Seven reasons your life depends on an accurate IMU (Inertial Measurement Unit) in a self-driving car

July 06, 2018 // By Mike Horton, CTO at ACEINNA
An inertial measurement unit (IMU) is a device that directly measures the three linear acceleration components and the three rotational rate components (6-DOF) of a vehicle. An IMU is unique among the sensors typically found in an autonomous vehicle because an IMU requires no connection or knowledge of the external world.

A self-driving car requires many different technologies, for example — LIDAR to create a precise 3-D image of the local surroundings, radar for ranging targets using a different part of the EM spectrum, cameras to read signs and detect color, high-definition maps for localization, and more. Unlike the IMU, each of these technologies involves the external environment in order to provide data back to the software stack for localization, perception, and control. This unique “independent” property of the IMU, makes it a core technology for both safety and sensor-fusion.

An accurate IMU can mitigate issues in red.

#1 Safety first

The system engineer needs to consider every scenario and always have a back up plan. Failure Mode Effects Analysis (FMEA) formalizes this requirement into design requirements for risk mitigation. FMEA will ask what happens if the LIDAR, Radar, and Cameras all fail at the same time? An IMU can dead-reckon for a short period of time, meaning it can determine full position and attitude independently for a short while. An IMU alone can slow the vehicle down in a controlled way and bring it to a stop … providing the best practical outcome in a bad situation. While this may seem like a contrived requirement, it turns out to be a fundamental one to a mature safety approach.

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