RU2499692C1 - Method of control over driver or dispatcher vigilance and device to prevent falling asleep - Google Patents

Abstract

FIELD: transport.

SUBSTANCE: invention relates to diagnostics of psycho physiological state and can be used for control over driver vigilance and prevention of falling asleep. Proposed method consists in measurement of induced variable electric potential of cerebrum. Note here that fractal magnitude of said potential is continuously calculated and compared to threshold magnitude which, when reached, makes awakening of driver a must. Device to prevent falling sleep comprises two electrodes of electroencephalographic signal. Electrodes are connected to measurements results processing unit, its output being connected to registration and analysis unit input. Registration and analysis unit output is connected with data and signal generator. Said registration and analysis unit incorporates signal fractal processor.

EFFECT: higher safety.

2 cl, 2 dwg

Description

The invention relates to the field of transport, in particular to devices for checking the alertness of a dispatcher and for monitoring the wakefulness of a vehicle driver.

It is used to diagnose the psychophysiological state in order to control the level of wakefulness and prevent falling asleep for drivers of vehicles, dispatchers, pilots, operators, etc., whose work is associated with increased risk.

The prior art method for controlling the level of wakefulness, which determines the moment preceding the onset of sleep (lower level of wakefulness) by measuring the bioelectric parameters of the operator, including skin electrical resistance [1, 2]. However, the electrical resistance of the skin in many respects depends not only on the level of wakefulness, but also on a number of other, both external and internal causes, therefore, periodic dynamic adjustment of the response threshold value is necessary, which impairs the accuracy of the method. In addition, the measurement of electrical resistance is possible only when the current flows through the surface of the skin, which makes this method quite energy-intensive and unsafe. Also, skin resistance is highly dependent on its moisture. Humidity can vary greatly due to objective factors, such as changes in temperature or humidity inside the cab or operator’s room, the presence or absence of blowing around the sensors. Humidity can also change due to unpredictable factors such as driver excitement. This can lead to false alarms, which impairs the accuracy of the monitoring device.

Also known is a method of monitoring and controlling the functional state of the operator - pilot, including recording physiological parameters of the state of the operator, comparing them with the reference ones and influencing the operator when there is information about an emergency situation and the corresponding device [3, 4]. The disadvantage of this method can be attributed to a large number of measured parameters (the compression force of the control handle, the force of the foot, the position of the head, respiratory rate, etc.), and, accordingly, the large number of sensors, which complicates the practical application. In addition, this method requires the presence of design features of a controlled vehicle, in this case an aircraft, which makes its implementation dependent on the design and unsuitable for drivers of other vehicles and dispatchers.

There is also a method of preventing operator falling asleep [5], which includes monitoring the level of wakefulness by registering the distribution of pressure of the operator’s body on the supporting surface, comparing the potentials of pressure sensors on this surface with reference ones, and the moment of the onset of the falling asleep phase is fixed by changing the position of the operator’s body, which determined by the abrupt redistribution of pressure - load on the supporting surface. However, this method does not allow to respond to a short-term loss of attention by the driver associated with a slight nap that occurs before the change in body position. Also, this method is difficult to use on bumpy roads, where the sensors in a standard situation will be subjected to accelerating loads every second. This reduces the accuracy of the control device. In addition, the position of the body of the driver or dispatcher can change after falling asleep with a sufficiently large delay, which reduces the response speed of the control device.

Also known is a method of continuous monitoring of the psychophysiological state of the operator in the process of controlling a moving object and a system for its implementation [6]. The method consists in measuring the parameters of the cardiac activity and external respiration of the operator in the course of labor activity, converting the pulsogram and respirogram data into the variational pulsogram (HSV) and variational respirogram (VRG) data, statistical and spectral analysis of these data. However, this method requires respiratory and pulse sensors, which significantly reduces the comfort of dispatchers and especially drivers.

Also known is a way to control wakefulness by recording the response time of the operator to light and sound stimuli [7, 8]. However, such a method is not reliable enough and is not suitable for preventing drivers or pilots from falling asleep, since it will periodically distract them from control, which will reduce the comfort and speed of operation of the control device itself.

Closest to the invention is a method for assessing the functional state of a driver of a vehicle during its operation by measuring the cutaneous electric potential [9]. This method involves the use of electrodes attached to the forehead and the wrist of the driver to assess the constant component of the electric potential. However, the constant component, the more so measured between electrodes so far apart, strongly depends on external pickups of a different nature [10], which can briefly pass the threshold state, causing frequent false alarms of the device, which reduces the accuracy of the method. In addition, the location of the electrode on the forehead limits the functionality of the driver or operator and reduces the comfort of work.

