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Metecs

Portfolio > Analysis Simulations

A screenshot of the simulation used by METECS to analyze the COTS simulation validity.

A screenshot of the simulation used by METECS to analyze the COTS simulation validity.

Analysis of robotic systems involves careful study of simulation responses to correlate observed system behavior with an understanding of the underlying physics, expected control system behavior, and knowledge of the operational requirements of the system. The two examples discussed below demonstrate how METECS works directly with clients to build simulations and components as well as perform analysis of simulation and test data for vehicles, robots, and mechanisms.

Free-Flyer Capture of Commercial Spacecraft

NASA recently approached METECS to upgrade the Latching End Effector (LEE) model in the Space Station Remote Manipulator System (SSRMS) simulation for analysis of free-flyer captures of commercial space vehicles. The existing LEE model had a number of deficiencies related to internal mechanism dynamics which limited the fidelity of the simulation and consequently the reliability of any analysis results. Of particular concern was the kinematic nature of the LEE latching motor model and its inability to provide the LEE Control Software (LCS) with transient responses from forces and moments produced during capture scenarios. Without considering these forces, and their effect on the snares, latches, and especially the carriage, NASA was uncomfortable with the simulation's ability to predict mechanism slow downs and stalls in high load conditions.

LEE and grapple fixture contact models created in PONG were used to generate reaction loads for the LEE EM model.

LEE and grapple fixture contact models created in PONG were used to generate reaction loads for the LEE mechanism models.

In addition to the lack of fidelity in the mechanism models, the contact model between LEE and the grapple fixture on the commercial spacecraft was deemed inadequate for the rigor of this analysis. METECS addressed this issue by using Pong to quickly generate LEE and grapple fixture contact geometries for use in the simulation. (A prototype PONG contact model is shown on the right.)

Working closely with NASA, METECS engineers upgraded the fidelity of the LEE simulation as follows:

  • Upgraded the existing FORTRAN LEE model to include dynamic electromechanical motor effects.
  • Integrated the new model with the mechanism and LEE geometry contact models using Pong.
  • Analyzed and verified the results against CSA provided reference data.

SSRMS Force Moment Accommodation

FMS/FMA validation contact models created for initial FMS integration.

FMS/FMA validation contact models created for initial FMS integration.

METECS was asked to analyze the SSRMS simulation response with the addition of an upgraded Force Moment Sensor (FMS) model, an upgraded version of the host software (AHS) filtering algorithms, and two simple contact models. As part of the analysis, the response was to be validated against Canadian Space Agency data.

The validation of FMS and FMA performance in NASA's Trick simulation environment utilized two simple contact models; the tripod model and the wheel-rail model, which are both shown below. METECS used the PONG contact modeling tool to create and modify these models in a graphical environment.

 

 

 

 

 

 

 

 

 

 

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