TABLE OF CONTENTS Inertial sensors comprise accelerometers and gyroscopes, commonly abbreviated to gyros. An accelerometer measures specific force and a gyroscope measures angular rate, both without an external reference. Devices that measure the velocity, acceleration, or angular rate of a body with respect to features in the environment are not inertial sensors.
Most types of accelerometers measure specific force along a single sensitive axis. Similarly, most types of gyros measure angular rate about a single axis. An inertial measurement unit (IMU) combines multiple accelerometers and gyros, usually three of each, to produce a three-dimensional measurement of specific force and angular rate. An IMU is the sensor for an inertial navigation system, described in Chapter 5, which produces an independent three-dimensional navigation solution. New designs of INS all employ a strapdown architecture, whereby the inertial sensors are fixed with respect to the navigation system casing. The alternative platform architecture is discussed in Section 5.7. Lower grade IMUs are also used in AHRSs, described in Section 10.1.4, and for PDR using step detection, discussed in Section 10.4. Inertial sensors also have many uses outside navigation as reviewed in [1].
This chapter describes the basic principles of accelerometer, gyro, and IMU technology, compares the different types of sensors, and reviews the error sources. Inertial sensor technology is reviewed in [1, 2].
Most accelerometers are either pendulous or use vibrating beams. Both technologies share the same basic principle and are described in Section 4.1. There are three main types of gyro technology:...
