Method and device for recognition of a collision with a pedestrian

#The present invention relates to a method and a device for detecting the impact of a pedestrian with a vehicle, at least one sensor being provided on the bumper and at least one sensor in the area of the front edge of the hood of the engine to measure the pressures or deformations caused by impact and to form a first criterion for the decision as to whether there has been an impact with a pedestrian on the basis of the sensor output signals by comparison with reference quantities.

#A method of detecting an impact of a pedestrian with a passenger vehicle is discussed in PCT Publication No. WO 97/18108. To protect the pedestrian from serious injuries in the event of an impact of a pedestrian with the front side of a vehicle, one or more airbags may be provided on the engine hood or on the windshield for deployment in the event of an impact with a pedestrian. Another safety measure for an impact with a pedestrian is for the engine hood to be inclined at an angle to catch the pedestrian. Deployment of such safety devices may depend upon the impact with a pedestrian being detected reliably and also being differentiated unambiguously from impacts with other objects. The related art discusses utilizing for detection of a pedestrian impact the basic kinematics of a pedestrian on impact with the front side of a passenger vehicle. As a rule, the first point of contact of a pedestrian with a vehicle is the bumper. Therefore, a first sensor which responds to the acting force or the deformation may be located on the bumper of the vehicle. Through contact with the bumper, the pedestrian may receive a rotational momentum which throws him onto the engine hood. In other words, impact with the bumper may be followed after a time lag by another impact with the engine hood. Therefore, a second sensor which responds to pressure or deformation may be situated on the front edge of the engine hood. The sensor output signals may be compared with reference quantities that are representative for impacts with a pedestrian. If they match or if there is a correspondence within a certain range of tolerance between the sensor output signals and the reference quantities, it may be decided that this is due to an impact with a pedestrian. As a result of this decision, the available safety devices may therefore be deployed.

#An object of the present invention is to provide a method and a device with which it is possible in the event of an impact on the front side of a vehicle to decide with the highest possible reliability whether this impact has been caused by a pedestrian.

#FIG. 1 shows a front view of a motor vehicle having two sensors.

#FIG. 2 shows a block diagram of a device for detecting an impact with a pedestrian.

#FIG. 3 shows curves of sensor output signals in an impact with a pedestrian.

#In an exemplary embodiment for detecting with the highest possible certainty whether a given impact with the front side of a vehicle is a pedestrian impact, vehicle 1 is equipped with a first sensor 3 on its bumper 2, as shown in FIG. 1, and a second sensor 5 on the front edge of its engine hood 4. Both sensors 3 and 5 may be pressure sensors or deformation sensors. Therefore, sensors 3, 5 may be mounted on bumper 2 as well as on the front edge of engine hood 4 because it may then be possible to detect the characteristic kinematics of a pedestrian impact with vehicle 1. In other words, if a vehicle strikes a pedestrian at its front side, the pedestrian may first come in contact with the bumper, so that sensor 3 on bumper 2 delivers a signal which depends on pressure or deformation. Bumper 2 absorbs only a small portion of the total kinetic impact energy. Contact with the bumper may impart to the pedestrian a rotational momentum, possibly throwing him onto the hood of the engine. Second sensor 5 on engine hood 4 may then detect this pressure or deformation produced by the impact with the pedestrian.

#FIG. 2 shows a block diagram of a device, and FIG. 4 shows a flow chart of a method, with which impact with a pedestrian may be detected with a high reliability. In FIG. 2, reference numbers 3 and 5 denote pressure and deformation sensors mounted on the bumper and on the engine hood of the vehicle.

#When sensor 3 on bumper 2 and sensor 5 on engine hood 4 are mentioned here, this also includes the possibility of multiple sensors or sensor elements being present on both bumper 2 and engine hood 4. Sensors based on different principles for measurement of pressure and deformation may be used. For example, the sensors may be wire strain gauges or piezoresistive films. Optical sensors having a pressure-dependent light transparency may also be used. Likewise, sensors based on the Hall effect or the anisotropic magnetoresistive effect may also be used. Any sensor which produces a pressure- or deformation-dependent signal, regardless of the method, may be suitable in principle.