Modlab The Modular Robotics Laboratory at the University of Pennsylvania

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Dynamic Locomotion of CKBot
Dynamic Locomotion of CKBot
CKBot is designed to be fast allowing it to achieve dynamic locomotion. Given that CKBot is reconfigurable gives us the unique ability to research different types of dynamic locomotions in different morphologies all with the same hardware.

Locomotion is one of the most basic functions of mobile robots. Robotics researchers have demonstrated a wide variety of locomotion modes, including legged, wheeled, snake-like and even amoeba-like locomotion. Not every locomotion mode is suitable for all tasks. For example, a car like vehicle may be well suited for travelling over roads, but would not be suitable for climbing through a rubble pile doing search and rescue. A snake-like robot maybe well suited for climbing through tightly constrained environments, but is probably very inefficient going long distances.

Dynamic Rolling

CKBot’s fastest gait is a dynamic rolling gait. A sensor-based feedback controller is used to achieve dynamic rolling. The robot senses its position relative to the ground and changes its shape as it rolls. This shape is such that its center of gravity is maintained to be in front of its contact point with the ground, so in effect the robot is continuously falling and thus accelerates forward. Using simulation and experimental results, we show how the desired shape can be varied to achieve higher terminal velocities. The highest velocity achieved in this work is 26 module lengths per second (1.6m/s) which is believed to be the fastest gait yet implemented for an untethered modular robot. One of the major findings is that more elongated shapes achieve higher terminal velocities than rounder shapes. We demonstrate that this trend holds going up as well as down inclines. We show that rounder shapes have lower specific resistance and are thus more energy efficient. The control scheme is scalable to an arbitrary number of modules, shown here using 8 to 14 modules.

Dynamic Running

CKBot can also run using by adding legs that are purely passive with no actuators. Locomotion is achieved using pure body articulation. Results are shown of a dynamical bouncing gait utilizing this hexapod configuration with a Spring Loaded Inverted Pendulum (SLIP) template for a dynamical model. The model and control is such that it is easily scalable to any number of legs, however so far we have only implemented 6 legged locomotion.

Related Projects

CKbot: Dynamic rolling and running is achieved with CKbot modules.

Related Papers

  • J. Sastra, W. G. Bernal-Heredia, J. Clark, and M. Yim, “A biologically-inspired dynamic legged locomotion with a modular reconfigurable robot,” , Ann Arbor, Michigan, USA, 2008.
    [Bibtex]
    @conference{sastra2008bid,
    Author = {J. Sastra and W. G. Bernal-Heredia and J. Clark and M. Yim},
    Address = {Ann Arbor, Michigan, USA},
    Month = {October},
    Title={A Biologically-inspired Dynamic Legged Locomotion with a Modular Reconfigurable Robot},
    Year = {2008},
    url = {http://modlab.seas.upenn.edu/publications/2008_DSCC_Centipede.pdf}
    }
  • J. Sastra, S. Chitta, and M. Yim, “Dynamic rolling for a modular loop robot,” Intl. j. of robotics research (invited), 2007.
    [Bibtex]
    @article{JS:SC:MY:07,
    author = {J. Sastra and S. Chitta and M. Yim},
    title = {Dynamic Rolling for a Modular Loop Robot},
    journal = {Intl. J. of Robotics Research (invited)},
    month = {January},
    year = {2007},
    url = {http://modlab.seas.upenn.edu/publications/2007_IJRR_DynamicRolling.pdf}
    }
  • J. Sastra, S. Chitta, and M. Yim, “Dynamic rolling for a modular loop robot,” in Proc. of intl. symp. on experimental robotics, Rio de Janeiro Brazil, 2006.
    [Bibtex]
    @conference{JS:SC:MY:06,
    author = {J. Sastra and S. Chitta and M. Yim},
    title = {Dynamic Rolling for a Modular Loop Robot},
    booktitle = {Proc. of Intl. Symp. on Experimental Robotics},
    address = {Rio de Janeiro Brazil},
    year = {2006},
    url = {http://modlab.seas.upenn.edu/publications/2006_ISER_DynamicRolling.pdf}
    }

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