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Automating artwork: motion controllers bring to life a world-renowned art piece doubles as a student laboratory.

Imagine being a prospective student at East Carolina University (ECU) arriving at the sprawling Greenville, North Carolina campus, parents in tow, you're eager to take a look around. Suddenly, two doors on the library's giant clock tower open and a trumpet emerges as a song plays out overhead. LCD monitors are on the clock where the analog numbers are supposed to be and, on the ground, a huge cloud of cold steam envelopes the plaza. Walking further along, a wall of water appears on the right, moving in concert with the music and movements of people walking past. At the far end of the plaza, a group of students dances alongside a bank of columns, but they aren't dancing alongside the columns, they are dancing with the columns. The columns are "singing" to the dancers who respond with moves of their own, and the columns sing in response to the dancers, creating a fully improvisational performance. This plaza has more vibrance and interactivity than the usual mosaics, sculptures, and sundials at other schools. Welcome to the Sonic Plaza, an art installation that shows off the technological advances at ECU while giving students and visitors a chance to participate.

The Sonic Plaza (watch videos at is one of 62 pieces in the North Carolina Artworks in State Buildings Collection spread throughout North Carolina. The public artwork is maintained by the state's Department of Cultural Resources and by ECU. Renowned sound artist Christopher Janney was selected to design the Sonic Plaza, which is comprised of four components: the Ground Cloud, in which a ring of jets approximately 15 feet in diameter produce a cold steam along the ground; the Percussion Water Wall, with 65 water jets that spray in patterns--designed by students--controlled by Arduino based Mega Pro MCU made by Sparkfun and connected to opto-isolated relays which then trigger the DC solenoids of the jets, creating a dancing-water effect; the Sonic Gates, sandstone columns equipped with individual sonar sensors that detect when someone moves through them, triggering one- to four-second musical tones; and the Media Glockenspiel, which resides within the library's 85-foot clock tower.

The Media Glockenspiel is adorned with 12 LCD monitors playing animations created by university art students. A set of doors is perched in the middle of the LCD ring, housing four different sculptures that emerge at specific times. A rooster sculpture comes out at sunrise to start the new day, and the trumpet, with its song, emerges at noon. The school's mascot is a pirate, so what better way to indicate sunset than with a cannon firing complete with smoke. At midnight, an illuminated jester comes out to perform while circus music plays.

The art of the "Artipult"

With four sculptures each taking their turn to perform in the single doorway, a robotic system was designed to open the doors and rotate each sculpture into place. Carl Twarog, professor of animation/interactive design at ECU and curator of the Sonic Plaza calls it an "artipult." The sculptures lie on a linear rack, facing vertically. Twarog uses a four-axis motion controller interfaced with the Sparkfun Arduino board, using one axis to control the trolley motor to place a sculpture perpendicular to the doorway. The second axis sends the sculpture out the door at its specific time. Sunrise and sunset shows are determined by a Java-script program, running on a Mac computer, which is based on the Navy's sunrise-sunset algorithm that not only calculates the time to the second, but also uses the longitude and latitude of six feet in front of the clock tower--the spot where the audience gathers. The other two axes are kept in reserve.

At the precise time a show begins, the computer signals the controller with the digital input (a 1, 2, 3, or 4). After a delay to make sure all shows have the same duration, the controller turns on the Y-axis and moves the rack to align the scultpure with the carriage for its short journey to the doorways. It also triggers the clamp that grabs the sculpture, as well as another analog motor to rotate the sculpture back to a horizontal position before it advances out the doors, which are opened by a hydraulic actuator. Sound plays an important role in Sonic Plaza, so the same computer makes sure the audio amplification system is in sync with each sculpture's show apex. The audio art pieces also come from Christopher Janney and the students.

Twarog uses a Galil DMC-4143 motion controller to bring the Media Glockenspiel to life because it can interface to his Mac with Ethernet 10/100BASE-T. Standard programming features include PID compensation with velocity and acceleration feed-forward, multitasking for simultaneously running up to eight programs, and I/O processing for synchronizing motion with external events such as those of an astronomical nature.

A computer lab and an amusement park

Sonic Plaza is protected by the 1990 Federal Artist Rights Act which is a subset of the copyright law. Therefore, the piece has to be maintained in perpetuity since it is officially considered part of American and North Carolinian culture. "We stuck with the Galil controller because of the support and the ability to better handle the robotic end of things," says Twarog. "They help me out and that support level is essential to keeping the Artipult going."

Keeping the Media Glockenspiel functioning automatically year round also involves participation from many segments of the ECU community. For instance, computers must be able to maintain and upgrade, software must be written, and components need to be replaced. Twarog has been approached by engineering students eager to volunteer their time to learn and contribute their ideas. "They have a real world example of motion controllers so they can see how the axes come into play and how the timing comes into play," Twarog says.

But unlike a typical industrial application that may be safely housed inside a plant, the clock tower has large louvers that present difficult maintenance issues, such as cold temperatures, dust, rain and moisture. When the wind blows, twigs and leaves and the occasional late night beer can find their way into the clock tower and potentially get stuck in the trolley track. These conditions also emphasize the importance of cleaning and lubricating the parts, without creating the grime that may burn out a motor.

"We have all the issues of a computer lab and an amusement park," says Twarog. "From a student's perspective, it's not a worst-case scenario, but you have to think about more than just getting the programming to work. That can be the easy part." Sonic Plaza must work all day, every day.

A piece for generations to enjoy

Sonic Plaza was envisioned with participation in mind, and no matter the student's area of study, they have plenty of opportunities to be a part of this internationally recognized art piece. They may be an art student creating animations for the Media Glockenspiel's LCD screens, or they may provide the sound pieces that accompany the sculptures during their shows, or perhaps write the sketches and patterns for the Water Wall. They may be an engineering student who writes code for the open source processing sketch for the computer that runs the robotics in the clock tower. They may study at the School of Theater and Dance and perform improvisational dances with the Sonic Gates columns. Thanks to Sonic Plaza, students can gain and demonstrate real-world experience to show future employers. They will also have something to show their friends, parents, and alumni, which they will be able to enjoy whenever they visit East Carolina University for generations to come.

Chris Warner, Executive Editor
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Title Annotation:Motion Control
Author:Warner, Chris
Publication:ECN-Electronic Component News
Date:Aug 1, 2014
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