DRIVER MONITORINGDESCRIPTIONThe invention relates to methods and apparatus for monitoring drivers, that is to say methods and apparatus for monitoring the actions of a vehicle driver and providing an alarm or applying corrective action to the control of the vehicle should it appear the drivers control of the vehicle has or will be lost, e.g. due to the driver falling asleep or becoming ill.
Such systems are known and are used, for example, to monitor drivers of railway locomotives; usually providing that the driver must hold a lever against a bias (the so called dead man's handle) or must repeat some action (e.g.
press a button) at predetermined short time intervals, in either Case if the action is not taken by the driver (i.e.
he lets loose the handle or does not press the button) it is assumed that the driver is incapacitated and an alarm is sounded (or the locomotive breaks are automatically applied).
Whilst such systems are effective in monitoring the actions of locomotive drivers they have the drawback of being "driver active" that is to say they require that the driver must continually do the required action. Thus while such systems are effective in locomotive driving cabs where the driver will normally have only one other control to operate (the locomotive speed controller) they are generally inapplicable in other vehicles, for example, motor vehicles where the vehicle driver needs to operate a variety of controls (accelerator, brakes, clutch, steering wheel and direction indicator warning lights) and any requirement for him to operate a further control would be deleterious to the operational safety of the vehicle.
Proposals have been made elsewhere to directly monitor the "vital signs" of a subject (e.g. heartbeat, aspiration rate) and in some circumstances a driver monitoring system could make use of such proposals however, any system directly monitoring a vehicle driver will require that the driver be coupled to the monitoring system that is to say, at least, that he or she wear special monitoring equipment and to that extent are considered by us to be driver invasive".
Objects of this invention include the provision of methods and apparatus for monitoring the actions of a vehicle driver which do not require action on the part of the driver and do not require that the driver be physically coupled to the monitoring system, i.e. a monitoring system which is neither driver active nor driver invasive.
In one aspect the invention provides a method of monitoring the driver of a vehicle which method comprises determining if the driver's eyes are open or closed and generating an alarm signal if the driver's eyes are found to be closed.
The 'method may preferably comprise sequentially generating signals indicative of an image of at least that part of the driver's face including his eyes1 comparing said sequentially generated signals and generating an alarm signal upon the occurance of a signal indicative of the absense of the driver's eyes from corresponding image so produced.
Each successive sequentially generated signal may be compared with the immediately preceding such signal, or be a reference signal.
In a second aspect apparatus for monitoring the driver of a vehicle comprising means for sensing if a driver's eyes are open or closed and ge in4 an alarm signal if the driver's eyes are closed.
The apparatus may comprise means for sequentially generating signals indicative of an image of at least that part of the driver's face including his eyes, means for comparing said signals and generating an alarm signal upon the occurance of a signal indicative of the absense of the drivtir' S eyes from corresponding image so. produced.
With advantage the apparatus includes a video camera directed toward the face of the driver, means for processing the output signal of the video camera for each image scanned thereby, means for storing the processed signals, and means for comparing the stored signals and generating an alarm signal if a feature associated with the eyes of the driver varies.
The apparatus may provide that the output signal of the video camera for each image scanned by the camera is digitised, that each succeeding digitised electrical signal is stored, and that said Comparator means compares each succocding digitised electrical signal with the immediately preceding digitised electrical signal held in said store and generates an output alarm signal if the signals so compared differ by more than a predetermined amount.
Alternatively, the apparatus may provide that the output signal of the video camera for each image scanned by the camera is is digitised, and that said comparator means compares each succeeding digitised electrical signal with a stored reference signal indicative of a predetermined image of the driver's face and generates an output alarm signal if the signals so compared differ by more than a predetermined amount.
Advantageously the comparator means comprises a processor adapted to read and storo the digitised electrical signal representative of each scanned image as it is produced and to compare each such signal with the signal corresponding to the last preceding scanned image stored therein and to generate said alarm signal if the signals so compared differ by more than a predetermined amount.
The apparatus may further include means operable to delay production of an alarm signal until a predetermined number of sequentially generated signals have been produced each representative of images in which the eye of the driver is absent; and means ambling generation of an alarm signal in dependence upon the vehicle motion or upon particular driver action.
The apparatus preferably includes a light source fur lllumlnsting thP rivers face and means for adjusting the output of the light source to ensure a substantially constant level of illumination of the drivers face under different ambient light conditions.
With especial advantage the video camera is sensitive to infra-red light ana the light source 1 is a source of such light.
