Because he can fire a baseball over the plate inning after relentless inning, Phillies ace Roy Halladay is sometimes likened to a machine.

With all appropriate deference to the reigning Cy Young Award winner, he is no machine.

Meet PhillieBot, a one-armed, three-wheeled contraption that is scheduled to throw out the ceremonial first pitch before Wednesday's game against the Milwaukee Brewers. It is a robot built by University of Pennsylvania engineers as the headline attraction for Science Day at the Ballpark.

Representatives from various museums and universities also will be on hand to demonstrate scientific principles to ticketholders at Citizens Bank Park.

There will be animals visiting from the Philadelphia Zoo, an explanation of the physics of the curve ball, and exhibits about insects, fossils, and mummies.

And the actual baseball game, starting at 1:05 p.m.

But before humans take the field, PhillieBot will have its moment.

The idea to build a robot pitcher came from Gerri Trooskin, director of the city science festival, which began Friday and runs through April 28. She pitched her proposal to the people at Penn's General Robotics, Automation, Sensing and Perception (GRASP) Laboratory, who were glad to oblige.

On Monday, after a month and a half of assembling parts and writing software in their spare time, Penn engineers Jordan Brindza and Jamie Gewirtz guided PhillieBot out to the mound for a final test.

At the touch of a button, the robot's silvery jointed arm reared back and then moved steadily toward home plate. At the top of its delivery - somewhat sooner than a human pitcher would do - the robot shot the ball homeward with a flick of its mechanical wrist.

The ball appeared to be traveling no more than 30 or 40 miles an hour, but that was by design. More accustomed to pitchers of the human variety, the Phillies organization, to ensure safety, did not want anything approaching the speeds of Halladay and his rotation mates.

Members of the team's grounds crew, busy tending the lush green field, eyed the electronic intruder with apparent skepticism.

But all had been cleared in advance with head groundskeeper Mike Boekholder, who was assured that PhillieBot would not tear up his playing surface.

"It's an interesting deal," Boekholder said of the robot pitcher.

You might think PhillieBot does the same thing as those machines that spit out baseballs at batting cages. But that'd be like describing Le Bec-Fin as a place to grab a snack.

The robot's computer brain can be infinitely tweaked to change pitch velocity and trajectory, and its arm is a sleek, programmable instrument that also can be used in surgical and manufacturing applications. Moreover, PhillieBot can move.

The engineers started with a Segway, one of those motorized, two-wheeled vehicles sometimes used by tourists and police patrols. They lopped off the top handlebar portion and replaced it with the robotic arm, made by Barrett Technology Inc. of Cambridge, Mass. They added a third wheel for stability.

On top of the arm, the engineers attached a "hand" - initially a store-bought plastic scoop used to play jai-alai. But by game time Wednesday, the plan is to have replaced the plastic hand with a lighter, stronger carbon-fiber model made by Christian Moore, a doctoral student in mechanical engineering.

Finally, just underneath the hand, the group attached a pneumatic cylinder, which delivers a burst of compressed carbon dioxide at just the right instant to snap the wrist forward and release the ball.

By game time, the robot will also have a small black head with one swiveling lens for an eye. But it will not be connected to the robot's computer brain, so the machine cannot aim its pitches.

The Phillies decided they were comfortable only with human pitchers with minds of their own.

Yet Brindza, who wrote the computer program that controls the robot's motions, said it would be easy enough to program the robot so it could adjust its pitches based on images captured through the lens.

That way it could lower the pneumatic pressure, say, and deliver a change-up.

Still, don't look for an electronic addition to the actual game any time soon. At least not for the pitching-rich Phillies.

"I know some teams are a little pitching-challenged," Boekholder said. "But we certainly don't have that problem."


Science Day at the Ballpark will feature hands-on activities on the concourse starting shortly before the 1:05 p.m. Wednesday game and during the first few innings.

Regular admission.

Events run through April 28 around the city.

Full calendar of events: or 215-448-1128.

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