Pedestrian detecting system

A pedestrian detection system is provided on a motor vehicle, in order to detect a pedestrian so that an appropriate safety device can be activated in order to provide protection to the pedestrian in the event of an impact with the pedestrian. The detection system has a first sensor arrangement (10) which is located at least 0.5 meters behind the front end of the motor vehicle. The first sensor arrangement (10) is configured to detect the speed of and/or distance to a part of an object (such as a pedestrian) located in front of the vehicle. That part of the object which is detected is part of the object which extends above a predetermined height, which is at least the height of the front edge of the hood or bonnet (3) of the motor vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Great Britain patent application 0308220.3, filed Apr. 9, 2003 and PCT/SE2004/000570, filed Apr. 8, 2004.

FIELD OF THE INVENTION

The present invention relates to a pedestrian detection system, and more particularly relates to a pedestrian detection system for detecting pedestrians in front of a vehicle to enable the deployment of a pedestrian protection safety device mounted on the vehicle.

BACKGROUND AND SUMMARY OF THE INVENTION

Various pedestrian detection systems have been proposed before, mainly incorporating sensors mounted on the front of the vehicle, such as in the bumper or fender of the vehicle. Such detection systems can easily give a false output signal, causing inappropriate deployment of a safety device, for example, when striking an item such as road-cone or an animal.

The present invention seeks to provide an improved pedestrian detection system.

According to the present invention there is provided a pedestrian detection system provided on a motor vehicle, the motor vehicle having a hood or bonnet, the detection system including: a first sensor arrangement located more than about 0.5 meters behind the front end of the vehicle to detect the speed of and/or distance to a part of an object located in front of the vehicle, the part of the object extending above a predetermined height, the predetermined height being at least the height of the front edge of the hood or bonnet; and a second sensor arrangement comprising a sensor mounted in the front bumper or fender of the vehicle responsive to an impact of the vehicle with an object.

Preferably, the first sensor arrangement is a microwave radar.

Advantageously, the first sensor arrangement is an infra-red radar.

Conveniently, the first sensor arrangement is a camera.

Preferably, the camera operates in the visible spectrum.

Advantageously, the camera operates in the infra-red spectrum.

Conveniently, the first sensor arrangement is a stereo-camera arrangement.

Preferably, the first sensor arrangement is mounted on the exterior of the vehicle in front of a windscreen or windshield provided on the vehicle.

Advantageously, the first sensor arrangement is mounted on the vehicle behind the windscreen or windshield of the vehicle.

Conveniently, the first sensor arrangement is mounted above the windscreen.

Preferably, a pedestrian protection arrangement is provided, the detection system being configured to activate the pedestrian arrangement device in response to the first sensor arrangement detecting the distance below a threshold and/or a speed above a threshold.

Conveniently, threshold distance is less than the distance between the sensor and the front of the vehicle.

Preferably, the second sensor arrangement further includes an accelerometer.

Advantageously, the accelerometer is configured to provide a signal indicative of a crash situation and wherein, upon receipt of said signal, an internal safety device on the vehicle is actuated.

Preferably, the sensor mounted in the front bumper is a contact sensor.

Advantageously, the second sensor arrangement is a sensor that can discriminate objects lighter than a pedestrian.

Conveniently, the pedestrian protection arrangement is activated only if the first sensor arrangement detects a distance below a threshold and/or a speed above a threshold, and also the second sensor arrangement detects an object.

Preferably, the pedestrian protection arrangement has at least two modes of activation.

Advantageously, the pedestrian protection arrangement incorporates at least two pedestrian devices.

Conveniently, the pedestrian protection arrangement incorporates a lifter to lift the front part of the hood or bonnet, and a lifter to lift the rear part of the hood or bonnet, one mode of activation being the lifting of the front part of the hood or bonnet, a second mode of operation including additionally the lifting of the rear part of the hood or bonnet.

Preferably, the pedestrian protection arrangement includes a mechanism to lift the rear part of the hood or bonnet, and at least one air-bag to cover part of the windscreen and/or part of A-Pillars provided on the vehicle, one mode of activation comprising the lifting of only the rear part of the hood or bonnet, the second mode including additionally the activation of at least one air-bag.

Advantageously, different modes are activated in response to a signal dependent on the first sensor arrangement reaching different thresholds.

