Electromagnetic Induction and Capacitance Dual-Modality Sensor for Seat Occupancy Detection

In the airbag system, it is usually important to determine the status of seat occupancy. In this paper, an efficient seat occupancy sensor has been proposed, which consists of three coplanar coils that arranged in a linear array. By combining the electromagnetic induction and capacitance sensing modalities, the sensor could offer more information in distinguishing between different objects. By exploiting the eddy current measurements, the sensor could detect ferromagnetic and non-ferromagnetic objects, while in the capacitance mode it could distinguish the presence of metallic or non-metallic object. The sensor has been evaluated by the numerical simulations as well as the experiments. Experimental and simulation results indicate that, the sensor can successfully distinguish occupants from metallic objects (ferromagnetic, non-ferromagnetic and earthed-metallic objects) and non-metallic objects, which make it suitable for seat occupancy detection.