GB2352860A

GB2352860A - A sensor system for moderating air bag deployment

Info

Publication number: GB2352860A
Application number: GB9918164A
Authority: GB
Inventors: Salomonsson Ove; Kan Prytz H
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1999-08-02
Filing date: 1999-08-02
Publication date: 2001-02-07
Anticipated expiration: 2019-08-02
Also published as: WO2001008930A1; GB9918164D0; AU6485700A; GB2352860B

Abstract

A sensor system is provided for sensing when a predetermined part of the occupant (1) of a seat (2) of a vehicle is located in a predetermined zone (3) in front of the ordinary position of the occupant of the seat. The sensor may be used to moderate or control the functioning of a safety device, such as an airbag, to prevent injury to the occupant. A plurality of sensors are provided adapted to detect the presence of objects. The sensors may comprise ultrasonic sensors. A first arrangement determines whether any object is present within the predetermined zone. A second arrangement determines the position of a predetermined part of the occupant of the seat. The system provides a predetermined output signal, such as a signal which modifies the deployment of an airbag, when the arrangement for detecting an object within a predetermined zone detects an object within that zone and also when the position determining arrangement determines the position of the predetermined part of the occupant.

Description

1 2352860 DESCRIPTION OF INVENTION "IMPROVEMENTS IN OR RELATING TO A

SENSOR SYSTEM" THE PRESENT INVENTION relates to a sensor system, and more particularly relates to a sensor system adapted to sense the position of an occupant of a seat of a vehicle.

It is known to provide a sensor system to sense the position of an occupant of a seat of a vehicle. Such sensor systems are typically used in conjuncfion with safety devices which may be actuated in the event that an accident should occur. In one specific example, the sensor that is provided to sense the position of the occupant of the seat of the vehicle provides an output signal which can modify the deployment of an air-bag. It has been found that if an air-bag is provided to be deployed in front of a person occupying a seat in a motor vehicle, if the person is leaning forwardly at the instant that the air-bag is deployed, the air- bag can impart severe injury to the occupant of the seat. Thus, it has been proposed that a sensor system should sense the position of the occupant and modify the deployment of the air-bag, either causing the air- bag to be inflated with less than the normal quantity of gas or even inhibiting inflation of the air-bag, when an accident situation arises, if the occupant of the seat is leaning forwardly.

2 It has been proposed to utilise a sensor system comprising a plurality of ultrasonic transducers adapted to transmit ultrasonic signals and adapted to detect reflections of the transmitted ultrasonic signals from parts of the body of the occupant of the seat, such as the head and torso of the occupant of the seat. The reflected signals may be processed to detennine the position of the head and torso of the occupant of the seat, enabling the deployment of the air-bag to be modified in dependence upon the position of the occupant of the seat.

Such a sensor system is, inevitably, prone to errors and has a predetermined statistical error rate. The present invention seeks to provide a sensor system which has an improved statistical error rate.

According to this invention there is provided a sensing system for sensing when a predeten-nined part of the occupant of a seat in a vehicle is located in a predetermined zone in front of the ordinary position of the occupant of the seat, the arrangement comprising sensors adapted to detect the presence of objects, there being a first arrangement adapted to determine, from signals from at least some of said sensors, whether an object is present in the predetermined zone, and there being a second arrangement adapted to determine the position of the predetermined part of the occupant of the seat, the system being adapted to provide a predetermined output signal when the arrangement for detecting an object within a predeten-nined zone detects an object within that zone, and the position detennining arrangement determines the position of the predetermined part of the occupant.

Preferably the position determining arrangement is only actuated when the object detection arrangement detects an object within the predetermined zone.

3 Conveniently the object detection arrangement provides an output signal to a control, the control arrangement controlling deployment of a safety device, the control arrangement being adapted to deploy the safety device in a predetermined manner on receipt of the signal from the object detection arrangement indicating that no object is present within a predetermined zone.

