heart rate signal, it is better to measure a potential difference signal using two positions resulting in a large potential difference as possible. Therefore, the device that implements the detection method measures a potential difference signal between electrodes located at two positions across the heart. The two positions across the heart are, for example, a combination of the right hand and the left hand, a combination of the right hand and the seat (the buttocks), a combination of the left hand and the seat, and the like.

For example, a plurality of electrodes to be contacted by a driver is installed in a steering part (a wheel) and a driver's seat, etc. of a vehicle. The electrode installed in the seat is contacted by driver's buttocks when a driver sits in the seat, and the electrode installed in the wheel is contacted by driver's hand when the driver holds the wheel, and then the device that implements the detection method measures a potential difference signal between the two electrodes.Patent document 1: Japanese Laid-open Patent Publication No. 2008-237379

SUMMARY

According to an aspect of an embodiment of the invention, an identification device includes a measuring unit that measures a potential difference signal between two contact electrodes contacted by a driver out of a plurality of electrodes installed in a handling unit of equipment and/or a potential difference signal between one contact electrode out of the plurality of electrodes installed in the handling unit of the equipment and a contact electrode different from the electrodes installed in the handling unit. The identification device includes an electrode identifying unit that identifies a contact electrode contacted by the driver out of the plurality of electrodes installed in the handling unit. The identification device includes a determining unit that determines whether driver's hand in contact with the contact electrode identified by the electrode identifying unit is the right hand or the left hand on the basis of a rotational state of the handling unit and a position of the contact electrode in the handling unit. The identification device includes a beat identifying unit that identifies a heart beat from the potential difference signal amplified by an amplification factor determined on the basis of a result of determination by the determining unit.

DESCRIPTION OF EMBODIMENTS

As described previously, the above-described detection detect a physiological state of a driver contributes to the deterrence of an accident due to the deterioration of the physiological state. However, the above-described detection method has a problem that a heart rate signal is apt to be buried in noise. The heart is located at a position slightly deviated from the center of body, and consequently the intensity of a heart rate signal included in a potential difference signal differs according to a combination of two positions across the heart. As a result, it is considered that an amplification factor suited to be used in identification of a heart rate signal from a potential difference signal also differs according to a combination of two positions across the heart. In the above-described detection method, whether the right hand or the left hand is in contact with the electrode installed in the wheel is not distinguished; therefore, it is not possible to apply an amplification factor suitable for a combination of the two positions of the electrodes, and the heart rate signal is apt to be buried in noise.

Incidentally, this invention is not limited to the embodiments. The embodiments can be arbitrarily combined within a scope which does not contradict the processing contents.

[a] First Embodiment

First of all, an example of a configuration of an identification device100according to a first embodiment is explained with reference toFIG. 1.FIG. 1is a block diagram for explaining about an example of a configuration of an identification device according to the first embodiment. In the example illustrated inFIG. 1, the identification device100has a measuring unit101, an electrode identifying unit102, a determining unit103, and a beat identifying unit104.

The measuring unit101measures a potential difference signal between two contact electrodes contacted by a driver out of a plurality of electrodes installed in a steering part of equipment. Furthermore, the measuring unit101measures a potential difference signal between one contact electrode out of the plurality of electrodes installed in the steering part of the equipment and a contact electrode different from the electrodes installed in the steering part.

The electrode identifying unit102identifies a contact electrode contacted by driver's hand out of the plurality of electrodes installed in the steering part. Then, the determining unit103determines whether the driver's hand in contact with the contact electrode identified by the electrode identifying unit102is the right hand or the left hand on the basis of a rotational state of the steering part and a position of the contact electrode in the steering part.

The beat identifying unit104identifies the heart beat from a potential difference signal amplified by an amplification factor determined on the basis of a result of determination by the determining unit103.

Namely, when a user holds the steering part in which electrodes are installed, the identification device100according to the first embodiment determines whether the right hand or the left hand is in contact with an electrode from a position of the electrode in contact with the hand and a rotation angle of the steering part, and identifies the heart beat using an amplification factor suitable for the determined hand.

As described above, according to the first embodiment, it is possible to distinguish whether the right hand or the left hand is in contact with an electrode installed in the steering part. The heart is located at a position slightly deviated from the center of body, and consequently the intensity of a heart rate signal included in a potential difference signal differs according to a combination of two positions across the heart. As a result, it is considered that an amplification factor suited to be used in identification of a heart rate signal from a potential difference signal also differs according to a combination of two positions across the heart. According to the first embodiment, it is possible to distinguish whether the right hand or the left hand is in contact with an electrode, and consequently the heart beat can be identified by using an amplification factor suitable for a combination of two positions of electrodes between which a potential difference signal is measured, and a weak heart rate signal which is apt to be buried in noise can be identified with a high degree of accuracy. Furthermore, no matter whether driver's hand in contact with an electrode is the right hand or the left hand, a heart rate signal can be detected with accuracy; therefore, it is possible to increase duration of detection of a heart rate signal.

Incidentally, in the embodiment, there is described the steering part installed in a vehicle as an example. However, an object equipped with the steering part does not have to be limited to a vehicle as long as the steering part is a part continuously and electrically contacted by both hands or one hand of a person who is an object of detection of an heart beat, and the part does not have to be limited to a steering part.

[b] Second Embodiment

Configuration of Identification Device According to Second Embodiment

Subsequently, an identification device200according to a second embodiment is explained. First, an example of a configuration of the identification device200according to the second embodiment is explained with reference toFIG. 2.FIG. 2is a block diagram for explaining about an example of a configuration of an identification device according to the second embodiment. In the example illustrated inFIG. 2, the identification device200according to the second embodiment has a wheel electrode201, a seat electrode202, a selection circuit203, a potential-difference measuring unit204, an amplifying unit205, a storage unit300, and a control unit400.

The wheel electrode201is connected to the selection circuit203. Furthermore, a plurality of the wheel electrodes201is installed in a steering wheel501of a vehicle. Incidentally, the steering wheel501is also referred to as a steering part and a steering wheel. Here, an example of the structure of the wheel electrode201is explained with reference toFIG. 3.FIG. 3is a diagram for explaining about an example of a wheel electrode in the second embodiment. InFIG. 3, as an example, there is illustrated a case where twelve uniformly-sized wheel electrodes201are installed along a circumferential direction of the steering wheel501. Numbers “1” to “12” inFIG. 3denote the wheel electrodes201. Incidentally, in the description below, there is described taking for example a case where “twelve” wheel electrodes201are installed in the steering wheel501unless otherwise noted. Furthermore, in the description below, the “twelve” wheel electrodes201are denoted by the wheel electrode “1”, the wheel electrode “2”, . . . , the wheel electrode “12”, respectively.

To return toFIG. 2, when the steering wheel501is held by a driver, the wheel electrode201is contacted by the driver. In an example illustrated in (2) ofFIG. 3, the wheel electrode “3” is contacted by driver's right hand, and the wheel electrode “9” is contacted by driver's left hand.

The wheel electrode201detects its own electric potential with an electric potential of the vehicle as a reference potential. Specifically, the plurality of wheel electrodes201detect their own electric potential. More specifically, a wheel electrode201contacted by driver's hand out of the wheel electrodes201detects an electric potential of the driver's hand with an electric potential of the vehicle as a reference potential.

Furthermore, the wheel electrode201sends the detected electric potential to the selection circuit203. Specifically, the wheel electrode201periodically detects an electric potential, and each time the wheel electrode201detects an electric potential, the wheel electrode201sends the detected electric potential.

