The US Navy seeks a new and innovative way to conduct full-scale fatigue testing on airframes, particularly for rotary wing airframes. Typical equivalent fatigue damage approaches, often successfully applied to airframe subsystems, have be found to be insufficient. Full-scale fatigue testing on airframes is difficult due to the multiple inputs and, more importantly, the nature of those inputs. The multiple loading inputs vary consistently in magnitude and phasing. Current test approaches are limited in frequency (low cycle counts), displacements and numerous other considerations necessary to properly test the airframe for equivalent, full life fatigue damage. A model-based (model-in the-loop) control system is sought to significantly improve upon typical reactive based control systems. The model-based multiple input multiple output (MIMO) control system will be predictive and adaptive based on feedback from typical sensors that are used in structural testing. For this Phase 1 project, Kaneys initial modeling will be of a simplified dynamic system using MATLAB-based simulations. The initial simplified system will include a simple model and a low number of inputs from pseudo-sensors to focus on achieving the minimum goals of the control system: a minimum loading frequency of 10 Hz with excitation sources that can achieve speeds of 100 in/s or more (~16 gpk/1.6 inpk at 10 Hz). This will allow for ease of adjusting and experimenting with different approaches for the predictive and adaptive control system that meet the minimum goals of loading frequency. A small-scale proof of concept (POC) will be created during this Phase of the program. In parallel with control system modeling, research will be conducted on existing excitation sources as well as existing technologies that can be altered to use as excitation sources that will meet or exceed the already discussed minimum goals of the test system. Kaney will leverage 20+ years of experience in Controls and Airframe subsystem fatigue testing to achieve the discussed goals. Successful achievement will allow for a scalable test system that, ultimately, could be applied to numerous airframe types as well as other industries in general.
