Finally . . . a Chair That Falls Down and Picks Itself Up Again

Thanks to machine vision, a sophisticated control algorithm, and 14 high-torque servomotors from MicroMo Electronics Inc., Clearwater, Fla., the wait for a self-collapsing, self-assembling chair is over. The battery-operated chair, intended as a work of art, looks like an ordinary kitchen chair until it collapses into six pieces — four legs, a chair back, and a seat which houses the robotics. For a moment, the chair seems lifeless. Then, it begins to move, rolling first to one leg, then another, gathering itself, so to speak. If a leg lands in an inopportune position, the seat nudges it into the proper orientation. After attaching its limbs, the chair seat still rests on the ground. Then, the chair slowly rises in a process designer Max Dean compares to a fawn gaining its footing (See it in action at ). Dean first thought of the chair in 1985. To build it, he teamed with artist and industrial designer Matt Donovan and Raffaello D’Andrea, a professor at ETH Zurich, Switzerland. The biggest challenge, says Donovan, was developing a way to lift the 28-lb chair off the ground. He started with a 26-mm servomotor fitted with a gearhead that provided a 1,526:1 reduction ratio for a peak torque of 4.5 Nm. He added his own 9:1 gearbox for a total reduction ratio of 13,734:1. “We solved the problem with sheer torque, flat out power,” says Donovan. The trade-off is a corresponding drop in speed. “Motors with enough torque to stand the chair up quickly would be too big and increase the weight so much we couldn’t get enough battery power to run them.” The lifting problem solved, Donovan turned to the challenge of attaching the legs. He fitted each leg with a projecting rod pierced crosswise by a hole. The rods fit into corresponding brackets in