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Quadruped Linux robot feels its way over obstacles

Aug 2, 2013 — by Eric Brown 1,535 views

The Italian Institute of Technology gave its first public demonstration of a Linux-based quadruped robot for navigating rough terrain. Meanwhile, a new version of the Hydraulic Quadruped (Hyq) robot is under development that can “feel” and step over obstacles using a step reflex algorithm, letting the robot navigate more easily in low-visibility environments.

Linux-based robots come in all shapes and sizes, from Biorob’s ankle-high Cheetah-cub Robot to the knee-high models that can be built from the Lego Mindstorms EV3 robot kit to NASA’s full-scale humanoid Robonaut 2. In the heavyweight class, we’ve seen Micromagic Systems’ 2.8-meter, 1800-Kilogram Mantis Hexapod Walking Machine. Now, the Department of Advanced Robotics at the Istituto Italiano di Tecnologia (Italian Institute of Technology, or IIT), has developed another heavyweight contender in the Hydrolic Quadruped (Hyq) robot.

IIT’s Hydraulic Quadruped robot (aka “Hyq”)
(click image to enlarge)


Like the Boston Dynamics RTOS-based Big Dog (pictured at right; click to enlarge), the Hyq (pronounced “high-cue”) is a Great Dane-sized quadruped robot designed to navigate over rugged terrain. It’s not as big and bad as the BigDog, let alone Boston Dynamics tougher, mule-sized LS3, and it can’t haul as big of a load. However, it does appear to be more nimble than any quadruped robot to date.


IIT announced the torque-controlled, hydraulically actuated Hyq last year, and released its first video demonstration in May. On Aug. 1, the Hyq gave its first public performance at the Living Machines conference at the London Natural History Museum, according to a Spectrum.IEEE report picked up by Engadget.

Thanks to its hydraulic actuators and clever programs running on a Xenomai Linux-based Pentium computer, the Hyq can walk, trot, jump, and kick. It can reach a top speed of up to two meters per second, jump a half meter high from a squat position, and can balance on unstable ground, according to IIT.

Hyq and its CAD rendering
(click images to enlarge)


A new version of the Hyq robot is under development that breaks new ground in robot obstacle avoidance, according to Spectrum.IEEE. With the help of a new step reflex algorithm, the Hyq’s sensors can feel its way over obstacles without relying on vision systems. The Institute recently posted a video demo showing the robot nimbly stepping over 11-centimeter planks (see below).

As Spectrum.IEEE’s Erico Guizzo explains, falling is a huge problem for heavy — not to mention expensive — robots like the Hyq. Unlike the knee-high Linux-based Aldebaran Nao (pictured at right; click to enlarge), big robots like the Hyq fall hard enough to break, and they can’t easily pick themselves back up.

“Robots don’t handle falls very well,” writes Guizzo. “Their stiff metal bodies can’t absorb shocks, and a crash often means broken parts and costly repairs.” Cameras can help avoid obstacles that might cause falls, and infrared cameras can handle typical darkness conditions, but cameras don’t work in heavy foliage or smoke. LIDAR systems can help penetrate such interference to some degree, but are very expensive.

As an alternative approach to obstacles, the IIT developers are adding step reflex algorithms that can react quickly to falls. The HyQ robot measures external forces on its feet. When the force reaches a certain threshold, a step reflex is triggered. It first absorbs the impact with its hydraulically compliant legs, and then steps higher than normal to help clear the obstacle.

The YouTube video below demonstrates the HyQ robot’s new animal-like step reflex.

Video demonstrating the HyQ robot’s new animal-like step reflex


The IIT is continuing to refine the method while also working on improving the vision system. It’s also developing “more dynamic gaits like bounding and galloping,” says the story.

Xenomai Linux under the hood

Like the similarly quadruped Cheetah-cub Robot (pictured at right; click to enlarge), the Hyq processes its algorithms using Xenomai real-time Linux on an x86 processor. In the case of the Hyq, it runs on an onboard Pentium-based PC/104 board, according to the IIT Advanced Robotics Hyq web page.

The 70 Kg robot measures 1 x 0.98 x 0.5 meters and has four jointed legs, each with three degrees of freedom (DoF). Of these 12 DoF sources, eight are hydraulic and the other four electric. Its joint range of motion is said to be 120 degrees.

Powered by DC brushless motors, the Hyq is equipped with 80mm-stroke, 16-bore hydraulic cylinders, and offers 145Nm maximum hydraulic torque and 152Nm for electric. The Hyq has sensors that measure the position and torque on each joint, as well as cylinder chamber pressure, inertial measurement unit (IMU), and hydraulic system.

Future applications for the Hyq include search and rescue, forestry, construction, and firefighting, as well as inspection and exploration tasks. The Hyq recently had its first sale when IIT sold a unit to ETH Zurich’s Agile and Dexterous Robotics Lab.

More information on the Hyq may be found at the IIT Advanced Robotics Hyq web page.

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