Frequency Based Composite Design for Multi-Axis Gimbal Systems
Typical FEA 2-axis gimbal model |
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OBJECTIVE
A company in the USA has developed a line of lightweight, advanced composite, multi-axis gimbals for use in precision applications. A gimbal is a device using Euler angles to measure the rotation of an object in three dimensions and to control that rotation.
To ensure that the structural frequency of the high-modulus Gimbal meets the control system specifications, finite element analysis is required to accurately predict its structural response.
METHODOLOGY
FEA models are first generated that include composite shell elements, solid bricks for the drive components, and general springs for bearings and fasteners. Spring constants are calculated to represent bearing axial and radial stiffness values, and the fasteners used within the structure. Mass elements are added as required to represent the payload, motor and other ancillary equipment embedded within the gimbal.
Eigenvalue analysis is conducted to extract Eigenvalues using the Lanczos method, with stress, strain and displacements saved for post processing. Composite ply schedules are varied until the first participatory mode meets the control specifications.
The company now has a convenient spreadsheet which has a listing of the modal participation factors of the critical modes. The company saved time and costs by not fabricating a Gimbal using a complicated manufacturing process.
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Case Studies