Inertial sensors are used to measure translational and rotational acceleration. By combining multiple inertial sensors into one inertial measurement unit, the acceleration and rotations around the three axes can be measured in six dimensions while driving. This makes it possible to use one inertial measurement unit for a variety of vehicle applications, as well as for driver assistance systems and automated driving.
dimensions
The inertial measurement unit measures in up to six dimensions: yaw, pitch, and roll rates as well as vertical, longitudinal, and transverse acceleration. Micromechanical measuring components are used to collect data. The yaw rate is recorded using the Coriolis principle, which uses the force of inertia of a swinging mass in a rotating system.
Due to the high resonant frequency of 25 kilohertz and the closed drive and evaluation circuit, the unit is very robust against mechanical disturbances. The acceleration is measured using the capacitive change in micromechanical structures.
Even for assisted driving, the specific requirements related to accuracy, reliability, and availability of the system can be stringent. And this applies even more to automated driving, since the driver hands over the responsibility for driving to the system and no longer has to monitor it. For this reason, ensuring the safety of the passengers throughout the entire system is absolutely crucial. Highly accurate, reliable localization is therefore essential, which is typically achieved by combining multiple technologies – such as surround sensors, satellite navigation, and inertial measurement units – and providing redundancy.
If the features of the surroundings are not enough for exact localization or the satellite connection is disrupted, inertial measurement units come into play. The overall system compensates for the missing information by calculating the vehicle’s relative change in position using information from the sensors, which maintains the localization and allows the entire system to remain active. Standard inertial sensors, however, are not sufficiently capable in this regard to satisfy the precision and performance requirements. Therefore, Bosch has developed highly precise inertial sensors especially for this purpose, which are part of a modular product family. This includes three variants, each of which are designed for specific markets and vehicle segments.
The modular approach of the inertial measurement unit meets a variety of performance requirements and covers a wide spectrum, from the affordable entry-level option to the high-performance sensor. With this high level of precision, the overall system – and therefore the vehicle – can keep to the originally planned path with only minimal deviation.
If critical errors are detected in the overall system and the driver is unable to take back control of the vehicle, the relative direction of travel of the vehicle can be determined using, among other information, the data from the inertial sensors, and the vehicle can be brought to a stop safely and reliably if needed.
Thanks to the integrated microcontroller, it is possible to process the output signals individually for different applications and make them available to multiple higher-level systems simultaneously. Preimplemented calibration functions and a standardized software architecture (AUTOSAR) enable flexible integration at the vehicle level.
In addition to this, the equipped hardware security module (HSM) protects the sensor data from being externally manipulated, adding to the safety of the overall system.
The inertial measurement unit contributes to the functionality of active and passive safety systems such as ESP and the airbag control unit; it also supports driver assistance systems such as adaptive cruise control. Thanks to the integrated microcontroller, it offers improved computing power. It enables a variety of applications that significantly improve the driving and parking experience.
These include advanced ABS and ESP, which ensures shorter braking distances and improves stability and vehicle dynamics. In addition, smart chassis control offers an improved driving experience and more sportiness, while stabilized trailer handling and improved off-road capabilities offer additional benefits.
Are you interested in our solutions? Then write us a message. Our sales team will be happy to help you.
