Design Parameters for Coaxial Rotary Wing MAVs with Passive Roll and Pitch Stability

In this work, design parameters are studied that lead to a coaxial micro helicopter which is passively stable in roll and pitch. Stabilization is not achieved with a stabilizer bar or any other active or passive device, but by tuning of relevant system design parameters. The problem is approached by introducing a simulation model for micro helicopters in coaxial rotor configuration, which is formulated in terms of physical design parameters. Starting from neutral initial conditions, the model is disturbed with a standard roll disturbance torque, and the passively stable response behavior is visualized. By means of systematic variation of the design parameters, namely blade flapping stiffness, blade flapping inertia and distance between lower rotor and helicopter center of gravity, a large domain of parameter combinations is run in the simulation and evaluated in terms of stabilization performance by use of a penalty integral. The results show that passive stabilization only due to blade flapping is possible for coaxial micro helicopters. Furthermore, parameter domains leading to passive stabilization are presented.