U.K. research into system identification for helicopter flight mechanics

The techniques of system encompass a variety of processes in the derivation of input/output relationships using experimental data., including control input design, state estimation, model structure estimation and parameter identification. For helicopter flight mechanics studies, research is still required to develop a reliable system identification procedure that can be used with confidence at the design and development stages of a new project. U.K. research in this filed is directed towards this aim with two principal objectives; firstly to develop a tool that can accurately gauge the validity and limitations of theoretical predictions methods, hence assisting the design process; secondly to provide a tool for use during development flight testing that can rapidly highlight problem areas and assist in establishing the degree of compliance with operational handling requirements. This paper reviews the status of a research programme in the U.K. from initial studies performed under a RAE/NASA collaboration through to the current collaborative activity between RAE Bedford and the University of Glasgow. The elements of the integrated process in use from control input design to model structure estimation are described and results using simulation and flight test data collected on the RAE research Puma are presented. The examples presented include the estimation of parameters affecting stability variations with flight path angle, highlighting aspects of the equation error, stepwise regression, model structure estimation process. Finally the direction of future research is discussed, with reference to both analysis software and test facilities