MetaSensor: Development of a Low-Cost, High Quality Attitude Heading Reference System

Current low-cost solutions to guidance, navigation, and control (GNC) of a small unmanned vehicle (underwater, ground, marine surface, or flight) still cost several thousands of dollars, and offer relatively poor performance at that price point. Tactical grade inertial navigation solutions (INS) run in the several tens of thousands of dollars, and often come with data restrictions due to arms treaties (ITAR). Given that navigation is, at its most basic, the enabling technology for unmanned systems, a lower cost solution becomes an enabling technology for the proliferation of these systems. The design philosophy is to reduce expenditures on sensors (which are expensive), and augment the system with better processing (which is cheap). We have embarked on the development of low-cost Attitude Heading Reference System (AHRS) that is based on MEMs technology sensors. The Metasensor consists of a three axis magnetometer, and three axis accelerometer, and a single axis rate gyroscope. Using novel calibration algorithms to correct for bias and scale factor errors, as well as non-linearities in the sensors, we are able to get superior performance using inexpensive sensors. The attitude is computed using a quaternion based estimation filter that linearizes the attitude in the Navigation frame. Our hardware/firmware combination achieves post-calibration results with standard deviations under 0.7 milli-g’s and 0.6 milli-Gauss on the accelerometers and magnetometers, respectively. Combined with the quaternion attitude estimation algorithms, we are getting static performance with standard deviations of 0.12 degrees in pitch, 0.04 degrees in roll, and 0.08 degrees in yaw, with min to max deviations of less than 0.6 degrees on all axes. The Metasensor is more than just a low-cost AHRS, however. Follow-on work will turn the basic Metasensor into a full dead reckoning navigator capable of providing basic GNC subsystem functions to small UGVs for less than a thousand dollars.