JPH0147175B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to an on-vehicle heart rate monitor that measures the heartbeat of a driver or the like on a vehicle, and particularly relates to an on-vehicle heart rate monitor that has a steering wheel equipped with a sensor that outputs an electrical signal corresponding to the human heartbeat. [Prior Art] When driving a vehicle, if the driver's health condition is not favorable, there is a high possibility that an accident will occur.
For example, if you continue to drive for a long time without taking a break, fatigue accumulates, your health condition worsens, and your ability to concentrate decreases. Heart rate is one barometer that can tell us about a person's health condition. Recently, small portable heart rate monitors have been sold as devices for measuring heart rate. Although this type of heart rate monitor can be carried anywhere, its measurement accuracy is low. For example, even if a driver who drives a car brings such a heart rate monitor into the vehicle in order to know his/her own health condition, the heart rate measurement must be carried out while the vehicle is stopped. In other words, in this type of general heart rate monitor, a light emitting diode, a photodiode, etc. are protruded from a substrate to form a reflective photo sensor, and this sensor is applied to the pad of a person's finger to further reduce the influence of extraneous light. To avoid this problem, the sensor and finger are covered with a black sponge, etc., so the driver cannot drive while wearing this on his or her finger. In addition, with this type of sensor, if the finger is moved during measurement, the position of the sensor and finger will shift and measurement will not be possible, so the person being measured is required to rest. Therefore, the present applicant has proposed an on-vehicle heart rate monitor (Japanese Patent Application No. 132,847/1982) that is capable of measuring heart rate even while driving the vehicle by equipping the steering wheel with a sensor for detecting heart rate. However, even in this case, in order to measure the heart rate, the heart rate signal cannot be obtained unless the fingertip is pressed against the sensor part on the steering wheel and maintained in that position, so it feels strange when measuring while driving, and it is normal. When you try to drive, your fingertip lifts off the sensor and measurement is interrupted. [Objective] An object of the present invention is to provide an on-vehicle heart rate monitor that can automatically measure the heartbeat even when the driver is driving naturally. [Configuration] In order to achieve the above object, in the present invention,
The heartbeat detecting means is disposed on the steering wheel with its optical axis facing upward in the axial direction of the steering wheel. As a result, when the driver grips the steering wheel under normal driving conditions,
The optical axis of the heartbeat detection means faces the driver's palm. That is, in the present invention, a heartbeat signal is detected from the driver's palm. Since fingers have a small surface area, driving a vehicle with the fingers pressed against a predetermined position on the steering wheel causes the hands to be fixed in an unnatural position, resulting in a feeling of discomfort. However, if the heartbeat can be detected in the palm of the hand, since the palm has a large surface area, there will be room to move the hand relative to the sensor position, and the heartbeat can be measured while continuing to drive the vehicle in a natural manner. Furthermore, even if the hand floats above the heartbeat detecting means and a gap is created between the two, since the heartbeat detecting means is covered by the hand, external light is blocked by the hand and does not enter the heartbeat detecting means. Therefore, heart rate measurement can be performed without being affected by external light. However, in the palm of the hand, blood vessels are not concentrated in relatively shallow areas like in the fingertips, and the palm tends to float above the steering wheel, so conventional detectors cannot extract heartbeat signals from the palm. Therefore, in the present invention, a plurality of light-receiving elements are arranged around a light-emitting element so as to surround the light-emitting element, and a detection unit configured such that the optical axes of the light-emitting element and the light-receiving element are directed in substantially the same direction is attached to a steering wheel. Provide at least one on the top. According to this, the heartbeat signal can be extracted from the palm of the hand, and the heartbeat can be measured in a natural manner even while driving. While driving a vehicle, there are times when it is desired to change the positional relationship between the steering wheel and the hands, such as when changing the direction of travel. Furthermore, the positions in which the steering wheel is held vary depending on the driver. Therefore, in the present invention, a plurality of heartbeat detection means are arranged at different positions on the steering wheel so that a heartbeat signal can be detected no matter where the driver grips the steering wheel. As a result, even if the driver holds the steering wheel with one hand or changes hands holding the steering wheel, heart rate measurement can be continued as long as the palm of the hand is facing one of the heart rate detection means. can. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the vicinity of the driver's seat of a vehicle equipped with an on-vehicle heart rate monitor according to an embodiment. Referring to FIG. 1, in the center of the steering wheel 4 there are a start switch SW1 for instructing the start of heart rate measurement, a cancel switch SW2 for instructing cancellation of the measurement, and a light emitting diode for displaying information according to the heart rate.
