The Defence Science and Technology Group (DSTG) of Australia leverages advanced MTS control techniques and model-based engineering expertise to accelerate highly complex and dynamic helicopter airframe testing.
Researchers at the Defence Science and Technology Group (DSTG) of Australia successfully concluded a six-year effort to build a prototype test rig capable of executing a full-scale fatigue test (FSFT) of a helicopter airframe in an accelerated timeframe, comparable to that of a fixed wing aircraft test. Known as the Helicopter Advanced Fatigue Test - Technology Demonstrator (HAFT-TD) Program, its aim was to develop the means to apply two lifetimes of dynamic flight loading to a full-scale helicopter test article in 2.5 years or less. To de-risk, tailor, and integrate the diverse technologies needed to realize the program’s objectives, DSTG partnered with the Royal Australian Navy (RAN), the United States Navy (USN), the Mercer Engineering Research Center (MERC), and MTS Systems.
Model-Assisted Compensation (MAC)
To develop a control system capable of the accelerated cycling rates, high accuracy, and multiple degrees of freedom required for HAFT-TD, DSTG collaborated with MTS engineers to develop an advanced model-assisted control methodology for servo-hydraulic actuation. Designed to minimize control errors so that complex, dynamic tests can run much faster, Model-Assisted Compensation (MAC) uses a real-time analysis model, comprising a reduced order specimen model and virtual test rig, running in sync with a physical servo-hydraulic test rig via shared, high-speed reflective memory. Valve commands needed to achieve the commanded forces flow from the analysis model and play out on the rig. Force and displacement signals flow from the rig back to the model, and the process repeats at each clock tick.
Test loading used throughout the HAFT-TD Program represented the most fatigue damaging and highest load and displacement conditions within the U.S. Navy's MH-60R Seahawk helicopter design usage spectrum (DUS).
DSTG and MTS researchers employed a 6-channel, 6 Degree-of-freedom Dynamic Demonstrator (6DDD) in the early stages of the HAFT-TD Program to develop and prove the model-in-the-loop control methodology that would become AeroPro MAC.
The MH-60R airframe on the full-scale 16-channel HAFT-TD rig: DSTG demonstrated the ability to reach the test cyclic rates, load accuracy, and airframe strains needed for accelerated replication of a range of MH-60R flight conditions.
