GB2314187A

GB2314187A - Motor vehicle roll detector and safety arrangement

Info

Publication number: GB2314187A
Application number: GB9612286A
Authority: GB
Inventors: Ola Bostrom
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1996-06-12
Filing date: 1996-06-12
Publication date: 1997-12-17
Anticipated expiration: 2016-06-12
Also published as: GB9612286D0; GB2314187B

Abstract

A roll detector for detecting a roll in a motor vehicle, for activating a safety arrangement, comprises a sensor(10) adapted to sense at least one variable relating to the roll angle and to provide a first signal representing roll angle * small Greek alpha * and a second signal representing angular velocity * small Greek omega *, these signals being provided to calculating means (11) to perform calculations involving the first signal and the second signal to generate a third signal to activate a trigger (12) which initiates operation of a safety arrangement. An angle sensor (13) associated with an inhibitor(14) may prevent activation of the safety device if the vehicle has not executed a predetermined angular movement. A further angle sensor(15) may activate the trigger (12) whenever a second predetermined angle of movement has been exceeded.

Description

DESCRIPTION OF INVENTION "IMPROVEMENTS IN OR RELATING TO A ROLL SENSOR" THE PRESENT INVENTION relates to a roll sensor, and more particularly relates to a sensor adapted to be mounted on a motor vehicle to detect a situation where a roll of the vehicle is imminent.

In this context a roll of a vehicle is a movement of the vehicle which involves a rotation of at least 900 about the longitudinal axis of the vehicle.

When a vehicle is involved in a roll, it is desirable to be able to trigger certain safety devices in the motor vehicle, such as air-bags, seat-belt pretensioners, or the like, in order to minimise the risk of injury occurring to the driver and/or occupants of the vehicle.

It is possible to utilise a roll sensor which responds to a predetermined angle of inclination of the vehicle, about the longitudinal axis. Such an angle will be achieved during a situation in which the vehicle effects a roll. However, in some cases, the roll that is effected by a vehicle is a relatively quick roll, and if the safety devices are not deployed, in such a quick roll, until a predetermined angle of roll has been reached, even if that predetermined angle is relatively small, it may be too late for the safety devices to act in the intended manner. On the other hand, if the roll effected by the vehicle is a relatively slow roll, even if the roll is such that said predetermined relatively small angle of roll is reached, nevertheless the angular momentum might not be large enough to cause the vehicle to rotate by 900, and thus the safety device should not be triggered.

It is thus very difficult to select a particular angle of roll at which the safety devices should be triggered which will be appropriate both for a slow roll and for a quick roll.

An alternative approach is to utilise a sensor which responds to angular acceleration in excess of a predetermined threshold. However, this is not a satisfactory solution to the problem, since many situations may exist where a vehicle undergoes a relatively high angular acceleration, but where there is no substantial risk of a roll occurring. For example, if a vehicle is travelling on a badly made road, it is quite possible that for short periods of time, the vehicle will be subjected to very high angular accelerations. The same is true for a sensor responsive to angular speed.

The present invention therefore seeks to provide a roll sensor adapted to respond to a situation where a roll is occurring, or is likely to occur, but also adapted not to respond to ordinary events that occur when a vehicle is in ordinary use.

According to this invention there is provided a roll detector for detecting a roll in a motor vehicle for activating a safety arrangement, the roll detector comprising a sensor adapted to sense at least one variable related to the roll angle and to provide a first signal representing the roll angle and a second signal representing the roll angular velocity, and calculating means adapted to receive the first signal and the second signal, and to perform calculations involving the first signal and the second signal to generate a third signal to activate the safety arrangement.

Preferably the detector incorporates means to determine roll angle, and to trigger the safety device when the roll angle exceeds a predetermined threshold.

Advantageously the detector incorporates means to determine roll angle and to inhibit triggering of the safety device unless the roll angle is in excess of a specified lower limit.

Conveniently the sensor incorporates means responsive to roll angle. Advantageously the sensor incorporates means responsive to roll angular velocity.

Conveniently the sensor incorporates means responsive to roll angular acceleration.

