| Rotorcraft can take off and land vertically, and can perform flight ranging from hovering to airplane-like cruising with agility and maneuverability. These qualities have made them indispensable vehicles for a variety of applications. Today, there is a growing interest in using small-scale rotorcraft as platforms for unmanned aerial vehicles (UAVs). Current RUAVs, however, fail to exploit the vehicles' full potential because of deficient flight control systems. The design of high performance control systems for a vehicle with complex dynamics requires a mathematical model that accurately describes the vehicle's dynamics. Linear, low order models are preferred, setting difficult constraints on the modeling task.; This thesis describes the development of a dynamic model for a small-scale Yamaha R-50 helicopter using rotorcraft system identification techniques. Based on experimental data collected from the vehicle, a parameterized model of its dynamics was identified. The parameterized model accounts for the presence of a stabilizer bar and an active yaw damping system; which are typical stability augmentation system on small-scale helicopters. Because rotorcraft dynamics change with operating conditions, both a hover and cruise flight condition were identified. The resulting models were validated against flight-test data and were shown to be highly accurate in predicting the vehicle responses, and the identified parameters were shown to be close to the theoretical values.; The model helped us understand typical characteristics of small-scale rotorcraft. We used dynamic scaling rules to determine the effect of scale on the dynamic characteristics of helicopters, and at the same time, we used these rules to compare between the characteristics of the R-50 and those of a full-scale Bell UH-1H helicopter. By explicitly accounting for the stabilizer bar, we were able to use our model to determine and simulate the effect that system has on the vehicle dynamics. Finally, by using the model to analyze and optimize the RUAV's attitude control system we demonstrated that the model lends itself to advanced control design. |