The seat electrode202is connected to the potential-difference measuring unit204. An example of the structure of the seat electrode202is explained with reference toFIG. 4.FIG. 4is a diagram for explaining about an example of a seat electrode installed in a seat in the second embodiment. The seat electrode202is an electrode different from the electrodes installed in the steering wheel501, and is installed in a seat502of the vehicle. In the example illustrated inFIG. 4, the seat electrode202has the structure that a lower electrode504, an insulating layer505, upper electrodes506and507, and a protective member508are sequentially stacked on a seat member503which is a member of the seat502.

Here, a conductive part509is installed in the protective member508. The conductive part509is connected to the upper electrodes506and507. Incidentally, the conductive part509is installed, for example, on an inner wall of a hole part having an opening formed on the protective member508. The upper electrodes506and507detect an electric state from the right and left sides of the driver's buttocks, respectively.

The lower electrode504is grounded, and is opposed to the upper electrodes506and507via the insulating layer505. As a result, a combination of the upper electrode506or507and the lower electrode504serves as an electrode installed in the seat502.

Incidentally, in the description below, there is described taking for example a case of not distinguishing between the upper electrodes506and507; however, the present embodiment is not limited to this case. For example, the upper electrodes506and507can be electrically independent and independently detect an electric state from the right and left sides of the driver's buttocks, respectively. Furthermore, in the case where the upper electrodes506and507are electrically independent, an individual lower electrode can be installed with respect to each upper electrode.

The seat electrode202is contacted by the driver when the driver sits in the seat502. In the example illustrated inFIG. 4, the seat electrode202is contacted by the driver in such a way that the driver sits in the seat502, and consequently the upper electrodes506and507are contacted by the driver's buttocks via the conductive part509. Incidentally, in the second embodiment, there is described taking for example a case where the seat electrode202is being contacted by the driver unless otherwise noted. Namely, there is described taking for example a case where the driver is sitting in the seat502.

The seat electrode202detects its own electric potential with an electric potential of the vehicle as a reference potential. For example, the seat electrode202detects an electric potential of the driver's buttocks when the seat electrode202is contacted by the driver's buttocks and bases an electric potential of the vehicle as a reference potential. Then, the seat electrode202sends the detected electric potential to the potential-difference measuring unit204. Specifically, the seat electrode202periodically detects an electric potential, and each time the seat electrode202detects an electric potential, the seat electrode202sends the detected electric potential.

Incidentally, the seat electrode202can be an electrode installed in a position other than the seat502as long as the position can be in continuous and electrical contact with a part of the body located on the different side of the hand across the heart of a person who is an object of detection of a heart beat.

How the wheel electrode201and the seat electrode202detect an electric potential is explained with reference toFIG. 5.FIG. 5is a diagram for explaining how the wheel electrode and the seat electrode in the second embodiment detect an electric potential. InFIG. 5, for the convenience of explanation, there is described taking for example a case where “two” wheel electrodes201are installed in the steering wheel501and the “two” wheel electrodes201are contacted by driver's right and left hands, respectively.

Here, a part from heart513to the arm of a driver is electrically considered as a resistance component. Driver's hand is electrically considered as a resistor capacitor (RC) parallel circuit. A part from the heart513to the buttocks of the driver is electrically considered as a resistance component. Furthermore, clothes, such as pants or a skirt, is electrically considered as an RC parallel circuit. As a result, an equivalent circuit including the driver himself is as illustrated inFIG. 5. Incidentally, inFIG. 5, a resistance component from the heart513to the right arm of the driver is denoted by a resistance514; the right hand is denoted by an RC parallel circuit515; a resistance component from the heart513to the left arm of the driver is denoted by a resistance516; the left hand is denoted by an RC parallel circuit517. Furthermore, a resistance component from the heart513to the buttocks is denoted by a resistance518, and the clothes is denoted by an RC parallel circuit519. Moreover, an operational amplifier is denoted by “OP”.

As illustrated inFIG. 5, an operational amplifier510has two inputs. A cardiac action potential of the heart513is input to one of the inputs of the operational amplifier510via the resistance514and the RC parallel circuit515, and an electric potential of a vehicle body frame, which is a reference potential, is input to the other input. Then, the operational amplifier510amplifies the cardiac action potential with the electric potential of the vehicle body frame as a reference potential, and outputs the amplified cardiac action potential. Furthermore, in the same manner as the operational amplifier510, a cardiac action potential of the heart513is input to an operational amplifier511via the resistance516and the RC parallel circuit517, and the operational amplifier511amplifies the cardiac action potential and then outputs the cardiac action potential. Moreover, in the same manner as the operational amplifier510, a cardiac action potential of the heart513is input to an operational amplifier512via the resistance518and the RC parallel circuit519, and the operational amplifier512amplifies the cardiac action potential and then outputs the cardiac action potential.

Namely, in the example illustrated inFIG. 5, the operational amplifier510detects a cardiac action potential from the driver's right hand, and amplifies the detected cardiac action potential and then sends the cardiac action potential to the selection circuit203. The operational amplifier511detects a cardiac action potential from the driver's left hand, and amplifies the cardiac action potential and then sends the cardiac action potential to the selection circuit203. The operational amplifier512detects a cardiac action potential from the driver's buttocks, and amplifies the cardiac action potential and then sends the cardiac action potential to the potential-difference measuring unit204.

Incidentally, the reason why the operational amplifiers510to512send a cardiac action potential after amplifying the cardiac action potential is because based on an electric potential of the vehicle body frame as a reference potential, a cardiac action potential is weak. Furthermore, the operational amplifiers510to512amplify a cardiac action potential by a fixed amplification factor.

To return toFIG. 2, the selection circuit203is connected to the wheel electrode201, the potential-difference measuring unit204, and the control unit400. The selection circuit203receives an electric potential from each of the plurality of wheel electrodes201installed in the steering wheel501, and sends the received electric potential to the potential-difference measuring unit204.

Specifically, the selection circuit203sends the electric potential received from any of the wheel electrodes201to the potential-difference measuring unit204instead of sending all the electric potentials received from the plurality of wheel electrodes201at the same time. Furthermore, the selection circuit203switches the wheel electrode201as a transmission source of electric potential to be sent to the potential-difference measuring unit204at every predetermined timing.

Here, an example of the selection circuit203is further explained with reference toFIG. 6.FIG. 6is a diagram for explaining about an example of a selection circuit in the second embodiment. InFIG. 6, for the convenience of explanation, the steering wheel501and the wheel electrodes201are also illustrated. In the example illustrated inFIG. 6, the selection circuit203has analog switches520respectively corresponding to the wheel electrodes201installed in the steering wheel501. The selection circuit203sets one of the analog switches520to “ON”. As a result, the selection circuit203sends an electric potential received from the wheel electrode201corresponding to the analog switch520set to “ON” to the potential-difference measuring unit204. Furthermore, when setting one of the analog switches520to “ON”, the selection circuit203sets the other analog switches520to “OFF”. As a result, the selection circuit203does not send electric potentials received from the wheel electrodes201corresponding to the analog switches520set to “OFF” to the potential-difference measuring unit204. Incidentally, as “GND” inFIG. 6suggests, there is illustrated an example where the selection circuit203has analog switches connected to the ground.

Furthermore, for example, the selection circuit203changes the analog switch520to be set to “ON” with every predetermined time. More specifically, the selection circuit203changes the wheel electrode201as a detection source of an electric signal to be sent to the potential-difference measuring unit204sequentially in the order from the wheel electrode “1” to the wheel electrode “12”. After changing to the wheel electrode “12”, the selection circuit203next changes to the wheel electrode “1”, and repeats the process to change the wheel electrode201as a detection source.

