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Monthly Report for Space Robotic FMS PreCommercialization Development Jun 30, 2018

Summary

studying drive segment combinations for optimium excitation of modes which will identify particular forcing degrees of freedom.

Specification

No change.

Design

No change.

Analysis

Continuing work on correlating FE predictions with test data sets and accelerometer pairs to identify mode shapes. Particular attention is being paid to torsion mode, because it is not directly excited. All other modes can be fairly excited to produce very sharp, easily defined peak. The torsion was is visible, but it would be nice to find a means of sharpening it.

Software Simulation

no change

Breadboard Manufacturing

no change; accelerometers on underside of loading plate.

Breadboard Testing

All but one of simple segment combinations have been tested. The combination of accelerometer pair results is being used to identify segment combinations which would enhance mode shape understanding.

testing configurations:

Plans for July.

Continue linear configuration testing (low frequency range) for some combined segments. Continue writing technical paper on issue of torsion degree of freedom result.

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