In one embodiment the signal related to roll angular speed is derived by differentiating the signal responsive to roll angle. In an alternative embodiment the signal relating to roll angle is derived by integrating signal to roll angular velocity. In a further embodiment the signal representing roll angular velocity is generated by integrating the output signal from the sensor responsive to angular acceleration, and the signal representative of roll angle is derived by integrating the signal representative of roll angular velocity.

Conveniently the sensor incorporates at least two accelerometers located at a distance from each other.

Advantageously the sensor incorporates a solid state gyroscope adapted to measure angular velocity.

Conveniently the calculating means comprise a variable threshold generator adapted to generate a threshold value in response to the first signal and a comparator to compare the second signal with the generated threshold value, the comparator generating the third signal.

Alternatively the calculating means comprise a variable threshold generator adapted to generate a threshold value in response to the second signal, and a comparator to compare the first signal with the generated threshold value, the comparator generating the third signal. In a further embodiment the calculating means comprise means to generate a signal which is the sum of one of the first and second signals and the other of the first and second signals multiplied by a constant, and a discriminator to discriminate the signal from the signal generating means and to pass the signal to comprise the third signal when a threshold is exceeded.

Preferably wherein means are provided to inhibit the activation of the safety arrangement when the first signal representative of roll angle is beneath a specific threshold.

Conveniently means are provided to generate a signal to activate the safety arrangement whenever the first signal representative of roll angle is in excess of a predetermined threshold.

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 1 is a diagrammatic view illustrating three successive stages in a typical example of a roll of a vehicle, FIGURE 2 is a graphical figure relating angular acceleration to time of the vehicle with reference to the example of Figure 1, FIGURE 3 is a graphical figure relating angular acceleration to angle of rotation of the vehicle with reference to the example of Figure 1, FIGURE 4 is a block diagram illustrating one embodiment of a roll sensor in accordance with the invention, FIGURE 5 is a block diagram illustrating a typical sensor device for use in Figure 4, FIGURE 6 is a block diagram illustrating an alternative sensor device for use in Figure 4, FIGURE 7 is a block diagram illustrating a different sensor device for use in Figure 4, FIGURE 8 is a block diagram of a further alternative sensor device for use in Figure 4, FIGURE 9 is a block diagram of a calculating means for use in the embodiment of Figure 4, FIGURE 10 is a block diagram of an alternative calculating means for use in the embodiment of Figure 4, FIGURE 11 is a block diagram of a further alternative calculating means for use in the embodiment of Figure 4, and FIGURE 12 is a graphical representation illustrating the relationship between the non-triggering and triggering situations plotted against angular acceleration and angle of roll.

Referring initially to Figures 1 to 3 of the accompanying drawings, it has now been understood that in a typical roll situation for a motor vehicle, the roll is initiated by a lateral force. The lateral force may come from a side impact, but more frequently comes from the wheels of the vehicle engaging a curb, a guard rail, or the like. Alternatively, the vehicle may drive into a ditch and consequently start to roll. A further possibility is that the vehicle is subject to lateral sliding with high friction between the wheels and the road surface.

Whilst research conducted in the U.S.A. has revealed that accidents that include a roll constitute about 2.4% of all recorded accidents, the costs of coping with the injuries received by vehicle occupants during such accidents is about 33% of the total injury costs caused by all motor vehicle accidents. A substantial number of passenger vehicles are involved in accidents which include a roll each year. For both urban accidents and rural accidents, the accidents that include a roll are most frequently initiated by the vehicle "tripping" by engaging a curb, a pavement edge or a guard rail or the like.

Another significant cause of these accidents is the vehicle encountering a ditch or slope.

During a first stage, 1, of a roll, as shown in Figure 1, one side of the vehicle begins to lift. Both the wheels of the vehicle are still, however, on the ground.

The suspension of the vehicle is able to cope with this situation.

Subsequently, during a second stage, 2, one wheel of the vehicle leaves the ground. During this phase a constant angular acceleration is experienced by the vehicle about its longitudinal axis, and the vehicle has a linear increasing angular velocity, as shown in Figure 2. In the third phase of the roll, 3, after the vehicle has rolled through a substantial angle, both wheels leave the ground.

