Apparatus for probing a conductive body and its application in a vehicle-airbag control system

摘要

The system for detecting the body position of a front seat vehicle passenger in order to modify commands to an airbag uses the capacitative coupling between emitting electrodes (11,12), the passenger (10) and receiving electrodes (14,15,16). Signals transmitted by an emitting electrode are received at an intensity which depends on the distances between the passenger and both the emitting and receiving electrodes. Confusion with signals emanating from other vehicle equipment or from the environment is avoided by cyclic or repetitive signal modulation. Very rapid changes in passenger body position, for example during braking before a crash, may be detected and incorporated with the static measurements by using the frequency change in a reflected wave compared to an incident wave.