PARAMETER IDENTIFICATION OF A HINGELESS ROTOR HELICOPTER

A research program for parameter identification of the BO 105 hingeless rotor helicopter was conducted. The program consisted of three fundamental steps, which are reported in this paper. First, the parameter identification methods used during the program are reviewed. These are a Least Squares Equation Error Method and a Maximum Likelihood Output Error Method. The main problems associated with the identification of rotary wing aircraft, in general, and with hingeless rotor aircraft, in particular, are briefly discussed. The second part gives results of computer simulation studies using both a linear 6 DOF rigid body model and a non-linear aeroelastic helicopter model including degrees of freedom of the rotor blades. These studies establish fundamental requirements of rotorcraft modeling and provide insight into the identifiability of rotary wing aircraft. The third part of the paper presents a summary of the flight test program and of the subsequent identification phase. After a short description of the test aircraft, the results of the derivative identification of a 6 DOF rigid body model are presented. Time history comparisons are made and derivatives are compared to an analytical quasi-static model and to identified derivatives from non-linear computer simulations.