Researchers at EPFL’s Biorobotics Laboratory (Biorob) announced a cat-like robot that is claimed to be the fastest quadruped robot under 30 kilograms. The Cheetah-cub Robot, which runs real-time Xenomai Linux on an x86-based RoBoard control board, mimics the biomechanics of a cat to increase the speed and stability of it quadroped legs, helping it achieve speeds of 1.42m/s.



The Cheetah-cub Robot was developed at the Biorob lab at Switzerland’s École Polytechnique Fédérale de Lausanne (EPFL), and announced in the June 17 issue of the International Journal of Robotics Research. The goal of the still early-stage project is to encourage research in biomechanics, with an aim toward building faster robots for search and rescue, or ground exploration.





Biorob Cheetah-cub Robot

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While previous EPFL designs have included robots based on salamanders (Amphibot) and lampreys (Salamandra), the Biorob researchers this time based the robot’s 15cm legs on a close study of the cat. The tri-segment “pantograph” leg design incorporates springs used to reproduce tendons, and actuators that replace muscles. The robot’s legs, which move with eight active degrees of freedom in a coordinated trot gait, are each actuated by two RC servo motors, which manipulate hip and knee joints.





Cheetah-cub Robot design features

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According to EPFL, the 1.1Kg (2.4-pound) Cheetah-cub Robot is the “fastest in its category, namely in normalized speed for small quadruped robots under 30Kg.” Operating on a tethered 8-14 V power supply, the WiFi-enabled robot was tested at moving at speeds of 1.42m/s, or nearly seven times its 21cm body length in one second. A special focus was given to auto-stabilization when running at full speed over an obstacle course.



Xenomai Linux inside

The Cheetah-cub Robot runs on a real-time enhanced version of Linux from Xenomai.org on a RoBoard RB110 robot control board. Xenomai is a hard real-time version of Linux based on the earlier RTAI (Real-Time Application Interface), and is on the road toward integrating PREEMPT_RT patches for greater integration with mainstream Linux kernel development.

RoBoard’s RB110 single-board computer (SBC) incorporates DM&P’s 1GHz Vortex86DX system-on-chip. (See its block diagram on the right; click image to enlarge.) Like other x86-based Vortex designs from DM&P, the 32-bit SoC is optimized for low power consumption, in this case claimed to be less than 1 Watt.

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RoBoard RB-110 SBC plain, and with feature callouts

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RoBoard’s 96 x 56mm, 40g RB-110 is equipped with 256MB of DDR2 RAM, as well as an Analog Devices AD-7918 ADC and a FTDI high-speed UART. A microSD slot and USB 2.0 port are combined with connectors for PWM, IDC, USB, Ethernet, mini-PCI, JTAG, and a variety of serial ports. Power consumption is claimed to be +5V @ 400mA.

The robot’s Linux-based brain works in conjunction with central pattern generators (CPGs), which EPFL describes as “networks of coupled neurons that can produce complex locomotor patterns while receiving only simple command signals from upper parts of the brain.” The CPGs help the robot move using a variety of trot-gait like locomotion patterns over an uneven surface. A special focus was given to biomechanically feasible control parameters like amplitude and offsets of hip oscillations, frequency of the locomotion cycle, phase relationship between hip angle and knee angle, and leg cycle duty factor.

The short YouTube video below provides a brief introduction to the CheetahCub Robot, and demonstrates it in action.







CheetahCub demonstration video

More information on the in-progress Cheetah-cub Robot may be found on EPFL’s Cheetah-cub Robot announcement page, as well as this description of the robot’s trot gain locomotion (PDF download), and this research paper (PDF download) on the same topic.

(Note: CheetahCub images are copyright Biorobotics Laboratory, EPFL)

