MIMO closed-loop subspace model identification and hovering control of a 6-DOF coaxial miniature helicopter

This paper concerns black-box modeling of a radio-controlled (RC) coxial miniature helicopter by closed-loop subspace model identification with a multi-input and multi-output (MIMO) state space model, as well as model-based control design of hovering flight using the identified black-box model. The RC helicopter has 6 degrees of freedom (6-DOF) in its motions, namely, the lateral (left/right), vertical (up/down), longitudinal (fore/aft), pitching, rolling and yawing axes. These 6 parameters of the position and posture, as the outputs of the RC helicopter, are measured by a motion capture system with 6 high-speed cameras. The helicopter maneuvers, as the inputs, are done by the aileron, elevator, rudder and throttle. A closed-loop system identification experiment of the hovering RC helicopter is performed. CL-MOESP, which is one of closed-loop subspace model identification methods, is applied to the sampled closed-loop data in order to obtain a state-space model with an estimated order. Using the identified model, an LQ controller with a full-state observer is designed. Finally, as verification of the identified model, an experiment of hovering flight of the helicopter is performed with the implementation of the feedback controller.