Inertial measurement units

Abstract

An inertial measurement unit (IMU) is an electronic device that consists of a set of inertial sensors. The purpose of an IMU is to measure inertial parameters of a moving object, such as the position (including altitude), orientation, velocity, rotation (i.e., angular speed), and sometimes the heading of the object. Inertia is a physical property of a mass to remain at its current state (such as moving along a straight line with a fixed velocity) as long as there is no external force acted upon it. An IMU is equipped with at least an accelerometer sensor and a gyroscope sensor. If the moving direction needs to be determined, one can use an IMU that is equipped with the magnetometer sensor in addition to the accelerometer and the gyroscope sensor. IMU was initially used almost entirely for navigation. That is why the device is also referred to as inertial navigation unit (INU). INU was first used in World War II as part of the inertial guidance system for rockets. It was later also used for spacecraft and aircraft. With the rapid technology development in microelectromechanical systems (MEMS), IMU has significantly shrunk its size and it has been embedded in many wearable devices (such as smartwatches and wristbands) and mobile devices (such as smartphones and tablets). That is why IMU is also referred to as a kind of wearable device.