An emergency controller design for transport airdrop subject to input saturation

During airdrop of heavy load, the aircraft's flight states vary continuous as the load moving back in the cargo hold, and then change suddenly when the load drops out or leave the hold. This process deteriorates the flight quality as the load becomes heavier. Under the backstepping and switch control methods, the flight state holding can be fulfilled under the assumption of unlimited actuation. And the control saturation problem is inevitable in engineering practices; this paper develops a control strategy with saturating actuators to tackle the actuator windup problem during the heavy load airdrop. With the piecewise linear least quadratic control (PLC) theory, the controller parameters were tuned to enlarge the domain of attraction under saturation. Then the high gain component is constructed and augmented to low feedback gain according to the Low-and-High Gain (LHG) design technique. Simulation results of transport airdrop closed-loop control process show the effectiveness of the proposed control algorithm.