In contemporary cars, the implementation of occupancy classification systems has become an increasingly standard configuration of security functions. At the time of the collision, the OCS ensures that the airbag is opened Sensor in the most efficient way to protect passengers and avoid injury. It is through the use of some form of sensor technology to determine the occupant's height and size.
The sensor system will first confirm whether a passenger occupies a seat and evaluates the physical characteristics of the passenger. Subsequently, this information is transmitted to the electronic control unit (ECU) in order to decide what kind of reaction to make, so that the airbag is triggered at full speed or at a slower speed. Early OCS systems often use a reasonable basic sensing mechanism, including a pressure sensor embedded within the seat frame, which can be used to measure the weight of the occupant and thus derive a rough height data. Similar to other methods used to estimate the tension through the seat belt, this method is also inaccurate. First, the correlation between weight and height can not be accurately determined. The above method does not take into account some other possibilities, such as the seat of the loaded goods box, rather than occupying Suction Control Valve the seat of the passengers, because this technology can not confirm in the seat is a passenger or other items without life. In addition, it is also very expensive to integrate sensors inside the seat frame, especially if maintenance or replacement is required.
As children's taller seats and rear-facing infant seats begin to appear on the market, the need for traditional technological change is further highlighted, which has also raised concerns about how to deploy airbags. Therefore, the automotive industry now has a trend is to adopt a more complex classification system, and often use the most is the photoelectric technology.
In the use of visible light as the OCS induction mechanism, of course, there are day / night light level changes, which requires the system should include active lighting inside the vehicle. Hats, long hair, beard, brightly colored items, clothing, etc. can also have an adverse effect on the optical classification process. Thus, this sensor technique and its accuracy for the judgment Pressure Sensor of irregularities is a major problem. Visible light sensing systems require considerable processing power and are equipped with fairly expensive microcontrollers.
One of the great advantages of far infrared imaging systems is that it can better distinguish between inanimate objects and a true passenger because of its ability to detect heat radiation at the frequency of the body's heat. This method does not depend on ambient light, there is no performance difference between day and night, so there is no need to take the initiative in the car lighting. In addition, it requires a relatively small processing power. Finally, these two points make the complexity and cost of the whole system significantly reduced.
The OCS based on the FIR mechanism does not require a wide dynamic range, and the sensor array needs to be able to operate between -40 ° C and 85 ° C. The requirements for optical resolution are not too harsh because the location of the passengers will be in a known area. But the thermal resolution is very important and needs to be in the range of ± 0.25oK. It is important to consider the thermal effects of sunlight entering the interior. To achieve this, the filter is required to filter out the visible and near infrared (NIR) spectra, so that these do not interfere with the sensor in any way. While the signal processing ABS Sensor of this type of sensing system is simpler than the visible light sensor, it still needs to reduce the overall complexity in order to ensure that the operating speed and signal to noise ratio are relatively high while reducing system cost and ease of implementation.
Melexis has a cost-effective FIR sensor array with technology from HeimannSensorGmbH, which combines high-sensitivity thermostatic stack technology with cutting-edge and streamlined signal processing capabilities. Each FIR detector has multiple A thermocouple sensor unit can be used to create a simple calorific value graph for the target area in real time. Each thermocouple unit in the array has its electrical signal amplifiers and data converters, which avoids time reuse of the thermostat stack signal, greatly reducing signal noise, and it also provides the necessary performance without Need to deliberately use a more expensive micro-radiation thermal equipment.
The FIR sensor array greatly simplifies the thermal imaging system, which, once integrated, captures data from 64 pixels immediately. It has an adjustable frame rate that is sufficient to support even the most demanding OCS system required for performance. When operating from 0 ° C to 50 ° C, the accuracy level of ± 1.5 ° K can be maintained. For each component of the sensor components, have their own signal processing capabilities, visible light OCS system noise problems here can be effectively avoided. In addition, the interface Speed Sensor is also easier to implement. The use of a high-speed I2C-compatible digital serial interface and a trigger mode synchronized with the control unit means that these devices can be used not only for stand-alone use but also in the case of a need to form an array with higher imaging resolution.
The importance of developing more efficient automotive safety systems can not be underestimated. The use of airbags has played a significant role in reducing the number of deaths, but there is still a need for further reductions. The passive occupancy recognition mechanism is being replaced by an intelligent system that can better determine who or what items are on the passenger's seat in order to further improve the effectiveness of the airbag deployment, thus minimizing the risk of harm. By implementing more advanced optoelectronic technology-based OCS systems, greater progress can be made in the safety of passengers. But it is clear that, due to changes in the level of light and other irregular behavior, work in the visible spectrum of the sensor often performance will be reduced. The FIR sensing technology Throttle Position Sensor is able to provide the same or better performance at a much lower data processing cost than the visible light program, so it can be used by car manufacturers more.