OpenSim-MATLAB/Simulink Interface

[Giuseppe Scaccuto]

Dear all!

I set up a Forward Dynamics Simulation in Simulink with these settings:
- solver = RungeKuttaMerson Integrator (ode4)
- fixed step value = 0.01

I forced OpenSim to use same step size and make it constant with an integrator accuracy of 0.1.

Now my simulation results have a fixed number of steps both in Simulink and OpenSim.

When I perform some test on that model, I notice something strange in the plot of fiberlength values on the Pectoral muscle in Simulink while I don't see it in OpenSim. Here's the screenshot.

Immagin.png (41.55 KiB) Viewed 404 times

There's a problem with the accuracy value or anything else?

Here's my .osim model:

Arm6.osim

(116.21 KiB) Downloaded 74 times

Thanks for your help.

[Dimitar Stanev]

There is method for setting the integrator step size:

https://simbody.github.io/simbody-3.6-d ... 15ae34a65e

You should not set the accuracy to such a low value. This may be causing the problem. It is also possible that the system is not realized to position stage when you access the muscle length.