Bipeds keep getting better. Instead of slow, heavy, and terrain-sensitive humanoids like ASIMO, researchers are building lightweight and agile bird-like robots, such as Cassie. The better the designs are mechanically, the less power and smarts are required to keep the robot upright. This is a virtuous cycle that's an encouraging sign that some of these biped research projects might actually be useful someday.

The Institute for Human and Machine Cognition in Florida just unveiled its Planar Elliptical Runner (via Engadget), and this robot is all mechanics. A single motor in the middle of the robot drives the legs in an elliptical motion, and the side-to-side motion of the robot is inherently stable when running — meaning it won't fall forward or backward.

The mechanical design also includes torsion springs which drive more power to a leg if it meets resistance, and moves the opposing leg accordingly, making the robot dynamically stable, without a power-hungry CPU in the loop crunching numbers and making decisions based on sensor data.

The dog-sized robot can run up to 10 mph, and the researchers say a human-sized version could run at 20 or 30 mph. Its throttle is controlled with a simple RC controller.

Right now, the robot runs with glass walls on each side to keep it going straight, which feels like cheating, but, according to simulations, the researchers think they know how to build a version that's stable from side to side without the walls for guidance.