Vehicle safety system

1. A safety system for a motor vehicle having at least a front wheel arrangement having one or more wheels and a rear wheel arrangement having one or more wheels, the system comprising:

a control unit;

one or more vehicle inertial sensors to detect acceleration experienced by the vehicle, the one or more vehicle inertial sensors being connected to the control unit so the control unit receives output signals from the one or more vehicle inertial sensors; and

one or more vehicle safety systems which may be activated by the control unit,

wherein the control unit is configured to process the output signals received from the one or more vehicle inertial sensors and to determine whether at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface over which the vehicle is driven;

wherein the one or more vehicle inertial sensors include a longitudinal acceleration sensor and a vertical acceleration sensor and the control unit makes a determination that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface if a vertical acceleration of the vehicle exceeds a predetermined vertical acceleration threshold of the vehicle and a longitudinal acceleration of the vehicle is below a predetermined longitudinal acceleration threshold.

2. The system according to claim 1 , wherein the one or more vehicle inertial sensors include a vertical acceleration sensor, and wherein the control unit makes a determination that at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface if a vertical acceleration of the vehicle exceeds a predetermined vertical acceleration threshold.

3. The system according to claim 1 wherein the one or more vehicle inertial sensors include a pitch sensor, and the control unit makes a determination that at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface if a rate of pitch of the vehicle exceeds a predetermined pitch threshold.

4. The system according to claim 1 , wherein the control unit is operable to confirm a determination that one or more of the wheel arrangements is not in contact with the surface if the conditions leading to a determination that at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface persist in excess of a predetermined length of time.

5. The system according to claim 4 wherein the control unit is operable if the control unit makes a confirmed determination that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, to calculate an estimated severity of an impact when the one or more of the wheel arrangements vehicle makes contact with the surface again.

6. The system according to claim 5 , wherein the estimated severity is based on the kinetic energy accumulated by the vehicle.

7. The system according to claim 5 , wherein the vehicle safety system is in the form of a reversible or irreversible seatbelt pretensioner which may be activated by the control unit, while the one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, if the estimated severity of the impact exceeds a predetermined threshold.

8. The system according to claim 7 , wherein-the one or more vehicle inertial sensors includes a pitch sensor, and wherein the reversible or irreversible seatbelt pretensioner is activated by the control unit, while the one or more of the wheel arrangements is not in contact with the surface, if the estimated severity of the impact is above a predetermined threshold, and the pitch angle of the vehicle measured by exceeds a predetermined threshold.

9. The system according to claim 1 wherein:

the one or more vehicle safety system is at least one front air-bag and a reversible or irreversible seatbelt pretensioner; and

if a determination is made that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, the control unit is adapted to make a determination as to whether the front air-bag will triggered when the vehicle strikes the surface, and the control unit is operable to activate, while the one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, the reversible or irreversible seatbelt pretensioner if it is determined that the front air-bag will be triggered.

10. The system according to claim 9 wherein the vehicle further comprises an occupant out of position sensor, and wherein the seatbelt pretensioner will be activated if it is determined that the front air-bag will be triggered and the occupant is out of position.

11. The system according to claim 1 wherein a seatbelt pretensioner is activated if a confirmed determination is made that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, and the vehicle inertial sensors indicate that the one or more of the wheels of the front and the rear wheel arrangements has made contact with the surface again.

12. A safety system for a motor vehicle having at least a front wheel arrangement having one or more wheels and a rear wheel arrangement having one or more wheels, the system comprising:

a control unit;

one or more vehicle inertial sensors to detect acceleration experienced by the vehicle, the one or more vehicle inertial sensors being connected to the control unit so the control unit receives output signals from the one or more vehicle inertial sensors; and

one or more vehicle safety systems which may be activated by the control unit,

wherein the control unit is configured to process the output signals received from the one or more vehicle inertial sensors and to determine whether at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface over which the vehicle is driven;

wherein the one or more vehicle inertial sensors include a pitch sensor and a longitudinal acceleration sensor for measuring the longitudinal acceleration of the vehicle;

wherein the control unit makes a determination that at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface if a pitch rate of the vehicle exceeds a predetermined pitch threshold and the pitch rate is substantially not correlated with the longitudinal acceleration of the vehicle.

13. The system according to claim 12 , wherein the one or more vehicle inertial sensors includes a vertical acceleration sensor and the control unit makes a determination that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface if a vertical acceleration of the vehicle exceeds a predetermined vertical acceleration threshold of the vehicle and a longitudinal acceleration of the vehicle is below a predetermined longitudinal acceleration threshold.

14. The system according to claim 13 wherein the vertical acceleration threshold is reduced if the longitudinal acceleration of the vehicle is below a further predetermined longitudinal acceleration threshold.

15. The system according to claim 12 , wherein

the one or more vehicle inertial sensors includes at least one of a vertical acceleration sensor for measuring the vertical acceleration of the vehicle, a pitch sensor for measuring the pitch of the vehicle, and a longitudinal acceleration sensor for measuring the longitudinal acceleration of the vehicle, the one or more vehicle inertial sensors being connected to the control unit so the control unit receives output signals from the one or more vehicle inertial sensors;

the one or more safety systems includes one or more of a reversible or irreversible seatbelt pre-tensioner and an airbag, and

wherein the control unit is configured to process the output signals received from the one or more vehicle inertial sensors and to determine whether at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface over which the vehicle is driven and activate the one or more vehicle safety systems;

wherein the seatbelt pretensioner will be activated if it is determined that the front air-bag will be triggered and the occupant is out of position.

16. The system according to claim 15 , wherein the control unit is operable to confirm a determination that one or more of the wheel arrangements is not in contact with the surface if the conditions leading to a determination that at least one of the wheels of the front and the rear wheel arrangements is not in contact with the surface persist in excess of a predetermined length of time.

17. The system according to claim 15 , wherein:

the one or more vehicle safety system includes both of the front air-bag and the reversible or irreversible seatbelt pretensioner; and

if a determination is made that one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, the control unit is adapted to make a determination as to whether the front air-bag will triggered when the vehicle strikes the surface, and the control unit is operable to activate, while the one or more of the wheels of the front and the rear wheel arrangements is not in contact with the surface, the reversible or irreversible seatbelt pretensioner if it is determined that the front air-bag will be triggered.