# Need to find the spring constant and dampening coefficient of a humarn arm.

## Main Question or Discussion Point

Hey.

Working on a project at the moment, where i have to simulate a human arm (hand and lower arm). I need to find the spring constant, k, and dampening coefficient, c.

You got any good ideas on how i can do that?

So far i tried by measuring the mechanical impedance, and saying the arm is a simple mass-spring-damper system. And trying to find the mass, k and c out from the imaginary and real parts of the graph. Thou these results seemed bit off. Perhaps the mass-spring-damper system is too simple??

Thanks in advance

PS: Meant human* in the title :)

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## Answers and Replies

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I think you can find the info you need to solve this problem in "Physiology of the Joints (Upper Extremities)" by I. A. Kapandji MD

Nice, thx I will give that a try :)

You are most welcome. There is not much info in your problem statement, so it is hard to understand exactly how comprehensive a model you need to make. There are probably over 100 degrees of freedom if you look at all the joints and the numerous muscles driving each one. So this could be a problem for a team of PhDs if you need to make the model comprehensive. A fair bit of work has been done in robotics and also in animation. For example, google "animate human hand" and "simulate human hand".

My suggestion would be to first browse the book, then better define exactly what the scope of the model is. I have the text on my bookshelf and used to know it by heart, so if you are still spinning your wheels, please do not hesitate to post again.

Thanks :) Had no luck finding the book at the libraries here in DK. Anyways, what i want to do, if possible, is to find a approximated spring constant value of the human lower arm+hand, and same with dampening coefficient. Just need to build a very simple simple system with 1 spring, 1 dampener and 1 mass. Need the "hand" for a vibration measurement setup.

Hi again,

The problem is still under-defined. A single spring model for which degree of freedom? For example, elbow flexion-extension, wrist flexion-extension, rotation, etc. Can you please post a drawing? Go to "advanced" reply option and there is an "insert image" icon where you can paste a URL link to an image. Alternatively, please PM me and I will provide an email address we can use.