Equipped with LED. steering wheel 4
Two cathode ray tube display devices CRT1 and CRT2 are provided on the left side of the screen. Details of the steering wheel 4 are shown in Fig. 2a,
Shown in Figures 2b and 2c. Referring to these drawings, on the upper surface of the steering wheel 4, reflective optical sensors SE1, SE2, ... SE8 are arranged dispersedly from each other. Each optical sensor consists of one light emitting diode (LE1) and four phototransistors (PT1) arranged around it.
~PT4) The light emitting diode provided in each optical sensor is an infrared light emitting diode that emits light in the infrared region. One light emitting diode and four phototransistors of each optical sensor have their optical axes oriented in the same direction (above the steering wheel 4). The steering wheel 4 is made up of an iron core 4b and a resin 4a covering it, and each optical sensor is fixed to a portion of the resin 4a. Electric wires drawn out from each optical sensor pass through the resin 4a and are connected to an electronic circuit in a panel at the center of the steering wheel 4. FIG. 3a shows an outline of the circuit configuration of the on-vehicle heart rate monitor mounted on the vehicle shown in FIG. 1. This will be explained with reference to FIG. 3a. The microcomputer CPU controls the entire circuit. The microcomputer CPU includes an oscillation circuit OSC2 and a speech synthesizer.
VGU, video memory VRAM1, VRAM2, buzzer BZ, A/D converter ADC, key switch
SW1, SW2, etc. are connected. The circuit provided between the key switches SW1 and SW2 and the CPU is a waveform shaping circuit. A speaker SP is connected to the output terminal of the voice synthesizer VGU, and cathode ray tube display devices CRT1 and CRT2 are connected to the video memories VRAM1 and VRAM2, respectively. Variable resistors VR1 and VR2 for setting a reference level are connected to input terminals 1 and 2 of the A/D converter ADC, respectively, and an output terminal of a demodulation circuit DEM is connected to an input terminal 3. The output terminal of the demodulation circuit DEM is the driver
Connected to a light emitting diode LED for display via DV. The output terminal of the oscillation circuit OSC1 is connected to the sensor unit SEU, and the sensor unit
The output terminal of SEU is connected to the input terminal of demodulation circuit DEM. Oscillation circuit OSC1 in Figure 3a, sensor unit
Details of the SEU and demodulation circuit DEM are shown in Figure 3b. This will be explained with reference to FIG. 3b. oscillation circuit
OSC1 is an astable multivibrator circuit, which outputs a 1KHz square wave signal in this example.
The sensor unit SEU consists of eight optical sensors SE1
~ I'm familiar with SE8. Each optical sensor SE1 to SE8
The light emitting diodes LE1, LE2, . . . are connected in series, and one end thereof is connected to the output terminal of the oscillation circuit OSC1. Therefore, the light emitting diode of each optical sensor is lit intermittently at a cycle of 1 msec. When any of the optical sensors SE1 to SE8 is positioned facing a human blood vessel, the light reflectance of that portion varies depending on the blood flow rate, that is, the heartbeat.
Therefore, the output terminal of the phototransistor of the optical sensor has an amplitude modulated signal corresponding to the heartbeat signal.
