Modeling and decoupling control of the coax micro helicopter

The dynamics of micro coaxial helicopters are coupled, especially in the presence of a stabilizer bar and in dynamic maneuvers. This paper presents a model-based approach for active decoupling of the dynamics of a micro coaxial helicopter. This allows for easier and more accurate operation of the system. The nonlinear model covers all degrees of freedom for attitude and altitude. It accounts for hover and cruise flight situations and explicitly captures the off-axis dynamics and the dynamics of the stabilizer bar. A six-axis force/torque sensor and an RPM measurement system are used in a custom built test bench. It is applied for analysis of the forces and torques generated by the rotors in combination with the dynamics of the drive train and the swashplate. The parameter identification and the model validation is obtained with flight data recorded with a vision-based motion tracking system. The decoupling controller is implemented on the commercial robotic helicopter CoaX and its performance is shown via a motion experiment.