Stability Augmentation System for Hovering Helicopter: A Preliminary Design

The extremely complex helicopter dynamics is converted to a linear time-invariant model representing the hovering flight. Cross-coupling between longitudinal and lateral dynamics during hover is least, which leads to the usual attempt of separation of these set of equations. The Eigenvalue analysis adopted in this paper necessitates the need for a feedback controller to bring the helicopter system back in its trim position after perturbing from the initial state. A linear static feedback gain that augments the stability property of the rotorcraft is obtained from infinite horizon Linear Quadratic Regulator (LQR) control design technique. The modified LQR controller is used that is capable of bringing the scaled rotorcraft system back to the trim/equilibrium state even in the presence of disturbance input.