When modeling complex robot systems such as branched robots, whose kinematic structures are a tree, current techniques often require modeling the whole structure from scratch, even when partial models for the branches are available. This paper proposes a systematic modular procedure for the dynamic modeling of branched robots comprising several subsystems, each composed of an arbitrary number of rigid bodies, providing the final dynamic model by reusing previous models of each branch. Unlike previous approaches, the proposed strategy is applicable even if some subsystems are regarded as black boxes, requiring only twists and wrenches at the connection points between them. To help in the model composition, we also propose a weighted directed graph representation where the weights encode the propagation of twists and wrenches between the subsystems. A simple linear operation on the graph interconnection matrix provides the dynamics of the whole system. Numerical results using a 38-DoF fixed-base branched robot composed of nine subsystems show that the proposed formalism is as accurate as a state-of-the-art library for robotic dynamic modeling. Additional results using a 39-DoF holonomic branched mobile manipulator composed of ten subsystems demonstrate the fidelity of our model to a modern robotics simulator.
翻译:当模拟复杂机器人系统,如分支机器人时,其运动学结构为树形结构,当前技术通常需要从头开始对整个结构进行建模,即使可用于分支的部分模型已经存在。本文提出了一种系统的模块化方法,用于动态建模由多个子系统组成的分支机器人,每个子系统由任意数量的刚体组成,通过重复使用每个分支的先前模型来提供最终的动态模型。与以前的方法不同,即使某些子系统被视为黑匣子,也可以适用所提出的策略,仅需要它们之间连接点处的扭矩和力矩。为了帮助模型组合,我们还提出了一个加权有向图表示形式,其中权重编码扭矩和力矩在子系统之间的传播。在图形互连矩阵上进行简单的线性运算,可以提供整个系统的动力学。使用由九个子系统组成的包括38度自由度的固定基础分支机器人的数值结果表明,所提出的形式与用于机器人动态建模的现代库一样精确。使用包括10个子系统的39度自由度全向分支移动机械手的附加结果证明了我们模型对现代机器人模拟器的精确性。