A 1KHz AC signal can be obtained. The phototransistors PT1, PT2, PT3, . . . of the optical sensors SE1 to SE8 are connected in parallel with each other, and one end thereof is connected to the input terminal of the demodulation circuit DEM. Demodulation circuit DEM amplifier
AM1, low pass filter LP1, amplifier AM2,
It consists of a low-pass filter LP2, an amplifier AM3, etc., and demodulates the original heartbeat signal from the amplitude-modulated 1KHz signal. FIG. 4 shows the video memory VRAM1 of FIG. 3a.
The configuration is shown below. The video memory VRAM2 is also
It has the same configuration as VRAM1. This will be explained with reference to FIG. The memory RAM stores brightness/darkness data corresponding to each pixel displayed on the cathode ray tube. The address lines of the memory RAM are connected to the multiplexer MX,
Address counter CO applied to inputs A and B of
A memory address is selected according to either the count value of the CPU or the output address of the CPU. This selection is made by the microcomputer CPU, and when writing data to memory RAM or reading data from RAM, MX
Specify input B of , and the CPU specifies the address. At other times, the address of the memory RAM is specified by the count value of the address counter CO. Address counter CO is oscillator OSC3
Counting is performed constantly using pulse signals corresponding to the number of pixels. Further, a synchronization signal generation circuit 100 is connected to the output end of the address counter CO, and this circuit generates a vertical synchronization signal and a horizontal synchronization signal at predetermined timing according to the count value of CO. A shift register SR is connected to the data line consisting of multiple bits of the memory RAM, and the SR
The serial output terminal of is connected to the signal synthesis circuit 110. Further, a data line of the CPU is connected to this data line via a bidirectional buffer BF2. When displaying a predetermined pixel on a cathode ray tube brightly, the CPU writes data with a predetermined bit set to "1" to the RAM address corresponding to that pixel. In this case, specify the B input of multiplexer MX, and input the CPU side of bidirectional buffer BF2.
The RAM side is designated as output, predetermined data is set in the address line and data line of the CPU, and a write designation signal is applied to the memory RAM. After this is completed, until the next write, specify MX as input A and use the bidirectional buffer.
The RAM side of BF2 is set to high impedance. In this state, a synchronization signal is generated at every predetermined timing, and RAM addresses are sequentially selected in accordance with the synchronization signal. When a predetermined address is specified by writing display data, multiple bits of data including pixel data are set in the shift register SR, and after a delay of a predetermined clock corresponding to the pixel position, the "bright" state of the predetermined pixel is indicated. Data is applied to signal synthesis circuit 110. In this way, serial data corresponding to the data of all pixels on the display screen is continuously output, and this image data and the synchronization signal are combined at 110 to form a composite signal, which is used in a cathode ray tube display device (monitor television). is applied to Figure 5 shows the microcomputer in Figure 3a.
This shows the general operation of the CPU. The operation will be explained with reference to FIG. First, interrupt processing will be explained. Since the signal from the oscillation circuit OSC2 is applied to the interrupt input terminal INT of the CPU, the CPU executes interrupt processing at predetermined intervals. In this interrupt processing, the contents of register N are incremented by one. In other words, the contents of register N change depending on the elapsed time, so if you clear the contents of N to 0 at a certain timing, by checking the value of N in the main routine, you can check the elapsed time since clearing. I understand. In the main routine, subroutine, etc., various processing timings are determined by checking the value of this register N. Next, the main routine will be explained. When the power is turned on, first check the start switch SW1. When this is turned on, the voltage set by variable resistors VR1 and VR2 is transferred to the A/D converter.
Convert it to a digital signal with ADC and store the converted data in registers MH and ML. The data in registers MH and ML serve as the heartbeat cycle variation upper limit value and heart rate lower limit value, respectively, for determining whether to issue an alarm. Table 1 below shows the average heart rate of 1/L.
and the variability (i.e. variance) of the heartbeat cycle ΔL
and a person's physical and mental state.

