Mechanical and Aerospace Engineering

MAE Ph.D. EXIT SEMINAR – By: Sean Donohoe

Development of a Graffiti Removing and Sign Cleaning Cable Robot 
By: Sean Donohoe Advisor: Professor Steven Velinsky 

This work focuses on the problem of graffiti removal from large overhead roadway signs. These signs are
important to the operational efficiency of the national road network and when they are painted with graffiti they
must be cleaned. Removing graffiti from these signs is often a labor intensive and dangerous proposition. As
such the goal of this work is to find a safer way to clean these signs. The cable robot is selected as the
particular type of robotic architecture to address this problem. In order to decrease worker exposure time,
setup time is decreased by only requiring two cable actuators be mounted to the sign. Using fewer cables
decreases setup time, but due to the well-known properties of such systems, it generally reduces the usable
workspace. As such, a novel cable robot system is developed that uses a set of pulley arms that can rotate in
the plane about their mounts over large angles while the system is operating. As the arms rotate, the
orientation of the cables that they guide is modified. This gives the system redundant degrees of freedom that
are not typically available with most cable robots. To take advantage of these extra degrees of freedom while
also reducing the redundancy, the net force that the end-effector can generate in an instantaneous anisotropic
desired direction is maximized. Through simulation, it is shown that maximizing the net force in a desired
direction improves the system’s performance. This work develops a workspace methodology that allows the
effect of moving the arms to be included. A proof of concept prototype is built to ascertain the suitability of the
system. This includes force generation ability, comparison to the theoretical results, and path following ability.
2  Full Abstract

Date/Time
Date(s) - 08/25/2014
2:00 pm - 3:00 pm

Location
2130 Bainer - MAE Conference Room

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