Efficient Dynamic Simulation of a Quadruped Using a Decoupled Tree-Structure Approach

Abstract

Efficient simulation of a dynamically stable, fast-moving quadruped vehicle has been undertaken at The Ohio State University. Individual leg-link inertial properties, espe cially important at high speeds, are incorporated into the simulation. Also incorporated are the ground contact con siderations of compliance, friction, and impulsive impact forces. Basic efficiency is gained by decoupling of the closed-chain system into a tree-structured, open chain through introduction of spring/damper systems at the ground. The ensuing tree-structure dynamics are solved by developing and applying an extended form of the effi cient O(N) open-chain algorithm of Brandl et al. (1986). Additional speedup in the computations is gained through application of multirate integration and parallelization. One second of real-time simulation on a single Intel iPSC/ 2 Hypercube node takes 66.7 s. Use of multirate integra tion improves four-node parallel performance, giving a total speedup factor of more than 3.