Conveniently, at least one of said different thresholds is dependent upon the vehicle speed as measured by a third sensor arrangement.

DETAILED DESCRIPTION OF THE INVENTION

The vehicle ofFIG. 1is provided with a frame or chassis1, and the front of the vehicle is provided with a bumper or fender2, and a hood or bonnet3. The hood or bonnet3is, as is conventional, located in front of a windscreen or windshield4. The windscreen or windshield4is provided, on either side, with an A-Post5. The vehicle is provided with two safety devices configured to provide protection for a pedestrian in the event that the vehicle should strike a pedestrian in an accident.

The first safety device is in the form of a lifter6located beneath the rear part of the hood or bonnet3. The lifter6may be actuated to raise the rear part of the hood or bonnet3so that a central region of the hood or bonnet3is spaced above the underlying engine block. Should the head of a pedestrian strike the raised central region of the hood or bonnet3, the central region of the hood or bonnet3will be deformed downwardly, decelerating the head of the pedestrian in such a way that the risk of injuries arising is minimised.

The second safety device is in the form of an inflatable air-bag unit7, the air-bag unit being mounted in position adjacent the base of the windscreen4and being configured, upon inflation, to extend over the lower part of the windscreen4, and also part of the A-Post5. The air-bag7will thus minimise the risk of a pedestrian receiving injuries by striking his head or her against the windscreen4or A-Post5.

The air-bag unit7may be controlled in such a way as to be inflated at different relative times or with different relative pressures depending upon various parameters related to the accident.

The two safety devices6and7are controlled by a controller8which receives various input signals from sensors provided on the vehicle. The controller8may, for example, receive an input from a speed sensor9, indicating the speed of the vehicle.

The controller8may also receive an input from a sensor10which is located in position, in the illustrated embodiment, just behind the windscreen4at a position above the rear part of the hood or bonnet3. The sensor10is thus located a substantial distance behind the front part of the vehicle, and certainly at a distance of at least 0.5 meters behind the front part of the vehicle. The sensor10is a sensor which operates on received radiation and may thus be a camera operative in the visible spectrum or in the infra-red spectrum. The sensor10may also be an infra-red radar or a microwave radar detector. The sensor10may alternatively be a stereoscopic camera or even two cameras which provide a stereoscopic effect.

Thus the sensor10will receive radiation emanating or reflecting from an object, such as a pedestrian, in front of the vehicle. In an alternative embodiment of the vehicle, the sensor10may be located just in front of the windscreen on top of the scuttle or rear part of the hood or bonnet3.

The sensor10is adapted to detect the relative speed between the vehicle and an object in front of a vehicle, such as a pedestrian, and may also be adapted to determine the distance of part of an object which is positioned in front of the vehicle, from the vehicle. The sensor10may perform one, or preferably both of these functions.

It is to be appreciated that the sensor10, in the described embodiment, is positioned to detect the relative speed of and/or the distance to part of an object which extends above the height of the front part of the hood or bonnet3at the front edge of the hood or bonnet. In this way, the sensor will not respond to a relatively small item such as a traffic cone or a small animal, which will effectively be hidden from the sensor10by the front part of the hood or bonnet3.

The sensor10is connected to the control unit8, and the control unit8can be configured to calculate a signal to activate one or both of the pedestrian safety devices6and7according to the following criteria where the following notations apply:

Speed of impacting vehicle Vvehicle

Relative speed towards object Vrel

Distance of object from sensor10Dsensor

Distance from front-end to sensor10D0

When Vvehicle<vehicle speed limit threshold, no decision can be taken to activate safety devices6and7.

When Vvehicle>vehicle speed limit threshold, the following conditions apply:

if switch status Sstatusindicates ON (switch to activate system)

calculate distance from sensor10Dsensor=D0−∫(Vrel) dt

If Dsensor<Dlevel 1and Vrel>Vlevel 1(Vvehicle) then the protection systems are activated in a first mode in which only the hood lifter6is actuated.

if Dsensor<Dlevel 2and Vrel>Vlevel 2(Vvehicle) then the protection systems are activated in a second mode in which both the hood lifter6and the air-bag7are actuated.

The bumper or fender2is provided with another sensor in the form of integral pedestrian sensor11. The pedestrian sensor11is mounted on the front part of a rigid beam12which is connected to the chassis1by means of a relatively strong, but yieldable mounting13. Mounted on the front part of the beam12is a yieldable element14provided on the front face of the bumper, the front part of the yieldable element14being provided with a contact sensor15. The combination of the yieldable element15and the contact sensor15is provided with an outer covering16of foam or the like.

