Magnetic Guidance of Autonomous Vehicles

Increasing interest in underwater autonomous vehicles has resulted in a search for suitable guidance systems. Magnetic techniques could provide supplementary guidance for autonomous vehicles that need occasional precise position fixes to update their standard navigational systems, or that want to return to a particular spot on the ocean bottom with great accuracy. A small permanent magnet resting at a precisely known spot on the ocean´s bottom or naturally occurring key features in a magnetic survey of the bottom could provide the necessary magnetic signal. Of the several magnetic guidance approaches considered, an adaptive search technique seems the most promising. In adaptive search, the location of each successive search pass is determined by information gathered on the previous pass. Computer simulation results show that three search passes are usually sufficient to locate the center of the magnetic anomaly to within several feet. The favored sensor configuration is a scalar magnetometer whose outputs are successively subtracted along the path of sensor motion to form an approximation to the spatial gradient of the sensor´s output. Data interpretation for this technique appears simple enough to be done automatically by either algorithmic or artificial intelligence techniques.