JPS60132537A - Heart rate mether for vehicle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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, etc. on a vehicle, and particularly relates to a vehicle equipped with a sensor on the steering wheel that outputs an electrical signal according to the human heartbeat. Regarding heart rate monitors.

[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 long periods of time without taking a break.

Fatigue accumulates, health condition worsens, and concentration 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. Furthermore, for example, even if a driver who drives a car were to bring a heart rate monitor into the vehicle in order to know his/her own health condition, the heart rate measurement would have to be done 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 photosensor, and this sensor is applied to the pad of a person's finger to further reduce the influence of external light. In order to eliminate this problem, the sensor and fingers are covered with black sponge, etc., so the driver cannot drive with this covered on his fingers. 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 developed an on-vehicle heart rate monitor (patent application No. 57-1980) that is capable of measuring heart rate even while driving the vehicle by equipping the steering wheel with a sensor for detecting heart rate.
132847).

If the steering wheel is equipped with a heart rate sensor,
Heartbeat detection can be performed even while driving.

By the way, in order to actually measure heart rate while driving, it is necessary to install a large number of heart rate sensors along the grip area of the steering wheel so that heart rate can be detected no matter where you hold the steering wheel. be. However, when trying to obtain heartbeat signals by connecting many heartbeat sensors in parallel, the number of sensors that can actually obtain heartbeat signals is small, so the level of noise due to the influence of external light increases, resulting in a low S/N ( The signal/noise ratio may be so low that it may become undetectable.

[Purpose] The first object of the present invention is to provide an on-vehicle heart rate monitor 11 that allows a driver to measure his or her own heart rate while driving, and which is less susceptible to external light. 2 objectives.

[Configuration] In order to increase the S/N ratio of the JL signal obtained from the sensor output, it is sufficient to select only the heartbeat sensor to which the hand is actually applied, and to separate the heartbeat sensor to which the hand is not applied.

However, heart rate measurement becomes cumbersome if the driver operates a switch placed at a predetermined position to select a specific sensor, and a selection switch is placed near the heart rate sensor so that only the sensor whose switch is pressed If this is selected, if the grip of the hand is weak, there is a risk that the switch will be deactivated and detection will not be possible even if a heartbeat signal is obtained.

Accordingly, in the present invention, the output level of each sensor is sequentially monitored, a sensor with a heartbeat signal of Jb is found, and the sensor is selectively connected to the measuring section to measure the heartbeat.

According to this, the selection of the sensor is performed automatically, so the operation is easy, and since the sensor to be used is selected by actually looking at the output of the sensor, selection errors do not occur.

The output of the sensor is a level obtained by adding the signal level of the heartbeat signal and the external light, but the intensity of the external light varies greatly depending on the position of the steering wheel. However, when determining the signal level by comparing it with a predetermined threshold, false detection may occur if the threshold is not set favorably. Therefore, in one preferred embodiment of the present invention, levels are compared between adjacent sensors,
By looking at the difference in levels, one can determine the beginning and end of the sensor to be used, and select a sensor within that range.

Since it is considered that the influence of external light acts on adjacent sensors in the same way, by shifting in this way, the influence of external light is canceled out.

Hereinafter, the present invention will be described in detail 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, the center of the steering wheel 4 is provided with a start switch SWI for instructing the start of heart rate measurement and a cancel switch SW2 for instructing cancellation of the measurement. Two cathode ray tube display devices CRTI and CRT2 are provided to the left of the steering wheel 4.

Details of the steering wheel 4 are shown in FIG. 2a.

Shown in Figures 2b and 2c. Referring to these drawings, on the top surface of the steering wheel 4.

Reflective optical sensor SEI, SE2. ...SEn are distributed and arranged at a predetermined interval wfI (at least an interval smaller than the width of a hand). Each optical sensor consists of a light emitting diode LES and a phototransistor p'rs arranged near it. The light emitting diode provided in each optical sensor is an infrared light emitting diode that emits light in the infrared region. The light emitting diode LES and phototransistor PTS of each optical sensor have their optical axes oriented in the same direction (above the steering wheel 4).

