Applying Damping Force

Hi AnyBody experts,

I am developing a head support system for high acceleration when no head rest is available. The system will apply damping force to the back of the head. I want to examine the impact of this system on the human body in AnyBody. What is the best method to apply the forces from this system to the human body to get valid results?

I am thinking of applying compressible rods with a damping force similar to the extensible rods in the exoskeleton webcast.

I have read on the forum to apply a damping force, apply the force with the AnyForce object. Is this valid for this application?

Thank you so much,
Tim

Hi Tim,

You are on the right track, I think. AnyForce object will be perfect for applying a damping force. Please see the reference manual for AnyForce. In brief, the force acts on a kinematic measure that you specify for the AnyForce object. You can make the force using mathematical expression and use variables like position and velocity that are calculated during kinematic analysis.

So, an example of a damping force could be:

F = DampingCoef * KinMeasure.Vel[0];

One question that I have for you: is this high acceleration movement a voluntary movement by the human model?

Best regards,
Dave

Awesome and thank you for the example Dave.

No, I will have the human head still or looking around slowly. But the high acceleration will come from outside motion of rollercoaster. Do you see any challenges with this?

I am thinking I will need to use position in the mathematical equation as using velocity in the AnyForce creates an issue since the head is meant to be static or low velocity. Would you agree?

Thanks again,
Tim

Hi Tim,

Sorry for the delayed reply. It has been a busy week.

I think there should be no problem in the simulation of a roller coaster. You would need a lot of frames in your motion data, depending on the speed of your roller coaster.

I think the force equation really depends on your system. If you say the head will be static, then if you use position, it will almost be a constant force. In any case, in your mathematical equation, you can use both position and velocity components. Basically, any variable that will be evaluated during the kinematics analysis is available. You are not limited to just one:

F = SpringCoef * KinMeasure.Pos[0] + DampingCoef * KinMeasure.Vel[0];

So, this way you can get both spring and damping force into your model.

Best regards,
Dave

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