GB2174226A - Device to prevent persons such as vehicle drivers falling asleep - Google Patents

Abstract

A device to alert the user when falling asleep or in a state approaching sleep, for use in monotonous driving conditions or other similar circumstances. The user repeatedly acts on the device to reset it, for example by tapping a touch sensitive pad or a rubber bulb 6. An alarm or a sequence of increasingly intrusive alarm actions is set off if the user fails to reset the device for longer than a period of a few seconds. The sensor is positioned comfortably on the steering wheel 8 or elsewhere, so that it can be operated with minimal disturbance to other tasks in hand. The alarm may be evident to all persons present or only to the user, for example through an earphone. An increasing frequency of alarms warns the user of the onset of extreme sleepiness even before he or she falls actually asleep. <IMAGE>

Description

SPECIFICATION Device to prevent persons such as vehicle drivers falling asleep This is a safety device to reduce the risk of vehicle drivers (or others engaged in similar tasks) falling asleep. It alerts the user when he or she is so close to sleep that gaps develop in the performance of a simple repetitive task such as tapping a finger every few seconds.

BACKGROUND Many vehicle accidents are caused by drivers falling asleep, especially in easy and monotonous driving conditions at night.

Drivers are not always aware when they are at serious risk of falling asleep. This invention satisfies the following requirements for a safety device to reduce this risk: 1. It must be easy to use and must not interfere with good driving practice or performance, or with the driver's comfort.

2. It must be both rapid and as nearly as possible 100% effective in detecting sleep.

3. It must produce a minimum of false alarms.

4. Its operation, its limitations and its effectiveness must be easily understood by the user so as to inspire confidence in its use.

5. It must be cheap to manufacture if it is to reach enough people to have a significant impact on Road Safety statistics.

A device to detect sleep may be either passive or active. A passive device requires no action by the user and detects, for example, a change in body posture or physiology. An active device requires constant or repetitive action of some sort by the user. Passive devices have the advantage that the user may in principle be quite unaware of their operation, but they tend to be unsatisfactory particularly in relation to requirement (2) above. This invention is an active device which offers a combination of (i) simplicity, (ii) rapid and reliable detection of sleep and (iii) advance warning of the onset of extreme sleepiness.

The onset of sleep is most insidious and dangerous in situations like monotonous driving, when the necessary tasks make few demands on the user. The additional actions required by this device can then be carried out with little or no effect on performance of the main tasks. The benefit comes (i) in improvements in vigilance, (ii) in the warning of the onset of extreme sleepiness which may not otherwise be evident and (iii) in an increased chance that the user may be awoken in time to prevent an accident if he or she actually falls asleep.

This device may be especially helpful to people such as narcoleptics or users of hypnotic drugs, who have an abnormal tendency to fall asleep.

TECHNICAL FEATURES The invention consists of three connected parts: a sensor, a control circuit and an alarm.

The sensor is an electrical device detecting a specific movement of a part of the user's body. It may consist of a switch or touch or temperature sensitive device or an optical or infrared or acoustic movement detector or electrodes detecting physiological signals associated with the movement. In some applications movements may with advantage affect the senses indirectly, for example through a pneumatic or hydraulic coupling, since this can permit the local device operated by the user to be small and comfortable while the sensor, circuitry and alarm may be remote and less constrained by considerations of size and power consumption (for example on the dashboard of a car). The sensor may also be coupled to the control circuit indirectly through an infrared or acoustic or electromagnetic link, thus obviating the need for cables or tubes.

The sensor must be comfortable and convenient to operate, for example by using a finger or foot in the user's normal posture.

The control circuit detects a discrete and deliberate action on the sensor. This action resets the circuit. If the reset action is not performed within a period of 1-5 sec or thereabouts of the previous reset action, the circuit sets off the alarm or alarm sequence. Continuous pressure on the sensor must not reset the circuit: at least a 'tap' is required, comprising both pressure and release. The control circuit may be designed to require more complex patterns of action such as double taps for reset if users become adept at making single taps every few seconds while falling asleep, but this is not likely to be an essential feature. If the alarm has been triggered, the normal reset action may conveniently terminate its effect.A switch or other means is provided by which the user can rapidly disable the device if conditions are foreseen that are inappropriate for its use. In order to cope with varying circumstances or aptitudes of different users, the period within which reset action is required may be made adjustable. The optimal period, usually a few seconds, is a balance between considerations on the one hand of convenience and on the other hand of rapidity of a sleep warning and of the greater ease of judging short intervals rather than long intervals with minimal effort.

