Research RHex: Robotic Hexapod


The RHex project arose from an earlier DARPA DSO effort initiated within the 1998 CBS/CBBS program called Computational Neuromechanics. In this prior work our team addressed hypotheses about the organization of locomotory control in animals in a mathematically sound and empirically refutable manner while exploring as well the prospects for using MEMS technology to create effectively an electronic harness for insects.

RHex: Robotic Hexapod

Goals and Methods

The overarching goal of the RHex project was to develop a robotic mobility system that could navigate over highly broken and unstable, natural terrain with a competence arising from insights about animal locomotion.

Observations from various comparative biological studies on insects combined with our team’s long history in robotic design led to the RHex concept which significantly diverged from the prior stereotypical approaches to robot design. This legged locomotion platform is a hybrid dynamical system that features only six active degrees of freedom – one actuator in each hip. The legs of the robot are made out of compliant material realizing passive actuation in radial and wing degrees of freedom. RHex’s base level locomotion behavior arises from appropriately tuned task level open loop control. Namely, actuation actions are performed according to a well timed schedule in the absence of sensory information relating the robot to its environment and to its goal.


RHex was the first legged machine to run over badly broken, unstable terrain, and the first autonomous legged platform to run at speeds above one body length per second. The RHex system has demonstrated extraordinary capabilities in harsh government test sites. Its performance comes close and in some cases exceeds that of commercial products like PackBot. RHex and its many siblings have demonstrated very interesting applications of real-world robotic designs.


The RHex project collaboration was led by the Kod*Lab (then located within the AI Lab at the University of Michigan). The original concept for RHex was introduced by Martin Buehler (then Director of the Ambulatory Robotics Lab at McGill University, Canada ), inspired by observations about cockroach running offered by Robert Full at the University of California, Berkeley. New sensor-based behaviors arose from the addition to the team of Al Rizzi (then at the CMU Robotics Institute). Philip Holmes at Princeton Unviersity and John Guckenheimer at Cornell University maintained a participation in the RHex effort stemming from their original participation in the Computational Neuromechanics project.


Relevant Publications







  • Robo Sapiens: Evolution of a New Species, by Peter Menzel and Faith D’Aluisio MIT Press, (Material

World Books) ISBN: 0262133822

Selected Media Appearances






  • Army call-up for rats, robots and reptiles: The US government is ploughing money into unconventional projects to toughen its defences against terrorismFinancial Times, June, 2003 (PDF Version)
  • A Bug’s Life for, Mar, 2003 (PDF Version)



  • Robots take a clue from NatureUnmanned Systems, Dec, 2001 (PDF Version)
  • World of Wildlife III – LocomotionPBS (U.K.), Partridge Films, Aug, 2001
  • Cool Robot of the Week AwardNASA Space Telerobotics Program, May, 2001


  • Interview with Peter Jennings, television appearance on ABC World News with Peter Jennings, Apr 15, 2000
  • radio interview on Scout II and RHex 0, radio interview on Science in Action in BBC World Service, July 8–9, 2000
  • Live TV interview from Place des Arts, with RHex and Scout II, television appearance on This morning live in Montreal Global TV, Aug 8, 2000
  • RHex and Scout II, television appearance on Discover Channel Canada, Sep 28–29, 2000
  • BiobotsDiscover Magazine, Sep, 2000 (PDF Version)
  • Building a better RobotMcGill Reporter, Jul, 2000 (PDF Version)
  • Better Than Nature Made ItScience Magazine, Apr, 2000 (PDF Version)
  • RHex, a new six-legged robotIn Focus, Spring, 2000 (PDF Version)

External Links