ELVIS: The inside story

Stockbridge, VT-Hiding in an unmarked, unassuming building off a quiet country road in Vermont, Elvis is still swiveling his hips and curling his lips. Contrary to tabloid reports, Elvis doesn't live. He's animatronic.

Powering his 32 individual rhythmic moves is a bevy of pneumatic and hydraulic technologies.

Engineers at Advanced Animations designed and built the animatronic Elvis for Madame Tussaud's wax museum in Las Vegas. Along the way they solved several technical problems, including motion, materials, and vibration damping, among others.

I'm all hooked up. Elvis just wouldn't be Elvis without the trademark sneer and pelvic swivel, and engineers strived to make every move as realistic as possible. It's very different from designing cartoon characters, says Bob Crean, vice president of operations. "Cartoons aren't lifelike, nor would anyone want them to be. With a figure as high-profile as Elvis, we couldn't take any chances."

Engineers began the five-month effort by scrutinizing the section of actual concert tape that Elvis' animatronic double would perform. By studying the exact motions made by the performer, they could then determine the specific mechanisms required to produce them.

"Some people might like you to think it's magic, but in the end it's all a function of the specific linkages in the structure and the technologies we use to accomplish and control the moves," says Crean.

A full third of Elvis' 32 independent moves are in his face, which exhibits a variety of expressions from serious to sneer to slight smile. One of the main challenges was coming up with a way to move the mouth in a natural-looking way. "A human mouth is very complex, since only one motion will affect motions in other directions. When you move your jaw, for example, the chin goes along for the ride, so we had to come up with a linkage that provided cross-axis freedom of motion," explains Crean.

To air is divine. Upper and lower lip moves-which only a handful of animatronics today feature-were crucial to achieving the sneer. Air (both analog and digital), which engineers used wherever possible to minimize cost, produces the muscle motions in both Elvis' face and wrists. "Since it's about one third the cost of hydraulics, we would prefer to use air everywhere, but we frequently need the power density of hydraulics for larger muscle motions," says Crean.

A major challenge with Elvis' face was the skin itself. "What you want is a material that has shape memory, you don't want it to stretch through repeated cycling," says Crean. "These figures go through their routines 16 hours per day, literally millions of operations, and they need to be built to industrial standards." Although he would not divulge the exact formulation or material type, Crean says that Elvis' skin has better shape memory characteristics than the early materials used for animatronics. "Traditional silicone loses its memory and sags, just like a flabby body. This material retains its elasticity, so Elvis has good muscle tone. Not a wrinkle on him."

Hydraulics produce the larger muscle motions in Elvis' arms and torso. Five body motions-torso forebend, torso sidebend, torso twist, pelvis forebend, and body sidesway, help to produce the requisite pelvic motion. A four-bar parallelogram linkage allows for a full 360-degree swivel.

There may be a "whole lotta shaking goin' on" when Elvis performs, but engineers had to figure out a way to damp out unintended body-shaking vibrations. (A certain amount of bounce, of course, is inherent in many body motions.) This phenomenon typically occurs as an animatronic figure quickly accelerates, then attempts to come to a dead stop at the actuator's end-of-stroke. The resulting vibration is merely the dissipation of kinetic energy.

"The challenge is to absorb the kinetic energy and turn it into good-looking motion," says Crean. Engineers smoothed Elvis' moves through the use of hydraulic compliance, which employs servo feedback to control the vibrations. The system gathers force and position signals, using load cells between the cylinder's body and rod end to offset any potential unwanted vibrations.

Finally, to ensure that Elvis is at the right place at the right time during the entire performance, each of his moves is carefully synchronized with the music through a time code overlayed onto each frame of the video-the same way films are produced. Should things get out of sync (only a few milliseconds, at most), a special electrical circuit on the servo cards helps the animatronic slew nicely back to position.

How successful were the engineers in their quest for realism? While reporting this story, we had an opportunity to observe Advanced Animatronics putting Elvis through his paces at the shop. Even without the trademark hair and the lycra jumpsuit, the figure's mannerisms, facial expressions, and pelvis motion were unmistakably the King. Elvis (fully clothed and with hair) can be seen at Madame Tussaud's Wax Museum at the Venetian Hotel in Las Vegas.

Whole lotta shaking goin' on

Design engineers used a combination of pneumatics and hydraulics to achieve 32 independent motions. At about a third of the cost of hydraulics, air was used wherever possible, specifically for smaller muscle motions in Elvis' face and wrists. Electrics were ruled out because of cost and heat dissipation issues.