When in this phase, even if the body of the vehicle still touches the ground, it is considered that the vehicle is substantially free to rotate about its centre of mass with a constant angular velocity. The rotation is effected about the longitudinal axis of the vehicle.

The three phases of the roll are illustrated in graphical terms in Figures 2 and 3, Figure 2 plotting angular acceleration relative to time and Figure 3 plotting angular acceleration relative to the angle of roll.

It has been found that in devising a roll sensor, care should be taken that the roll sensor does not provide an output when the angle of roll is less than a predetermined limit. This serves to prevent the roll sensor producing output signals which trigger the associated safety devices merely when the vehicle is travelling along a badly made road.

It has also been found that it is desirable, in any event, to trigger the safety devices when the angle of rotation exceeds a predetermined threshold. It has now also been determined that, between these two angles, the associated safety devices should be triggered when the instantaneous angular velocity is high, and also when the sum of a signal related to the angular velocity and a signal related to the actual angle of rotation is above a predetermined threshold.

It has therefore been found that the following criteria for triggering of the associated safety devices, which relate to a, the angle of rotation about the axis, and o, the angular velocity of the rotation about the axis, are satisfactory:- Criterion 1: X + C2 a > C1 and a > CO Criterion 2: a > C3 When C1 and C2 are constants which relate to the geometry of the motor vehicle, and where CO and C3 are arbitrarily selected constants. The arrangement is adapted to trigger the safety device whenever one of the two criteria has been met.

Figure 4 is a block diagram, illustrating a roll sensor in accordance with the invention. The roll sensor comprises a sensor device 10, adapted to provide an output representative of the angle of roll, (a) and an output representative of the angular velocity (o). Various examples of sensor devices which perform this function will be described in more detail below.

The output signals representative of a and X are supplied to calculating means 11. Various examples of calculating means will be described in more detail below, but the calculating means perform an algorithm utilising the values of a and X supplied by the sensor device and provide an output to activate a trigger arrangement 12.

The trigger arrangement is adapted to trigger one or more safety devices provided in the motor vehicle such as, for example, air-bags or seat-belt tensioners.

Referring now to Figure 5, the sensor device 10 may comprise an angle sensor 20 adapted to sense the angle of roll a at any particular instant and an angular velocity sensor 21 adapted to sense the angular velocity of roll Z at any particular instant. Many types of angle sensor have been proposed before including a gyroscope. Various types of angular velocity sensor have also been proposed. For example, a solid state device which measures angular velocity by measuring the coriolis force on a tuning fork may be utilised.

As indicated in Figure 6, in an alternative arrangement, it is possible to utilise, as the sensor device 10, a single angle sensor 20, the output of the angle sensor 20 a being differentiated by a differentiator 22 to provide a second output .

As shown in Figure 7, a further alternative for the sensor device 10 is to use a single angular velocity sensor 21, integrating the output U using an integrator 23 to provide an output a.

Figure 8 illustrates yet another alternative arrangement for the sensor device 10 in which an angular acceleration sensor 22 is utilised, the output of which is integrated by an integrator 24 to provide an output signal , that signal being further integrated by integrator 25 to provide an output a. Angular acceleration could be measured by two lateral accelerometers.

As can be seen, in each of Figures 5 to 8, at least one sensor is provided which senses a parameter associated with the angle of rotation, that parameter being either the angle of rotation itself, or the instantaneous angular velocity or the instantaneous angular acceleration. Where only one sensor is provided, the output signal of the sensor is processed to provide two signals, one representative of the angle of rotation a and the other representative of the angular velocity .

The calculating means 11 is thus provided with the two signals a and .

Figure 9 illustrates one example of the calculating means 11. The signal a is applied to a variable threshold generator 30. The variable threshold generator 30 generates an output signal which is dependent upon the value of the signal a supplied to it. The output of the threshold generator 30 is fed to a comparator 31 which also receives the signal . The comparator 31 compares the instantaneous signal U with the signal generated by the threshold generator 30. An output from the comparator 31 is fed to the trigger 12 when the instantaneous value of the input U is greater than the threshold generated by the threshold generator 30. The arrangement is such that when the value of a is high, the threshold generated by the threshold generator 30 is low. Alternatively, when the instantaneous value of a is low, the threshold generated by the threshold generator 30 is high.

