Application of Control Allocation Methods to SAT-II UAV

Abstract

This paper focuses on applying various control allocation schemes to SAT-II UAV system. Control allocation is a useful method for controlling an aircraft with redundant control surfaces and deals with distributing control commands among individual actuators when some control surfaces are failed. In order to implement control allocation scheme in the aircraft control system, control system has to be designed through two step procedures. The first step is to design a baseline control system specifying total control command to be produced, and the second step is to design a control allocator that maps the total control command on individual actuators. The baseline control system of the SAT-II UAV is constituted of speed, altitude, and lateral deviation controllers for tracking a predetermined glide path during automatic landing phase. In the baseline control system, proportionalintegral controllers and lead/lag compensators are effectively combined to assure enough gain and phase margins. Several control allocation methods such as pseudoinverse control allocation method, daisy chain control allocation method, direct control allocation method, and optimization based control allocation methods are considered in this paper. The performance of these methods is evaluated and compared to each other through the nonlinear simulation under the assumption that right aileron failed and are stuck at fixed deflection position during the glide approach phase.