mot nan RRA low new mass large Fy

[Yan Junlan]

Dear Experts,
I also encountered some problems when I run RRA and mot file.
The torque in the mot file is -nan(ind),and the cop is nan.It appeared nan when the volunteer did not step on the force platform, and when the first force platform was stepped on, the second and third blocks had no data.Only the force platform stepped on has the appropriate data.
When I perform RRA, the model always disappears and the new mass is always very low, about 0.01kg, and the Fy is also very large. I am not sure if this is due to the influence of the mot file.
Therefore,I would like to know is there any way to solve this problem. I have been troubled for a long time, so I look forward to your reply.

Yan

[Carmichael Ong]

It's difficult to know what the problem is exactly from the info given, but it does seem related to not provided accurate external forces.

If you are new to RRA, you may want to run through one of our tutorials that takes a simple model through RRA, CMC, an Static Optimization: https://simtk-confluence.stanford.edu/d ... +and+Swing

[Yan Junlan]

Hi Carmichael ,
Thanks for your reply.
I implemented the examples in the opensim tutorial and my own,and checked the message window. I found that when applying GRF,there was a difference.
The following is in the tutorial:
Storage::read data file =subject01_walk1_grf.mot (nr=1501 nc=19)
ExternalForce::right
Data source being set to subject01_walk1_grf.mot
ExternalForce::left
Data source being set to subject01_walk1_grf.mot

Computing average residuals between 0.744 and 1.24
Storage: read data file =subject01_walk1_grf.mot (nr=1501 nc=19)
ExternalForce::right
Data source being set to subject01_walk1_grf.mot
ExternalForce::left
Data source being set to subject01_walk1_grf.mot

The following is my example:
ExternalForce::GRF_1
Data source being set to
ExternalForce::GRF_2
Data source being set to
ExternalForce::GRF_3
Data source being set to

Computing average residuals between 6.7 and 7.5
ExternalForce::GRF_1
Data source being set to
ExternalForce::GRF_2
Data source being set to
ExternalForce::GRF_3
Data source being set to

In addition, a file of RRAExternalLoads_2 is generated, and the settings inside are as follows:
<?xml version="1.0" encoding="UTF-8"?>
-<OpenSimDocument Version="40000">
-<ExternalLoads name="Ex1">
<objects/>
<groups/>
<!--Storage file (.sto) containing (3) components of force and/or torque and point of application.Note: this file overrides the data source specified by the individual external forces if specified.-->
<datafile/>
<!--The option is deprecated and unnecessary to apply external loads.A motion file (.mot) or storage file (.sto) containing the model kinematics used to transform a point expressed in ground to the body of force application.If the point is not expressed in ground,the point is not transformed-->
<external_loads_model_kinematics_file/>
<!--Optional low-pass cut-off frequency for filtering the model kinematics corresponding used to transform the point of application. A negative value results in no filtering.The default value is -1.0,so no filtering.-->
<lowpass_cutoff_frequency_for_load_kinematics>-1</lowpass_cutoff_frequency_for_load_kinematics>
</ExternalLoads>
</OpenSimDocument>

Therefore, I think it is because GRF is not properly applied. However, I don't know how to adjust to add GRF properly, my operation is the same as in the tutorial. Do you know where the problem is and how to solve it?

Thanks
Yan