Controllability of Aerospace Static Mechanical Loading Coupled with Dynamic Forces

Abstract

The objective of this testing activity was to examine and verify the interactions of a hydraulic mechanical load control system loading a thin skinned aerospace structure coupled with applied acoustic vibrations. The goal was to be able to actively control the load of four hydraulic cylinders loading two end plates while an electrodynamic shaker attached to the skin imposed simulated acoustic loading. The objective was to achieve mechanical load control within ±1% of desired static load for each load control channel. The mechanical loads applied ranged from the noise floor to Design Limit Load (DLL) (2000 lbf) using varying ramp rates in conjunction with the random dynamic vibration. The presence of dynamic load introduced an error of 0.4% DLL with traditional PID tuning methods. The testing also quantified the suitability of 2 channel master/slave control vs. 4 channel individual control. It was determined that using a dedicated servo control channel (non-slaved servo channel) per load cylinder drops the maximum difference to 2.2% of full scale applied load (25% DLL), as opposed to 7.8% of full scale applied load (25% DLL) when the top two load cylinders are slaved to one servo and the bottom two load cylinders are slaved to another. This amounted to a 72% reduction in error using non-slaved servos. The test activity’s technical approach and test data will be presented.

Distribution Statement

Distribution A. Approved for public release: distribution unlimited. Case Number: 88ABW-2016-5380