The steering wheel 4 has an iron core 4b and a resin 4 covering it.
Each optical sensor is fixed by being embedded in the resin 4a, leaving the light emitting part and the light receiving part.6 The electric wire drawn out from each optical sensor passes through the inside of the resin 4a and is fixed to the steering wheel. It is connected to an electronic circuit in a panel in the center of the wheel 4.

Figures 3a, 3b and 3c show the configuration of the electronic circuit of the on-vehicle heart rate monitor. A microcomputer CPU controls the entire circuit. In this example, the microcomputer CPU includes a voice synthesizer VGU, a buzzer BZ,
Video RAM RAMI.

RAM 2, analog/digital converter ADC, etc. are connected. 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 output ends of the video rams RAM1 and RAM2, respectively.

The oscillation circuit 03C2 connected to the interrupt input terminal INT of the microcomputer
periodically issues an interrupt request. Start switch SW1
and cancel switch SW2 are each connected to the input port of the CPU via an inverter or the like.

Referring to FIG. 3b, the light emitting diodes LES provided in the optical sensors SEI to SEn are connected in series, one end of which is connected to the oscillation circuit o'set, and the other end of which is grounded. In this example, the oscillation circuit 08CI oscillates at a frequency of +lz to 1 and generates a square wave voltage. However, the low level of voltage is not zero. Therefore, the intensity of light emitted by the light emitting diode LES of each optical sensor changes binary with a period of 1 m5ec. When any of the optical sensors SE1 to S E n 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, at the output terminal of the phototransistor of the optical sensor, an AC signal of 1Kllz whose amplitude is modulated according to the heartbeat signal is obtained.

A differential amplifier D is connected to the output terminal of each optical sensor 5E1=SEn.
FI to D F n are connected. Each differential amplifier is connected to amplify the potential difference between adjacent optical sensors. That is, the differential amplifier D
An output line SGI of an optical sensor fsEl is connected to one input terminal of PI.

The output line SG2 of the optical sensor SE2 adjacent in the clockwise direction is connected to the other input terminal of the differential amplifier DPI, and the same applies to the other differential amplifiers DF2 to DFn.

The output lines of the differential amplifiers DFI to DFn are connected to each other via analog switches ASI to ASn, and this signal line SGX is connected to one input terminal CH2 of the analog/digital converter ADC. There is. Each control input terminal of the analog switches ASI to ASn is connected to a different output port of the microcomputer CPU.

Output lines SGI to S of each optical sensor SE1 to SEn
G n are commonly connected to each other via analog switches BSI to BSn, and this signal line is connected to the input terminal of the demodulator OEM. Each control input terminal of the analog switch BS1''BSn is connected to a different output port of the microcomputer CPU.

The demodulation circuit DEM includes an amplifier AMI and a low-pass filter L.
PI, amplifier AM2. Low pass filter LP2. amplification@
AM3 or the like, and demodulates a one-dimensional heartbeat signal from an amplitude-modulated 1Kllz signal.

The output terminal of the demodulator DEM is connected to one input terminal CHI of the analog/digital converter ADC. Other input terminals CH3 and CH4 of the analog/digital converter ADC are connected to variable resistors VRI for setting the upper and lower limits of the dispersion (variation) of the heartbeat cycle, respectively.
and VR2 are connected.

FIG. 4 shows the configuration of the video RAM VRAM1 shown in FIG. 3a. Note that the video ram VRAM2 also has the same configuration as the VRAM1. This will be explained with reference to FIG. Memory R
AM corresponds to each pixel displayed on the cathode ray tube. Light/dark data is stored. The address line of the memory RAM is connected to a multiplexer MX,
A memory address is selected according to either the count value of the address counter CO applied to inputs A and B of X or the output address of the CPU.

This selection is made by the microcomputer CPU, and when writing data to the memory RAM or reading data from the RAM, input B of MX is designated and the CPU designates the address.

Otherwise, the address of the memory RAM is .

It is specified by the count value of address counter Go.

