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


Beginning investigation of drive segment combinations for optimium excitation of modes which will identify particular forcing degrees of freedom. The out of plane modes (ie those suitable for measuring axial and moment, and to related extent shear DOF's) have nice clear, easy to identify peaks which are very good for overall resolution. The peaks for torsion dof is not as good, and so this investigation is to understand means of improvement.


No change.


No change.


Combination of test data sets are being performed to identify characterists of modes. A means of defining modal participation factors, suitable to segmentially poled driving element is underway.

Software Simulation

no change

Breadboard Manufacturing

no change; accelerometers on underside of loading plate.

Breadboard Testing

Some additional testing is being done to consider participation factors, and to allow for segmential combination checking. Testing is in below 3300 Hz (segments 0 to 3) range. Most peaks are sharp and easy to identify (better than initial work a year ago). Frequency peaks are quite similar to original results.

Plans for May.

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