Miniature Inertial and Augmentation Sensors for Integrated Inertial/GPS Based Navigation Applications

Recent developments in the miniaturization of inertial instruments and GPS receiver hardware have led to the introduction of small, low cost integrated navigation systems which advertise better than 10 m position accuracy under circumstances where GPS remains available. Under situations where GPS is unavailable or intermittent such as urban, indoor or subterranean environments, navigation performance is limited by inertial sensor performance; given the size, power and cost constraints of miniature systems, currently only tactical grade MEMS gyros and accelerometers (performing at around 1 deg/h and 1 milli-g bias stabilities, respectively) are suitable for use in these applications. Consequently position accuracy rapidly degrades in a tactical grade inertial/GPS system when GPS is denied. To recover navigation accuracy in miniature systems then, it is necessary to use additional sensors (e.g., velocity meters, magnetometers, barometers) and algorithms to augment the inertial system. This paper discusses some of the ongoing activities in the technology development of small inertial navigation sensors and augmentation sensors that could be used to improve performance in applications with little or no GPS signal. A brief overview of developments that could lead to higher performance miniature inertial sensors is presented, followed by a more extensive discussion on miniature magnetometers, velocity meter technologies and MEMS precision clocks and MEMS barometers. Emphasis is placed on component miniaturization and the pathway to future miniature navigation systems. Simulations of position error over time are compared for certain GPS-unavailable missions based on hypothetical IMU performance expected from these inertial sensors, with and without a velocity meter, and with/without barometer and magnetometer. The benefit of higher performing inertial sensors is discussed based on these simulations. Algorithms used to implement integration of barometers This paper is an updated and expanded version of the paper Small Inertial Navigation Sensors for GPS-Unavailable Environments by Barbour, Gustafson, Hopkins, published in the proceedings of the NATO SET 104 symposium, Military Capabilities Enabled by Advances in Navigation Sensors, held in Antalya, Turkey, October 2007. See also ADA569232, Low-Cost Navigation Sensors and Integration Technology (Capteurs de navigation a faible cout et technologie d'integration), RTO-EN-SET-116(2010).