Real Time Control of a Fin Loading System

Fin actuation systems are one of the most essential parts of missiles since they actuate the fins and consequently provide missiles to carry out certain tasks during their mission. The designed control algorithm for the fin actuation system (FAS) must cope with the disturbances where the most prominent of them are the aerodynamic loads on the fins. Even though the control algorithm can be tested by computer simulations one may not be sure if the system works as required. Hence, the realistic aerodynamic loads must be applied to the tin shaft. In this study, a fin loading system (FLS) will be presented and the torque model of a fin loading system is derived. Omitting nonlinearities due to dead-zone and viscous friction, the parameters of the FLS are obtained by system identification technique using a predelined system structure. Since, there are modelling inaccuracies and external disturbances, Sliding Mode Control (SMC) approach is chosen as it is known to be robust to matched uncertainties once it reaches to the sliding hyper-plane. SMC is shown to have good tracking performance and disturbance rejection property in real time application in the presence of modelling inaccuracies and high disturbances due to fins movement.