Axially Symmetric Quadruped Moves in Any Direction

When we think of a legged robot, something like Boston Dynamics’ SpotMini or hexapods of many forms typically come to mind. These can move in many different amazing ways, but normally have a front and back and sets of left and right legs, similar to other land animals. What if, however, four legs were arranged symmetrically about a central axis? As shown by ALPHRED2: Autonomous Legged Personal Helper robot with Enhanced Dynamics by Dennis Hong’s RoMeLa lab (Robotics and Mechanisms Laboratory) at UCLA, this kind of configuration can mean all kinds of exciting movement possibilities — not to mention an impressive array of acronyms.

ALPHRED 2 can get around with its four symmetrical legs or push a button using one of its limbs as an arm. (📷: RoMeLa)

Using its axisymmetric configuration, ALPHRED2 can run, walk, and jump in any direction without a front-back preference. It can also use its appendages to manipulate and carry objects, even sitting down for better stability and reach when needed, then standing up to reach a higher plane. Finally, the bot can go into a sort of tripod mode to let the fourth leg/arm knock on a door, or as seen at just after 2:00 in the video below, punch through a board in an impressive display of robotic martial arts (Panzer Kunst?).

ALPHRED2 can stroll at stable speeds of up to 1.5 meters per second — or around 3.4 miles per hour — and can accomplish bipedal motion, though this is a less reliable as of now. It can also scoot around with the body lowered to the floor and the legs pushing, which looks extremely efficient in the correct circumstances. The build uses custom actuators for motion, with a DC motor, 10:1 gearbox and optional liquid cooling, which produce a maximum torque of 32 Nm — roughly 24 ft-lbs.

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Author: Jeremy S. Cook

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