Dynamic Locomotion for the MIT Cheetah 2
The MIT Cheetah II is a unique research platform that enables the study of dynamic locomotion capabilites in an experimental robot. Previous work on the MIT Cheetah I robot and optimal actuator design have come together to enable efficient running in this new machine at speeds from 0-6.4 m/s. Extensions to the running controller have enabled the robot to execute mild running turns and to autonomously jump of obstacles. The video below showcases many of the recently developed capabilites of the Cheetah II.
High-Speed Running Control Through Impulse Scaling
Control of high-speed running uses a fundamental concept of momentum balance as a guiding principle to shape the propreties of the gait across speeds. As shown in the figure below, the Cheetah pushses off the ground harder in shorter periods of stance, in order to balance the vertical impulse delivered through gravity over the stride. Additional feedback control is layered on top of these force profiles to balance the robot as it runs. The focus on these fundamental principles, realized through high-performance force-control, enables the Cheetah to run both in the laboratory and across rougher terrain outside.
More recently, the cheetah has demonstrated the capability to autonomously detect and jump over obstacles as it runs. The Cheetah can jump over obstacles up to 40cm in height (80% of leg length) while running at 2.5 m/s. The cheetah is able to take advantage of its speed and momentum to dynamically clear terrain obstacles that are well beyond the capabilites of previous legged machines that moved more statically. The video below describes some of the main algorithms that have been used to acheive this feat.
Park, H-W., and S. Kim, "Quadrupedal galloping control for a wide range of speed via vertical impulse scaling", Bioinspiration & Biomimetics, vol. 10, issue 2, pp. 025003, 2015.
Park, H-W., P. M. Wensing, and S. Kim, "Online Planning for Autonomous Running Jumps Over Obstacles in High-Speed Quadrupeds", Robotics: Science and Systems, 2015.
Park, H-W., SI. Park, and S. Kim, "Variable-speed quadrupedal bounding using impulse planning: Untethered high-speed 3D Running of MIT Cheetah 2", Robotics and Automation (ICRA), 2015 IEEE International Conference on, May, 2015.
Park, H-W., M. Yee Chuah, and S. Kim, "Quadruped bounding control with variable duty cycle via vertical impulse scaling", IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2014), Sept, 2014.