Vehicle safety system

1. A vehicle safety system for detecting and responding to a side impact of the vehicle, the system comprising

at least one sensor operable to detect one or more parameters relating to the rate of yaw of the vehicle, and to provide an output that is dependent upon the longitudinal position along the vehicle of the side impact;

a processor operable to output an activation signal to activate passive safety devices of the vehicle safety system if it is determined from the one or more parameters that a side impact is occurring or has occurred;

the processor operable to determine whether an in-zone side impact is occurring or has occurred and to determine if an off-zone side impact is occurring or has occurred;

an in-zone activation signal is output if it is determined that an in-zone side impact is occurring or has occurred and it is determined that a parameter relating to the lateral acceleration of the vehicle exceeds a first threshold, and an off-zone activation signal is output if it is determined that an off-zone side impact is occurring or has occurred and it is determined that at least one of the detected rate of yaw and angular acceleration of the vehicle exceeds a respective yaw threshold and angular acceleration threshold; and

the processor operable to selectively activate the passive safety devices in different ways depending on whether the side impact is determined to have occurred in-zone or off-zone.

2. A vehicle safety system according to claim 1 , wherein the passive safety devices are selected as one from the group of front, rear, and side air bags, inflatable curtains, and combinations thereof.

3. A vehicle safety system according to claim 1 , wherein the activation signal is output if it is determined that both the detected rate of yaw and angular acceleration of the vehicle are above the respective yaw and angular acceleration thresholds.

4. A vehicle safety system according to claim 1 , wherein the processor is operable to make a determination as to the longitudinal position along the vehicle of the side impact.

5. A vehicle safety system according to claim 1 , wherein the at least one sensor comprises a gyroscope.

6. A vehicle safety system according to claim 1 , wherein the at least one sensor comprises at least two accelerometers.

7. A safety system according to claim 6 , wherein the accelerometers are displaced from one another in a direction which is substantially parallel with the longitudinal axis of the vehicle.

8. A vehicle safety system according to claim 6 , wherein the accelerometers are displaced from one another in a direction which is substantially perpendicular to the longitudinal axis of the vehicle.

9. A vehicle safety system according to claim 6 , wherein the accelerometers are sensitive to acceleration perpendicular to a line connecting the accelerometers.

10. A vehicle safety system according to claim 6 , wherein the accelerometers are sensitive to acceleration parallel with a line connecting the accelerometers.

11. A vehicle safety system according to claim 1 , wherein the at least one sensor comprises a gyroscope and at least two accelerometers, and wherein the parameter relating to the yaw of the vehicle is determined from the acceleration sensed by the two accelerometers, and also from the gyroscope.

12. A method for detecting a side impact to a vehicle, comprising the steps of:

detecting one or more parameters relating to the rate of yaw of the vehicle;

providing an output, based at least on the one or more parameters, which is dependent upon the longitudinal position along the vehicle of the side impact;

outputting an activation signal to activate a passive impact protection arrangement when it is determined from the at least one parameter that a side impact is occurring or has occurred;

the step of outputting the activation signal further comprising the steps of

determining whether an in-zone side impact is occurring or has occurred and determining whether an off-zone side impact is occurring or has occurred;

outputting the activation signal as an in-zone activation signal if it is determined that an in in-zone side impact is occurring or has occurred and it is determined that a parameter relating to the lateral acceleration of the vehicle exceeds a first threshold, and

outputting the activation signal as an off-zone activation signal if it is determined that an off-zone side impact is occurring or has occurred and it is determined that the detected rate of yaw or angular acceleration of the vehicle exceeds a second threshold; and

causing the passive impact protection arrangement to react in different ways depending on whether the side impact is determined to be an in-zone side impact or an off-zone side impact.

13. A method according to claim 12 , further comprising the step of making a determination as to the longitudinal position along the vehicle of the side impact.

14. A computer program comprising a computer program code stored in non-transitory memory of the vehicle safety system and operable to perform all of the steps of claim 12 when run on a computer forming a part of the vehicle safety system.

15. A computer program according to claim 14 , embodied on a non-transitory computer readable medium.

16. A vehicle safety system according to claim 1 , wherein when it is determined that an in-zone side impact is occurring or has occurred the output of the activation signal activates passive safety devices positioned between the point of impact and the occupants of the vehicle.

17. A vehicle safety system according to claim 1 , wherein when it is determined that an off-zone side impact is occurring or has occurred the output of the activation signal activates passive safety devices positioned on the opposite side of the vehicle from the side of impact.