Robust control for a 3-DOF helicopter system based on unknown input observer

摘要

In this paper, a new robust control method based on an unknown input observer (UIO) is proposed for a benchmark 3-DOF helicopter system to deal with unknown time-varying nonlinear dynamics and disturbances. The objective is to make the helicopter track the given elevation and pitch references. For this purpose, we propose a novel simple UIO to estimate the lumped unknown dynamics, which are then used in the control design as a compensator. By defining the auxiliary filter variables, an invariant manifold is obtained and used to design the UIO. This new estimator needs to set a scalar only and achieves exponential convergence. Then, the proposed control design based on the estimator can achieve accurate output tracking. This control method is applied to a benchmark 3-DOF helicopter to validate the efficacy by simulations and results.