Dr. M. Anthony Lewis, Director of the Robotics and Neural Systems Lab at the University of Arizona, and Theresa J. Klein (PhD student) have been working on a biarticulate muscle leg model. In a paper published in 2008 (available at the lab’s website), they describe how motors pulled on stiff, tendon-like Kevlar straps to reproduce the action of key muscle groups.
Their new biped robot features an improved leg design that models even more muscles. And it’s already walking (though it relies on a babywalker-like support for balance). It stands 55 cm (22″) tall with the legs fully extended and weighs approximately 4.5 kg (10 lbs).
A relatively simple motor controller based on a central pattern generator (CPG) produces a rhythmic output, causing the muscles to essentially “flex” back and forth. The amazing thing is that a naturalistic walking gait emerges dynamically from the interaction between its musculoskeletal architecture, its reflex system, and the CPG. And their research suggests the CPG stabilizes the walking gait against disturbances.
Similar results were obtained by a quadruped robot project back in 2010 (see PIGORASS ). Meanwhile, the same lab at the University of Arizona is developing a Cheetah robot to compete in DARPA’s legged locomotion challenge (see here).