[Table] Generally, when driving a vehicle, one is physically relaxed and mentally tense. However, when the driver falls asleep while driving due to fatigue or the like, the mental tension disappears and the heart rate returns to the state during sleep. In other words, referring to Table 1, if you start falling asleep while driving a vehicle,
The dispersion of the heartbeat cycle increases rapidly. Therefore, in this embodiment, a heart rate cycle variation reference value (upper limit) MH and a heart rate reference value (lower limit) MH are set to issue an alarm when the variation is large and the heart rate is below a predetermined value. I have to. After completing the MH and ML settings, wait for the predetermined time To required for the detection signal to stabilize before starting heart rate measurement. The heart rate measurement subroutine will be explained in detail later. After the heart rate measurement is completed, the variance of the heartbeat cycle, that is, the variation ΔL, is calculated based on the results. This calculation is performed using the following formula, where S is the heartbeat cycle of a predetermined sample (16 in this example). Variance = average value of S ² - (average value of S) ² Next, the heart rate, that is, the heart rate per minute, is calculated from the average value of S. According to this result, predetermined numerical display data stored in advance in the ROM (read-only memory) in the CPU is read out and set at a predetermined address in the video memory VRAM2. As a result, the numerical value of the heart rate is displayed on the cathode ray tube display device CRT2, for example, as shown in FIG. 3a. Next, the A/D converter ADC samples the heartbeat signal at predetermined intervals for a predetermined time, and displays the sampled data as a waveform on the cathode ray tube display device CRT1. Note that before performing this display, clear the memory RAM in advance. In the display processing, the following processing is performed. As shown in FIG. 6, a pixel on the display screen is specified by coordinates (X, Y) in the X direction and Y direction, and a predetermined plot subroutine (not shown) is executed to set a predetermined address in the memory RAM. Set the specified bit to “1”
Set to . A voltage of 0V is specified at a predetermined Y coordinate (for example, 10), and the specified Y coordinate is changed according to the value of sampled data. For example voltage 0.1V
If the sampled voltage is 1.5V, the specified Y coordinate will be 25 (10
+15). The X coordinate has an initial value of 0 and is changed by +1 each time sampling is performed. That is, when this process is performed, the pixels at the Y coordinate corresponding to the voltage are sequentially displayed brighter from the left side of the screen to the right side. This process is performed until the X coordinate reaches the right end, that is, X=XM. As a result, a heartbeat waveform as shown in FIG. 6 is displayed on the display CRT1. It is checked whether the cancel switch SW2 is on, and if it is off, the next process is performed. If the variance ΔL is larger than the contents of register MH,
Moreover, if the heart rate 1/L is smaller than the contents of register ML, there is a high possibility that the driver fell asleep at the wheel, so the buzzer BZ is energized for 1 second, the voice synthesizer VGU is given an instruction, and the speaker SP is ``take a break''. "Please," the voice outputs. If the above two conditions are not met, only the heart rate and heartbeat waveform are displayed. Next, the heart rate measurement subroutine will be explained. Note that this subroutine uses registers A, R1, and a plurality of registers R2 ( ) specified by the contents in parentheses. First, the memory (register) is cleared, and the heartbeat signal is sampled every 2 msec by the ADC. Check whether an R wave has arrived, and if it is an R wave, then check whether it is the peak of the signal. The R wave is a large peak in the heartbeat signal, and in this example, the differential value, that is, the change in data for each sampling, is checked to see if it is larger than a predetermined value, and if it is large continuously a predetermined number of times, it is checked. It is determined that it is an R wave only when Furthermore, in this example, a peak is determined when the change in the sampling value is 0 or less twice in a row. When a peak is detected, the contents of the counter N (timer) are cleared to 0, and the time (L) from peak detection to the next peak detection is measured. This time is the so-called RR interval (heartbeat cycle). Every time a measurement is made, the contents of register A are counted up,
Each measurement result is stored in register R2(A). 16
Once wave minute data is obtained (when A=16),
Finish the measurement. Now, 16 cycles of cycle data are stored in the 16 registers of register R2(A). Therefore, from the contents of this register, the variance value and heart rate data can be obtained by performing the above processing. In the above embodiment, two cathode ray tube display devices are used to display the heartbeat waveform on one and the heart rate on the other. It may be possible to provide multiple units and use them instead, or the waveform and heart rate may be displayed in a superimposed manner on a surface display for displaying the heartbeat waveform, or the waveform and heart rate may be displayed in a superimposed manner by a switch or at a predetermined cycle. It may be configured to switch and display. In the above embodiment, the light emitting element and the light receiving element are mounted directly on the wheel of the steering wheel. It may also be configured to guide light. If optical fibers are used, the number of light emitting elements and light receiving elements can be increased by connecting multiple optical fibers to the light emitting surface of one light emitting diode or connecting multiple optical fibers to the light receiving surface of one phototransistor. It can be reduced. Note that since it is difficult to bend the optical fiber at right angles in a narrow portion, it is necessary to use a mirror or the like to direct the optical axis above the steering wheel as in the embodiment. [Effects] As described above, according to the present invention, the heartbeat detection means is located in the steering wheel, and its optical axis is arranged so as to face the palm of the driver's hand when the driver normally holds the steering wheel. Even if the relative positional relationship between the hands and the steering wheel changes slightly due to steering wheel operations, the heartbeat signal can be detected, and the heartbeat can be measured in a natural state even while driving.
