Leg Design and Control for Fast Locomotion

The Problem: Running with segmented legs. (a) Why do biological limbs operate as they do? What are the mechanical advantages? (b) How to transfer the nature’s patents to technical solutions? Motivation: A linear spring-like leg behavior is found in human and animal running [4, 2]. Although some tech-nical systems were able to mimic running with such elastic legs within a range of different speeds and gaits [7, 8] it is still not known why biological legs employ this behavior. Until now there is no running robot with segmented legs. With regard to the reduced contact times at high speeds a smart design of the actuators andmaterial properties and a careful selection of the leg geometry (segmentation, intersegmental angular arrangement) becomes crucial for stable running. Figure 1: Previous Work: Blickhan [9] and McMahon and Cheng [11] introduced a simple spring-mass model to approxi-mate this generally observed force pattern. This representation of the leg by a linear spring was successfully applied by biologists [2, 10] and bioengineers [6] to describe and predict animal and human locomotion. Recently, it was found [1] that running with properly adjusted elastic legs is self-stabilizing and covers slightly changed leg adjust-294 ments (e.g. leg stiffness) and rough terrain. On themusculo-skeletal level a spring-like leg operation can be obtaine