It wasn't easy getting Ardie, the quarter-pint animatronic aardvark, to keep up with the documentary's flesh and blood star, said inventor Stefan Hrabar.

Even without a programmed walking pattern and an on-board processor, the full-size, breathing quadruped named Timmy was more than a match for the aluminum-silicon version, especially as night fell and the time came for eating termites. But walk Ardie does. He also turns his head, opens his mouth, and bats his eyelashes.

Wildlife filmmakers Lynne and Philip Richardson, through their production company, Africa Wildlife Films, commissioned the animatron's construction with the hope that he'd help with a behind-the-scenes making of a film that could be packaged along with their main work, a program about the living aardvark.

Hrabar gave life to little Ardie in about three months, while completing an M.S. degree in mechanical engineering at the University of Cape Town in South Africa.

Knowing the complexity of replicating an aardvark's dynamically stable gait, Hrabar decided early that Ardie would have to amble along while keeping three points on the ground at all times. That's distinctly different from a typical quadruped's walk, in which the creature essentially falls into the next step.

Hrabar also began by building legs with two degrees of freedom—a hip and knee—to see how well the animatron could walk without ankles.

At first, the inventor considered powering each limb directly with servo motors on all joints, but quickly discarded the notion for lack of space. Servos would drive only hip movement directly, he decided.

For knee motion, Hrabar experimented with a progression of prototypes—servos driving pulleys and cords in various configurations—until he hit upon a durable solution of servos, gears, and tie rods that produced strong, repeatable torque transmission. As a bonus, hip and knee working together kept Ardie's back from lifting while the foot moved backward.

He found that the servos he had selected initially could not exert sufficient torque to hold the creature upright. He tried high-torque versions of the same motors, but they proved weak as well. The next size motor he dismissed as being too big and costly. Eventually, he shortened Ardie's legs until the high-torque servos could handle the load.

Having proven his concept in wood and plastic, Hrabar switched to machined aluminum in order to make the final legs.

Said Lynne Richardson, "We wanted to come up with another angle for the film." By having the animatron shadow Timmy, the Richardsons wanted to tell the story of the film through Ardie's eyes.

The result, perhaps a bit childish for the main documentary's adult audience, is perfectly suitable for children, Richardson said. Her company is pursuing a possible showing of the mini-documentary through channels that specialize in kids' programming.

Steadiness afoot, or the lack thereof, kept Ardie above ground while on location, even though much of the real animal's story was to be found down in his subterranean burrows. Even without Ardie's participation on this part of the endeavor, the filmmakers and researchers were able to map much of the animal's underground home by tracking him through radio-telemetry.

Teaching Ardie to walk turned out to be a struggle in itself.
Hrabar wrote a software routine to test various gaits. Once he found one that worked, he stored the sequence of moves in the animatronic's on-board processor. In the field, he could move Ardie along by depressing a single button on a hand-held controller.

To speed Ardie along, Hrabar tried shifting the battery pack fore and aft. This helped a little with the walk and gave the creature the mobility necessary to stand up from a seated posture.

The head, jaw, and eye movements worked flawlessly. By communicating with Ardie via cable instead of an infrared remote, Hrabar was able to move the facial features simultaneously and in real time to make Ardie appear as if he were watching Timmy dig.

Hrabar has gone on to the University of Southern California to pursue doctoral studies. The Richardsons remain afield. Timmy is back underground. And Ardie? Let's just hope Hollywood has lots of termites.

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