A control actuation system (CAS) for a missile is an important subsystem that controls the position of control surfaces. In the design stage of missiles, two major subjects related to the CAS should be considered: dynamic stiffness and servo control algorithm.
Recently, increasing numbers of an electromechanical actuator (EMA) application have required an accurate dynamic stiffness model to analyze the aeroservoelasticity of a flight vehicle. In this study, a modeling method of the dynamic stiffness of the EMA is presented. The validation of the dynamic stiffness model is verified through experiments and simulations. Additionally, in order to analyze the effect of nonlinear parameters of the EMA, pragmatic experimental approaches are explained and performed using a real EMA hardware and a hydraulic excitation system. The experimental data and simulation results showed that the dynamic stiffness of the EMA changed depending on the magnitude of external load, preload, free play, and static stiffness. These results suggest that it is necessary to consider the dynamic stiffness of the EMA when designing the CAS. Servo control algorithm is also an important subject in the design stage of the CAS. In the conventional servo control scheme, three commanded deflection angles of the autopilot are distributed to four commanded deflection angles of control surfaces. However, the EMA has several constraints, such as voltage, current, and angle limits. The conventional servo control method may result in significant performance degradation of flight vehicles under presence of the physical constraints. In the integrated servo control scheme, three controllers for roll, pitch, and yaw correspond to the three deflection angles of the autopilot directly. This paper proved that the integrated servo control algorithm exhibited better performances in several conditions by simulations and experiments.