Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Vehicle subsystem or accessory control
Reexamination Certificate
2002-05-03
2004-01-13
Arthur, Gertrude (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Vehicle subsystem or accessory control
C701S046000, C180S268000, C280S735000
Reexamination Certificate
active
06678598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and a method for seat supervision in motor vehicles and in particular to a device vice and a method for optical seat supervision which are suitable able for controlling the activation state of one or more airbags.
2. Description of Prior Art
A centrally situated airbag should fire in the event of an accident if the seat is occupied by a person in the upright position. If a person bends forward too close to the airbag or if there is a child's seat or some other object on the seat, so that a person or a child could be injured or the airbag be triggered unnecessarily, this situation must be detected by a seat supervision system so as to prevent the airbag from firing or to modify the unfolding dynamics of the airbag.
The advantages of an airbag far outweigh potential disadvantages. However, an airbag can only provide protection with full efficacy if the occupant of the motor vehicle is belted up, so the airbag must be regarded as a supplementary unit of the so-called restrain system, SRS (SRS =Supplemental Restrain System). The airbag supports the restraining action of the belt in the event of a frontal collision and prevents direct impact of the thorax, neck and head with the dashboard.
An airbag normally fires 10 to 40 ms after the collision has occurred if the change in speed resulting from the collision exceeds a specified value, 25 km/h in Europe and 15 km/h in the USA. The airbag envelope then emerges from the airbag cover at a speed of 250 to 300 km/h. The time taken to inflate the airbag is 25 to 40 ms, which is faster than the eyelid reaction time. Only after this inflation time does the airbag provide its full protection. If, at the moment an accident occurs, an occupant is not in the normal sitting position, a situation which is referred to as OOP (Out of Position), or if there is a child's seat on the front passenger seat, the high acceleration rates during the unfolding phase of the airbag, which can be of the order of 100 G, can result in serious injuries, independently of whether the change of speed when the airbag is fired is low or high. Thus it is possible that the consequences of an accident which would not be that serious may be made worse. The airbag can only exhibit its full efficacy when the occupant is situated at a sufficient distance from the airbag cover. In the normal sitting position the distance between the driver's chest and the hub of the steering wheel is usually about 30 cm, whereas the distance between the front passenger's chest and the airbag cover is usually about 50 cm, the normal sitting positions varying according to the interior configuration of the vehicle.
In the field of technology dealt with here a plurality of methods for seat supervision in motor vehicles is already known by means of which airbag activation state control can be effected on the basis of seat supervision.
First of all, it is possible to deactivate and activate the airbag manually so as to avoid the chance of being exposed to danger by the airbag in certain special cases. However, with this approach it is easy to forget the need to activate the airbag. Using a pressure sensor arrangement to measure the weight exerted on a seat of the motor vehicle is a method which is often used to detect seat occupancy, the activation/deactivation of the airbag being effected on the basis of the measured weight. With this method, however, children's seats which weigh less than the weight threshold employed are not detected. Furthermore it is possible for the airbag to be activated unnecessarily if there is a load on the front passenger seat.
It is also possible to detect seat occupancy by performing a capacitive measurement of the object, usually a dielectric, which is situated between the seat and the instrument panel. For this purpose electrodes are located in the seat and in the instrument panel. With the aid of the permittivity measurement it is possible to detect the occupancy state of a seat, though an error-free distinction between a human being and an object will not generally be possible.
Also known is the practice of employing propagation time measurement methods using active signal sources, e.g. radar signal sources or laser light sources, to survey seat surfaces to obtain a “profile” for the occupancy evaluation.
Methods for children's seat detection are also known which are based on the use of special children's seats equipped with transponder technology. These transponders in the children's seats deactivate the airbag. With these methods based on transponder technology it is not, however, possible to detect either foreign children's seats or vehicle occupants.
From the article “Future Applications of Microsystem Technologies in Automotive Safety Systems” by P.Steiner and S.Schwehr, in Ricken/Gessner: Advanced Microsystems for Automotive Applications 1998, Springer Verlag Berlin, 1998, a passenger state detection method is known in which a person endangering zone immediately in front of an airbag is defined, this zone being supervised at various points by means of active monochromatic light sources (LEDs) and traditional CCD image sensors. When an occupant of the motor vehicle abandons the normal position, which is situated at a typical distance from an airbag module, and thus possibly comes too close to the airbag, the system described in the above article deactivates the airbag or reduces the firing power of the airbag. According to this publication the evaluation of the occupancy detection follows the triangulation principle, whereby the location of an object can be established from the position of a light spot in the image plane of a camera. The triangulation principle is known in this area of technology.
Another alternative method for selectively controlling airbag activation and deactivation is to define a person endangering zone immediately in front of the airbag and to supervise this zone with the aid of a light curtain or a light barrier. If the light curtain or the light barrier is interrupted, indicating that someone is in the danger zone, the airbag is deactivated.
The major problem with the above-cited optical methods for seat supervision using active light sources arises because of the extreme differences in illumination which can occur in a motor vehicle. The illumination can vary between 1 mlx on a dark night and 100 klx in direct sunlight. Especially in the case of simultaneous direct sunlight, the light beams emitted into a supervised space by active monochromatic sources can no longer be resolved. Furthermore, as a consequence of the statuary, country-specific safety regulations for guaranteeing the radiation safety of laser beams, the monochromatic light source may only emit a small amount of light energy.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a device and a method for seat supervision in motor vehicles which permit rapid detection of seat occupancy as a means of activating and deactivating an airbag under all illumination conditions.
According to a first aspect of the invention, this object is achieved by a device for seat supervision in motor vehicles which features a pulsed monochromatic light source for the short-time illumination of a space to be supervised. In addition an image sensor array for recording an image of the supervised space is provided which has a global electronic shutter unit which enables the illumination time of the image sensor array to be set independently of the readout clock of the image sensor array. Also provided is a synchronization unit for synchronizing the operation of the pulsed laser source and of the image sensor array. The device according to the present invention also has a control unit for controlling the light source and the image sensor array so as to create a first image of the supervised space during illumination of the same at a first time and to create a second image of the supervised space without illumination of the same
Conde José Santos
Hillebrand Matthias
Hosticka Bedrich
Stevanovic Nenad
Teuner Andreas
Arthur Gertrude
Fraunhofer-Gesellschaft zur Foerderung der Angewandten Forschung
Glenn Michael A.
Glenn Patent Group
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