Volume 23 Issue 2 - Publication Date: 1 February 2004
Stride Period Adaptation of a Biomimetic Running Hexapod
Jorge G. Cham, Jonathan K. Karpick and Mark R. Cutkosky Center for Design Research (CDR), Stanford University, Stanford, CA 94305-2232, USA

We demonstrate an adaptation strategy for adjusting the stride period in a hexapedal running robot. The robot is inspired by discoveries about the selfstabilizing properties of insects and uses a sprawled posture, a bouncing alternatingtripod gait, and passive compliance and damping in the limbs to achieve fast (over four bodylengths per second), stable locomotion. The robot is controlled by an openloop motor pattern that activates the legs at fixed intervals. For maximum speed and efficiency, the stride period of the pattern should be adjusted to match changes in terrain (e.g., slopes) or loading conditions (e.g., carrying an object). An ideal adaptation strategy will complement the design philosophy behind the robot and take advantage of the selfstabilizing role of the mechanical system. In this paper we describe an adaptation scheme based on measurements of ground contact timing obtained from binary sensors on the robot's feet. We discuss the motivation for the approach, putting it in the context of previous research on the dynamic properties of running machines and bouncing multilegged animals, and we show the results of the experiments.

Multimedia Key
= Video = Data = Code = Image
Example One: Video showing Sprawlita running despite large disturbances. This disturbance rejection is accomplished without sensory feedback through the robot’s passive properties and open-loop control. (3.7MB)
Example Two: Video showing Sprawlita overcoming hip-height obstacles. (1.6MB)
Example Three: Video showing sample results of implementing the adaptation strategy based on binary contact information from a switch in one the robot’s feet. The video shows experiments on flat ground in which the robot’s stride periodwas started at suboptimal values. (2.8MB)
Example Four: Video sample results of the adaptation strategy on an uphill slope of 5 degrees. The video shows experiments in which the robot’s stride period was started at suboptimal values. (3.9MB)
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