Hi Christian, A couple things to try/consider: (1) Try turning the tracking weight on the GRF way high and seeing if the solution then has good tracking of them. This will most likely come at the cost of other terms in the cost function, but it can help with identifying the issue. (2) From the image...

I just started using AddBiomechanics (it's awesome, thanks!) and have some questions similar to Nicos above: 1. Is it expected that markers tagged with <fixed>true</fixed> will be adjusted a bit? 2. If I upload a C3D file that includes both markers and GRF, how does AddBiomechanics figure out the fo...

Thanks all

Hi all,

Can anyone point me to a download of the "example2Dwalking" example for Python? I'm only seeing a Matlab version in the codes that come with OpenSim by default. A summer student is working on a project that it would be helpful for.

Ross

Hi Nick, "Stride" and "Gait Cycle" are the same thing to me, a full periodic cycle from one gait event to the next instance of that same event, for example right heel-strike to the next right heel-strike. Over a full cycle you typically want all the states and controls to be periodic, except the pel...

The "initial states" problem here can be a big problem. The way that the system dynamics are enforced as constraints, at least in most collocation schemes that I know of, are with finite difference calculations that involve the current state and the previous state, or something similar. But for the ...

If you are simulating the stance only (and not a full stride) then the periodicity goal will not be appropriate. I would look into the various goals with Initial in the name. For limb loss since it is presumably asymmetric, the periodicity over even a full step is not applicable, would need to be a ...

There is not a lot of documentation on the technical side of JointReaction. You would probably have to find the CPP code for it to really figure out what it is doing. It reads and looks to me like it sums the net joint force with the actuator forces at the joint e.g. muscle forces. Since your GRF lo...

Hi Nicholas, What do the hip muscle forces in early stance for the Moco solution look like? I have not done hip but I get reasonable-looking knee contact forces in Moco solutions with the method here. Some small changes in syntax may be necessary, this code is from an early version of Moco: Hi Nick,...

Hi Adam, Moco I think only does open-loop controls in its present state. It is possible to use direct collocation methods on closed-loop control problems (recent example: https://journals.plos.org/ploscompbiol/article?id=10.1371/journal.pcbi.1009338) but doing so in Moco I think would take a fairly ...