The alarm generates a signal that will alert the user if fallen asleep. it may be audible or visible or (perhaps especially for deaf users) may involve mechanical or electrical or thermal stimulation of the user's body. It may be 'private' in that only the user is aware of it (for example through an earphone) or it may be a 'general' alarm, apparent to other people such as car passengers. A private alarm has the advantage that it does not disturb other people, while a general alarm may be more com fortable or convenient for the user. The first effect of the alarm should be to alert the user, who may not be asleep, that the reset action is overdue. For this effect, a stimulus capable of awakening the user is not necessary.A hybrid alarm sequence is therefore advantageous but not essential, whereby the alarm has a sequence of effects, for example at first a light on the dashboard or a quiet noise and after a few seconds a greater stimulus that would serve to awaken the user.

SPECIFIC EXAMPLES Two specific versions of the invention are described, both suitable for use in a car.

The first version, with a 'general' alarm, is illustrated in Fig. 1. A box (3) houses a microswitch sensor and the control circuit and a 9 volt battery and ON/OFF switch (2) and the alarm consisting of a piezoelectric audible warning device (1) capable of emitting a loud tone at approximately 3kHz. The box sits on a shelf or is attached to the crossbar of the steering wheel. The sensor microswitch is operated by a 40X 14mm rubber bulb (as used by chemists in Pasteur pipettes), connected pneumatically to a similar external bulb (6) by an 80cm length of thin rubber tubing (4). The external bulb can be comfortably held in the hand and has a collar of velcro tape (5) glued to it that enables it to be fixed securely to a steering wheel (8) in any convenient position using a velcro ribbon (7). Movements of a finger operate the sensor through the pneumatic link.

The control circuit for this first version em ploys two integrated-circuit timers (Type 555).

The output of the principal timer (Timer 1) is connected directly to the alarm device so that the alarm is activated continuously from about 4sec after power-up or after a reset. The sec ond timer is triggered by discharge of a capa citor when the microswitch contacts are closed and generates a 0.1 sex pulse that serves to discharge the timing capacitor of Timer 1, thereby resetting the principal timing cycle and silencing the alarm if already acti vated.

The second version has a 'private' alarm sequence consisting of an initial quiet whistle and a later more piercing tone, both administered through an earphone. The power re quirements of this are substantially less than for the first version and the control circuit and a miniature 1.5 Volt battery are all housed in a small box (50X30X15mm) attached when required with velcro ribbon to the rim of the steering wheel. The sensor is a pressure sen sitive pad mounted on the box and connected directly to the circuit. The circuit is switched on and off by connecting a jack plug on the earphone lead to its socket on the box. The alarm sequence is generated by a conventional transistor multivibrator oscillator, which is sup plied with gradually increasing power as a timing capacitor charges up over several seconds. Whenever pressure is applied to the touch pad following a period of at least some tenths of a second without such pressure, the timing capacitor is discharged by a pulse of current through a transistor amplifier.

Figure 1. Drawing of the first described example of the invention.

Claims (14)

1. A device to alert the user when falling asleep or in a state approaching sleep, comprising a sensor acted on by the user and a control circuit detecting specific actions described as reset actions affecting the sensor and an alarm activated by the control circuit whenever the interval between reset actions exceeds a preset interval of a few seconds or thereabouts.

2. A device as claimed in Claim 1 wherein the sensor is a switch or other electrical device sensitive to pressure.

3. A device as claimed in Claim 1 wherein the sensor is an optical or infrared or ultrasonic or acoustic or thermal device detecting movement or proximity of a part of the user's body.

4. A device as claimed in any foregoing Claim wherein the sensor is affected indirectly by a movement or force exerted by the user's body through a mechanical or pneumatic or hydraulic link.

5. A device as claimed in Claim 1 wherein the sensor comprises electrodes and circuitry detecting physiological signals associated with an action by the user.

6. A device as claimed in any foregoing Claim wherein the sensor is coupled to the control circuit by infrared or acoustic or electromagnetic signals or other similar indirect means.

7. A device as claimed in any foregoing Claim wherein the specific action detected by the sensor and control circuit comprises at least one sequence of the application and release of pressure by a part or parts of the user's body.

8. A device as claimed in any foregoing Claim wherein the alarm has an audible or visible or mechanical or electrical or thermal effect or a combination of such effects.

9. A device as claimed in any foregoing Claim wherein the alarm has a sequence of different effects.

10. A device as claimed in any foregoing Claim wherein the reset action terminates the effect or effects of the alarm if this or these have begun.

11. A device as claimed in any foregoing Claim wherein the alarm or alarm sequence or part thereof is detectable only by the user.

12. A device as described in any foregoing Claim wherein the preset interval referred to in Claim 1 is adjustable by the user.

13. A device as claimed in any foregoing Claim wherein the user can disable the device by a switch or other means.

14. A device substantially as described herein with reference to either of the two described examples.