Actuators for Engine Nozzles and Aerosurfaces Control

Actuators are commonly used in flight vehicles for positioning control surfaces or engine nozzles. This chapter presents three actuator models which are typically used in flight control system analysis to pivot control surfaces or TVC engines: electrohydraulic, electromechanical, and pneumatic. It also demonstrates the dynamic coupling between the flight vehicle and the actuator systems, and describes the different types of stiffnesses. The actuator models in addition to the actuator dynamics and the local control system that controls the shaft extension, also include the rotational dynamics of the effector load relative to the hinge, and the stiffness of the support structure, shaft, and load linkage. The chapter also presents the dynamic model of a flight vehicle that is controlled by three aerosurfaces (elevon, aileron, and rudder), where each surface is controlled by a separate actuator subsystem.