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FIELD AND SPACE ROBOTICS LABORATORY |
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Down-Well Tactile Exploration
Principal investigator Steven Dubowsky Group members Dan Kettler, MS student; Francesco Mazzini, PhD student
Motivation Modern oil wells are composed of a main well and several lateral wells that depart from it at different depths and with different angles. Rising oil demand, increasing oil prices, and improved extraction technologies make the exploitation of abandoned lateral branches economically valid. In order to re-enter and rehabilitate these branches, the position and the shape of the junction has to be known with accuracy. The harsh down-well environment makes this problem challenging. The presence of a viscous and opaque fluid prevents the use of any visual or laser sensor. Acoustic sensors do not provide the desired resolution. Finally, very high pressures and temperatures down-well complicate the use of any sensor including force-torque sensors. Approach The proposed solution is tactile exploration with a robotic arm. This arm would be mounted at the end of a down-well tool and brought close to the junction. Once this base is fixed, the robot starts the autonomous tactile inspection: like a man finding his way in a dark room, the tip of the robot is moved in order to touch different points on the surface of the junction, creating a detailed map of its geometry.
A model of the four-link manipulator while exploring the junction
Kinematic design Since a well junction is a highly constrained space, a specialized kinematic design is required. A number of different solutions have been analyzed, and it was discovered that kinematic redundancy is necessary. The design chosen consists of four independent links: a first translational joint along the main well axis and a three-link anthropomorphic arm. An experimental version of the manipulator and down-well junction is currently under construction in our laboratory.
Exploded view of the manipulator under construction (well junction not included)
Autonomous exploration Concurrently with the design and construction of the manipulator, the control strategies required by such a system are being developed and tested. The robot, provided with only joint angle sensors, needs to autonomously move in the environment and tactily probe the surface. Information obtained this way is used to incrementally guide the robot in order to complete the exploration in the least possible time, and to create a three-dimensional map of the environment. As a generalization of the oil well problem, this approach is currently being extended to the tactile mapping of a generic man-made environment. The primary areas of investigation are:
Workbench experiments for exploration of a generic environment
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