Can anyone provide a bit of clarity regarding the following point of the ESA
rowing machine model? Specifically,
the FootRestForce in the Environment.any file. I am just looking at the first
1.3 seconds, where that force
(FootRestForce.F) is positive. It is defined in the code I have downloaded as:
F = .Force(t)*(1);
The force is positive and applied to the FootRestGuideJnt, which is positive in
the +x global direction. Does this
mean that the force transferred to the feet is a pulling force? (My expectations
were that it should be a pushing
force…).
When I looked at the knee moment when using the ‘nomuscle’ model, I found the
knee moment is producing a
moment in extension (for the first 1.3 seconds). This is because the neg-muscle
of the knee joint has a value
(pos-muscle should be 0). So this then made me think I had something backwards
and the force was really a
pushing force. But then I thought maybe the dynamics of the leg were
overcompensating for the applied force.
So I multiplied the force by 100 (thinking that the extension moment in the knee
would go up) and found that
the knee moment changed from a neg-muscle value to a pos-muscle value, meaning
that the knee was now
producing a flexing moment. This suggests that the knee, to remain bent, was
resisting the high pulling force
of the applied force.
I played around with some static cases and compared them with the elbow flexion
moment. Everything seems
right in my head for that one. Am I missing something here? Do I have my
flexion/extension for the knee
backward for the pos/neg muscle?
You are right. The forces point in positive direction. In fact both forces,
on the feet as well as on the hand are contrary to what you may expect from
traditional rowing.
The rowing machine model is part of a preliminary study to show the
feasibility to analyse countermeasure exercises, and of course also to use
it for design purposes.
So in this case a modified design is analysed, several version of the model
exist and this is one of three versions we have.
Therefore, in order to analyse ‘real’ rowing you have to invert both forces.
Can anyone provide a bit of clarity regarding the following point of the ESA
rowing machine model? Specifically,
the FootRestForce in the Environment.any file. I am just looking at the
first 1.3 seconds, where that force
(FootRestForce.F) is positive. It is defined in the code I have downloaded
as:
F = .Force(t)*(1);
The force is positive and applied to the FootRestGuideJnt, which is positive
in the +x global direction. Does this
mean that the force transferred to the feet is a pulling force? (My
expectations were that it should be a pushing
force…).
When I looked at the knee moment when using the ‘nomuscle’ model, I found
the knee moment is producing a
moment in extension (for the first 1.3 seconds). This is because the
neg-muscle of the knee joint has a value
(pos-muscle should be 0). So this then made me think I had something
backwards and the force was really a
pushing force. But then I thought maybe the dynamics of the leg were
overcompensating for the applied force.
So I multiplied the force by 100 (thinking that the extension moment in the
knee would go up) and found that
the knee moment changed from a neg-muscle value to a pos-muscle value,
meaning that the knee was now
producing a flexing moment. This suggests that the knee, to remain bent, was
resisting the high pulling force
of the applied force.
I played around with some static cases and compared them with the elbow
flexion moment. Everything seems
right in my head for that one. Am I missing something here? Do I have my
flexion/extension for the knee
backward for the pos/neg muscle?
Thank you in advance!
David
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