SYNTHESIS OF AIRCRAFT MOTION CONTROL LAWS USING AGGREGATIVE CONTROLLER ANALYTICAL DESIGN PROCEDURE DURING AUTOMATIC IN- FLIGHT REFUELING

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1 SYNTHESIS OF AIRCRAFT MOTION CONTROL LAWS USING AGGREGATIE CONTROLLER ANALYTICAL DESIGN PROCEDURE DURING AUTOMATIC IN- FLIGHT REFUELING S.P.Kostukov Beriev Aircraft Copan Kewords: snergic snthesis autoatic in-flight refueling Abstract The report is aied to solve the proble of autoatiation of in-flight aircraft refueling. The stated above process is quite coplicated and requires etreel precise fling skills fro the pilot. As for the otion control sste it shall be ver accurate and fleible. The report contains the solution to the tasks of autopilot snergic snthesis to enable control of otion of the aircraft being refueled at the stage of final approach and fuel-feed line drogue capture. The snthesied adaptive controllers ensure high positioning accurac including copensation of force and wind disturbances taking into consideration aircraft ass variation during fuel servicing. In-flight refueling etends aircraft functional capabilities significantl. Therefore currentl the interest to the in-flight refueling has considerabl increased in particular as deands related to operation of unanned vehicle grow up. Unfortunatel the refueling procedure is ver difficult and haardous to be ipleented therefore currentl it is used onl for ilitar aircraft. To carr out autoatic inflight refueling it is required to use the sste able to carr out autoatic approach to the tanker aircraft within the selected range of design paraeters as well as stabiliation of otion during fuel transfer process. In this regard the sste shall be stable to environental disturbances such as: wind gusts aircraft force ipact as well as aircraft weight variation associated with refueling process. In the present docuent the task of snthesis of adaptive autopilots ensuring safe functioning at various environental disturbances for otion control at the stage of approaching the tanker is being reviewed. The results of coputer siulation deonstrate operabilit of in-flight aircraft autoatic refueling sste.. Control object atheatic odel The dnaics of aircraft approach to the refueling point when in-flight a be described using differential equation sste []: X H Z P ( C C (( C (( 0 ( C ) )(( ) ) ) ) S cos( ) g a ) S sin( ) a. ) S a A standard sste of coordinates is used. The refueling point (current position of feed pipe drogue) is a datu point X is in-between distance to the refueling point in horiontal plane; Y is the distance to the refueling point in vertical plane; Z is the cross-track deviation fro the refueling point; is the bank angle; is horiontal speed of tanker travel; is horiontal speed of aircraft travel related to the (.)

2 tanker; is the projection of speed of aircraft travel to the vertical ais; is the projection of speed of aircraft travel to the lateral ais; is aircraft ass; G g is aircraft weight; P is engine thrust; Y c S is lifting force c c is lifting force coefficient; is air densit S is wing area ( ) is aircraft speed relative to air asses Q c S is drag force c c is drag force coefficient 0 c T a [a a a] is acceleration vector resulted fro eternal disturbance.. Autopilot snthesis procedure Let s assue the autopilot snthesis task as the task of deterination of thrust variation laws angle of attack and bank angles using odel status variable functions (.) ensuring aircraft asptotical approach to the refueling point. In this case the terinal distance between the aircraft and refueling point as well as target speed of relative travel in the point of contact shall be equal to ero. Whereas copensation of environental disturbance for instance wind disturbance shall be ensured. To resolve the specified above task the philosoph of snergic control concept and the procedure of aggregative controller analtical design [] based on the theor of ipleentation of attracting invariant variet within the controllable sste state space are used. For environental disturbance counteraction such as gusts force ipact or weight variation resulted fro fuel transfer a technique of variable status space etension is applied b eans of introduction of additional differential equations. As for the case currentl reviewed odel (.) shall be copleted with two differential equations as stated below: Within the first snthesis stage the stated below cobination of invariant varieties is introduced as: X 7 Y 8 Z (.) The target forula for P and shall be deterined b solving the set of the stated below functional equations: T ( t) 0 T ( t) 0 T 0 in view of etended sste odel (.) (.). Coefficients k i i 9 are chosen based on the conditions of stabilit of decoposed sste describing the invariant variet intertion dnaics (.): X Y Z. X 4 X 7 H 5Y 8 Z Z 6. Coputer siulation results Closed-loop sste coputer siulation was carried out using paraeters of odel (.) under the stated below initial conditions: 00 kg a c c a X Y Z. S (.) 9 pr a 0

3 The results of coputer siulation for closed-loop sste for refueling aircraft approach are given in Fig. 5. Fig.4. Transient process along Z-coordinate ais. Fig.. Aircraft flight path during approach to the refueling point when started fro various initial conditions Fig. 5. Thrust versus tie variation. Fig.. Transient process along X-coordinate ais. The results of siulation for closed-loop sste during refueling at piecewise-constant disturbance at eternal force of W=/ (vertical gust velocit) Fp=500kgf (uncoupling force) are given in Fig Fig.. Transient process along H-coordinate ais. Fig.6. Transient process along X coordinate ais

4 Fig.7. Transient process along H coordinate ais. Fig.0 Aircraft altitude hold during fuel servicing Fig.8. Transient process along Z coordinate ais. Fig. Thrust variation during fuel servicing Fig. 9. Thrust versus tie variation. The results of siulation for closed-loop sste Fig. Law of angle of attack variation during fuel servicing at weight variation caused b fuel transfer are given in Fig. 0 ; 4

5 Based on the diagras it is clear that autopilot ensures counteraction of environental disturbance and holds aircraft position at a refueling point thus preventing fro fuel transfer discontinuit. The results of siulation of closed-loop sste deonstrate the copletion of the target control tasks during approach to the refueling point as well as during fuel transfer under conditions of environental disturbance. Consequentl application of procedures of snergic control theor enables iproveent of in-flight autoatic refueling control sste. References []. N. Bukov Adaptive predictive flight control sstes M.: Nauka: Phsico-atheatic literature ain office 987. [] A. A. Kolesnikov Applied snergetics: Sste snthesis principles - Taganrog: TTI YFU 007. Contact Author Eail Address ailto: spk-ksp@ande.ru Copright Stateent The authors confir that the and/or their copan or organiation hold copright on all of the original aterial included in this paper. The authors also confir that the have obtained perission fro the copright holder of an third part aterial included in this paper to publish it as part of their paper. The authors confir that the give perission or have obtained perission fro the copright holder of this paper for the publication and distribution of this paper as part of the ICAS 04 proceedings or as individual off-prints fro the proceedings. 5