Driving made safer with the new rollover detection MEMS sensors from Bosch. The vehicle rollover protection builds on electronic stability and its three chassis control systems already in the vehicle – anti-lock braking system, traction control and yaw control apart from detection of an impending rollover. Excessive lateral force, generated by excessive speed in a turn, may result in a rollover. It automatically responds whenever it detects a potential rollover and rapidly applies the brakes with a high burst of pressure to the appropriate wheels and sometimes decreases the engine torque to interrupt the rollover before it occurs.
Sometimes, to counteract trip events where a vehicle hit is on the side but kept from moving laterally by a curb would produce a moment about the center of gravity sufficient to produce a rollover, the stability systems incorporate an active suspension system in rollover protection. To accomplish this, the on-board computer uses data from the inertial measurement unit (IMU) to determine when a vehicle is in a rollover condition independent of yaw rate and vehicle speed. When the computer determines that the vehicle is at risk of rollover, it calculates the direction of roll and activates the active suspension system. The force produced in the suspension creates a moment (torque) opposite to that created by the lateral force, and keeps the vehicle safe.
According to the press release, Bosch has launched four types of sensors in two categories: type SMI720 and type SMI740 sensors for basic applications, and type SMI700 and type SMI710 sensors for more demanding applications. The SMI720 sensor is designed specifically for rollover detection. Its housing contains a yaw-rate sensor (x axis) and a 1-axis acceleration sensor (z axis) states the release. A yaw-rate sensor is a gyroscopic device that measures a vehicle’s angular velocity around its vertical axis. The angle between the vehicle’s heading and vehicle actual movement direction is called slip angle, which is related to the yaw rate.
Highlighting the product launch from Bosch, the media release states, “The SMI700’s housing contains a yaw-rate sensor (z axis) and a 2-axis acceleration sensor (x and y axis). This sensor can optionally register high accelerations of up to 35g. In addition to its SPI, the SMI700 comes with a PSI5 interface and a CAN interface – two standard data output interfaces in automotive electronics. These characteristics make the SMI700 the ideal sensor for use in ESP systems and in demanding vehicle dynamics applications such as hill hold control, adaptive cruise control and active front steering. The SMI710 also combines a yaw-rate sensor (x axis) with a 2-axis acceleration sensor (this time y and z axis). It features a PSI5 interface and a CAN interface. This means it is capable of detecting a rollover and meets the requirements for use in demanding driver assistance functions such as roll and pitch stability programs.”