A Micro Air Vehicle Navigation System

Abstract

A description of the design, operation, and test results of a Micro-Electro-Mechanical (MEMS) based navigation system for the Micro Air Vehicle (MAV) is presented. The MAV is a small Unmanned Aerial Vehicle (UAV) built by Honeywell. It is one of the first applications to use Honeywell's new HG1930 MEMS inertial measurement unit (IMU). The raw IMU measurements are transmitted via a serial interface to a processor board where the inertial solution is blended in a Kalman filter with measurements from GPS, a barometric altimeter, and a magnetometer. The navigation is performed by Honeywell's ECTOS IIc navigation software. The modular ECTOS architecture allows easy customization for use with various IMUs and aiding sources, creating a flexible naviga- tion solution which can be customized to the user's requirements. The MAV has been extensively flight tested both on and off tether. Results are presented showing the performance of the MAV navigation system. I. MICRO AIR VEHICLE OVERVIEW The Micro Air Vehicle (MAV) is a small unmanned aerial vehicle (UAV) built by Honeywell. The MAV's unique design represents a new generation of lightweight, low cost UAVs. The MAV and accompanying ground station can be transported in a backpack by a single soldier, providing unprecedented situational awareness to front line commanders, and short circuiting the traditional long intelligence chain to the field. The airframe is a ducted fan design, allowing the MAV to hover and stare for extended periods of time. Made of lightweight composite materials, the airframe encloses a bladder style fuel tank which provides consistent fuel flow to a small engine regardless of vehicle orientation. The MAV is fitted with forward and down looking cameras, which are located in a payload pod. Exchangeable pods, containing different types of sensors, can be easily mounted in the field without tools. The Micro Air Vehicle environment represents some chal- lenging navigation problems. The navigation system is greatly constrained in size, weight and cost. It must operate in an environment characterized by high vibration and exposure to the elements and extreme temperatures. It must remain functional with temporary degradation or loss of GPS signals, as well as magnetic interference affecting the compass. The navigation system must be simple and reliable enough to be operated by soldiers with minimal training, and be capable of self diagnostics. In addition, the ducted fan design of the airframe presents some unique flight characteristics which the navigation system must tolerate. These include long periods of hovering, high yaw rates, and large forward pitches during flight which can change the visible GPS constellation.