To return toFIG. 2, the potential-difference measuring unit204is connected to the selection circuit203, the seat electrode202, and the amplifying unit205. The potential-difference measuring unit204measures a difference in potential between a contact electrode contacted by the driver out of the plurality of wheel electrodes201installed in the steering wheel501of the vehicle and the seat electrode202contacted by the driver.

Specifically, first, the potential-difference measuring unit204receives an electric potential detected by the wheel electrode201from the selection circuit203, and also receives an electric potential detected by the seat electrode202from the seat electrode202. Then, the potential-difference measuring unit204measures a potential difference between the electric potential received from the selection circuit203and the electric potential received from the seat electrode202. As a result, if any of the wheel electrodes201is being held by the driver, the potential-difference measuring unit204receives an electric potential of the contact electrode, and measures a potential difference between the contact electrode and the seat electrode202.

Furthermore, the potential-difference measuring unit204sends the measured potential difference to the amplifying unit205. The potential difference sent by the potential-difference measuring unit204is further explained with reference toFIG. 7.FIG. 7is a diagram for explaining about an example of a potential difference signal sent to an amplifying unit by a potential-difference measuring unit in the second embodiment. InFIG. 7, the vertical axis indicates a potential difference, and the horizontal axis indicates the time axis. In the description below, without limiting a potential difference to a value of potential difference at a certain moment, each of values of potential difference continuously measured from a certain time-position is referred to as a potential difference signal.

Here, “measurement period” inFIG. 7denotes a period of time for one round of the output of potential difference signals measured using electric potentials detected by the plurality of wheel electrodes201. Namely, the “measurement period” inFIG. 7denotes a time from when the output of a potential difference signal on the wheel electrode “1” is started till when the output of a potential difference signal on the wheel electrode “12” is completed. In the example illustrated inFIG. 7, “1” on the time axis inFIG. 7denotes a potential difference signal on the wheel electrode “1”, and “2” on the time axis inFIG. 7denotes a potential difference signal on the wheel electrode “2”.

Incidentally, the plurality of wheel electrodes201is installed in the steering wheel501; some of the wheel electrodes201are contacted by the driver's hands and others are not. Here, a value of potential difference on a contact electrode contacted by driver's hand is different from a value of potential difference on a non-contact electrode not contacted by driver's hand.

Specifically, the driver is in contact with the vehicle. Therefore, when the wheel electrode201is contacted by the driver, the wheel electrode201detects an electric potential close to a reference potential which is an electric potential of the vehicle. In other words, a contact electrode detects a value closer to the reference potential as compared with an electric potential detected by a non-contact electrode. Furthermore, the seat electrode202is contacted by driver's buttocks. Therefore, the seat electrode202detects a value closer to the reference potential than an electric potential detected by a non-contact electrode.

As a result, a value of potential difference between an “electric potential detected by the seat electrode202” and an “electric potential detected by a contact electrode” is smaller than a potential difference between an “electric potential detected by the seat electrode202” and an “electric potential detected by a non-contact electrode”. For example, when the wheel electrodes “3” and “9” are contacted by driver's hands, as illustrated inFIG. 7, a potential difference on the wheel electrode “3” and a potential difference on the wheel electrode “9” are smaller than potential differences on the other wheel electrodes201.

To return toFIG. 2, the amplifying unit205is connected to the potential-difference measuring unit204and the control unit400. The amplifying unit205receives a potential difference signal measured by the potential-difference measuring unit204. Then, the amplifying unit205performs various filtering on the received potential difference signal, thereby reducing noise included in the received potential difference signal. Namely, the amplifying unit205reduces components other than a component related to cardiac action potential out of components included in the received potential difference signal.

For example, the amplifying unit205performs filtering using a notch filter, a band-pass filter, and a correlation filter sequentially. Incidentally, the notch filter is a filter that attenuates a signal of a particular frequency. The band-pass filter is a filter that allows passage of a particular frequency. The correlation filter is a filter that performs back-diffusion processing (correlation processing) on a signal.

A difference between before and after a filtering process performed by the amplifying unit205is explained with reference toFIGS. 8A to 8D.FIGS. 8A to 8Dare diagrams for explaining about a difference between before and after the filtering process. Incidentally, inFIGS. 8A to 8D, the vertical axis indicates a potential difference, and the horizontal axis indicates the time axis. In examples illustrated inFIGS. 8A to 8D, data measured when a resistance value of a part from the seat to driver's right hand is “200 kΩ” is illustrated as an example.

First,FIG. 8Aillustrates a potential difference signal when the amplifying unit205has received it from the potential-difference measuring unit204. Namely,FIG. 8Aillustrates an example of a potential difference signal before a filtering process is performed on the potential difference signal by the amplifying unit205. Incidentally, for the convenience of explanation, the potential difference signal illustrated inFIG. 8Ashall be a potential difference signal on a contact electrode. For example, the potential difference signal illustrated inFIG. 8Ais a potential difference signal that the potential difference signal on the wheel electrode “3” or “9” on the time axis inFIG. 7is enlarged.

Then,FIG. 8Billustrates a potential difference signal obtained by performing a filtering process using the notch filter on the potential difference signal illustrated inFIG. 8A. Then,FIG. 8Cillustrates a potential difference signal obtained by performing a filtering process using the band-pass filter on the potential difference signal illustrated inFIG. 8B. Then,FIG. 8Dillustrates a potential difference signal obtained by performing a filtering process using the correlation filter on the potential difference signal illustrated inFIG. 8C.

As illustrated inFIG. 8A, the potential difference signal when the amplifying unit205has received it from the potential-difference measuring unit204includes a lot of noise, and is not in a state where a component related to cardiac action potential can be easily identified. However, as illustrated inFIGS. 8B to 8D, after the various filtering processes are performed on the potential difference signal, the potential difference signal has reduced noise, and is in the state where a component related to cardiac action potential can be easily identified.

Incidentally, when a potential difference signal to be filtered by the amplifying unit205is a potential difference signal on a non-contact electrode, noise remains. For example, a potential difference signal on a non-contact electrode is a potential difference signal on a wheel electrode other than the wheel electrodes “3” and “9” on the time axis inFIG. 7. The potential difference signal does not include a component related to cardiac action potential in the first place; therefore, even after the potential difference signal is filtered, only noise remains.

Furthermore, the amplifying unit205changes an amplification factor to be applied to a potential difference signal in the various filtering processes. Specifically, the amplifying unit205receives information on “timing” to change an amplification factor used in the various filtering processes and an “instruction” on content of the change from a determining unit403. Then, at the “timing” received from the determining unit403, the amplifying unit205changes conditions used in the various filtering processes on the basis of the “instruction” received from the determining unit403.

There is further explained taking for example a case where the wheel electrode “3” is contacted by the right hand. The amplifying unit205receives information on “timing” to receive a potential difference signal on the wheel electrode “3” from the determining unit403. Furthermore, the amplifying unit205receives an “instruction” to amplify the potential difference signal using an amplification factor suitable for a combination of the right hand and the buttocks. Then, at the received “timing”, the amplifying unit205changes an amplification factor used in the various filtering processes to a value suitable for the combination of the right hand and the buttocks.

In this manner, the amplifying unit205amplifies a potential difference signal by an amplification factor suitable for “a combination of two positions across the heart” corresponding to the received potential difference signal on the basis of the “timing” and “instruction” received from the determining unit403. As a result, no matter which one of the plurality of wheel electrodes201is a contact electrode, no matter what “a combination of two positions across the heart” is, the amplifying unit205sends a potential difference signal that is easy for a beat identifying unit404to identify to the control unit400.

