原有运用Newton-Euler法建立的6-UPS (universal-prismatic-spherical) Stewart平台的经典闭环动力学模型存在一些不足，逐渐有学者从三个方面改进，即建模过程中考虑支杆绕自身轴线的旋转自由度，修正万向铰约束力矩的方向，应用平行轴定理计算各结构的转动惯量。本文在此基础上，考虑到上、下支杆关于下铰接点的力矩平衡属于不同情况，选择合理形式的动量矩定理建立支杆及上平台的欧拉方程，并结合前三点最终得到两种闭环动力学改进模型。使用相同的算例，比较改进模型和原模型的动态响应的不同，说明改进模型的必要性。从理论推导的角度来看，改进的模型比原模型更加合理、准确。
Abstract
The classical closed-loop dynamic model built with Newton-Euler approach for a 6-UPS Stewart platform has some shortcomings. It was improved by some scholars in three aspects including considering rotational DOF of rods around their axis, modifying restraint moment direction of universal joint and adopting the parallel axis theorem to calculate moments of inertia of each structure. Here, Euler equations for rods and upper platform were established according to reasonable forms of the momentum moment theorem, based on torque balance of upper rods about a lower hinge point and that of lower ones about the same hinge one being different cases. Finally, two different closed-loop improved dynamic models were deduced combining the above three aspects. Using the same example, the necessity of improving the model was explained by comparing dynamic responses of the improved models with those of the original model. It was shown that from the view point of theoretical derivation, the improved models are more reasonable and more accurate than the original one be.
关键词
6-UPS Stewart平台 /
改进动力学模型 /
Newton-Euler法
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Key words
6-UPS Stewart platform /
improved dynamic model /
Newton-Euler approach
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