Comparison of frequency responses with PID and two degree-of-freedom PID control for underactuated flying object

Flying object used in our research is an experimental device like a helicopter. Helicopter, which has a special characteristics such as hovering, vertical ascent and vertical dive. Therefore, it is widely used at the time of disaster. For example, manned helicopter is used for rescue work, emergency transport and fire fighting. On the contrary, unmanned helicopter is used to get precious information in a danger area for human. But there are problems that the structure is complicated, it has a high nonlinearity. And it is difficult to keep the attitude, because it is influenced by wind in flight. An experimental device in our research has an underactuated system having 2-input and 3-output that has number of input less than number of output. So, this system is able to reduce cost, but to keep the posture is difficult. Therefore, in our research, a stabilization method called two degree-of-freedom PID control has been proposed. It is the system having three degree-of-freedom. Although the effectiveness has been confirmed through the simulation and experimental results in time-domain, the characteristics of the proposed method was just explored by the result of output for step-type reference signal. Therefore, this paper confirms the effectiveness of the proposed method through the simulation and experimental result in frequency-domain in order to check the characteristics of the proposed method.