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.
The following list of 7 Top Reasons is just a start, additional reasons and benefits of an accurate IMU are welcomed as responses to this post.