A Thesis Submitted to the Department of Mechanical Engineering in partial fulfillment of the requirements for the degree of Master of Science
Degree Awarded: Summer Semester, 2010

The ability to traverse over unknown, rough terrain is an advantage that legged locomotion has over wheeled systems. However, due to the complexity of multi-legged systems, researchers in legged robotics have not been able to reproduce the agility found in the animal kingdom. In an effort to reduce this complexity, researchers have developed single-legged models, or templates, to gain insight into the fundamental dynamics of legged running. Inspired by studies of animal locomotion, researchers have proposed numerous control strategies to achieve stable one-legged running over unknown, rough terrain. One such control strategy incorporates energy variations into the system during the stance phase by changing the force-free leg length as a sinusoidal function of time. In this research, a one legged planar robot capable of implementing this and other state-of-the-art control strategies was designed and built. Both simulated and experimental results are used to determine and compare the stability of the proposed controllers as the robot is subjected to unknown drop and raised step perturbations equal to 25% of the nominal leg length. This study illustrates the relative advantages of utilizing a minimal-sensing, active energy removal control scheme to stabilize running over rough terrain.