To return toFIG. 2, the storage unit300is connected to the control unit400, and stores therein data for various processes performed by the control unit400. The storage unit300is, for example, a semiconductor memory device, such as a random access memory (RAM), a read-only memory (ROM), or a flash memory, or a storage device, such as a hard disk or an optical disk. In the example illustrated inFIG. 2, the storage unit300has a potential-difference storage unit301and a determination-result storage unit302.

The potential-difference storage unit301stores therein a potential difference signal filtered by the amplifying unit205. Here, an example of a potential difference signal stored in the potential-difference storage unit301is explained with reference toFIG. 9.FIG. 9is a diagram for explaining about an example of information stored in a potential-difference storage unit in the second embodiment. Incidentally, inFIG. 9, the vertical axis indicates a potential difference, and the horizontal axis indicates the time axis.

A potential difference signal stored in the potential-difference storage unit301is a potential difference signal filtered by the amplifying unit205. Therefore, as illustrated in (1) ofFIG. 9, a potential difference signal on the wheel electrode201contacted by the driver has reduced noise, and is in the state where a component related to cardiac action potential can be easily identified. On the other hand, as illustrated in (2) ofFIG. 9, a potential difference signal on a non-contact electrode does not include a component related to cardiac action potential in the first place, and is in a state where only noise is identified. Incidentally, information stored in the potential-difference storage unit301is stored by a potential-difference storing unit401of the control unit400, and is used by an electrode identifying unit402of the control unit400.

The determination-result storage unit302stores therein information indicating a combination of a result of determination by the determining unit403and identification information identifying a contact electrode which is an object of the determination result. An example of information stored in a determination-result storage unit in the second embodiment is explained with reference toFIG. 10.FIG. 10is a diagram for explaining about an example of information stored in the determination-result storage unit in the second embodiment.

In the example illustrated inFIG. 10, the determination-result storage unit302stores therein information indicating a combination of identification information and a determination result in association with a time. For example, the determination-result storage unit302stores therein information indicating a combination of identification information “3” and a determination result “right hand” and information indicating a combination of identification information “9” and a determination result “left hand” in association with a time “10:10:10”. The “time” illustrated inFIG. 10denotes a time at which a determination process has been performed by the determining unit403.

Namely, in the example illustrated inFIG. 10, the determination-result storage unit302stores therein a result of determination made at “10:10:10” by the determining unit403. Specifically, the determination-result storage unit302stores therein a determination result indicating that the wheel electrode “3” is contacted by driver's right hand and a determination result indicating that the wheel electrode “9” is contacted by driver's left hand as a result of determination.

Incidentally, when driver's one hand is in contact with the wheel electrode201, the determination-result storage unit302stores therein one combination of identification information and a determination result in association with a “time”. In the example illustrated inFIG. 10, there is described a case where the determination-result storage unit302stores therein identification information indicating a contact electrode as identification information; however, the present embodiment is not limited to this case. For example, the determination-result storage unit302can store therein information indicating whether it is contacted by a driver or information indicating whether driver's hand is the right hand or the left hand with respect to each piece of identification information identifying a wheel electrode201.

Furthermore, information stored in the determination-result storage unit302is input by the determining unit403each time the determining unit403performs a determination process. Namely, when the determining unit403performs a determination process, if the determining unit403has performed the determination process before, a result of previous determination has been stored in the determination-result storage unit302.

To return toFIG. 2, the control unit400is connected to the amplifying unit205and the storage unit300. The control unit400has an internal memory storing therein programs in which procedures of various processes are defined, and performs the various processes. The control unit400is, for example, an integrated circuit, such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA), or an electronic circuit, such as a central processing unit (CPU) or a micro processing unit (MPU). In the example illustrated inFIG. 2, the control unit400has the potential-difference storing unit401, the electrode identifying unit402, the determining unit403, and the beat identifying unit404. The potential-difference storing unit401receives a potential difference signal from the amplifying unit205, and stores the received potential difference signal in the potential-difference storage unit301.

The electrode identifying unit402acquires a potential difference signal stored in the potential-difference storage unit301, and identifies a contact electrode contacted by driver's hand out of the plurality of wheel electrodes201. A contact-electrode identifying process performed by an electrode identifying unit in the second embodiment is explained with reference toFIGS. 11A to 11C.FIGS. 11A to 11Care diagrams for explaining about a process to identify a contact electrode. Incidentally, inFIGS. 11A to 11C, the vertical axis indicates a potential difference, and the horizontal axis indicates the time axis.

For example, the electrode identifying unit402identifies a point having a smaller potential difference than other points out of received potential difference signals, and identifies that the wheel electrode201corresponding to the identified point is a contact electrode. In an example illustrated inFIG. 11A, there are two points having a small potential difference within the measurement period, and the electrode identifying unit402identifies that the points corresponding to the wheel electrodes “3” and “9” are small in potential difference. As a result, the electrode identifying unit402identifies that the wheel electrodes “3” and “9” are contact electrodes.

In an example illustrated inFIG. 11B, there is one point having a small potential difference within the measurement period; however, the width of the point having a small potential difference is long, and the electrode identifying unit402identifies that potential differences on the wheel electrodes “3” and “4” are small. As a result, the electrode identifying unit402identifies that the wheel electrodes “3” and “4” are contact electrodes.

In an example illustrated inFIG. 11C, there is one point having a small potential difference within the measurement period, and the electrode identifying unit402identifies that the point corresponding to the wheel electrode “3” is small in potential difference. As a result, the electrode identifying unit402identifies that the wheel electrode “3” is a contact electrode.

For example, the electrode identifying unit402measures an average potential difference at intervals of the measurement period, and identifies a point indicating a smaller potential difference than the measured average potential difference as a point having a small potential difference. Furthermore, for example, when a threshold value for distinguishing between a point which is small in potential difference and a point which is not small is set by a user in advance, the electrode identifying unit402can identify a point having a small potential difference using the set threshold value.

Furthermore, the electrode identifying unit402identifies a contact electrode, thereby identifying whether the wheel electrode(s)201is contacted by driver's both hands or one hand. When identifying two contact electrodes as illustrated inFIGS. 11A and 11B, the electrode identifying unit402identifies that the wheel electrodes201are contacted by driver's both hands. Furthermore, when identifying one contact electrode as illustrated inFIG. 11C, the electrode identifying unit402identifies that the wheel electrode201is contacted by driver's one hand.

Moreover, the electrode identifying unit402identifies a contact electrode at intervals of the measurement period, and sends a result of the identification to the determining unit403. For example, the electrode identifying unit402sends information that contact electrodes are the wheel electrodes “3” and “9” and the wheel electrodes201are contacted by “both hands” of the driver to the determining unit403.

To return toFIG. 2, the determining unit403is connected to the selection circuit203, the amplifying unit205, the determination-result storage unit302, and the electrode identifying unit402. Furthermore, although not illustrated inFIG. 2, the determining unit403is connected to a control device of the vehicle. The determining unit403receives a result of identification from the electrode identifying unit402, and acquires a rotational state of the steering wheel501from the control device of the vehicle.

In a case where it is the first time to perform a determination process, the determining unit403determines whether the driver's hand by which the contact electrode is contacted is the right hand or the left hand on the basis of the rotational state of the steering wheel501and the identification result actually received from the electrode identifying unit402. The identification result actually received from the electrode identifying unit402is, in other words, the current identification result. Furthermore, except when it is the first time to perform a determination process, the determining unit403determines whether driver's hand by which a contact electrode is contacted is the right hand or the left hand on the basis of a previous determination result stored in the determination-result storage unit302and the current identification result.

