Abstract
An innovative design of a Large Angle Flexure Pivot (LAFP) is described. It combines the advantages of flexure mechanisms while surpassing one of their few flaws, small displacement strokes. The LAFP design exceeds these angular limitations to reach a deflection of 180° (±90°). The centre shifts laterally by less than ±35 μm throughout the full rotation range. The LAFP is meant to be mounted in pairs, coaxially and with the payload between them. The intended application of the LAFP is to angularly guide an optical component in a space environment for future science missions operating in a cryogenic environment. A dedicated performance test bench was developed and manufactured to test the pivot characteristics notably the lateral shift using Eddy current sensors. The test bench incorporates a representative dummy payload for mass and inertia. Extensive FEM analysis has been performed to validate the design at component level and further analysis with the pivots mounted with a representative payload on a test bench for random vibration, shock and thermal cycling environment. The second test bench for the vibration and shock tests has been manufactured incorporating a simplified launch locking device. The performance tests have confirmed a lateral shift of less than ±35 μm over an angular range of ±90°. The pivots have been successfully tested and survived vibration loads for high level sine at 24 g and random vibration at 12 grms in all three directions.
Highlights
An innovative design of a Large Angle Flexure Pivot (LAFP) has been developed (Fig. 1) combining the advantages of flexure mechanisms – no friction, no backlash, no need for lubricant, no wear – while surpassing one of their few flaws, small displacement strokes
2.2 FEA performance evaluation Extensive FEM analysis has been performed to validate the design at component level and further analysis with the pivots mounted with a representative payload on a test bench for random vibration, shock and thermal cycling environment
The test bench was modelled with solid elements and the model shown in Figure 6 was used for the pivots
Summary
An innovative design of a Large Angle Flexure Pivot (LAFP) has been developed (Fig. 1) combining the advantages of flexure mechanisms – no friction, no backlash, no need for lubricant, no wear – while surpassing one of their few flaws, small displacement strokes. These are usually comprised between 10° and 20° for typical flexible angular pivots. The LAFP design exceeds these angular limitations to a range where previously only ball bearings would be adequate. In order to meet future science missions in a cryogenic environment, they can operate in a temperature ranging from -140°C to +65°C. The intended application of the LAFP is to angularly guide an optical component in a space environment
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