Advantageously the control is adapted to receive a signal from the position determining arrangement, the control being adapted to inhibit or modify deployment of the safety device in response to the signal received from the position determining arrangement.

Preferably the safety device is an air-bag, the air-bag being adapted, when inflated, substantially to fill the predetermined zone.

Conveniently there are plurality of sensors, some of the sensors being adapted to provide signals to the object detection arrangement, and all of the sensors being adapted to provide signals to the position determining arrangement.

Preferably the sensors comprise ultrasonic sensors.

Conveniently means are provided to determine the weight of the occupant of a seat, the arrangement only being enabled when the weight sensor senses that the weight of the occupant of the seat is in excess of a predetermined threshold.

4 Advantageously the control arrangement is adapted to control an audible alarm in response to the occupant of the seat being detected in a predetermined position.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE I is a schematic illustration showing an occupant of the seat in a first position, FIGURE 2 is a view corresponding to Figure I showing the occupant of the seat in a second position, FIGURE 3 is a view corresponding to Figures I and 2 showing the occupant of the seat in a third position, FIGURE 4 is a view of a transducer arrangement, FIGURE 5 is a block diagram of processing circuitry, FIGURE 6 is a first error diagram, FIGURE 7 is a second error diagram, and FIGURE 8 is a third error diagram.

Referring initially to Figure 1, an occupant I of a vehicle seat 2 is shown diagrammatically. The occupant of the seat I is sitting in the "normal" position. Thus the torso of the occupant is resting against the back-rest of the seat. No part of the occupant is present within a predetermined zone, namely zone 3, which is located in front of the occupant of the seat in a region that will be occupied, in the presently described embodiment, by an air-bag when the air-bag inflates in response to an accident situation. It is to be appreciated that with the occupant of the seat in this position it is not desired to modify or inhibit the deployment of the air-bag if an accident situation is detected.

Figure 2 illustrates the occupant 1 of the seat in a second position which the arms 4 of the occupant extend forwardly so that the forearm and hand of the occupant of the seat is present within the zone 3. It is to be noted that in this position of the occupant I of the seat 2 it would still be appropriate for the deployment of the air-bag to be unmodified and uninhibited.

Consequently it can be seen that a sensor arrangement which seeks to modify or inhibit the deployment of the air-bag simply by detecting an object present within the zone 3 might well lead to inhibition or modification of the deployment of the air-bag when such inhibition or modification is not desirable.

Figure 3 illustrates the occupant I of the seat 2 when in a further position in which the torso of the occupant is leaning forwardly relative to the back of the seat and part of the head of the occupant is present within the zone 3, together with the whole of the upper arm, the whole of the forearm and the hand of the occupant of the seat. It is to be appreciated that the occupant of the seat is thus no longer in the "normal" position and can be considered to be 44 out of position". It is desirable that with the occupant of the seat in this position, the deployment of an air-bag to fill the space in front of the occupant 6 should be modified or inhibited, since otherwise there is a risk that injury will be effected on the occupant of the seat as a consequence of the deployment of the air-bag. In such a situation, the air-bag would not be considered to be a device enhancing the safety of the occupant, but instead could be considered to be a danger to the occupant.

Turning now to Figure 4, part of a motor vehicle is shown in plan view. The seat 2 is illustrated ftom above, the seat 2 comprising a squab 5 and a back-rest. The seat is located ad. acent a door 6 and in front of the seat is mounted a dashboard 7. A first sensor in the form of an ultrasonic transducer 8 is provided located in position adjacent one end of the dashboard 7 and forward end of the door 6. The transducer 7 transmits a beam which extends diagonally across the squab 5 of the seat, the beam extending almost to the back-rest 5. Thus the transducer 8 directs a beam which extends across a large portion of the zone 3. Located towards the centre of the vehicle, on the dashboard, is a second sensor in the forin of an ultrasonic transducer 9. The second sensor 9 is a transducer which directs a beam diagonally across the vehicle, extending across the forward part of the squab 5 of the seat towards the door 6.

