Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1998-01-29
1999-12-21
Lee, Benjamin C.
Communications: electrical
Condition responsive indicating system
Specific condition
340666, 340667, 340668, 340669, 340670, 340436, 280735, 180271, 180290, 701 45, G08B 2100
Patent
active
060054859
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
The present invention concerns an arrangement: for detecting the type of occupancy of a seat in a motor vehicle.
It is known that airbags are provided in motor vehicles not only for the driver but also for the passenger. However, the passenger's airbag should be activated in an accident only when the passenger's seat is actually occupied by a passenger. If the passenger's seat is not occupied or is occupied only by baggage or a child's seat, activation of the airbag should be suppressed. Activation of an airbag in such cases would cause unnecessary repair costs and could actually be harmful for other occupants of the vehicle due to the additional increase in pressure generated in the vehicle interior. European Patent 0 458 102 A1 proposes deriving a force and/or pressure distribution pattern by means of force and/or pressure sensors to obtain detailed information regarding whether the passenger's seat is occupied by a person or baggage. An example of a force and/or pressure sensor is the pressure-dependent resistance mat (interlink mat) is described in German Patent DE 42 37 072 C1. In Patent Abstracts of Japan, vol. 018, no. 620 (M-1711), Nov. 25, 1994, JP 62 39 173, an arrangement for detecting seat occupancy is described. In this arrangement, several filters are provided to analyze by frequency selection the output signal of at least one sensor provided in the vehicle. A decision-making criterion for whether or not the vehicle seat is occupied by a passenger is obtained by comparing the frequency-selective components.
SUMMARY OF THE INVENTION
The object of the present invention is to create an arrangement for detecting the type of occupancy of a seat in a motor vehicle. That will generate the most reliable possible criterion for deciding whether or not a vehicle seat is occupied by a person.
The present invention is based on the finding that a vehicle seat occupied by a person is exposed to different dynamic movements than when a rigid object such as baggage or a child's seat is placed on it. A person's inherent motion and even his pulse will induce vibrations of different frequency ranges than a rigid object in the seat and a motion sensor provided in the seat. If the output signal of the sensor is analyzed, different frequency ranges are dominant with a person sitting on the seat than with a rigid object. Frequency-dependent analysis of the sensor output signal thus leads to a very reliable conclusion regarding whether the vehicle seat is occupied by a person or a rigid object. Since vehicle operation parameters--e.g., engine rpm or vehicle speed--also have an effect on the occupancy sensor in the vehicle seat, it is expedient to include these parameters in the decision-making criterion derived from the sensor output signal.
BRIEF DESCRIPTION OF THE DRAWINGS
The FIGURE illustrates an exemplary embodiment of the arrangement according to the present invention.
DETAILED DESCRIPTION
The single FIGURE shows a block diagram of an arrangement that detects whether or not a vehicle seat is occupied by a person. Only if a person is sitting on the vehicle seat, i.e., the seat is neither unoccupied nor occupied by a rigid object (e.g., baggage or a child's seat), should a restraint system (airbag and/or seatbelt) be activated in an accident, for example, or a seat heating system be activated. For this purpose, the vehicle seat is equipped with one or more sensors 1. The sensor might be, for example, a piezoelectric cable which is installed in the seat and undergoes changes in its conduction properties as a function of the vibration to which the vehicle seat is exposed because of a person sitting on it or an object placed on it. Instead of a piezoelectric cable, sensors operating according to other physical principles may also be used, e.g., pressure-dependent resistance maL, capacitive sensors, optical fibers, etc., which react similarly to vibrations of the vehicle seat.
The output signal of sensor 1 is sent to an amplifier 2. To this is connected a filter bank 3 which has the fu
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Flaig Helmut
Kursawe Frank
Lee Benjamin C.
Robert & Bosch GmbH
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