Hi all, We've been hearing reports that OpenSim 3.3 gui has been unable to launch the 3D visualizer for some Windows 10 users. If you are experiencing this problem, it is likely that a few core Microsoft libraries are missing from your Windows 10 installation. To fix this, you must install these mis...

Hi Rachel, The usual culprit is a mismatch in data sources. For IAA, you must provide kinematics, ground reaction forces, and actuations as separate files. You have to be sure that the model, kinematics, grf, and actuation files are from the same trial and synchronized. If they aren't, you're in eff...

Hi Claudio, Thanks for the great and very detailed question! The short answer is this. It's not ok to just set all muscle forces to zero in the inputs to the JointReactionAnalysis. If you do, you no longer have a dynamically consistent system, and the joint reaction calculations will incur all the e...

You should not equilibrate muscles. If you've performed CMC, you already have all trajectories of the muscle states (activation, fiber length) and initial conditions for muscle were already equilibrated. Did you check the JointReaction documentation? http://simtk-confluence.stanford.edu:8080/display...

<t>Hi Hang Xu,<br/> <br/> The JointReaction Analysis simply reports the reaction forces occurring at a joint due to the structure, or definition of that joint. For example, JoinReaction will only report 3 non-zero forces and two moments for a pin joint, and will report 3 non-zero moments for a ball ...

<t>Ideally yes. If you you're interested in a generalized force then Inverse Dynamics will tell you exactly that. JointReactions should give you zero moment/force along a generalized coordinate, however it is possible to set up the analysis so that it mistakenly reports forces in these free directio...

<t>Hi Kang,<br/> <br/> You can decrease the strength of the residual actuators be decreasing their optimal force value. You can find that tag in the xml file for the model. You should run inverse dynamics first and look at the required generalized forces for the 6 pelvis degrees of freedom. The maxi...

<t>This is exactly right. To put it a little more concretely:<br/> <br/> The joint moment calculated by inverse dynamics is a generalized force (for example the knee moment) actuating a generalized coordinate (for this example, the knee angle).<br/> <br/> The forces and moments calculated by JointRe...

It depends on how they are actuated. If your RRA is driven only by torques actuators (as it is normally) and your CMC is driven by muscle actuators which are just complicated force actuators, then JointReactions will give very different results.

<t>Could you be more specific? What errors are being thrown?<br/> <br/> The tool will work with RRA results. The key is that the states you supply must match the states in the model. In the analyze tool, just supply the RRA states file, load the RRA actuators (be sure to replace the model's actuator...