Figure 10 illustrates an alternative arrangement in which the calculating means comprises a comparator 32 which is supplied with the signal a, and a controllable threshold generator 33 which is supplied with the signal X and which generates an output signal which is fed to the comparator 32. An output from the comparator 32 is fed to the trigger 12 when the instantaneous value of the input a is greater than the threshold generated by the threshold generator 33. The arrangement is such that if the signal U is high, the threshold generated by the threshold generator 32 is relatively low, whereas if the value of the signal X is low, then the threshold generated by the threshold generator 33 is relatively high.

Figure 11 illustrates yet another arrangement in which the calculating means is supplied with the signal a and with the signal . The calculating means are adapted to inhibit the trigger whenever the angle of rotation is less than a predetermined threshold, which corresponds to the constant CO. The calculating means is also adapted to operate so that the trigger is activated whenever the angle of rotation exceeds a predetermined threshold, this threshold corresponding to the constant C3. The calculating means is also adapted to generate an output which activates the trigger whenever the sum + C2 a is greater than C1 and also a alone is greater than the threshold that corresponds to the constant CO.

Referring to Figure 11, both of the input signals representative of the angle of roll a and the angular velocity of roll U are supplied to a calculating unit 34 adapted to calculate the instantaneous value of Z + C2 a, where C2 is the constant identified above. A signal representative of this value is applied to a discriminator 35 adapted to pass the signal only when the value is greater than a predetermined value related to the constant C1. The output of the discriminator is supplied as one input to an AND-gate 36.

The signal representative of the angle of roll a that is supplied to the calculating means shown in Figure 11 is applied to a further discriminator 37 adapted to pass the signal only when the instantaneous value of a is greater than a value which is related to the constant CO, the output of this discriminator being supplied is the other input to the AND-gate 36, and the signal representative of the instantaneous value of a is also supplied to yet another discriminator 38 which is adapted to pass the signal only if the value of the signal is in excess of a predetermined value related to the constant C3.

The output of the AND-gate 36 and the output of the discriminator 38 are both supplied to an OR-gate 40, the output of the OR-gate being fed to the trigger 12.

It is to be appreciated that whenever the instantaneous value of a is lower than the relatively low threshold established by discriminator 37, that is to say the threshold related to the constant CO, there will be no output from this discriminator, meaning that there can be no output from the AND-gate 36. However, when the instantaneous value of a is such that the threshold defined by the discriminator 37 is exceeded, then the AND-gate 36 is provided with one input. As soon as the value of o + C2 a exceeds the threshold set by discriminator 35, which relates to the constant C1, then a further positive input will be supplied to the AND-gate 36. A positive output will then be provided by the AND-gate 36 to the OR-gate 40, and the OR-gate 40 will provide an output which is supplied to the trigger 12.

Should, at any instant, the value of the signal representative of the roll angle a exceed the threshold, related to the constant C3, set by the discriminator 38, an output will be passed from that discriminator 38 to the ORgate 40 and thus to the trigger 12.

Figure 12 is a graphical figure illustrating the operation of the device shown in Figure 11, with Figure 12 illustrating, in a graphical way, the boundary between a "no trigger" situation and a "trigger" situation plotted against U and a.

It can be seen that in a first part 41 of the graph, where the angle a is less than the constant CO, the triggering arrangement is inhibited by the fact that no output signal is passed by the discriminator 37 to the ANDgate 36. Also, in region 42 of the graph where the angle of roll exceeds the constant C3, the trigger is activated because an output signal is passed by the discriminator 38 to the OR-gate 40.

In the intermediate part 43 of the graph of Figure 12, there is a linear boundary between the nontriggering and triggering situations. This is defined by the first criterion outlined above.

