To paint from a standstill, a precise CNC mechanism was needed. Rather than use a cartesian motion system, pan and tilt was selected for its smaller general footprint. The two axis of motion can be tightly controlled with two sets of timing belts and pulleys.
Early designs focused on achieving the maximum rotational resolution through gearing and micro-stepping. Higher resolutions allow paintings to be precise and sharp. A mobile painter must be both fast and exact.
SIMPLIFYING THE LAUNCHER
Finding the perfect launcher proved difficult. With desired paintings of six by six feet with high resolution imagery, smaller paintballs were needed. Forced air solutions lack the power to burst smaller paintballs while compressed air solutions jam from smaller paintball residue.
The launcher was redesigned using a new compressed air system and larger .63 caliber paint balls. Although the overall resolution decreased slightly, the algorithm was easily adjustable to fit the new standard.
THE BUILD — LAUNCHER, ALGORITHM, AND WALL
The hopper, the chassis, the trigger, and even the wall were manufactured. Precise press fit components were laser cut using wood and acrylic. Custom pieces such as the launcher mount were 3D printed.
Bearings, collars, and steel axis were mounted following construction using various fasteners. The painting path algorithm was built within MATLAB and ran from Arduino Uno.
The painter ran operationally during demo day through 4 sets of images. As an open loop system, the painter's accuracy gradually degraded over the course of the paintings from vibrational effects and kick back.
In the future, an image processing algorithm paired with a camera can provide precise feedback to the gun. By correcting discrete error, the launcher can operate faster and at even higher resolution.