The address counter CO constantly performs counting using a pulse signal corresponding to the number of pixels from the oscillator 03C3. Further, a synchronization signal generation circuit 100 is connected to the output terminal of the address counter CO, and this circuit is connected to the output terminal of the address counter CO.
A vertical synchronization signal and a horizontal synchronization signal are generated at predetermined timing according to the count value of .

The data line consisting of multiple bits of memory RAM has
A shift 1 register SR is connected, and the serial output terminal of SR 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, data with a predetermined bit set to 'l' is written from the CPU to the RAM address corresponding to that pixel.In this case, the B input of multiplexer MX is specified, and the bidirectional buffer BF2 Specify the CPU side as input and the RAM side as output, set predetermined data to the address line and data line of the CPU, and apply a write designation signal to the memory RAM.After this is completed, the next write is performed. Until you do.

Specify MX as input A, and write RAM of bidirectional buffer BF2.
side is set to high impedance.

In this state, a synchronization signal is generated at predetermined timings, and RAM addresses are sequentially selected in accordance with the synchronization signal. When a predetermined address is specified by writing display data, data of multiple pins 1- including pixel data is set in the shift register SR, and after a delay of a predetermined clock corresponding to the pixel position, the [bright] of the predetermined pixel is set. Data indicating this is applied to the signal synthesis circuit 110. In this way, serial data corresponding to the data of all pixels on the display screen is continuously output, and the image data and synchronization signal are combined at 110 to form a composite signal, which is used in a cathode ray tube display (monitor). television).

FIGS. 5a and 5b schematically show the operation of the microcomputer CPU (II) shown in FIG. fJS3'a. This will be explained with reference to FIGS. 5a and 5b. When the start switch SW1 is turned on, first, the set values of the variable resistors VR1 and VR2 are read through the analog/digital converter ADC, and these are set as the dispersion upper limit value MH and dispersion lower limit value M.
L, and then executes the sensor selection subroutine.

In the sensor selection subroutine, CH2 is first selected as the input channel of the analog/digital converter ADC. Next, after turning off the analog switches ASI to A S n and BSI to BSn, the initial value 1 is set in the 5 counter (register) C. A specific analog switch A S (C) determined by the contents of the counter C is turned on and the output of the analog/digital converter ADC is read.

That is, in this case, the signal level of the signal line SGX is read, so if the counter C is 1, the difference between the output levels of the optical sensors SEI and SF2 is read.

For example, now the driver is the optical sensor SE6. When gripping SE7 and SF8, the output level of each sensor becomes as shown in FIG. 7a. In other words, for the output level of the optical sensors SEI to SE5 and SE9 to SE n, the optical sensors SE6 to SE in the part where the hand is present
The output JJ level of SE8 will be high. Therefore, the difference between the output levels of adjacent optical sensors can be divided into two threshold levels Tl-11 and T as shown in FIG. 7b.
By comparing H2, three states are determined: when the two levels are equal, when one level is higher than the other level by more than a certain value, and when one level is lower than the other level by more than a certain value. Then, when the value of the counter C is 5, the output level of the differential amplifier DF5 becomes a plus predetermined level (greater than THI).

When the value of the counter C is 8, the output level of the differential amplifier DF8 becomes a minus predetermined level (less than TH2), and in all other cases, the level becomes between THI and TH2.

Therefore, the optical sensors from which heartbeat signals can be obtained are SE6 to SE.
8, so if the case of plus a predetermined level is defined as the start detection level, and the case of minus predetermined level is defined as the end detection level, then the content of counter C +1 when the start detection level is obtained is the end detection level. If you select the outputs of all the optical sensors (SE6 to SE8 in this case) indicated by the contents of counter C when S
A heartbeat signal with a high /N ratio can be obtained.

In this example, the contents of counter C are changed from 1 to Cmax, that is, n, the output levels of differential amplifiers DFI to DFn are scanned, and when the start edge detection level is obtained, the contents of counter C at that time are changed to start edge register R5. When the termination detection level is obtained, the contents of counter C at that time are stored in termination register RE, and after scanning is completed, the contents of register R5 and RE are checked and an analog switch ( BS). That is, in this example, analog switch BS6. Set r3S7 and BS8 on.

