An H_∞ Design Approach for the Heading Hold Autopilot of a Flying Wing UAV

Abstract

The paper presents a modified loop shaping approach for the design of the automatic flight control system of an unmanned air vehicle’s lateral-directional dynamics. The design objectives include robust stabilization with respect to modeling uncertainties, heading angle tracking of an ideal model, coordinated turn and reduced sensitivity with respect to low frequency measurement errors. Based on the resulting full order controller one determined a reduced order controller. The numerical results show that both the full order and the reduced order autopilots accomplish the design objectives.

Autopilot Design Dor the Lateral-Directional Motion of an Uav

“…The only modification is instead of the value used in [7] because if sensitivity is pushed down in the low frequency range (i.e, good load disturbance rejection and reference tracking), it increases by an equal amount at others frequencies amplifying for instance control command or noise propagation. Thus using 0.5 instead of 100 for will still keep the sensitivity acceptable for low frequency range disturbances while providing a reasonable values for the control input, the elevon deflection .…”

“…The controller architecture can be found in [7], where the authors also used a balanced realization technique in order to reduce the order of the controller from 8 to 5.…”

“…The third section provides some insight on the structured μ-Synthesis controllers, but more details can be found in [8]. Simulation results, for the Hirrus UAV, that include atmosphere turbulences are provided in section four as a comparison between three controllers: the full eight-order controller and its truncated fifth-order version obtained in [7] and the structured μ-Synthesis controller which is only second-order. The paper ends with some concluding remarks.…”

“…A drawback of these types of UAV is that their dynamics are usually unstable, thus they require automatic control in order to obtain the desired maneuverability qualities. In order to ensure stability several control techniques have been proposed in the available literature such as PID control [1], dynamic inversion and μ-Synthesis [2], LQR and LQG control [3,4], L 1 norm based techniques [5], H ∞ norm minimization [7]. All these methods require ensuring a trade-off between their achievable performance and the robustness requirements.…”

“…This UAV was designed and manufactured by a private Romanian company in collaboration with academics from Faculty of Aerospace Engineering of University "Politehnica" of Bucharest. In [7] the design approach is based on a modified version of the so-called two degrees of freedom (2 DOF) H ∞ loop-shaping and it`s able to accomplish simultaneously several objectives as robustness stability, model tracking and disturbances attenuation requirements. A comparison between the full order controller and the reduced order controller obtained through truncation using a balanced realization procedure [7] and the reduced order controller using structured μ-Synthesis is provided.…”