How to apply motion for Standingmodel in Anybody

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1

Hello,

I’m Phuong Bui. I’m new with Anybody software.
Now, I’m writing a inverse dynamics analysis program to calculate
net joint moment and joint active force. After that I want to calculate
muscle forces.
I have a given data. They are joint angle, angular velocity, angular acceleration.
I want to apply this data to the model in Anybody software with one simple motion,
for example Stand to Sit movement, to see the motion and get the muscle force results.
Now I can apply motion for hip and knee by define posture and velocity for two these joints
for Standingmodel: A basic static full-body model standing on a floor in Anybody.
But when I try to apply flexion motion for ankle joint, there are errors.
I don’t know how this motion. And I don’t know how to apply the motion I have for this model.
If i have the data above how can I apply to this model.
If can’t, can you show me how to build the model that can apply the motion I want ( Stand to Sit in 2D)

Thank you,

Thanh Phuong

2

Hello Thanh Phuong,

What happens is that the StandingModel has a driver that constrains the CoM of the body to be above the ankles. So when you add your data to make the body move you probably end up with contradictory drivers. So please remove the CoM driver. It is possible that you will have to remove or modify more of the existing drivers.

It is a good idea in general to make a clear list of the driver together with a description of wich degree of freedom they are driving. That way you have the whole picture of the model and you can see which of the existing drivers have to be modified and which new ones are needed in order to input your data.

Best regards, Sylvain.

3

Thank you very much for your help. I’ll follow your suggestion. And I hope I’ll solve this problem soon.

And I have one more question. Do you know if Anybody provide some information about muscular properties, for example: max isometric force, optimal fiber length, damping, Kshape active, K shape passive…?

I only found the information about muscular attachment points in some example.

Thanh you,

Phuong Bui

4

Hi Phuong Bui,

The muscle properties are available in the file MusPar.any for each body part. Those are defined when constructing a model and typically comes from the literature.
You can also find them in the output tree of the Chart window for each muscle. Please notice that you have to use the 3 elements muscles to take into account those parameters. The simple muscle model only uses the maximum strength as parameter.

Best regards, Sylvain.

5

Hi Sylvain,

I found it

Thanh you very much

6

I want to make the standing model move until hip and knee flexion are both 50 degrees (very rough model of a squat). After changing the driver position and velocity, the model goes directly to the final position without running through any kinematics. Can you give me a pointer about what to do to achieve motion?

7

Hi,

Which number of ‘nStep’ did you use for AnyBodyStudy class object in your model? It should be bigger than 1.

For instance, you can try like this:

  AnyBodyStudy Study = {
    AnyFolder &Model = .Model;
    
    [b]tStart = 0;[/b]
    [b]tEnd = 1.0;[/b]
    Gravity = {0.0, -9.81, 0.0};
    [b]nStep = 10;[/b]
    
  };

Best regards,
Moonki

8

Thank you. I cannot believe I did not realize I had to change the nstep.