Contents 1. Introduction
Inertial measurement components, which sense either acceleration or angular rate, are being embedded into common user interface devices more frequently as their cost continues to drop. These devices hold a number of advantages over other sensing technologies as they directly measure important parameters for human interaction and they can easily be embedded into mobile platforms. The operating principles for measuring orientation and position of a moving body using only gyroscopes and accelerometers have been well established in the field of inertial navigation systems(INS) [3], [4]. Inertial navigation is accomplished by integrating the output of a set of sensors to compute position, velocity, and attitude. The sensors used are gyros and accelerometers. Gyros measure angular rate with respect to inertial space, and accelerometers measure linear acceleration, again with respect to an inertial frame. Integration is a simple process, complexities arise due to the various coordinate frames encountered, sensor errors, and noise in the system. Many of the early military applications were closed-loop systems, where the inertial sensors are mounted on a controlled gimballed platform which attempts to remain aligned with the world frame regardless of the motion of the body. Such systems can operate over a much smaller dynamic range and therefore provide higher accuracy, but they also tend to be fairly large and costly.
