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Monthly Report for Space Robotic FMS PreCommercialization Development April 30, 2019

Summary

Continued testing with nominal strut tension. Modified method of viewing data has increased number of trackable modes below 3300 Hz.

Specification

No change.

Design

No change.

Analysis

no change.

Software Simulation

no change

Breadboard Manufacturing

no change

Breadboard Testing

Have identified phase shift excitation that excites almost all modes below 3300 Hz. Two modes seem to have split and it may be the tensioning on shear modes that causes it.

testing configurations:

Plans for May.

complete testing of nominal strut tension condition and modify it slightly to consider influence.

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