Autonomous landing experiments with an underwater vehicle for multi-resolution wide area seafloor observation

Abstract

The autonomous underwater vehicle has proven to be an important tool for study of the seafloor. Detailed seafloor analysis often requires wide area observations with high resolution information. Certain sensors require close proximity to the seafloor or contact, with stable footing to perform integrated measurements over a period of time. Such wide area high resolution surveys cannot be performed by a cruising or hovering type vehicle alone. In this research the authors propose a new class of AUV along with a survey technique in which an underwater vehicle can generate meter order resolution wide area maps of the seafloor, but at intermediate locations, obtain higher, centimeter order resolution information by lowering scanning speed and altitude and finally, by landing to obtain micrometer order resolution measurements or to perform integrated measurements at the same position. A new underwater vehicle with slight negative buoyancy has been developed which has hardware and software to perform landing on the seafloor. Since the seafloor can change abruptly and at short intervals, the reliability and functioning of such technology requires real-time seafloor classification for detection of suitable landing sites. A landing algorithm has been developed which uses laser profile data to calculate a landing vector coordinate for safe landing in realtime and this has been implemented on a newly developed landing vehicle. An autonomous landing system has been developed which uses this algorithm to perform landing operations. Experiments were conducted at a tank facility to demonstrate real-time computation of the landing algorithm and autonomous landing of the vehicle using the proposed system. Results from the landing experiments conducted are presented in this paper.