About internal joint load

Main Forum
1

Hi AnyBody support.

I would like to know joint reaction forces and internal joint load at the hip, knee, and ankle. But I don’t know how to obtain data about joint reaction forces and internal joint load.

Please tell me how to obtain that data.

I upload the file for “GaitFullBody_TUT_With_Force”.

AMS is ver5.1 and AMMR is ver 1.4.
I beg your kindness,
Shinsuke.

2

Have a look here:
http://wiki.anyscript.org/index.php/All_about_Kinetics

Especially look at this subsection http://wiki.anyscript.org/index.php/All_about_Kinetics#How_to_understand_the_reactions_listed_in_a_AnyStdJoint.3F

3

Hi pat

Thank you for your reply.

I looked wiki, but I don’t know for sure about how to obtain data.
Are joint reaction force shown below?

“Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.Jnt.Ankle.Constrants.Reaction.Fout” “Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.Jnt.Knee.Constrants.Reaction.Fout” “Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.Jnt.Hip.Constrants.Reaction.Fout”

If that case, Hip has F[0],F[1] and F[2], but Knee and Ankle have F[0],F[1],F[2].F[3], F[4].
Why there is a difference between Hip and Knee, Ankle?
Does joint reaction force indicate X-Y-Z coordinate system?

If not so, are joint reaction forces shown below?
“Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.MomentMeasure.AnklePlantarFlexionNetMoment”
“Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.MomentMeasure.KneeNetMoment”
“Main.Studies.InverseDynamicStudy.Output.Humanmodel.Right.Leg.MomentMeasure.HipNetMoment”

AMS is ver5.1 and AMMR is ver 1.4.
I beg your kindness,
Shinsuke.

4

Hi Shinsuke,

  1. Those values that you found are the right ones to see.
    The reason why hip reaction forces have 3 components is that hip joint is a sort of the spherical joint. Knee joint is a kind of the revolute joint so it has 5 components(3 reaction forces and 2 reaction moments)
    The direction of these reaction forces will follow the orientation of the first referred reference frame.

Best regards,
Moonki

5

Hi Moonki

Thank you for your reply.

I could obtain joint reaction force data.
But, I have some questions.
Are F[0], F[1],F[2] measured in force units, i.e. Newton?
Are F[3],F[4] measured in moment units, i.e. Newton meter?

AMS is ver5.1 and AMMR is ver 1.4.
I beg your kindness,
Shinsuke.

6

Hi Shinsuke,

Yes. You are right. AnyBody uses the MKS units.
So force is in newton and moment is in newton-meter.

Best regards,
Moonki

P.S) I hope that you can upgrade to our latest AMS and AMMR versions if possible. We can’t support all our users who are using very old versions. Sorry.

7

Hi Moonki

Thank you for your reply.
Thanks to you, I could obtain joint reaction force.

I’m sorry for I didn’t upgrade to AMS and AMMR version.
I will upgrade to AMS and AMMR in March.

Thank you again for your help.
I appreciate your continued support.

Shinsuke.

8

Hi AnyBody support.

I checked joint reaction force of F[2].
The results of ankle and knee was been positive value.
But only hip result was been negative value.
Why become a negative value only hip ?

I beg your kindness,
Akira

9

Hi Akira:

Just would like to share my thoughts. The JRF are calculated in local coordinate systems. The negative direction at the knee is not the same as the negative directions at other locations.

Hope it helps.

-Phoebe

10

Hi Phoebe.

Thank you for your reply.
“The negative direction at the knee is not the same as the negative directions at other locations”
I think the joint reaction force of the knee is acting in the same direction as the hip, and ankle is not same direction.
Why joint reaction force of ankle acts to reverse ?
Why does it not act in the same direction?

I beg your kindness,
Akira

11

Hi Akira,

The direction of a joint reaction will follow the direction of the first reference frame in that joint definition.

So I would recommend you to add a ‘AnyDrawRefFrame’ class instance in the first reference frame of that joint.

Best regards,
Moonki

12

Hi Moonki

Thank you for your message.

I want to add ‘AnyDrawRefFrame’ in first reference frame of each joint.
But I don’t know where the first reference frame of that joint.
In addition I can’t find AnyDrawRefFrame in class list.
what should I do in order to add ?

I beg your kindness.
Akira

13

Hi Akira,

  1. You should see the definition of the joint to figure out which reference frame is the first reference frame.

  2. You can use the reference of any joint to add an AnyDrawRefFrame object.
    For example,

Main.Studies.HumanModel.BodyModel.Right.Leg.Jnt.Knee = 
{
  ThighNode = 
  {
    AnyDrawRefFrame DrwFrame = 
    {
      RGB = {1, 0, 0};
      ScaleXYZ = 0.1*{1, 1, 1};
    };
  };
};

Best regards,
Moonki