The invention is aimed at creating an accurate, quick, reliable way to prevent the occurrence of an emergency - falling asleep to the driver or dispatcher and a device for its implementation, suitable, including for use on a vehicle and not containing sensors that limit the movement and functionality of the operator, as well as structurally unrelated to the operator’s workplace, which will ensure safety and comfort of management.

The solution to this problem is provided by the fact that in the method of preventing falling asleep of the driver or dispatcher, including monitoring the level of wakefulness, the scalp bioelectric potential is recorded from sensors located in the parotid region and the fractal value of the signal of the scalp electrodes is calculated to compare the obtained fractal value with a threshold value, in the case the achievement of which is triggered by automation, taking control from the driver or dispatcher with parallel switching on SRI signaling waking.

As you know, the induced potentials of the brain are the most objective indicators of the level of wakefulness of the driver or controller, and in the case of falling asleep, they are the first to change their parameters. Determining the time of falling asleep by electroencephalographic signals allows you to increase the speed and accuracy of operation of the control device. It also increases the safety of the vehicle or the operation of the site controlled by the dispatcher. In addition, the location of the scalp electrodes in the parotid region on the headset allows you to get rid of the restrictions in the movement of the driver or dispatcher associated with the location of the sensors on his body, which limit his mobility, and in his chair or control panel. This enhances driving comfort.

In the proposed method, the induced biopotentials of the brain are removed from the electrodes located near the ears of the operator, as, for example, shown in Fig. 1 and the calculated values of the fractal value of this signal determine the response time of the device, which will allow both to wake the driver or operator, and pick up him management. The recorded induced potentials of the brain are variable, and their informational potential lies in the frequency range from 0.5 Hz to 42 Hz. This allows you to get rid of fluctuations of the constant component, the frequency of which lies in the region below 0.5 Hz, and also allows you to get rid of the pickups of the city lighting network, the frequency of which lies in the region of 50 ± 10% Hz. This makes the method more noise immunity, and, accordingly, more accurate. Since the potentials are induced, the input resistance of the differential amplifier amplifying them can be quite large, which is safer and less resource intensive. In addition, a change in the level of consciousness primarily affects the functioning of the brain, and only then on the other physiological parameters. It follows that the decision on the electroencephalographic signal is the fastest according to the criterion of response speed, which increases the response speed of the control device. Since the electrodes themselves are supposed to be located in the parotid region of the driver or controller by placing them on the headset, an example of which is shown in figure 1, they will not limit the functional activity of the driver or controller, which will increase their comfort.

A device is known for preventing operator falling asleep [5], in which the level of wakefulness is controlled by recording the distribution of pressure of the operator’s body on the supporting surface, comparing the readings of sensors built into this surface with reference values and influencing the operator. In this case, the moment of the onset of the falling asleep phase is fixed by the change in the position of the operator’s body, which is determined by the jump-like redistribution of pressure - load on the supporting surface. However, this method requires a specially pre-installed system of sensors located inside the chair. This implies their pre-installation even in the production process of the vehicle. It is also possible false alarms on bumpy roads, where the sensors in a standard situation will be subjected to accelerating loads every second. This reduces the accuracy of the control device. In addition, the position of the body of the driver or dispatcher can change after falling asleep with a sufficiently large delay, which reduces the response speed of the control device.

The invention is aimed at creating an accurate, fast, reliable device for preventing an emergency occurrence - falling asleep for a driver or dispatcher and a device for its implementation, suitable, including, for use on a vehicle and not containing sensors that limit the movement and functionality of the operator, and structurally unrelated to the operator’s workplace, which will ensure the safety and comfort of management.

The solution to this problem is provided by the fact that in the device for preventing the operator from falling asleep, which contains sensors of the state parameters of the operator connected to the measurement processing unit, the output of which is connected to the input of the registration and analysis unit, the output of which is connected to the information and generation unit of the command, sensors of the state of the operator made in the form of two electrodes of an electroencephalographic signal for placement on the scalp region of the operator, and the recording and analysis unit contains a processor unit fractal signal processing and comparing device, interconnected, while the block information and generating a command contains a signaling device.

The proposed device for preventing falling asleep of a vehicle driver or dispatcher, the structural diagram of which is shown in figure 2, structurally consists of the following elements: 1 - scalp electrode; 2 - reference electrode; 3 - differential amplifier; 4 - analog-to-digital Converter (ADC); 5 - signal transmitter; 6 - signal receiver; 7 - processor block fractal signal processing; 8 is a comparison device; 9 - preliminary request block; 10 - alarm device; 11 - user interface; 12 - registration device; 13 - tactile vibrator; 14 - a sound signaling device; 15 - light signaling device; 16 - shutdown device; 17 - block removal signal; 18 is a block analysis, registration and response.