Therefore, the input terminal of the demodulator OEM is inputted with the added signals output only from the optical sensors from which heartbeat signals are actually obtained. When the sensor selection subroutine is completed, the input channel of the analog/digital converter ADC is set to CI-11, and interrupts are enabled.

When the interrupt is enabled, the NSOSC will oscillate 5 times after that.
An interrupt request is made to the microcomputer CPU once in each cycle of the signal output by the microcomputer 2, and the CPU executes the interrupt process. In interrupt processing, the contents of register T used as a timer are incremented by 1, the input level of the analog/digital converter is A/D converted and read, and the signal level is determined to determine whether an R wave has been detected or not. Determine whether the peak of the wave has been detected, and if the R wave is detected, set a predetermined flag, and if the peak of the R wave is detected, store the contents of register T in a predetermined heartbeat register. , clears the flag and register T.

The R wave is a waveform component that corresponds to a large peak included in the heartbeat signal, and in this example, the differential value, that is, the level change for each sampling, is checked to see if it is larger than a predetermined value. It is determined that the wave is an R wave when the wave continues a predetermined number of times. Furthermore, in this example, the change in the signal level sampled after detecting the R wave is 0.
It is determined that a peak is reached when the value is less than or equal to that value twice in a row.

Each time the peak of the R wave is detected, the contents of register T are cleared, so the contents of register R immediately after the peak is detected are based on the elapsed time between the peak of the previous R wave and the peak of the current R wave. corresponds to the period of the R wave (R-R interval).

In the main routine, the CPU first waits until heartbeat data for 32 beats are stored by interrupt processing, and then proceeds to the next distributed calculation/discrimination subroutine. In the distributed calculation/discrimination subroutine, wait until one beat's worth of heart rate data is stored,
The new heart rate data and the previous 31 beats of data (the oldest data is discarded) are processed as follows. First, calculate the average value of 32 beats of detau and calculate the average heartbeat cycle. Next, calculate its reciprocal, or heart rate. Furthermore.

Calculate the variation or dispersion of the heartbeat cycle. The variance value M in this case can be determined by the following equation, where S is each heartbeat cycle.

Dispersion M=Average value of 82 - (Average value of S) 2 Next, the obtained dispersion value M is compared with the dispersion upper limit value M l-1 and the dispersion lower limit value M L. If M<ML, clear register S and add 1 to the contents of register N.

If M>MH, register N is cleared and the contents of register S are incremented by 1; if MH>M>ML, the contents of registers S and N are cleared. When the contents of register N or S reach 20, a flag indicating 1-dispersion abnormality is set.

That is, if the dispersion value is too large or too small for 20 consecutive beats, it is determined that the dispersion is abnormal. The dispersion calculation/discrimination subroutine is executed every time each heartbeat data is sampled until the cancel switch SW2 is pressed or the dispersion becomes abnormal. A heartbeat waveform is displayed on the cathode ray tube display device CRTI, and a heartbeat rate is displayed on CRT2.

If a flag indicating a dispersion abnormality is set, this is detected in the main routine, the buzzer BZ is activated for one second, and a voice warning is issued saying "Take a break".

If the output level difference between adjacent sensors is determined as in the above example, even if the external light or noise is strong, the effect will be the same on both, so it is possible to determine which optical sensor It is possible to reliably determine whether the sensor should be used for heartbeat detection. In the embodiment, differential amplifiers D1"1 to DFn were used, but if the conversion time of the A/D converter and the processing time of the microcomputer CPU are sufficiently short, the differential amplifiers can be omitted and all The configuration may be such that the CPU reads the output level of each sensor and calculates the level difference between adjacent sensors, or conversely, an analog comparator may be connected to the output terminals of the differential amplifiers DFI to DFn. The level may be determined and the analog switch (BS) may be controlled based on the result.

In the embodiment, in order to cancel the influence of extraneous light, the difference in the output levels of adjacent sensors is determined when selecting a sensor, but the output level of all the sensors is averaged and the difference is determined. The influence of external light can also be eliminated even with a configuration that discriminates the difference between the two. In that case, the average value may be determined by calculation, or one optical sensor may be provided at a position where an average level can be obtained, for example, in the center of the steering wheel, and its output level may be used as the average value.

