Identification of mathematical derivative models for the design of a model following control system

Accurate mathematical models were required for the design of a model following control system for the DLR BO 105 fly-by-wire helicopter ATTHeS (Advanced Technology Testing Helicopter System). These models were extracted from flight test data by system identification techniques. Conventional 6 DOF rigid body models turned out to be not appropriate, because they cannot accurately represent the initial response characteristics of the helicopter. Therefore, an extended model with 8 DOF, including rotor dynamic effects, was derived and identified. Both, identification and verification results demonstrate the improved short term response of the extended model and prove its applicability for the control system design. Results obtained from in-flight simulation measurements confirm the reliability of the 8 DOF model.