A Tandem Active Disturbance Rejection Control for a Laboratory Helicopter With Variable-Speed Rotors

This paper introduces a laboratory helicopter with a variable-speed rotor system based on decentralized active disturbance rejection control. The new control scheme is composed of two independent stages that are utilized to achieve the precise trajectory tracking of the generalized coordinates of the system. A simplified model is proposed at each stage, which highly simplifies the controller design task. High-gain generalized proportional integral observers are considered in order to locally estimate all the disturbances affecting each subsystem online. These estimated disturbances are used in the control law of each stage to eliminate the effects of these disturbances on the system performance. Some of the advantages of the proposed control are: it only requires the knowledge of the input gain to the subsystems (minimum information required from the dynamical models to control them); the robust controller design procedure is simplified; easier and safer implementation with regard to standard controllers; and high robustness to large initial errors, unmodeled unmatched perturbations, noisy measurements, and parametric uncertainties in the model. The effectiveness of the proposed approach has been verified with real experiments conducted on a laboratory platform.