inverse dynamics in AnyBody

Main Forum
1

I was going through the forums and ran in to some comments by AnyBody experts saying that AnyBody does NOT solve the inverse dynamics in the traditionally taught way of going through the kinematic chain one joint at a time (starting from the furthest/free end) and solving the equilibrium equations at each joint.

So, how does AnyBody solve the inverse dynamics? Could you point me to a link where the mathematics is discussed?

Thank you,

Vikas

2

Dear Vikas,

There is a paper which was written by our core developer regarding the principles of AnyBody:
[i]Damsgaard, Michael, et al. “Analysis of musculoskeletal systems in the AnyBody Modeling System.” Simulation Modelling Practice and Theory 14.8 (2006): 1100-1111.
http://www.sciencedirect.com/science/article/pii/S1569190X06000554

[/i]Also there is a previous webcast which explains the principles of muscle recruitment inside AnyBody Modeling System.
http://www.youtube.com/watch?v=Ttd8UdNMaqk

Best regards,
Moonki

3

Hi Moonki,

Thank you for those links. I have gone through the inverse dynamics video and the tutorial and, although the video briefly goes over it, neither one goes in to the mathematics as much as I would’ve liked.

I am going through the journal publication and the book that is cited in it. Those should help.

So, again, thank you.

Best,

Vikas

4

Vikas,

The “traditionally taught way” as you mention it is to go from external forces to joint moments and compute muscle forces from there. This method will only work in a simple, open-chain system, and such is not the nature of the human body. AnyBody solves kinematics using a full Cartesian formulation that handles any combination of open and closed chains, and we formulate the equilibrium equations directly in terms of muscle and joint forces. This is a much more general and versatile approach.

Best regards,
John

5

John:

Thank you for your clarification. I got that message from the video (link provided by Moonki) and the paper too.

I am new to the world of rigid body dynamics and still trying to learn the basics when I am able to find time; I suspect it will be a while before I start asking more interesting questions :slight_smile:

Thank you,

Vikas