Contactless seat occupation detection system based on electric field sensing

Abstract

In this paper we present an occupant detection system based on a capacitive sensing technique. The capacitive detector is designed to distinguish between an empty and occupied vehicle seat. Additionally, the coupling between the seated passenger and the car-body can be investigated. This occupant detection system provides valuable additional information for airbag controlling system. By launching airbags well matched and controlled, the injuring risk of a passenger can be minimized in case of a car crash. In comparison to standard pressure sensors capacitive sensors are contactless and have no wearing parts [1], this leads to economic benefits. The detector operates in a frequency range between 50 kHz and 5 MHz with 5 mV RMS sine signals, by using a precision impedance analyzer. In our laboratory setup, the car seat measuring assembly is shielded by a copper chassis cage which can be connected either to the low or high-potential of the impedance analyzer or can be kept floating. This feature enables us to analyze the effect of the variable passenger to ground coupling. Each of the 16 sensor electrodes, located at the backrest and seating surface area, can be switched to low potential, high potential or can be left unconnected during a measurement. In order to determine the posture of the passenger body, we record coupling capacitances between single electrode pairs. Furthermore impedance characteristics over a wide frequency range can be analyzed based on appropriate impedance models in order to receive more information about the occupancy status of the car seat.

Finding Common Ground

“…The other option is using a sensor with very high input impedance to detect small displacement currents [50,79]. We refer the reader to additional literature on the various aspects of grounding [68,100,176,202].…”

“…Detecting the presence of adult passengers to ensure the safe deployment of airbags is a common application of capacitive sensing [54,55,202]. Other applications have focused on user distinction [150] and gesture recognition using sensors in the steering wheel [46,166] and armrests [17].…”

“…Hardware for the shunt, transmit, and receive modes is similar and usually consists of an oscillator connected to the transmit electrode to generate an electric field, and an amplifier and analog-to-digital converter (ADC) connected to the receive electrode. In loading mode, [42,64,132,162] →Ink [59,57,58] →Paint [18] →Metalization [208] Gold -non-corrosive, skin-friendly →Gold leaf [98] →Gold coating [11] Aluminum -flexible, high availability →Foil [70,147,196,202] →Mylar [190] Silver -non-corrosive, flexible →Ink [76,87,105,108,203]+ →Thread/Yarn [185] →Plate [67] Carbon -enabling electrical conductivity →Ink [203] →Carbon-filled PDMS (cPDMS) [217] →Filament [20,123,177] ITO -transparent electrodes [64,119,199] Anisotropic materials -directing e-fields →Anisotropic 'Zebra' tape [91] →Anisotropic 'Zebra' rubber [24] Other materials →Water [41,173] & Plants [153] →Ionized gas [72] →Metal objects [43,68,173,207,226]+ →Electro-optic crystal [...…”

Where to Go? Smart Guidance Based on Iot Sensor-Data

“…However, it cannot distinguish between a student and his bag. A more expensive pressure sensor that uses electric field sensing can be used to achieve this (Tumpold and Satz, 2009). Capacitive pressure sensors sense the difference impedance between two areas of a chair to detect the presence of a person.…”

A metamaterial-inspired sensor for combined inductive-capacitive detection

“…Proximity sensing techniques have been developed for many years. [1][2][3][4][5][6][7][8][9][10][11][12] Nowadays, owing to the great significance to many industrial applications, there tends to be a great demand on not only sensing the approaching of the objects but also discriminating between metals and dielectrics. For instance, an automatic drilling machine uses such sensors for intelligently detecting and distinguishing metallic and nonmetallic parts so as to avoid unexpected damages of the drilling bits.…”