As part of our Bachelor of Science design project, we (J. de Bruijckere, R. Smit and L. Valk) have developed a mechanical, electrical and software design for a lightweight, mobile exploration robot that employs the half-circle leg morphology. The morphology is based on TU Delft’s Zebro robot, which in turn is based on the RHex project, developed by a group of universities led by the Kod*Lab. The Zebro Light reduces the weight of the original Zebro from 7.5 to 3.2 kg, while also reducing the top surface area by 50%.
The robot’s structure is designed to be lightweight, without compromising its robustness. The electronics and software are designed to make each leg follow specified reference trajectories, by actively controlling motor position using feedback from rotary encoders. A prototype of the design has been constructed and tested, demonstrating a stable walking behavior. Adaptability of the mechanical design and high performance of the on-board computer allow this design to be used as a versatile platform for research on walking exploration robots. More details can be found in this short paper.
The Zebro Light is able to cross various types of terrain, as shown in the figures above and below. The robot has been demonstrated at the NASA exhibition “A Human Adventure”, in Utrecht, the Netherlands.
Video
Mechanical structure
The robot’s frame consists of six identical motor units held together by two polycarbonate plates. This results in a lightweight yet robust construction, as shown in the figures below.
Electronics
The position of each motor is actively controlled in order to make each leg follow reference trajectories that result in a stable gait. An overview of the system is given below. The on-board computer is the Beaglebone with a custom cape design to interface with the incremental motor encoders. The robot uses three Dimension Engineering Sabertooth 2×12 drivers to power all six Maxon Motors.
About the designers
The Zebro Light has been designed and prototyped by J. de Bruijckere, R. Smit and L. Valk. They are three mechanical engineering students at Delft University of Technology (the Netherlands), who developed this robot as part of their final Bachelor of Science design project.
References
[1] Saranli, U., et al. ”RHex: A simple and highly mobile hexapod robot.” The International Journal of Robotics Research 20.7 (2001): 616-631.
[2] Kersbergen, B., et al. ”Optimal gait switching for legged locomotion.” Intelligent Robots and Systems (IROS), 2011 IEEE/RSJ International Conference on. IEEE, 2011.
[3] Moore, E. Z., et al. ”Reliable stair climbing in the simple hexapod ’RHex’.” Robotics and Automation, 2002. Proceedings. ICRA’02. IEEE International Conference on. Vol. 3. IEEE, 2002.
[4] Molloy, D. ”Getting started with the Beaglebone.” Available: derekmolloy.ie.
