抄録
In this study, the optimal mechanical design method for fixed-pitch coaxial-rotor helicopter is proposed. The fixed-pitch coaxial-rotor helicopter has several advantages compared with any single-rotor type or variable-pitch rotor type helicopters. For example, it has great simplicity of the mechanisms, well maintainability, and well energy conversion efficiency, and so on. However, fixed-pitch coaxial-rotor helicopter has a drawback in forward flight named pitch-up phenomenon. The pitch-up phenomenon causes a little cruise speed of the helicopter, and it is fatal problem in the practical operations. To overcome such a problem, optimal mechanical design of the fixed-pitch coaxial-rotor helicopter is proposed. The optimal design is based on the precise mathematical model of the helicopter and numerical optimization method. The mechanical parameters are examined to maximize the cruise speed of the helicopter. First, the dynamics of a fixed-pitch coaxial-rotor helicopter is modeled by using multi-body dynamics technique and aerodynamics theory. In the modeling, the helicopter is considered as a rigid body system consist of multiple rigid bodies, mission and frame unit, and rotors. Additionally, the aerodynamic interaction between upper and lower rotor is considered in the model. Second, mechanical parameter optimization based on derived mathematical model and Particle Swarm Optimization (PSO) method is proposed. Finally, the fundamental optimization of mechanical parameter is performed to show the validity of proposed optimal design method. In the simulation, the position of the universal joint is optimized to maximize the cruise speed of the helicopter.
