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Monthly Report for Space Robotic FMS PreCommercialization Development February 28, 2019

Summary

Investigating interaction w.r.t shear modes and torsion mode. Reviewing interface spec for potential Lunar Gateway robotics to understand FMS implications.

Specification

No change.

Design

No change.

Analysis

Shear modes have increased in frequency. But the resolution on the torsion mode has deteriorated, which might be the result of shear mode pair changes. Studying possibility of travelling wave impact.

Software Simulation

no change

Breadboard Manufacturing

no change

Breadboard Testing

Performance testing has begun with nominal, but undefined tension in struts. Mostly just correlating with previous results.

testing configurations:

Plans for March.

Consider alternate means of exciting torsion mode. Investigate apparent double peak for first shear mode. Investigate discrepancies between FE model and test results, at system level (ie external boundary condition assumptions)

What's so tough?

Temperature Lack of atmosphere drives temperatures to be either hot in sun or cold in shade. Robots are for moving things around, so they go into and out of shade repeatedly.

Force not directly measureable. It can be inferred from strain or deflection. Such measures are affected by thermal distorsion.

Large dynamic range linear vs rotation forces. Long robot arms and the need to capture 'free flyers' generates large rotational forces.

High Stiffness A high stiffness requirement, makes measurement of strain or deflection more difficult to isolate from thermal distorsion.

Drift Space operations tend to be slow - often taken over a period of hours.

6 dof It is important to distinguish all 6 degrees of force measurement, but the shear and moment loading cases can produce difficult to distinguish effects