The scalp electrode 1, located in the region above the ear and the reference electrode 2, located in the region below the ear, remove the bioelectric scalp potential at the input of the differential amplifier 3, after which it is digitized by the ADC 4. The signal is then transmitted to the transmitter 5 so that electromagnetic waves get to the input of the receiver 6, for subsequent transmission to the processing unit of the fractal signal processing 7. Here the signal is processed by the fractal method, giving the value of some For fractal quantities such approximation entropy. Approximation entropy is a measure of deterministic chaos and is intended to obtain information about the complexity of the processes occurring in the system based on short time series X = [x (1), x (2), ..., x (N)], where N is the length of the series under study , and is from about 75 to 5000 samples [11]. The value of the approximation entropy depends on the dimension of the pseudophase space m, which is constructed according to the Takens method, the “filtration factor” r, the length of the series N under study, and is determined from the expression [11, 12]:

$$ApEn\left(m,r,N\right)=\frac{\mathrm{one}}{N-m}\left[{\displaystyle \sum _{i=\mathrm{one}}^{N-m}\ln }\left(\frac{\frac{\mathrm{one}}{N-m+\mathrm{one}}{\displaystyle \sum _{j=\mathrm{one}}^{N-m+\mathrm{one}}\theta \left(r-\left|x\left(i\right)-x\left(j\right)\right|\right)}}{\frac{\mathrm{one}}{N-m}{\displaystyle \sum _{j=\mathrm{one}}^{N-m}\theta \left(r-\left|x\left(i\right)-x\left(j\right)\right|\right)}}\right)\right]$$

- абсолютное расстояние между точками в пседофазовом поространстве размерности m. Для подобных рядов из-за их малости в соответствующих работах [11, 12] значение ApEn(m,r,N) рассчитывается только при переходе от двумерного к трехмерному псевдофазовому пространству, то есть m=2, а "фактор фильтрации" берется равным 20% от стандартного отклонения исследуемой величины. Далее задается так называемое окно w - количество отсчетов временного ряда предшествующих последнему на данный момент, для которого вычислялось значение ApEn. Таким образом, длина ряда, для которого вычисляется ApEn, составляет w отсчетов, и, соответственно, N=w. Отступив от конца исследуемого ряда на длину окна, для каждого следующего отсчета до текущего момента, вычисляется значение ApEn.where θ () is the Heaviside function, a $$\left|x\left(i\right)-x\left(j\right)\right|$$

is the absolute distance between points in the pseudophase space of dimension m. For such series, because of their smallness in the corresponding papers [11, 12], the value of ApEn (m, r, N) is calculated only when passing from two-dimensional to three-dimensional pseudophase space, that is, m = 2, and the “filtering factor” is taken equal to 20 % of the standard deviation of the investigated value. Next, the so-called window w is set - the number of samples of the time series preceding the last at the moment for which the value of ApEn was calculated. Thus, the length of the series for which ApEn is calculated is w samples, and, accordingly, N = w. Departing from the end of the series under study by the window length, for each subsequent count to the current moment, the ApEn value is calculated.

The resulting value is sent to the comparator 8, where it is compared with the value of the threshold value. If this value decreases below a threshold value associated with a decrease in the level of consciousness, a corresponding signal is sent to the preliminary request unit 9. The preliminary request unit, in turn, requests information about the wakefulness of the driver or dispatcher by sending signals to the tactile vibrator 13, the sound signaling device 14 and the light signaling device 15, which can optionally be connected to the device. If the driver or the dispatcher did not respond to this request through the user interface 11, then the corresponding signal is supplied to the alarm device 10, which, in turn, sends a signal to the shutdown device 16, which turns off the gas supply for the vehicle driver or turns on the automation that replaces the dispatcher. Also, it is proposed that the information coming from the receiver 6, the processor unit of the fractal signal processing 7 and the user interface 11 be recorded on the recording device 12, which will facilitate the process of finding out the cause of the emergency, if any.

