Scalar H∞ autopilot synthesis for control systems and evaluation via HIL simulation

Abstract

The improvement in calculation capabilities conciliate the design and performing of advanced robust control. Among the critical applications are the anti-tank missiles systems. The present work is concerned with enhancing the performance of an antitank guided missile system via robust synthesis of autopilot and guidance systems. This paper is concerned to the derivation of the missile airframe transfer functions. The obtained transfer functions are expanded with formulation for the system uncertainty to be considered during the robust design. The next objective for this paper is to design an autopilot using robust technique with complete justification against related work putting into consideration the overall requirements of flight tactics characteristics. The proposed design is implemented within the simulation model. The obtained results explain the capability of the designed controller to maintain the stability of the system in the presence of un-modeled dynamics. These autopilots proved its robustness to thrust uncertainties within 30% degradation, and about ± 30% of nominal aerodynamic coefficients. It is limited to wind speed of about 20 m/s in both directions. It proved its capability of less sensitivity to measurement noise and reject disturbance of 50% within 0.09 s and 95% within 0.22 s. Then, the actuator hardware is implemented within the simulation via interfacing cards using the designed robust autopilot in presence of the prescribed uncertainty. The results show the accuracy via using the hardware-in-the loop simulation. The obtained results revealing that the developed autopilot has the capability to stabilize the system in presence of noise and disturbance. Keywords Command guidance systems • CLOS • Robust control • H ∞ • Uncertainties List of symbols Symbols X 1 , Y 1 , and Z 1 Vectors components along the board reference axes X g , Yg, and Z g Vectors components along the ground reference axes X, Y, and Z Vectors components along the velocity reference axes δ jp and δ jy Thrust jetivator angles in pitch and yaw planes F TX 1 , F TY1 and F TZ 1 Thrust forces along the board reference axes F AX , F AY and F AZ Drag, lateral, and lift forces along the velocity axes S Characteristic area q Dynamic pressure given by q = 0.5ρ (Vm) 2 (kg/m/s 2) ρ Air density (kg/m 3) V M Missile velocity C x , C y , and C z Dimension-less aerodynamic coefficients g Vector of gravity acceleration M Mach number and given by M = V m /V a V a Sound velocity at missile position