Thus the beam from the ultrasonic transducer also extends primarily across the zone 3.

A third sensor in the fonn of an ultrasonic transducer 10 is located 'in the centre of the vehicle on the dashboard adjacent the sensor 9. However, the transducer 10 directs a beam more towards the rear of the vehicle, with the beam being directed across the squab 5 of the seat towards the back-rest of the seat.

7 A fourth sensor in the form of an ultrasonic transducer I I is mounted on the B-Post of the motor vehicle adjacent the rearward edge of the door 6, with this transducer directing a beam forwardly and diagonally across the seat.

It is to be appreciated that the arrangement of transducers described above may be utilised to transmit ultrasonic signals which are reflected from parts of the body of the occupant, and the reflected signals may be processed to determine the position of the body of the occupant of the seat relative to the seat.

Turning now to Figure 5, a sensor arrangement adapted to sense the position of the occupant of the seat comprises a weight sensor 20 adapted to sense the weight of an occupant of the seat. If the seat is unoccupied, no weight will be sensed. If only a small person, such as a child, or, more particularly, a child in a rearward facing child-seat, occupies the seat, only a very low weight is sensed. It is only if a weight on the seat is sensed which is greater than a predetermined threshold before the following components of the arrangement being described are activated or enabled. The consequence of this is that the air-bag will not be deployed in an accident situation unless a person having a weight in excess of a predetermined weight is sitting on the seat.

If a person having a weight in excess of the predetermined weight is sitting on the seat, the weight sensor provides an output which enables an object detector 21. The object detector 21 is adapted to detect an object, any object, within the zone 3 in front of the occupant of the seat. If there is no object within this zone, then the occupant of the seat cannot possibly be "out of position", and consequently the air-bag should be fully inflated, with de loyment of the air-bag not being modified in any way.

p I 8 In the described embodiment the object detector 21 receives input signals from the first two described sensors, namely sensors 8 and 9. It is to be recalled that the sensors 8 and 9 comprise transducers which direct ultrasonic beams substantially across the zone 3, meaning that the outputs from these two sensors can be relied on to provide a very accurate indication of whether there is or is not an object present within the zone 3. If no object is present within the zone 3, then an output signal is supplied, on lead 22, to a control arrangement 23 to enable deployment of the air-bag in the "ordinary" or unmodified way 'in an accident situation.

However, if an object, any object, is detected by the object detector 21 to be present within the zone 3, then an output signal is passed, over the output 24, to arrangement 25 adapted to determine the position of the occupant of the seat.

The arrangement 25 adapted to determine the position of the occupant of the seat, in this embodiment, takes input signals from each of the four described sensors 8, 9, 10 and 11. These input signals are processed in a conventional way to detennine the position of the occupant of the seat. The determination of the position of the occupant of the seat is converted into an appropnate signal which is passed, by lead 26, to the control arrangement 23.

The position determining arrangement 25 may determine that the occupant is not "out of position" but is in the "ordinary" position. An appropriate signal will thus be passed to the control arrangement 23 which will enable deployment of the air-bag in the "ordinary" manner, with deployment of the air-bag being unmodified, in an accident situation.

9 However, should the position detennining arrangement determine that the occupant of the seat is "out of position", then an appropriate signal will be passed, through the lead 26, to the control arrangement, so that the control arrangement can either inhibit deployment of the air-bag, or so that the control arrangement can modify deployment of the air-bag, in an accident situation.

It is to be noted that the air-bag will, in any event, only be deployed should an accident situation arise and be detected by the conventional detectors associated with the air-bag. Thus, should the occupant of the seat be in the "ordinary" position when an accident is detected the airbag will be deployed in the ordinary way, but if the occupant of the seat is leaning forwards and is thus "out of position" when accident is detected, then either the air-bag will not inflate at all, or the air-bag will only inflate in a gentle manner so as to minimise the risk of the air-bag itself imparting injury to the occupant of the seat.

