Hi everyone, kindly help me out in resolving my problem. Can we find out eigen vectors (mode shape vectors) from frequency response function matrix. I know that ,value of frf matrix at eigen value(nat freq) is the sum of eigen vector values? but how

Hi everyone, kindly help me out in resolving my problem. Can we find out eigen vectors (mode shape vectors) from frequency response function matrix. I know that ,value of frf matrix at eigen value(nat freq) is the sum of eigen vector values? but how?

[KALYAN ACHARJYA]

Can you share the representation maths, what you looking for?

Always mention the problem:

what is input? what result you are expecting and

what you have tried so far (code)

[Walter Roberson]

That does not make sense. Eigen vectors are not unique: each one can be multiplied by any non-zero scale. They are vectors in the geometric sense, indicating direction but not magnitude.

Because of this, there is little meaning to adding the eigen vector values, because you could multiply any one of the eigen vectors by a non-zero scalar and get a different sum.

There might be some applications involving null space or row spans of eigen vectors to describe some kinds of theoretical possibilities, but I would not think those would directly have to do with modes.

[Ayisha Nayyar]

Thanks for your guidance Kalyan, actually I have a frequency response function matrix size 2500x21,where 2500 represents frequency and 21 represents point on a beam, from which this data is collected from an accelerometer. I know eigen values/natural frequencies of this matrix through modal analysis. Now I wish to find out mode shape vectors/eigen vectors, from this frf matrix directly. I used modalfit command, but I don't know why matlab gives error by saying, incorrect syntax. I want to know that is there any other method with the help of which mode shape vectors are calculated durectly from this frf matrix...

[Ayisha Nayyar]

Moreover read literature, which shows that we can find eigen vectors from stiffness matrix and mass matrix, but problem is that I just have frf matrix, can I find mass and stiffness from that, I guess no...