December 10, 2012
Cpt. Anthony Ferrari USN
Commanding Officer Naval Research Laboratory
U.S. Naval Research Lab
4555 Overlook Ave.
SW Washington, DC 20375
Enclosed is a copy of our investigation and recommendations for a method of autonomous naval hull climbing robots as requested by Dr. John Montgomery, Director of Research.
Dr. Montgomery requested an assessment of options for robot climbing methods as a replacement for current submarine hull inspection robots, and with long-term goals of augmenting inspection Navy dive teams. Cutting-edge hull scaling methods allow minimal operator involvement and inspection while steaming at full speed.
Due to the immature nature of the field of specialized climbing mechanisms, few solutions showed viability or had been tested for wet surface or submerged conditions. As this was a main criterion, vibrating suction cups show the most promise for immediate applications.
Vibrating suctions cups are currently capable of supporting 11.3kg each, negotiating many surfaces, and attaining speeds of 0.13 meters per second. Vibrating suction cups could be improved for future applications with faster leg motion and tuning of oscillations with ship hulls underwater. Several of the other investigated technologies also show promise for long-term solutions, provided research and testing is done under submerged conditions.
Components Research Division
Encl.: Engineering Report
Office of Naval Research
U.S. Naval Research Laboratory
Whithaus, Carl. Director
REPORT OF INVESTIGATION
ENGINEERING REPORT ON
Adhesion Technology for Wall-climbing Robots
UC Davis Department of Mechanical Engineering
December 10, 2012
Table of Contents
Compliant Microspine Arrays3
Bio-Inspired Dry Directional Adhesives7
Flexible Magnetic Rollers13
Dynamic Magnetic Adhesion15
Impeller Based Suction Cup18
Vibration Suction Cup22
In order to inspect the hull of naval vessels while underway, we recommend the use of vibration suction cups as a method for wall climbing robots to adhere to the skin of a ship hull. Wall climbing robot adhesion technology is crucial to the future of automated ship hull inspection. Current ship hull inspection technology requires either a diver to go in the water, or a remote controlled surveying vehicle. These technologies both require a great deal of human effort and impose stringent restrictions on operating capability during inspection. Navy dive teams require the ship to be at full stop, and many systems to be shut down to reduce risk of injury. Nuclear ships impose even greater restrictions on divers since reactors have less shielding on the bottom, and continue to have potentially harmful radiation levels hours after shutdown. To move away from these human-intensive techniques, an autonomous robot capable of inspecting ship hulls must be developed. Robots for hull inspection are currently used, but are only capable of in-port inspection. These robots are submersibles that move around the ship in the water at low speed. Due to the low speed capability of the robots, ship speed is also very limited. This setback means that a robot capable of hull inspection while the ship is underway would have to adhere to the skin of the hull. The key component of this hull-adhering robot is the adhesion method of the robot. The technologies we have researched for robotic wall adhesion are:
(1) Compliant Microspine Array uses small spines to interact with minute surfaces. Each spine is lifted from the surface and then...