TY - GEN
T1 - Active wing load alleviation with an adaptive feed-forward control algorithm
AU - Wildschek, Andreas
AU - Maier, Rudolf
AU - Hoffmann, Falk
AU - Jeanneau, Matthieu
AU - Baier, Horst
PY - 2006
Y1 - 2006
N2 - The latest subsonic civil transport aircrafts with high aspect ratio at low structural weight/payload ratio have been equipped with active wing-load control systems based on robust feedback of modal accelerations. The aim of these systems is to increase handling qualities and passenger comfort as well as to reduce dynamic wing-loads mainly induced by atmospheric disturbances. Structural control must be robust regarding variations in the plant transfer functions caused by the varying flight and load conditions to which an aircraft structure is exposed to. Such robustness criteria limit performance of robust wing-load control. Since robust structural control law design requires very accurate aero-elastic plant models, it is generally optimized iteratively during the flight test phase, where the accuracy of plant models is successively improved and the flight and load envelope is continuously expanded. This paper shows that introduction of an adaptive structural feed-forward control system could dramatically increase attainable performance of active wing-load control due to the feed-forward character on the one hand, and due to adaptivity on the other. The authors found that the best performance and robust stability of the adaptive wing-load alleviation system can be reached with an adaptive feed-forward controller in combination with error-feedback based on a stochastic-gradient-descent algorithm. The proposed algorithm rapidly adapts to any changes in plant transfer functions and excitation, so that extra robust stability margins no longer have to be taken into account. Additionally, the plant transfer functions have to be known in advance only approximately, since the controller optimizes itself online to the actual plant transfer function. Iterative design with the help of flight test optimized plant models is no longer necessary to perform. Thus it is estimated that the design period and design costs for active wing-load control can be dramatically decreased. After introducing the basic principle and integration of the proposed adaptive controller, the mathematical background of the algorithm is briefly discussed. This is followed by a detailed stability analysis to ensure stable adaptation of the algorithm. Finally, results of numeric simulations are presented to underline the validity of found stability conditions and to highlight improved performance, compared to a robust structural feedback control system.
AB - The latest subsonic civil transport aircrafts with high aspect ratio at low structural weight/payload ratio have been equipped with active wing-load control systems based on robust feedback of modal accelerations. The aim of these systems is to increase handling qualities and passenger comfort as well as to reduce dynamic wing-loads mainly induced by atmospheric disturbances. Structural control must be robust regarding variations in the plant transfer functions caused by the varying flight and load conditions to which an aircraft structure is exposed to. Such robustness criteria limit performance of robust wing-load control. Since robust structural control law design requires very accurate aero-elastic plant models, it is generally optimized iteratively during the flight test phase, where the accuracy of plant models is successively improved and the flight and load envelope is continuously expanded. This paper shows that introduction of an adaptive structural feed-forward control system could dramatically increase attainable performance of active wing-load control due to the feed-forward character on the one hand, and due to adaptivity on the other. The authors found that the best performance and robust stability of the adaptive wing-load alleviation system can be reached with an adaptive feed-forward controller in combination with error-feedback based on a stochastic-gradient-descent algorithm. The proposed algorithm rapidly adapts to any changes in plant transfer functions and excitation, so that extra robust stability margins no longer have to be taken into account. Additionally, the plant transfer functions have to be known in advance only approximately, since the controller optimizes itself online to the actual plant transfer function. Iterative design with the help of flight test optimized plant models is no longer necessary to perform. Thus it is estimated that the design period and design costs for active wing-load control can be dramatically decreased. After introducing the basic principle and integration of the proposed adaptive controller, the mathematical background of the algorithm is briefly discussed. This is followed by a detailed stability analysis to ensure stable adaptation of the algorithm. Finally, results of numeric simulations are presented to underline the validity of found stability conditions and to highlight improved performance, compared to a robust structural feedback control system.
UR - http://www.scopus.com/inward/record.url?scp=33845728124&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:33845728124
SN - 1563478196
SN - 9781563478192
T3 - Collection of Technical Papers - AIAA Guidance, Navigation, and Control Conference 2006
SP - 237
EP - 257
BT - Collection of Technical Papers - AIAA Guidance, Navigation, and Control Conference 2006
T2 - AIAA Guidance, Navigation, and Control Conference 2006
Y2 - 21 August 2006 through 24 August 2006
ER -