The output of the contact sensor15is provided to an on/off enabling circuit17, the output of which is provided to the control unit8.

It is to be appreciated that in use of the described pedestrian detection system, should the vehicle strike a pedestrian, the contact sensor15will generate an output signal provided to the on/off circuit17which will enable or actuate the control unit8. If the object struck by the vehicle is a relatively small object, the sensor10will not sense the presence of the object because the object will be hidden from the sensor10by the front part of the hood or bonnet3, and the pedestrian detection system will provide no further response.

However, should the vehicle strike a pedestrian located in front of the vehicle, the pedestrian will have a greater height than the height of the hood or bonnet3at the front part of the hood or bonnet, and thus the sensor10will sense the presence of the pedestrian. The sensor10will determine the relative speed between part of the pedestrian and the hood or bonnet3, or will determine the distance of the pedestrian from the hood or bonnet. The sensor10will continue to take such measurements during the following period of time. The initial situation during such an accident is thus generally as shown schematically inFIG. 2.

The control unit8may, if appropriate parameters are met with regard to the speed of the pedestrian relative to the vehicle, the overall speed of the vehicle and/or the distance between the pedestrian and the main part of the vehicle, actuate the bonnet or hood lifter6to lift the rear part of the hood or bonnet3as shown inFIG. 3. The sensor10will also continue to monitor the position of the pedestrian over the following moments of time and, again, if appropriate parameters are met, the air-bag unit7may be actuated (as illustrated schematically inFIG. 4) and indeed, depending upon the precise value of certain parameters, may modify or control the moment of deployment of the air-bag7, adjusting the time of deployment of the air-bag and/or the pressure or quantity of gas supplied to the air-bag.

WhilstFIGS. 1 to 4illustrate one embodiment of the present invention, it is to be appreciated that many modifications may be effected without departing from the scope of the invention. For example, instead of a single lifter6being provided to lift the rear part of the hood or bonnet3, a lifter may be provided to lift the front part of the hood or bonnet, or, alternatively again, two or more lifters may be provided to lift both the rear part of the hood or bonnet and the front part of the hood or bonnet.

Instead of having a single air-bag7to cover the lower part of the windscreen4and the A-Post5, separate air-bags may be provided to cover these parts of the vehicle.

In a preferred embodiment of the invention, the contact sensor15provided within the bumper or fender2is a force responsive sensor that can discriminate objects having a mass lighter than the mass of a typical pedestrian. In such an arrangement, the on/off circuit17will therefore not be actuated unless an object is struck which has a mass equivalent to that of a pedestrian.

To discriminate heavier objects (such as other vehicles) from a pedestrian, a central accelerometer18could be provided on the vehicle. In such an arrangement, the generation of a signal from both the accelerometer and the sensor10, indicates a severe crash situation and so, in such a situation, the control unit8could be configured to activate an internal safety device such as an air-bag or seat-belt pretensioner25to provide protection to occupants of the vehicle.

FIG. 5is a diagrammatic view corresponding toFIG. 1illustrating an embodiment of the invention in which the sensor10is mounted on the exterior of the vehicle at the base of the windscreen4and in which the hood or bonnet3is provided with a lifter20at the front of the hood or bonnet.

FIG. 6is a view illustrating a further embodiment of the invention in which the vehicle is provided with a lifter20at the front of the hood or bonnet, and a further lifter21at the rear of the hood or bonnet. In the embodiment shown inFIG. 6the sensor10is mounted on the roof of the vehicle at a position behind the windscreen.

FIG. 7is a perspective view of a further vehicle in accordance with the invention illustrating the sensor10of the previous embodiment replaced within a pair of spaced-apart stereoscopic cameras10a,10bmounted on the exterior of the vehicle adjacent the base of the windscreen4.FIG. 7also illustrates a first air-bag22which, when inflated, covers the lower part of the central region of the windscreen or windshield4, and two separate air-bags23and24each of which, when inflated, covers a respective body post, such as the A-Post5.

It is thus to be appreciated that the pedestrian detection system of the present invention may selectively control a number of different types of safety devices to provide protection for a pedestrian. The safety devices may be deployed simultaneously or sequentially.