In the described embodiment of the invention it is envisaged that the control arrangement 23 may, in addition to controlling the deployment of the air-bag, pass a signal to an audible alarm 28 if an occupant of the seat is "out of position" for a period of time in excess of a predetermined time-limit. Thus, if an occupant of the seat leans forwardly for more than, say, five seconds, so that the head or torso of the occupant of the seat are present within the zone 3, the audible alarm may sound. The audible alarm may, of course, comprise a prerecorded, or voice-synthesised, message advising the occupant of the seat to return to the "ordinary" position.

Turning now to Figure 6, it is to be appreciated that when the occupant of the seat is in the "ordinary" position as illustrated in Figure 1. the air-bag is to be deployed in the normal way. In the arrangement described above, the object detector would initially attempt to detect an object within the zone 3. If the object detector made a correct conclusion, then the air- bag would be activated in the normal way. However, if the object detector made an incorrect conclusion, then the consequence would be that the position determining arrangement 25 would be activated. If the position detennining arrangement made the correct conclusion, then the air-bag would be inflated in the "normal" way. For the deployment of the air-bag to be modified or inhibited, both the object detector 21 and the position determining arrangement 25 would have to function incorrectly. In the schematic illustration of Figure 6, oval 30 represents the statistical error of the object detector arrangement 21, whereas oval 31 represents the statistical error of the position determining arrangement 25. It is only where the ovals overlap, a relatively small area, that the deployment of the air-bag would be erroneously modified or inhibited.

It is thus to be appreciated that with the occupant of the seat in the position illustrated in Figure 1, the overall reliability of the system is enhanced as compared with prior proposals, in that the risk of the airbag not inflating, or inflating in a modified manner, is substantially reduced. The occupant of the seat is occupying the "ordinary" position as shown in Figure I for a very substantial proportion of the time that the occupant is present within the motor vehicle, and consequently, for a large proportion of the time, the occupant of the seat will enjoy the benefit of a substantially reduced error rate.

Considering now the situation when the occupant of the seat is in the position illustrated in Figure 2, the object detector arrangement 21 should detect an object present within the zone 3, in the form of the forearm and hand of the -occupant. However, the position deten-nining arrangement 25 should subsequently deten-nine that the head and torso of the occupant are in the "ordinary" position, so that deployment of the air-bag will not be modified or I I inhibited. If the object detector 21 falls to detect the object present within the zone 3, then the air-bag will be inflated in the ordinary way, which is the desired objective. However, if the occupant position determining arrangement25 fails to detennine that the occupant is in the "ordinary" position, and falsely concludes that the occupant is out of position, then deployment of the air-bag will be modified or inhibited. However, as can be seen, the erTor will only occur in the portion of oval 31 where there is no overlap with the oval 30. Thus, even in this situation, the error rate is reduced as compared with the prior proposed arrangement.

Turning finally to the situation when the occupant of the seat is in the position shown in Figure 3, the object detector arrangement 21 should detect an object present within the zone 3, and thus the deployment of the air-bag should be modified so that the bag inflates gently or is not inflated at all. If the object detector arrangement 21 fails to detect the presence of the object within the zone 3, then the air-bag will be deployed in the ordinary way. Additionally, if the object detector arrangement 21 does detect an object present with the zone 3, but if the position determining arrangement 25 then falsely concludes that the occupant is in the correct position, then again the air-bag will be deployed in the ordinary way. Thus, in this situation, the total error is a combinafion of the areas of the ovals 30 and 3 1. Thus, in this situation, there is a slightly increased error rate. However, it is to be fully understood that the increase in error rate only occurs when the occupant of the seat is in the position illustrated in Figure 3, and, typically, an occupant of the seat is only in the position illustrated 'in Figure 3, that is to say in the "out of position" position, for a very low proportion of the time.