Scalp 1 and reference 2 electrodes are made of weakly polarizing material with silver-silver chloride or gold or another coating, which has low resistance and is chemically and mechanically resistant to aggressive environments. Differential amplifier 3, is a low-noise differential DC amplifier with a sensitivity of up to several microvolts. The frequency range of the brain informative signal lies in the range from 0.5 to 42 Hz. An analog-to-digital converter 4 samples the signal so that the sampling rate is at least 200 samples per second, and the signal level varies from a few microvolts to one millivolt. The transmitter 6 and receiver 7 may either be present in the case of wireless communication, or absent in the case of wired communication. The fractal processing unit performs a continuous calculation of the fractal value of the signal in real time, which ensures the highest response speed of the device. The electrodes 1 and 2, as well as elements 3-6 are structurally combined into one unit located in the parotid region of the driver or dispatcher. Elements 6-12 are structurally combined into a single unit of analysis, registration and response 18, which can be performed either as a separate device or be programmatically implemented on the basis of a laptop computer. The tactile vibrator 13 can be located in any place with which the body of the driver or dispatcher is directly and constantly in contact. The light signaling device 14 should be constantly located in the visibility zone of the driver or the dispatcher, and the sound signaling device 15 should be located in the zone of its hearing, respectively. The location of the scalp electrodes in the parotid region on the headset allows you to get rid of the restrictions in the movement of the driver or dispatcher associated with the location of the sensors on his body, limiting his mobility, and in his chair or control panel. This increases the comfort of the driver or controller. Analysis of electroencephalographic signals allows you to more accurately and more quickly respond to falling asleep driver, which increases its safety.

INFORMATION SOURCES

1. Device for monitoring the wakefulness of a vehicle driver: US Pat. 1681844A1 USSR No. 4660843/14; declared 03/10/89; published on 10/07/91. Bull No. 37 А61В 5/18.

2. A way to control the level of wakefulness: US Pat. 459216 USSR No. 1935081 / 31-16; stated on June 21, 73; publ. 02/05/75. Bull. No. 5. A61B 5/18.

3. The method for determining human fatigue: US Pat. 1598969A1 of the USSR No. 4338603 / 30-14; Declared December 3, 87; publ. 10/15/90. Bull. No. 38. A61B 5/16.

4. A method for monitoring and controlling the functional state of a pilot in flight and a device for implementing the method: US Pat. 2150886 C1 Ros Federation No. 9911497128/28, claimed 07/08/1999; publ. 06/20/2000. A61B 5/16 G09B 9/10.

5. A method of preventing falling asleep of an operator and a device for preventing falling asleep of an operator: US Pat. 2197177 C1 Ros. Federation. No. 20011132300/14, declared 11/30/2001; publ. 01/27/2003. A61B 5/18, A61B 5/16.

6. The method of continuous monitoring of the psychophysiological state of the operator in the process of controlling a moving object and a system for its implementation: US Pat. 2091057 C1 Ros. Federation. No. 93004065/14, declared 01/28/1993; publ. 09/27/1997. A61B 5/16.

7. Awakening control device: US Pat. 1438712 A1 of the USSR No. 4130934 / 28-14, declared 06/24/1986; publ. 11/23/1988. A61B 5/18.

8. A method for assessing the functional state of the central nervous system of a person and a device for its implementation: US Pat. 2153847 C2 Ros. Federation No. 97100298/14, declared January 9, 1997; publ. 08/10/2000. A61B 5/16.

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11. Approximate Entropy in the Electroencephalogram During Wake and Sleep / Naoto Burioka, Masanori Miyata, Germaine Cornelissen, Franz Halberg, Takao Takeshima, Daniel T. Kaplan, Hisashi Suyama, Masanori Endo, Yoshihiro Maegaki, Takashi Nomura, Yutaka Tomita Ken Eiji Shimizu // Journal of Clinical EEG & Neuroscience, January 2005.36 (1). - PP.21-24.

12. Srinath Vukkadala, Vijayalakshmi.S, and Vijayapriya.S, Automated Detection Of Epileptic EEG Using Approximate Entropy In Elman Networks // International Journal of Recent Trends in Engineering, Vol 1, No.1, May 2009 PP.307-312.

Claims (2)

1. A method of controlling the level of wakefulness of a driver of vehicles, which consists in attaching electrodes to the driver’s body to determine the physiological parameter, fixing the threshold value of the determined physiological parameter and signaling the driver when the physiological parameter reaches the threshold value, characterized in that the electrodes are located in the parotid region and determined in as a physiological parameter, the induced variable electric potential of the brain in the frequency range from 0.5 to 42 Hz, after which the fractal value of the value of the given signal is calculated for comparison with the threshold value. 2. A device for preventing operator from falling asleep, containing sensors of the state parameters of the operator connected to the measurement processing unit, the output of which is connected to the input of the recording and analysis unit, the output of which is connected to the information and generation unit, characterized in that the sensors of the state parameters in the form of two electrodes of an electroencephalographic signal for placement on the scalp region of the operator, and the recording and analysis unit contains a processor unit for fractal signal processing and a comparator connected to each other, wherein the information and command generation unit comprises an alarm device.

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