This work investigates the performance on the aircraft control system during air refuel purposes of the Linear Quadratic Regulator (LQR) control alone, and the integration between fuzzy control and LQR. LQR is modern linear control that is suitable for multivariable state feedback and is known to yield good performance for linear systems or for nonlinear systems where the nonlinear aspects are presented. The fuzzy control is known to have the ability to deal with nonlinearities without having to use advanced mathematics. The LQR integrated fuzzy control (LQRIFC) simultaneously makes use of the good performance of the LQR in the region close to switching curve, and the effectiveness of the fuzzy control in region away from switching curve. A new analysis of the fuzzy system behavior presented helps to make possible precise integration of LQR features into the fuzzy control. The LQRIFC is verified by simulation to suppress the uncertain instability more effectively than the LQR alone besides minimizing the time of the mission proposed. The aerial refueling process has been divided into 3 basic stages (initial stability stage, tracking stage, alignment stage) to meet all the process requirements and constraints with minimizing the whole mission time period. GA has been used to tune the fuzzy logic controller parameters and some PID’s. The control strategy was applied to both aerial refueling methods. And the MATLAB simulation results show the validity and the efficiency of using the proposed control approach.

1. ‫الرحيم‬ ‫الرحمن‬ ‫ا‬ ‫بسم‬
In the name of GOD

2. DEVELOPMENT OF FUZZY LOGIC LQR CONTROLDEVELOPMENT OF FUZZY LOGIC LQR CONTROL
INTEGRATION FOR FULL MISSION MULTISTAGEINTEGRATION FOR FULL MISSION MULTISTAGE
AERIAL REFUELING AUTOPILOTAERIAL REFUELING AUTOPILOT
By
Eng. Ahmed Momtaz Hosny
School of Astronautics, Beihang University
Beijing, China
2008

4. Aerial Refueling
Significance1-Most of fighter aircrafts can’t exceed a certain range of
2000 Km and endurance of about 2 hours according to
the small fuel capacity
2-To perform an air domination and stability over far
territories during the military operations specially for large
number of fighters
3-Providing aerial refueling autopilot for each fighter
aircraft permits the tanker aircraft to supply large number
of fighters in short time without any mishaps that could
happen during the manual process

5. Introduction to Air Force Aerial Refueling Methods
Flying Boom versus Hose-and-Drogue

8. Main Objectives
1- Satisfying Flying Qualities standard
2- Minimizing the mission time
3- Satisfying the Tanker-Fighter safety
constraints

9. 3 Stages Aerial Refueling
Autopilot
1- Initial Stability Stage (LQR)
2- Tracking stage (LQRIFL)
3- Alignment Stage (LQR with Phase Lead
compensator)

10. F-16 Nonlinear model

11. F-16 Control Channels

12. Aircraft linearized model
Aircraft Trimming at Prescribed points
Model Linearization using the Jacobean
matrices
)()()()()( tutBtxtAtx +=•
)()()()()( tutDtxtCty +=
)()()( txtCty =

14. Aircraft Lateral Dynamics in Linearized
form

16. 1-Initial Stability Stage1-Initial Stability Stage

20. LQ Formulation of the Tracker Problem

22. Pitch Rate Controller

23. Lateral – Directional
Controller

24. PID Fuzzy Logic Controller

25. LQ Integrated Fuzzy Logic Controller

26. Flowchart of GA Functions

27. Optimizing Fuzzy Output
Gains

28. Tuning of Fuzzy Sets

30. Comparison between LQR with and without Fuzzy PID
for Longitudinal and Lateral Motion
Up to 8% improving the (PI)

31. 2- Tracking Stage2- Tracking Stage

33. Input Commands to
Receiving Aircraft

36. 3-Alignment Stage

37. Plane Formation Geometry

38. Alignment Stage
Controller

40. Trajectory scenario in x-y plane for both wingman
and leader

41. (Boeing KC 767 Tanker – Boom configuration) versus (KC-130J Tanker with Hose –
Drogue configuration) (case study)

47. Control Strategy

48.  Final ConclusionFinal Conclusion

It is clear from the present work that there is some basic requirements should be satisfied inIt is clear from the present work that there is some basic requirements should be satisfied in
order to establish efficient aerial refueling autopilots such as (1- flying qualities requirements, 2-order to establish efficient aerial refueling autopilots such as (1- flying qualities requirements, 2-
safety and secured approaching in the final docking, 3- minimization the whole mission timesafety and secured approaching in the final docking, 3- minimization the whole mission time
period) which implies that a multistage autopilot is needed for this purpose. Therefore LQRperiod) which implies that a multistage autopilot is needed for this purpose. Therefore LQR
technique was used to satisfy the flying qualities, providing control integration with fuzzy logictechnique was used to satisfy the flying qualities, providing control integration with fuzzy logic
controller that enhance the output performance index. Applying an optimal trajectory during thecontroller that enhance the output performance index. Applying an optimal trajectory during the
tracking stage had a great effect in minimizing the total mission time. Using flight formationtracking stage had a great effect in minimizing the total mission time. Using flight formation
principle in last stage (alignment stage) had satisfied the required tanker geometrical constrainsprinciple in last stage (alignment stage) had satisfied the required tanker geometrical constrains
mentioned before. Thus a multistage autopilot could be realized in such described sequencementioned before. Thus a multistage autopilot could be realized in such described sequence
verifying the safety and security with minimizing the mission time interval that permit severalverifying the safety and security with minimizing the mission time interval that permit several
aircrafts to be refueled in such an optimum time period. In this way it is possible to avoid anyaircrafts to be refueled in such an optimum time period. In this way it is possible to avoid any
mishaps from the pilots during manual process.mishaps from the pilots during manual process.
 Recommended Future WorkRecommended Future Work

It is recommended to apply the final multistage autopilot for a several aircrafts or a completeIt is recommended to apply the final multistage autopilot for a several aircrafts or a complete
squadron to optimize the air refueling process time for a number of aircrafts so that decreasesquadron to optimize the air refueling process time for a number of aircrafts so that decrease
the time required for the tanker aircraft to stay in the air especially in the operations time.the time required for the tanker aircraft to stay in the air especially in the operations time.
Consequently reducing the time needed for the fighter aircrafts to be refueled thus decreasingConsequently reducing the time needed for the fighter aircrafts to be refueled thus decreasing
the time to be exposed to any aggressors. This will require also different guidance lawsthe time to be exposed to any aggressors. This will require also different guidance laws
according to the aircraft position with central controller installed in the tanker aircraft.according to the aircraft position with central controller installed in the tanker aircraft.

50. Thank You