Incidentally, “when it is the first time to perform a determination process” means at the time of first processing and when no previous determination result is stored in the determination-result storage unit302. Furthermore, “when no previous determination result is stored in the determination-result storage unit302” means when there is no result of determination previously performed in a predetermined time frame at the time for the determining unit403to make a determination.

Moreover, “when it is the first time to perform a determination process” includes when a previous determination result does not correspond to the current identification result. For example, “when it is the first time to perform a determination process” also includes when while the current contact electrodes are the wheel electrodes “3” and “9”, the determination-result storage unit302does not store therein determination results indicating the contact electrodes “3” and “9” in association with the latest time.

The process for the determining unit403to determine whether driver's hand is the right hand or the left hand is explained in more detail. The determining unit403identifies which one of the following five cases is met using the current identification result and a previous determination result. Then, the determining unit403performs a determination process corresponding to the identified case.

“Case 1” is a case where the current identification result indicates “contact by both hands” and there is “no” previous determination result stored.

“Case 2” is a case where the current identification result indicates “contact by both hands” and the previous determination result indicates “contact by both hands”.

“Case 3” is a case where the current identification result indicates “contact by both hands” and the previous determination result indicates “contact by one hand”.

“Case 4” is a case where the current identification result indicates “contact by one hand” and there is “no” previous determination result stored.

“Case 5” is a case where the current identification result indicates “contact by one hand” and the previous determination result indicates “contact by both hands” or “contact by one hand”.

Respective determination processes performed by the determining unit403in the above “Case 1” to “Case 5” are explained below. Incidentally, the “Case 1” and the “Case 4” are the case where there is “no” previous determination result stored, and correspond to “when it is the first time to perform a determination process”. Furthermore, the “Case 2”, the “Case 3”, and the “Case 5” are the case where there is a previous determination result stored, and correspond to “except when it is the first time to perform a determination process”.

Determination Process in Case 1

First, a determination process in the “Case 1” is explained. The determining unit403determines whether driver's hand in contact with a contact electrode is the right hand or the left hand on the basis of a rotational state of the steering wheel501and the current identification result. Specifically, the determining unit403determines that the hand in contact with a contact electrode on the right side from the driver is the right hand. Furthermore, the determining unit403determines that the hand in contact with a contact electrode on the left side from the driver is the left hand. Namely, in the “Case 1”, the previous determination result is not used at all, so the determining unit1403determines whether driver's hand in contact with a contact electrode is the right hand or the left hand anew.

Here, the “Case 1” is explained taking for example a case where the current contact electrodes are the wheel electrodes “3” and “9”. In this case, the determining unit403identifies whether the contact electrode “3” or “9” is on the left side or the right side of the driver using a rotational state of the steering wheel501. Then, when the contact electrode “3” is on the right side of the driver and the contact electrode “9” is on the left side of the driver, the determining unit403determines that the wheel electrode “3” is contacted by driver's right hand and the wheel electrode “9” is contacted by driver's left hand. Incidentally, details of the process of determination using a rotational state of the steering wheel501will be described later, so detailed description of the process is omitted here.

Determination Process in Case 2

Subsequently, a determination process in the “Case 2” is explained. The determining unit403acquires a previous determination result from the determination-result storage unit302, and takes the acquired previous determination result as a determination result. Namely, in the “Case 2”, the previous determination result and the current identification result both indicate contact by driver's both hands, and the determining unit403determines that the same contact has been made continuously from the previous time.

Here, the “Case 2” is explained taking for example a case where the current contact electrodes are the wheel electrodes “3” and “9”. Furthermore, there is explained under the assumption that the previous determination result is information indicating a combination of identification information “3” and a determination result “right hand” and information indicating identification information “9” and a determination result “left hand”. In this case, the determining unit403determines that the wheel electrode “3” is contacted by driver's right hand and the wheel electrode “9” is contacted by driver's left hand.

Determination Process in Case 3

Subsequently, a determination process in the “Case 3” is explained. The determining unit403acquires a previous determination result from the determination-result storage unit302. Then, the determining unit403first uses the acquired previous determination result as a determination result. After that, the determining unit403determines that hand in contact with the remaining contact electrode is the remaining hand. Namely, in the “Case 3”, as for a common contact electrode with the previous determination result out of the current two contact electrodes, the determining unit403determines that the same contact has been made continuously from the previous time. Then, as for the other contact electrode which is not a common contact electrode with the previous determination result, the determining unit403determines that the contact electrode is contacted by driver's hand which has had no contact with any contact electrode in the previous time.

Here, the “Case 3” is explained taking for example a case where the current contact electrodes are the wheel electrodes “3” and “9”. Furthermore, there is explained under the assumption that the previous determination result is information indicating a combination of identification information “3” and a determination result “right hand”. In this case, the determining unit403first determines that the wheel electrode “3” is contacted by driver's right hand. After that, the determining unit403determines that the remaining contact electrode, i.e., the wheel electrode “9” is contacted by the remaining hand, i.e., driver's “left hand”.

Determination Process in Case 4

Subsequently, a determination process in the “Case 4” is explained. The determining unit403determines whether driver's hand in contact with a contact electrode is the right hand or the left hand on the basis of a rotational state of the steering wheel501and the current identification result. Specifically, if the contact electrode is on the right side of the driver, the determining unit403determines that the hand in contact with the contact electrode is the right hand; on the other hand, if the contact electrode is on the left side of the driver, the determining unit403determines that the hand in contact with the contact electrode is the left hand. Namely, in the “Case 4”, the previous determination result is not used at all, so the determining unit403determines whether driver's hand in contact with a contact electrode is the right hand or the left hand anew in the same manner as in the “Case 1”.

Here, the “Case 4” is explained taking for example a case where the current contact electrode is the wheel electrode “3”. In this case, the determining unit403identifies whether the contact electrode “3” is on the left side or the right side of the driver using a rotational state of the steering wheel501. Then, when the contact electrode “3” is on the right side of the driver, the determining unit403determines that the wheel electrode “3” is contacted by driver's right hand. On the other hand, when the contact electrode “3” is on the left side of the driver, the determining unit403determines that the wheel electrode “3” is contacted by driver's left hand. Incidentally, details of the process of determination using a rotational state of the steering wheel501will be described later, so detailed description of the process is omitted here.

Determination Process in Case 5

Subsequently, a determination process in the “Case 5” is explained. The determining unit403acquires a previous determination result corresponding to the current contact electrode from the determination-result storage unit302. Then, the determining unit403takes the acquired previous determination result as a determination result. Namely, as for the current contact electrode common with the previous determination result, the determining unit403determines that the same contact has been made continuously from the previous time.

Here, the “Case 5” is explained taking for example a case where the current contact electrode is the wheel electrode “3”. Furthermore, there is explained under the assumption that the previous determination result is information indicating a combination of identification information “3” and a determination result “right hand”. In this case, the determining unit403determines that the wheel electrode “3” is contacted by driver's right hand.

About Determining Unit Taking Rotational State of Wheel into Account

As described above, in the “Case 1” and the “Case 4”, the determining unit403identifies whether a contact electrode is on the left side or the right side of the driver using a rotational state of the steering wheel501. Here, the reason why the determining unit403takes a rotational state of the steering wheel501into account is explained with reference toFIGS. 12A and 12B.FIGS. 12A and 12Bare diagrams for explaining about a relation between a rotational state of a wheel and positions of wheel electrodes.FIGS. 12A and 12Billustrate an example of the steering wheel501held by the driver; in the example, the steering wheel501is on the front side, and the driver is located behind the steering wheel501.

