The remediation of graffiti from highway signs is a labor intensive and potentially hazardous task. Accordingly, this paper presents the initial design stages of tools that could be used to clean graffiti from signs. Two design concepts are presentedone for pedestrian accessible signs and one for overhead signs -and the concepts share a common end-effector design. The paper is primarily aimed at developing an understanding of the interactions between the end-effector's scrubbers and the sign's resultant retroreflectivity. This is accomplished through a factorial experiment to test the effects of load, speed, brush type, and sign surface material on the retroreflectivity. This work shows the feasibility of such a tool for cleaning graffiti from signs along the roadways.
This article reports on the testing and comparison of a prototype hydrogen fuel cell light tower (H 2 LT) and a conventional diesel-powered metal halide light trailer for use in road maintenance and construction activities. The prototype was originally outfitted with plasma lights and then with light-emitting diode (LED) luminaires. Light output and distribution, lighting energy efficiency (i.e., efficacy), power source thermal efficiency, and fuel costs are compared. The metal halide luminaires have 2.2 and 3.1 times more light output than the plasma and LED luminaires, respectively, but they require more power/lumen to provide that output. The LED luminaires have 1.6 times better light efficacy than either the metal halide or plasma luminaires. The light uniformity ratios produced by the plasma and LED towers are acceptable. The fuel cell thermal efficiency at the power required to operate the plasma lights is 48%, significantly higher than the diesel generator efficiency of 23% when operating the metal halide lights. Due to the increased efficiency of the fuel cell and the LED lighting, the fuel cost per lumen-hour of the H 2 LT is 62% of the metal halide diesel light tower assuming a kilogram of hydrogen is twice the cost of a gallon of diesel fuel.
This paper presents a planar, underconstrained cable robot designed to operate on the vertical face of overhead roadway signs. The cables that actuate the robot extend over a set of rotatable pulley arms mounted at the top corners of the sign. The redundant degrees of freedom due to the pulley arms allow for improved force generation ability of the robot at all desired locations on the sign. Redundancy is resolved by optimizing the anisotropic force generated in a desired direction. There are four distinct solution regimes dependent on the desired force angle. Of the four solution regimes, two are constraint-bound solutions for each cable force and the complementary cable angle based on monotonicity analysis. The two additional solutions are constraint-bound in the cable angles resulting in a fixed geometry, and the well-known attainable force set solution is applied.
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