When the amount of energization of the light emitting element (light emitting diode LES) of the optical sensor is periodically changed as in the embodiment, the amplitude of the periodic change obtained in the light receiving element is not affected by external light. Therefore, only the frequency component of the signal output from the oscillator circuit o s' c i is extracted using a narrow band filter,
The level may be determined. Also A/D conversion @ADC
If the conversion time of is sufficiently shorter than the period of 08C1,
It is also possible to sample the output level of the same sensor many times in a short period of time and compare the results with each other to calculate the amplitude.
+ In the embodiment, a warning is issued according to the dispersion of the heartbeat cycle, but it may be determined whether a warning is to be issued according to both the dispersion and the heart rate.

[Effects] As described in Section 2 below, according to the present invention, since a large number of optical sensors are provided on the steering wheel, heart rate measurement can be performed even while driving, and since a specific optical sensor is selected and used, S /N ratio is high, and malfunctions due to external light do not occur.

[Brief explanation of the drawing]

FIG. 1 is a front view showing the vicinity of the driver's seat of an automobile equipped with an on-vehicle heart rate monitor according to the present invention. FIG. 2a is an enlarged front view showing the steering wheel 4 of FIG. 1, and FIGS. 2b and 2c are lines II b - II b and II c - II c of FIG. 2 a, respectively.
It is a sectional view seen from a line. FIGS. 3a, 3b, and 3c are block diagrams showing the configuration of the electronic circuit of the car's second heart set installed in the automobile of FIG. 1. FIG. 4 is a block diagram showing the configuration of the video ram VRAMI shown in FIG. 3a. FIGS. 5a and 5b are a flowchart 1- showing a schematic operation of the microcomputer CPU shown in FIG. 3a. FIG. 6 is a plan view showing the screen display on one display device CRTI. FIG. 7d is a graph showing an example of the output level of some optical sensors, and FIG. 7b is a timing chart showing the waveforms of the output signal level of the optical sensor and the output level of the differential amplifier. 4 Steering Wheel LES: Jl! Photodiode (light emitting means) PH8: Phototransistor (light receiving means) SEI to SEn: Optical sensor (heartbeat detection means) CPIJ: Microcomputer (
Electronic control means) O3CI: Oscillation circuit (light emission energizing means) A S 1 to A S n , B S 1 to B S
n: Analog switch (switching means) D F 1 = D F n: Differential amplifier ΔDC: Analog/digital converter T:) EM: Demodulator VGtJ: Voice synthesizer (notification means) CRT 1,
CRT 2 Ni cathode ray tube display device SWI Ni start switch SW2: Cancel switch Patent applicant Aisin Seiki Co., Ltd. and 1 other person Figure 1 Figure 2a Figure 2b Bundle 2C diagram

Claims (4)

[Claims] (1) Heartbeat detecting means arranged on the steering wheel, each comprising a plurality of light emitting means and a plurality of light receiving means disposed near the light emitting means; a switching means for selecting at least one light receiving means of the heartbeat detecting means; the light emitting means; A light emitting energizing means for energizing the means; a notification means for performing at least one of display and sound output; and a switching means to sequentially select the light receiving means and determine the output signal level of each light receiving means for use. Identify the light receiving means, monitor the output signal level of at least one light receiving means selected according to the result, calculate the number of fluctuations of the signal level per predetermined time or the value according to the fluctuation period, and use the result as The notification means is energized accordingly. An on-vehicle heart rate monitor comprising electronic control means; (2) The electronic control means sequentially selects the light receiving means and identifies the light receiving means to be used by determining the difference between the output signal levels of adjacent light receiving means. The on-vehicle heart rate monitor according to claim (1). (3) The light emitting energizing means periodically repeats a large energizing state and a small energizing state.
On-vehicle heart rate monitor described in section. (4) Claims (1), (2), or (3) above, wherein the electronic control means energizes the notification means in accordance with variations in the period of the signal output by the light receiving means. In-vehicle heart rate monitor mentioned.