Here, the wheel electrode “3” may be on the left side of the driver and the wheel electrode “9” may be on the right side of the driver as illustrated inFIG. 12A, or the wheel electrode “9” may be on the left side of the driver and the wheel electrode “3” may be on the right side of the driver as illustrated inFIG. 12B. Namely, the steering wheel501is rotated, so even when it is found that contact electrodes are the wheel electrodes “3” and “9”, the determining unit403does not identify which one of the contact electrodes is on the right side or left side of the driver.

Therefore, the determining unit403acquires a rotation angle of the steering wheel501rotated to the right (or the left) by the driver, for example, based on a position of the wheel when the vehicle goes straight ahead. Then, the determining unit403determines that either one of the two contact electrodes located on the right side than the other is on the right side of the driver, and determines that either one of the two contact electrodes located on the left side than the other is on the left side of the driver.

In an example illustrated inFIG. 12B, the determining unit403identifies that the wheel electrode “9” is on the left side than the wheel electrode “3” from a rotation angle of the steering wheel501. As a result, the determining unit403determines that driver's hand in contact with the wheel electrode “9” is the left hand. Furthermore, the determining unit403identifies that the wheel electrode “3” is on the right side than the wheel electrode “9” from the rotation angle. As a result, the determining unit403determines that driver's hand in contact with the wheel electrode “3” is the right hand.

Example of Determination Process Performed by Determining Unit

Here, an example of a determination process performed by the determining unit403is further explained with reference toFIG. 13.FIG. 13is a diagram for explaining about a process performed by a determining unit in the second embodiment. In (1) to (3) ofFIG. 13, there is illustrated for example a case where twelve uniformly-sized wheel electrodes201are installed along a circumferential direction of the steering wheel501. Furthermore, (1) to (3) ofFIG. 13indicate an example of a relation between the steering wheel501and driver's hands when the driver steers to the left.

First, as illustrated in (1) ofFIG. 13, the driver is holding the steering wheel501with both hands. As a result, the determination-result storage unit302has stored therein information indicating a combination of identification information “3” and a determination result “right hand” and information indicating a combination of identification information “9” and a determination result “left hand” as a previous determination result.

After that, as illustrated in (2) ofFIG. 13, the driver begins to steer to the left, and releases the left hand from the steering wheel501. At this point, the determining unit403determines that it is not the first determination process, and reads out a previous determination result associated with identification information identifying the contact electrode “3” from the determination-result storage unit302. For example, the determining unit403reads out information indicating a combination of identification information “3” and a determination result “right hand”. As a result, the determining unit403determines that the wheel electrode “3” is contacted by driver's right hand.

Then, as illustrated in (3) ofFIG. 13, the driver further steers to the left, and the wheel electrode “6” on the left side of the driver is contacted by the left hand. At this point, the determining unit403determines that it is not the first determination process, and reads out a previous determination result associated with identification information identifying the contact electrode “3” or “6”. For example, the determining unit403reads out information indicating a combination of identification information “3” and a determination result “right hand”. As a result, the determining unit403first determines that the wheel electrode “3” is contacted by driver's right hand, and then determines that the remaining contact electrode, i.e., the wheel electrode “6” is contacted by the remaining hand, i.e., driver's “left hand”.

Process After Determination Made by Determining Unit

Subsequently, a process performed after the determination is made by the determining unit403is explained. The determining unit403stores a result of the determination in the determination-result storage unit302. There is further explained taking for example a case where the determining unit403has determined that driver's hand in contact with the wheel electrode “9” is the left hand and driver's hand in contact with the wheel electrode “3” is the right hand. In this case, the determining unit403stores a combination of identification information “3” and a determination result “right hand” and a combination of identification information “9” and a determination result “left hand” in association with a current time in the determination-result storage unit302.

Furthermore, the determining unit403sends information on “timing” and an “instruction” to the amplifying unit205on the basis of the determination result. As a result, the determining unit403causes the amplifying unit205to amplify a potential difference signal by an amplification factor determined on the basis of the determination result.

There is further explained taking for example a case where the determining unit403has determined that driver's hand in contact with the wheel electrode “9” is the right hand and driver's hand in contact with the wheel electrode “3” is the left hand. In this case, the determining unit403sends an instruction to amplify a potential difference signal on the wheel electrode “9” by an amplification factor suitable for a combination of the right hand and the buttocks to the amplifying unit205. Furthermore, the determining unit403sends the timing for the amplifying unit205to receive the potential difference signal on the wheel electrode “9”. Moreover, for example, the determining unit403sends an instruction to amplify a potential difference signal on the wheel electrode “3” by an amplification factor suitable for a combination of the left hand and the buttocks to the amplifying unit205. In addition, the determining unit403sends the timing for the amplifying unit205to receive the potential difference signal on the wheel electrode “3”.

Namely, on the basis of facts that the heart is located at a position slightly deviated from the center of body and consequently the intensity of a heart rate signal differs according to a combination of two positions across the heart, the determining unit403sends an instruction to amplify a potential difference signal by an amplification factor suitable for a combination of two positions. For example, as for a potential difference signal on the wheel electrode201contacted by the right hand, an instruction to use an amplification factor suitable for the intensity of a heart rate signal included in a measured potential difference between the buttocks and the right hand is sent.

Furthermore, for example, a potential difference signal measured by using a combination of the right hand and the seat includes a stronger heart rate signal than that is included in a potential difference signal measured by using a combination of the left hand and the seat. Therefore, the determining unit403sends an instruction to use, with respect to a potential difference signal on the wheel electrode201contacted by the left hand, a higher amplification factor than that is used with respect to a potential difference signal on the wheel electrode201contacted by the right hand.

To return to the explanation ofFIG. 2, the beat identifying unit404acquires a potential difference signal stored in the potential-difference storage unit301, and identifies a component related to cardiac action potential from the acquired potential difference signal. Namely, the beat identifying unit404identifies the heart beat. As described above, the amplifying unit205amplifies a potential difference signal by an amplification factor based on an instruction issued by the determining unit403. Consequently, the potential-difference storage unit301stores therein the potential difference signal amplified on the basis of the instruction issued by the determining unit403. Therefore, the beat identifying unit404identifies the heart beat from the potential difference signal amplified on the basis of the instruction issued by the determining unit403.

A processes to identify the heart beat in a case where the wheel electrodes201are contacted by driver's both hands and a processes to identify the heart beat in a case where the wheel electrode201is contacted by driver's one hand are further explained.

First, the process in the case where the wheel electrodes201are contacted by driver's both hands is explained. The beat identifying unit404subtracts a potential difference signal on the wheel electrode201contacted by the driver's left hand from a potential difference signal on the wheel electrode201contacted by the driver's right hand, thereby measuring a potential difference signal corresponding to a combination of the right hand and the left hand. For example, the beat identifying unit404acquires a potential difference signal on the wheel electrode201contacted by the driver's right hand out of potential difference signals stored in the potential-difference storage unit301, and further acquires a potential difference signal on the wheel electrode201contacted by the driver's left hand. Then, the beat identifying unit404performs subtraction using the acquired potential difference signals, thereby measuring a potential difference signal corresponding to a combination of the right hand and the left hand. Then, the beat identifying unit404identifies the heart beat from the potential difference signal corresponding to the combination of the right hand and the left hand.

