ADAMS中计算悬置出现9个方向能量的原因

sososwim

在ADAMS的官方论坛上看到有人问过这个问题，现拿来和大家讨论下。What are the RXZ, RYX,RYZ in the distribution of kinematic engergy?normally, the eigenfrequency come from the eigen values of a matrix,and the mode vectors are the corresponding directions of the eigen values. and both the number of the eigen value and the mode should be 6, when considering one mass supported by three dampers.
But in the vibration analysis result of ADAMS, there are 9 parts of distribution of energy, can you guide me what are they calculated and what do they mean?
（Rxz、Ryx、Ryz贡献的动能表示什么？通常的，固有频率来自于矩阵的特征值，模态向量应该和特征值相对应，并且当只考虑被三个阻尼器支承的一个质量块时特征值和特征向量都是6阶的，但是在ADAMS的振动分析结果中，动能贡献的部分却有9个，能指导我他们是怎么计算的并且都是什么意思吗？）

sososwim

有个人是这么回答的：For your 6dof model there will be 6 complex modes or upto 12 real modes. This depends on the damping you specified in your bushing. For zero damping - 6 complex modes; for critical damping or greater 12 real modes.（对于你的6自由度模型有6个复模态或者12个实模态，这取决于你在衬套里制定的阻尼。零阻尼——对应6复模态，零界阻尼或者大阻尼——12实模态。）

sososwim

This is unrelated to the 9 values in the kinetic energy distribution table. The cross terms (RXY...) are due to the fact that the distribution is given about the global XYZ axes which, in general, are not parallel to the part principal axes. So in the global frame, in which this distribution is given, the part may have off-diagonal terms in the inertia tensor resulting in cross terms in the kinetic energy distribution. （这和9个动能贡献表的9个值是没有关系的，交叉项(RXY...)取决的事实是整体的XYZ轴的贡献，总的来说，不是平行于零件主要的轴，所以整体框架下，在这里计算贡献，在惯性轴下零件也许有非对角元素是导致动能贡献出现交叉项的原因。）

sososwim

It is X, Y, Z, Rxx, Ryy, Rzz, Rxy, Ryz, Rzx!!!
The first three terms are for tranlational KE, next three terms are for pure rotational KE and last three for coupled rotational KE.（X,Y,Z,Rxx,Ryy,Rzz,Rxy,Ryz,Rzx，前三项是平动动能，中间三项是旋转动能，最后三项是旋转耦合动能。）

sososwim

It's a question about coordinate system.
If you report the kinetic energy in a given coordinate system, you will in general get all nine components x,y,z,xx,yy,zz,xy,xz,yz.（这是一个关于坐标系的问题，如果你在一个给定的坐标系计算动能，一般来说都有9个组成部分。）
But it is always possible to find a transformation (another reference system) where the cross-terms are zero. (and the other terms add up to 100% then)但是找到另一个坐标系使交叉项都为0，其他项上升到100%是可能的。
(Compare this to specifying inertias in the vehicle coordinate system or a principal-axis system).

sososwim

If I where to write an article or compendium to discuss kinetic energy distribution, I would of course choose my coordinate system to coincide with the principal system so I don;t have to drag the cross terms along（如果我要写个论文或者摘要讨论动能的贡献，我肯定会将我的坐标系和系统的惯性主轴一致，所以我就不会出现交叉项的问题）

sososwim

最后Goto online help of A/Vibration for v2007: there is a good derivation for all these terms.

sososwim

最后Goto online help of A/Vibration for v2007: there is a good derivation for all these terms.

sososwim

晕，多发了一个，想要让最后3项都变成0，简单的做法就是将整体坐标系改为惯性主轴的坐标系。在ADAMS2005之前都没有交叉项（Rxy,Ryz,Rzx）的，从2005才开始有，不过个人始终觉得通过在MATLAB里面编写函数是方便快捷直观的方法。

guanye

也就是说只有在惯性轴坐标系下后三项才为0，在整车坐标系下或者扭矩轴坐标系下后三项不为0。楼主有没有相关的文献分享一下呢？

yjg314

ADAMS默认计算出来的是按照惯性主轴坐标系？还是质心坐标系？？