12 Thus the described arrangement provides enhanced safety for a great proportion of the time, with a consequent reduction in safety during a very small proportion of time.

VAi-ilst the invention has been described with reference to a safety device in the form of an air-bag, it is to be appreciated that various other safety devices are utilised in motor vehicles which are deployed in the event that an accident should occur, and it is believed that an arrangement of the type described above may be of benefit in connection with such devices. Examples of such devices are pre-tensioners adapted to pre-tension seat-belts. Thus it is envisaged that the mode of deployment of a pre-tensioner may be modified if the occupant of the seat is in the "out of position" position.

Whilst the invention has been described with reference to an arrangement in which four sensors are used, more sensors, or fewer sensors could be utilised in alternative embodiments of the invention. Whilst the mvention has been described with reference to an embodiment in which a predetermined set of sensors is used to detect an object present within the zone 3, with those sensors and additional sensors being used to determine the position of the occupant of the seat, in further embodiments of the invention discrete sets of sensors may be provided, with one set of sensors being provided to determine the presence of an object within the zone 3, and a second set of sensors being provided to deten-nine the position of the occupant of the seat.

VVItilst the invention has been described with reference to an embodiment in which ultrasonic sensors are utillsed, it is to be appreciated that the invention may be utilised with any type of sensor, including optical sensors and sensors which detenuine the weight distribution of the occupant of the seat on the seat itself, or a combination of sensors of different types.

13 It is to be appreciated that it is envisaged that the object detection arrangement 21 may have a very high performance rate. The task of the object detector is relatively simple, and is clearly much simpler than the task of the position determining arrangement 25.

Claims

14 CLAIMS:

1. A sensing system for sensing when a predetermined part of the occupant of a seat in a vehicle is located in a predeten-nined zone in front of the ordinary position of the occupant of the seat, the arrangement comprising sensors adapted to detect the presence of objects, there being a first arrangement adapted to determine, from signals from at least some of said sensors, whether an object is present in the predetermined zone, and there being a second arrangement adapted to determine the position of the predetermined part of the occupant of the seat, the system being adapted to provide a predetermined output signal when the arrangement for detecting an object within a predetermined zone detects an object within that zone, and the position determining arrangement determines the position of the predetermined part of the occupant.

2. A sensor system according to Claim I wherein the position determining arrangement is only actuated when the object detection arrangement detects an object within the predetermined zone.

3. A sensor system according to Claim I or Claim 2 wherein the object detection arrangement provides an output signal to a control, the control arrangement controlling deployment of a safety device, the control arrangement being adapted to deploy the safety device in a predetermined manner on receipt of the signal from the object detection arrangement indicating that no object is present within a predetermined zone.

4. A sensor system according to Claim 3 wherein the control is adapted to receive a signal from the position deten-nining arrangement, the control being adapted to inhibit or modify deployment of the safety device in response to the signal received from the position detennining arrangement.

5. A sensor system according to any one of the preceding Claims wherein the safety device is an air-bag, the air-bag being adapted, when inflated, substantially to fill the predetermined zone.

6. A sensor system according to any one of the preceding Claims wherein there are plurality of sensors, some of the sensors being adapted to provide signals to the object detection arrangement, and all of the sensors being adapted cl- to provide signals to the position deten-nining arrangement.

7. A sensor system according to any one of the preceding Claims wherein the sensors comprise ultrasonic sensors.

8. A sensor system according to any one of the preceding Claims wherein means are provided to determine the weight of the occupant of a seat, the arrangement only being enabled when the weight sensor senses that the weight of the occupant of the seat is in excess of a predetermined threshold.

9. A sensor system according to any one of the preceding Claims wherein the control arrangement is adapted to control an audible alarm in response to the occupant of the seat being detected in a predetermined position.

10. A sensor system substantially as herein described with reference to and as shown in the accompanying drawings.

16 Any novel feature or combination of features disclosed herein.