Incidentally, the measurement can be made by subtracting a potential difference signal on the wheel electrode201contacted by the driver's right hand from a potential difference signal on the wheel electrode201contacted by the driver's left hand. In the case of using the potential difference signal corresponding to the combination of the right hand and the left hand, noise can be further reduced as compared with a case of using a potential difference signal corresponding to a combination of the right hand and the seat or a combination of the left hand and the seat, and therefore the beat identifying unit404can identify cardiac action potential more definitely.

The process in the case where the wheel electrode201is contacted by driver's one hand is explained. The beat identifying unit404acquires a potential difference signal on the wheel electrode201contacted by the driver's hand, and identifies the heart beat from the acquired potential difference signal. For example, when the contact electrode is the wheel electrode “3”, the beat identifying unit404acquires a potential difference signal on the wheel electrode “3”, and identifies the heart beat.

In this manner, when it is possible to measure a wheel potential difference signal which is a potential difference signal between two contact electrodes contacted by a driver out of a plurality of electrodes installed in the steering wheel501of the vehicle, the determining unit403identifies a heart rate signal using the wheel potential difference signal. On the other hand, when it is not possible to measure a wheel potential difference signal, the determining unit403identifies a heart rate signal using a potential difference signal between one contact electrode out of the plurality of electrodes installed in the steering wheel501of the vehicle and a different contact electrode from the electrodes installed in the wheel.

Incidentally, the beat identifying unit404identifies whether the wheel is contacted by driver's both hands or one hand using a potential difference signal stored in the potential-difference storage unit301. For example, when there are two points having a small potential difference every measurement period as illustrated inFIG. 11Aor11B, the beat identifying unit404identifies that the wheel is contacted with both hands. Furthermore, for example, when there is one point having a small potential difference every measurement period as illustrated inFIG. 11C, the beat identifying unit404identifies that the wheel is contacted with one hand. Incidentally, the beat identifying unit404can identify whether the wheel is contacted with driver's both hands or one hand upon receipt of a determination result from the determining unit403.

Process Performed by Identification Device

Subsequently, an example of the flow of a process performed by the control unit400in the second embodiment is explained with reference toFIG. 14.FIG. 14is a flowchart for explaining about an example of the flow of the process performed by the control unit400in the second embodiment.

As illustrated inFIG. 14, when it comes to a time for the process (YES at S101), the electrode identifying unit402identifies a contact electrode contacted by driver's hand out of a plurality of electrodes installed in the steering wheel501(S102). For example, the electrode identifying unit402identifies that contact electrodes are the wheel electrodes “3” and “9”.

Then, the electrode identifying unit402identifies whether contact by both hands or contact by one hand (S103). For example, when identifying two contact electrodes, the electrode identifying unit402identifies that the wheel electrodes201are contacted by driver's both hands. Furthermore, for example, when identifying one contact electrode, the electrode identifying unit402identifies that the wheel electrode201is contacted by driver's one hand.

Here, there is explained a case where contact by driver's both hands is identified by the electrode identifying unit402(YES at S104). The determining unit403determines whether it is the first time to perform a determination process (S105). Then, when determining that it is the first time (YES at S105), the determining unit403determines that one of the two contact electrodes on the right side than the other is contacted by driver's right hand and the other contact electrode on the left side than the one is contacted by driver's left hand (S106).

Furthermore, at S105, when determining that it is not the first time (NO at S105), the determining unit403acquires a previous determination result out of determination results stored in the determination-result storage unit302(S107). Here, if the previous determination result indicates contact by both hands (YES at S108), the determining unit403uses the acquired determination result as-is (S109). There is explained a case where the determining unit403has acquired, for example, information indicating a combination of identification information “3” and a determination result “right hand” and information indicating a combination of identification information “9” and a determination result “left hand”. In this case, the determining unit403determines that the wheel electrode “3” is contacted by the driver's right hand and the wheel electrode “9” is contacted by the driver's left hand.

On the other hand, when the previous determination result does not indicate contact by both hands (NO at S108), i.e., when the previous determination result indicates contact by one hand (S110), the determining unit403first uses the acquired determination result (S111). For example, when the determining unit403has acquired information indicating a combination of identification information “3” and a determination result “right hand”, the determining unit403determines that the wheel electrode “3” is contacted by the driver's right hand. Then, the determining unit403determines that the remaining contact electrode is contacted by the remaining hand (S112). For example, the determining unit403determines that the remaining contact electrode, i.e., the wheel electrode “9” is contacted by the remaining hand, i.e., driver's “left hand”.

Furthermore, there is explained a case where at S104, the electrode identifying unit402identifies not contact by driver's both hands (NO at S104) but contact by driver's one hand (S113).

Here, the determining unit403determines whether it is the first time to perform a determination process (S114). Then, when determining that it is the first time (YES at S114), the determining unit403determines that a contact electrode is contacted by driver's right hand if the contact electrode is on the right side of the driver. Furthermore, if a contact electrode is on the left side of the driver, the determining unit403determines that the contact electrode is contacted by driver's left hand (S115).

On the other hand, at S114, when determining that it is not the first time (NO at S114), the determining unit403acquires a previous determination result (S116), and uses the previous determination result (S117).

After that, the determining unit403causes the amplifying unit205to amplify a potential difference signal measured by the potential-difference measuring unit204using an amplification factor determined on the basis of the determination result (S118). Then, the beat identifying unit404identifies the heart beat from the potential difference signal amplified by the amplifying unit205(S119).

Incidentally, the flow of the process described above is not limited to the flow illustrated inFIG. 14. For example, all of the above-described process does not have to be performed in series. For example, the identification device200performs the processes at S101to S118in series, and causes the amplifying unit205to amplify a potential difference signal by an amplification factor determined on the basis of a determination result. Then, the identification device200can identify the heart beat from the potential difference signal at the different timing from the timing to perform the amplification process.

Effects of Second Embodiment

As described above, according to the second embodiment, the identification device200measures a potential difference signal between one contact electrode out of the plurality of wheel electrodes201and the seat electrode202different from the electrodes installed in the steering wheel501. Then, the identification device200identifies a contact electrode contacted by driver's hand out of the plurality of wheel electrodes201, and determines whether the driver's hand in contact with the contact electrode is the right hand or the left hand on the basis of a position of the contact electrode in the wheel and a rotational state of the wheel. Then, the identification device200identifies the heart beat from the potential difference signal amplified by an amplification factor determined on the basis of the determination result. Consequently, it is possible to distinguish whether driver's hand in contact with the wheel electrode201installed in the steering wheel501is the right hand or the left hand. Furthermore, whether the hand in contact with the electrode on the wheel is the right hand or the left hand can be determined, and as a result, it is possible to identify the heart beat using an amplification factor suitable for a combination of two positions of electrodes between which a potential difference signal is measured, and also possible to identify a weak heart rate signal which is apt to be buried in noise with a high degree of accuracy. Furthermore, no matter whether the hand in contact with the wheel electrode201is the right hand or the left hand, or even both hands, a heart rate signal can be detected with accuracy; therefore, it is possible to increase a duration of detection of a heart rate signal.

For example, if the amplifying unit205continues to apply the same amplification factor, when the combination of two positions across the heart is switched, a component related to cardiac action potential is likely to be buried in noise. There is further explained taking for example a case where the combination of two positions is switched, and as a result, a component related to cardiac action potential becomes weaker than it is before switching of the combination of two positions. In this case, the component related to cardiac action potential is weaker than it is before switching of the combination of two positions, and consequently the component related to cardiac action potential is likely to be buried in noise. However, according to the second embodiment, the identification device200can identify the heart beat using an amplification factor suitable for a combination of two positions of electrodes between which a potential difference signal is measured; therefore, even if the combination of two positions is switched, the identification device200can identify a weak heart rate signal which is apt to be buried in noise with a high degree of accuracy.