Further, since the heartbeat detection means is composed of a light emitting means and a plurality of light receiving means surrounding the light emitting means, a heartbeat signal can be detected even when the palm of the hand is lifted from the heartbeat detection means. Furthermore, since multiple heartbeat detection means are placed at different positions on the steering wheel, heartbeat signals can be detected without interruption even when the driver changes hands on the steering wheel or when gripping the steering wheel with one hand. .

[Brief explanation of drawings]

FIG. 1 is a front view showing the vicinity of a driver's seat of a vehicle equipped with an on-vehicle heart rate monitor according to an embodiment. 2a is an enlarged plan view showing the steering wheel 4 of the vehicle shown in FIG. 1, FIG. 2b is a cross-sectional view taken along line bb--b in FIG. 2a, and FIG. 2c is a cross-sectional view taken along line c--c in FIG. 2a. FIG. 3a is a block diagram showing a schematic configuration of the on-vehicle heart rate monitor mounted on the vehicle of FIG. 1, and FIG. 3b is an electric circuit diagram showing the main parts of FIG. 3a. FIG. 4 is a block diagram showing the structure of the video memory VRAM1 of FIG. 3a. FIG. 5 is a flowchart showing the general operation of the microcomputer CPU shown in FIG. FIG. 6 is a plan view showing the screen display on the display device CRT1. 4: Steering wheel, SE1, SE2,
..., SE8: Optical sensor (heartbeat detection means), SEU:
Sensor unit, LE1, LE2, LE3...: Light emitting diode (light emitting means), PT1, PT2, PT3
...: Phototransistor (light receiving means), SW1:
Start switch, SW2: Cancel switch, OSC1: Oscillation circuit (light emission energizing means), VGU:
Speech synthesis device (notification means), CRT1, CRT2:
Cathode ray tube display device, DEM: demodulation circuit, CPU:
Microcomputer (electronic control means).

Claims (1)

[Scope of Claims] 1 Each includes a light emitting means and a plurality of light receiving means disposed near the light emitting means in positions surrounding the light emitting means with optical axes directed in substantially the same direction as the light emitting means, A plurality of sets of heartbeat detecting means arranged at different positions on the steering wheel, arranged on the steering wheel with the axis facing upward in the axial direction of the steering wheel; Light emitting energizing means for energizing the light emitting means; a switch means for instructing the start of heart rate measurement; a notification means for performing at least one of display and sound output; and a means for controlling the number of fluctuations per predetermined time or period of fluctuation of the electrical signal from the light receiving means in accordance with the operation of the switch means. An on-vehicle heart rate monitor comprising: electronic control means for calculating a value and energizing the notification means according to the result. 2. The on-vehicle heart rate monitor according to claim 1, wherein the light emitting energizing means intermittently energizes the light emitting means at a predetermined period.