MEMS sensors address airbags, body applications
The sensors that control the airbag systems are typically distributed across the vehicle – some are in or near the airbag control system, others are located in the front or rear section or in the doors for early crash detection. The SMA6xy family takes this into account – there are versions available designed for peripheral deployment and for the airbag control unit. The types for peripheral are designed for forces of up to 120g or 480g, depending on the type. In addition to the normal x and y channels, these sensors are In addition to the normal x and y channels, these sensors are also available with a z channel for measuring acceleration in the vertical axis. So whatever the desired orientation of the sensor’s installation, there is a version to match. This gives airbag system developers greater design freedom. Compared to previous versions, the new sensors are better protected against microcuts – extremely brief interruptions in power supply to the sensor as a consequence of an impact. The sensors now tolerate interruptions of up to 10 microseconds.
The implementation for integration in the airbag control unit senses forces of up to 120g in all three axes. To facilitate the requirements of individual car designs, the sensors are available in implementations with one or two axes as well.
The other series of MEMS sensors Bosch released today are designed for utilisation in a broad range of body and ADAS applications – from ESP to hill-hold systems or rollover detection. This series measures forces of up to 35 g and bears the type designation SMI7xy and is optimised robust operation in environments with limited space conditions. Again, this family embraces two categories – the SMI720 and SMI740 are designed for basic applications whereas the SMI700 and SMI710 meet higher requirements. Depending to the application, the devices meet safety levels up to ASIL D (the highest). The SMI700 and SMI710 contain a yaw rate sensor and a 2-axis acceleration sensor each; the axis configuration varies by type. The SMI720 is optimised for rollover detection and contains a yaw rate and an acceleration sensor, each with one axis. The SMI740 features similar characteristics but is optimised for vehicle dynamics control.
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