Furthermore, according to the second embodiment, the identification device200further includes the determination-result storage unit302that stores therein a result of determination by the determining unit403and identification information identifying a contact electrode which is an object of the determination result in an associated manner. Then, the identification device200identifies a contact electrode, thereby identifying whether driver's both hands or one hand is in contact with the wheel electrode201. Then, when identifying contact by driver's one hand of, the identification device200reads out a previous determination result by referring to the determination-result storage unit302, and, if the read previous determination result indicates that the contact electrode is contacted by the right hand, determines that the contact electrode is contacted by the right hand. Furthermore, similarly, if the read previous determination result indicates that the contact electrode is contacted by the left hand, the identification device200determines that the contact electrode is contacted by the left hand. As a result, if it is not the first process, it is possible to continuously distinguish whether driver's hand by which the wheel electrode201installed in the steering wheel501is contacted is the right hand or the left hand. For example, even if the driver steers and a position of the hand in contact with the wheel electrode201is changed, whether the hand by which the wheel electrode201is contacted is the right hand or the left hand can be distinguished.

Moreover, according to the second embodiment, when the wheel electrodes201are contacted by driver's both hands, the beat identifying unit404identifies a heart rate signal using a wheel potential difference signal. Furthermore, when the wheel electrode201is contacted by driver's one hand, the beat identifying unit404identifies a heart rate signal using a potential difference signal between the one contact electrode out of the wheel electrodes201and the seat electrode202. As a result, no matter whether the wheel electrode201is contacted by driver's both hands or one hand, the heart beat can be continuously identified.

The other embodiments are explained below.

Electrode

For example, in the above embodiment, there is described the case where an electrode installed in the seat502of the vehicle is used as a different electrode from electrodes installed in the steering wheel501; however, the present embodiment is not limited to this case, and, for example, an electrode can be installed in a seat belt of the vehicle and used instead of the electrode installed in the seat502.

Furthermore, in the above embodiment, there is described the case where driver's hand is in contact with one wheel electrode201at a time; however, the present embodiment is not limited to this case. Specifically, driver's hand can be in contact with a plurality of wheel electrodes201at a time. Namely, for example, each wheel electrode, such as the wheel electrode “1” or “2”, can be divided into a plurality of electrodes.

Wheel Potential Difference Signal

Moreover, in the above embodiment, there is described the case where the beat identifying unit404measures a wheel potential difference signal using a potential difference signal stored in the potential-difference storage unit301; however, the present embodiment is not limited to this case. For example, the potential-difference measuring unit204can measure a wheel potential difference signal.

For example, the selection circuit203selects two wheel electrodes201as detection sources of electric potential to be sent to the potential-difference measuring unit204, and sends respective electric potentials detected by the selected two wheel electrodes201. Furthermore, the selection circuit203changes a combination of the two wheel electrodes201on a regular basis. Then, the potential-difference measuring unit204measures a difference between the two electric potentials received from the selection circuit203. As a result, when the wheel electrodes201are contacted by driver's both hands, the potential-difference measuring unit204measures a wheel potential difference signal.

After that, when the wheel potential difference signal has been stored in the potential-difference storage unit301, the beat identifying unit404identifies the heart beat from the wheel potential difference signal. Namely, the beat identifying unit404identifies whether any of potential difference signals corresponding to a combination of the two wheel electrodes201out of potential difference signals stored in the potential-difference storage unit301is a potential difference signal including the heart beat. Then, when identifying that there is a potential difference signal including the heart beat, the beat identifying unit404identifies the heart beat from the identified potential difference signal. On the other hand, when no wheel potential difference signal is stored in the potential-difference storage unit301, the beat identifying unit404identifies the heart beat from a potential difference signal between driver's one hand and the seat.

System Configuration

Furthermore, out of the processes described in the present embodiments, all or part of the process described as the one that is automatically performed can be manually performed. For example, the heart beat can be manually identified from a potential difference signal. In addition, the control procedures, specific names, and information including various data and parameters illustrated in the above description and the drawings (for example,FIGS. 1 to 14) can be arbitrarily changed unless otherwise specified.

Moreover, the elements of the devices illustrated in the drawings are functionally conceptual ones, and do not always have to be physically configured as illustrated in the drawings. Namely, specific forms of dispersion and integration of the elements in the devices are not limited to those illustrated in the drawings, and all or part of the elements can be configured to be functionally or physically dispersed or integrated in arbitrary units depending on respective loads or usages, etc. For example, the wheel electrodes201and the seat electrodes202can be configured as an external device of the identification device200and connected to the identification device200via a network (such as a wireless LAN (Local Area Network)). Furthermore, the above-described functions of the identification device200can be implemented in such a way that other devices have the potential-difference storage unit301and the determination-result storage unit302, respectively, and the other devices are connected to the identification device200via a network and work in cooperation with the identification device200.

Computer

Furthermore, the various processes described in the above embodiments can be realized by causing a computer, such as a personal computer or a workstation, to execute a program prepared in advance. An example of the computer that executes an identification program having the same functions as those described in the above embodiments is explained below. Incidentally,FIG. 15is a diagram for explaining an example of a computer that executes an identification program according to the second embodiment.

As illustrated inFIG. 15, a computer3000in the second embodiment is composed of a potential-difference measuring circuit3001, an amplifying unit3002, a communication unit3006, a CPU3010, a ROM3011, an HDD3012, and a RAM3013that are connected by a bus3009and the like. Incidentally, the potential-difference measuring circuit3001corresponds to the potential-difference measuring unit204inFIG. 2, and the amplifying unit3002corresponds to the amplifying unit205inFIG. 2.

In the ROM3011, a control program that fulfills the same functions as the potential-difference storing unit401, the electrode identifying unit402, the determining unit403, and the beat identifying unit404illustrated in the above second embodiment, i.e., a potential-difference storing program3011a, an electrode identifying program3011b, a determining program3011c, and a beat identifying program3011dare stored in advance as illustrated inFIG. 15. Incidentally, these programs3011ato3011dcan be arbitrarily integrated or dispersed in the same manner as the elements of the identification device200illustrated inFIG. 2.

The CPU3010reads these programs3011ato3011dfrom the ROM3011and executes these programs3011ato3011d, thereby the programs3011ato3011dwork as a potential-difference storing process3010a, an electrode identifying process3010b, a determining process3010c, and a beat identifying process3010d, respectively, as illustrated inFIG. 15. Incidentally, the processes3010ato3010dcorrespond to the potential-difference storing unit401, the electrode identifying unit402, the determining unit403, and the beat identifying unit404illustrated inFIG. 2, respectively.

Then, the CPU3010reads the potential-difference table3012aand the determination-result table3012band stores data on the tables3012aand3012bin the RAM3013, and executes an identification program using the potential-difference data3013aand determination-result data3013bstored in the RAM3013.

Others

Incidentally, the identification program described in the present embodiment can be distributed via a network, such as the Internet. Furthermore, the identification program can be recorded on a computer-readable recording medium, such as a hard disk, a flexible disk (FD), a CD-ROM, an MO, or a DVD, and the computer can execute the identification program by reading out the identification program from the recording medium.

According to an aspect of an identification device disclosed herein, the identification device can distinguish whether the right hand or the left hand is in contact with an electrode installed in a wheel.