  Robot art presents an opportunity to both showcase and advance
state-of-the-art robotics through the challenging task of creating art.
Creating large-scale artworks in particular engages the public in a way that
small-scale works cannot, and the distinct qualities of brush strokes
contribute to an organic and human-like quality. Combining the large scale of
murals with the strokes of the brush medium presents an especially impactful
result, but also introduces unique challenges in maintaining precise, dextrous
motion control of the brush across such a large workspace. In this work, we
present the first robot to our knowledge that can paint architectural-scale
murals with a brush. We create a hybrid robot consisting of a cable-driven
parallel robot and 4 degree of freedom (DoF) serial manipulator to paint a 27m
by 3.7m mural on windows spanning 2-stories of a building. We discuss our
approach to achieving both the scale and accuracy required for brush-painting a
mural through a combination of novel mechanical design elements, coordinated
planning and control, and on-site calibration algorithms with experimental
validations.