Whilst in the embodiment of Figure 11, the calculating means are so designed that the trigger can never be activated when the roll angle is less than a first threshold value, and are also arranged so that the trigger is always activated when the roll angle exceeds a second threshold value, in other embodiments of the invention, a similar effect may be achieved by providing a trigger inhibitor which inhibits activation of the trigger, when the roll angle is beneath a first threshold value, and by providing a trigger override device which activates the trigger whenever the roll angle exceeds a second threshold.

Claims

CLAIMS:

1. A roll detector for detecting a roll in a motor vehicle for activating a safety arrangement, the roll detector comprising a sensor adapted to sense at least one variable related to the roll angle and to provide a first signal representing the roll angle and a second signal representing the roll angular velocity, and calculating means adapted to receive the first signal and the second signal, and to perform calculations involving the first signal and the second signal to generate a third signal to activate the safety arrangement.

2. A detector according to any one of the preceding Claim wherein the sensor incorporates means responsive to roll angle.

3. A detector according to Claim 1 or 2 wherein the sensor incorporates means responsive to roll angular velocity.

4. A detector according to any one of the preceding Claims wherein the sensor incorporates means responsive to roll angular acceleration.

5. A detector according to Claim 2 wherein the signal related to roll angular velocity is derived by differentiating the signal from the means responsive to roll angle.

6. A detector according to Claim 3 wherein the signal relating to roll angle is derived by integrating the signal from the means responsive to roll angular velocity.

7. A detector according to Claim 4, wherein the signal representing roll angular velocity is generated by integrating the output signal from the sensor means responsive to roll angular acceleration, and the signal representative of roll angle is derived by integrating the signal representing roll angular velocity.

8. A detector according to any one of the preceding Claims wherein the sensor incorporates at least two accelerometers located at a distance from each other.

9. A detector according to any one of the preceding Claims wherein the sensor incorporates a solid state gyroscope adapted to measure angular velocity.

10. A detector according to any one of the preceding Claims wherein the calculating means comprise a variable threshold generator adapted to generate a threshold value in response to the first signal and a comparator to compare the second signal with the generated threshold value, the comparator generating the third signal.

11. A detector according to any one of Claims 1 to 9 wherein the calculating means comprise a variable threshold generator adapted to generate a threshold value in response to the second signal, and a comparator to compared the first signal with the generated threshold value, the comparator generating the third signal.

12. Any novel feature or combination of features disclosed herein.

12. A detector according to any one of Claims 1 to 9 wherein the calculating means comprise means to generate a signal which is the sum of one of the first and second signals and the other of the first and second signals multiplied by a constant, and a discriminator to discriminate the signal from the signal generating means and to pass the signal to comprise the third signal when a threshold is exceeded.

13. A detector according to any one of the preceding Claims wherein means are provided to inhibit the activation of the safety arrangement when the first signal representative of roll angle is beneath a specific threshold.

14. A detector according to any one of the preceding Claims wherein means are provided to generate a signal to activate the safety arrangement whenever the first signal representative of roll angle is in excess of a predetermined threshold.

15. A roll detector substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings modified by any one of Figures 5 to 8 and as modified by any one of Figures 9 to 11.

16. Any novel feature or combination of features disclosed herein.

Amendments to the claims have been filed as follows CLAIMS: 1. A roll detector for detecting a roll in a motor vehicle for activating a safety arrangement, the roll detector comprising a sensor adapted to sense at least one variable related to the roll angle and to provide a first signal representing the roll angle and a second signal representing the roll angular velocity, and calculating means adapted to receive the first signal and the second signal, said calculating means comprising means to generate a signal which is the sum of one of the first and second signals and the other of the first and second signals multiplied by a constant, and a discriminator to discriminate the signal from the signal generating means and to pass the signal to comprise the third signal when a threshold is exceeded in order to activate the safety arrangement, said calculating means further comprising further means to generate a further signal to activate the safety arrangement whenever the first signal representative of roll angle is in excess of a further predetermined threshold.

10. A detector according to any one of the preceding Claims wherein means are provided to inhibit the activation of the safety arrangement when the first signal representative of roll angle is beneath a specific threshold.

11. A roll detector substantially as herein described with reference to and as shown in Figure 4 of the accompanying drawings modified by any one of Figures 5 to 8 and as modified by Figure 9.