Device and method for differentiating between a person and an object on a motor vehicle seat using multiple sensors

1. A device for distinguishing whether a person is seated on a seat surface of a motor vehicle seat or an object is disposed thereon, the object having a substantially planar contact surface covering a large part of said seat surface, including a central area thereof, the device comprising:

a seat mat carrying a plurality of weight sensors distributed over the seat surface of the motor vehicle seat, said weight sensors including first weight sensors disposed in a central area of the seat surface and second weight sensors disposed in a region of the seat surface covered by the object and outside the central area;

at least one of said first weight sensors being different from a plurality of said second weight sensors within a weight range to be detected by the device such that said at least one first weight sensor always emits a sensor signal that is lower by more than a rated measuring inaccuracy of the device when subjected to an equal weight load.

2. The device according to claim 1 , wherein said at least one first weight sensor, when subjected to the same weight load, emits a sensor signal that is lower by 50% than at least one of said plurality of second weight sensors.

3. The device according to claim 1 , wherein said at least one first weight sensor, when subjected to the same weight load, emits a sensor signal that is lower by 30% than at least one of said plurality of second weight sensors.

4. The device according to claim 1 , wherein said at least one first weight sensor, when subjected to the same weight load, emits a sensor signal that is lower by 5% than at least one of said plurality of second weight sensors.

5. The device according to claim 1 , wherein said at least one first weight sensor is one of a plurality of first weight sensors having substantially identical features.

6. The device according to claim 1 , wherein the object is a child seat.

7. The device according to claim 1 , which further comprises an evaluation unit disposed to receive signals issued by said first and second weight sensors.

8. A method for distinguishing whether a person is seated on a seat surface of a vehicle seat or an object with a substantially flat bearing surface extending over a large part of the seat surface, including a central area thereof, is disposed on the seat surface, the method which comprises:

providing a device with a seat mat having a plurality of weight sensors distributed over the seat surface of the vehicle seat, and an evaluation unit connected to receive signals of the weight sensors;

detecting a first signal of at least one first weight sensor disposed in a central area of the seat surface;

detecting second signals of a plurality of second weight sensors disposed outside the central area, in a region of the seat surface covered by the object;

comparing the first signal of the first weight sensor with the second signals of the second weight sensors; and

determining that the object is present when the first signal of the first weight sensor is less than 50% of at least one second signal of a second weight sensor.

9. The method according to claim 8 , which comprises determining that the object is present when the first signal of the first weight sensor is less than 30% of at least one second signal of a second weight sensor.

10. The method according to claim 8 , which comprises determining that the object is present when the first signal of the first weight sensor is less than 5% of at least one second signal of a second weight sensor.

11. The method according to claim 8 , which comprises the following steps:

detecting the signals of a plurality of first weight sensors;

detecting the signals of a plurality of second weight sensors, wherein the second weight sensors are disposed outside the central area in a region of the seat surface covered by the object;

comparing the signals of the first weight sensors with the signals of the second weight sensors;

detecting the object as soon as the signal of at least one first weight sensor is less than 50% of at least one signal of a second weight sensor.

12. The method according to claim 11 , which comprises detecting the object as soon as the signal of at least one first weight sensor is less than 30% of at least one signal of a second weight sensor.

13. The method according to claim 11 , which comprises detecting the object as soon as the signal of at least one first weight sensor is less than 5% of at least one signal of a second weight sensor.

14. The method according to claim 11 , which comprises detecting the object as soon as the signals of the first weight sensors are less than 50% of the signals of the second weight sensors.

15. The method according to claim 8 , which comprises, upon determining that the object is present, entering a setting that an activation of restraint means for occupants in a motor vehicle should always be suppressed.

16. A method for distinguishing whether a person is seated on a seat surface of a vehicle seat or an object with a substantially flat bearing surface extending over a large part of the seat surface, including a central area thereof, is disposed on the seat surface, the method which comprises:

providing a device with a seat mat having a plurality of weight sensors distributed over the seat surface of the vehicle seat, the weight sensors including first weight sensors disposed in a central area of the seat surface and second weight sensors disposed in a region of the seat surface covered by the object and outside the central area, and at least one of the first weight sensors being different from a plurality of the second weight sensors within a weight range to be detected by the device such that the at least one first weight sensor always emits a sensor signal that is lower by more than a rated measuring inaccuracy of the device when subjected to an equal weight load;

providing an evaluation unit connected to receive signals of the weight sensors;

detecting a first signal of at least one first weight sensor disposed in the central area of the seat surface;

detecting second signals of a plurality of second weight sensors disposed outside the central area, in the region of the seat surface covered by the object;

comparing the first signal of the first weight sensor with the second signals of the second weight sensors; and

determining that the object is present when the first signal of the first weight sensor is less than 50% of at least one second signal of a second weight sensor.