A driver monitoring system embodying the invention will now be described with reference to the Figure of the accompanying drawing which shows the system in schematic form.
With reference to the Figure, a video camera 10 is mounted within a vehicle driving cab immediately above the windscreen 12 of the vehicle. Camera 10 is preferably of the kind typically used in security systems and is fitted with an auto-iris lens allowing the camera to automatically adjust to different ambient light levels. The camera is sensitive to infra-red light and is trained toWL'd the head of a driver of the vehicle (indicated at 14) but out of his line of sight. An infra-red light source 16 is provided in the cab, preferably adjacent the camera 10, also directed towards the drivers head. The level of the output of light source 16 is controlled by means responRlve to the ambient light level to ensure the illumination of the drivers face is maintained at a edetermined suitablo level.
The output of camera 10 is fed to an analog to digital converter or digitiser 18 in which the analog output of the camera 10 is converted into digital electrical signals which are passed to a processor 20. Within processor 20 the signals from the digitiser are fed to a store 22 and to a comparator 24. comparator 24 is arranged to compare the signals fed to it from tlle digitiser 1R and from the store 22 and to provide an output if the differences between those signals indicates that the drivers eyes have closed.
The arrangement within the processor is such that the digitised signals representative of each image from camera 10 are fed to the store 22 and to the comparator 24.
As each image is digitised and read into the processor 20 (and into the store 22) the last stored set of signals are read from the store and compared with the those now fed to the processor. In this way the signals representative of each image axe compared with the last stored signals representative of the immediately preceding image which has been digitised and fed to the processorThe comparator 24 provides an output on line 26 changing state if the differences between the signals fed to it from the digitiser 18 and the store 22 differ by more than a predetermined amount indicative of the fact that the drivers eyes have closed.
The presence of a signal on line 26 indSr.t.1 YR af the drivers eyes having closed trips on an alarm signal generator 28 which is arranged to sound an audible warning in the vehicle cab (for example, ring a bell) which will continue to ring until the signal generator is reset by the driver operating a reset switch 30.
Optionally, the alarm signal generator may be disabled by a signal on line 32 from a device 34 responsive to the vehicle motion and/or power consumption. When the vehicle is at rest (e.g. waiting in traffic) there is clearly no requirement to generate an alarm signal; similarly if the vehicles motion is rapidly changing (e.g under acceleration, breaklng or turning) or if the break/turn indicator lights are operative it can be assumed the driver is awake ahd that any outputs frail Lhe comparator 24 are due to the driver turning his head to look at other traffic. The device 34 may therefore comprise any suitable device measuring the acceleration of the vehicle and/or its electrical power consumption.
Thus the apparatus will be enabled to generate an alarm signal only when the vehicle is travelling at relatively constant speed and with relatively constant power consumption - that is to say under normal motorway drivingConditions when the danger of the driver falling asleep is at its greatest.
As described the comparator is arranged to compare each video image produced by the camera 10 with the immediately preceding image. In certain circumstances this may trip the alarm signal generator 28 umlecesarl}y and in those circumstances the processor may include circuitry (indicated in dotted outline at 36) operable to delay generation of the alarm signal until a predetermined number of images have been received by the processor at a level indicating the drivers eyes are closed.
It is thought that the auto-iris mechanism of the camera 10 coupled with the level control of the light source 16, will react sufficiently quickly to rapid changes in illumination level of the drivers face caused by the headlights of oncoming vehicles; however, should this not be th case the processor may include circuitry disabling the alarm generator or the comparator if the digitised signals input to the comparator indicate that the illumination of the drivers face exceeds a predetermined level.
A modification to the arrangement disclosed above provides that the signals from digitiser 18 representative of each image scanned by the camera 10 are compared with an initial reference or datum signal read into the store 22 when the apparatus is activated. In this modified form of the arrangement the apparatus is arranged to store the first received signal from digitiser 18 (or an averaged value of a predetermined number of such signals) in store 22 and thereafter each signal output from digitiser 18 is compared with that reference signal.
To overcome possible difficulties which may arise if the driver is wearing spectacles we provide in such circumstances that the camera 10 may be coupled by optical fibres to the spectacle frames such that the image monitored by the apparatus is that of the drivers eye.
It will be appreciated that the described ratus may be implemented using discrete. devices commercially available or by making use of a processing unit - such as that sold by TRW Inc. under the designationTDC1014PCB - which is appropriately programmed to effect the desired functions.
Modifications other than that noted above may be made to the described arrangement without departing from the scope of the present invention