Research On Large Civil Aircraft Based On Active Control Technology

With the development of modern aviation industry, it is reasonable tostudy how to safely and effectively get a better flight performance andflying qualities. As to civil aircraft, Atmospheric disturbance will increaseaircraft structural load, lead to a loss of ride quality and have negativeeffect on operation of pilot, it will not meet the safety and comfortdemands of civil aircraft, so it is important to provide solutions duringaircraft design process. Besides, due to high economic requirements ofcivil aircraft, it is also indispensable to design a suitable system to cutflight cost.In regard to the problem above, gust load alleviation and relaxedstatic stability which are based on active control technology can be used tosolve the problem. The former can effectively reduce aircraft load andimprove ride quality, the latter is meaningful to reduce aircraft trimmingdrag, fuel consumption and wing structural weight. Hence, the paper aimsto make research on gust load alleviation and relaxed static stability. Forone thing, the research will meet safety，comfort and economic demands ofcivil aircraft. For another thing, the research is beneficial to improve flightperformance and flying qualities.The contents of this paper are:（1）A civil aircraft is selected, besides, turbulence and discrete gustare studied, and then, it is easy to get aircraft longitudinal equations whichinclude atmospheric disturbance model.（2）Due to the fact that system designed with PID method is not thatgood at disturbance rejection, synthesis algorithm is selected, after that, Two feedback systems are designed with the presence of turbulence anddiscrete gust, then, simulation results are compared. The results show thatthe robust control system using synthesis algorithm can achieve a betterload alleviation performance.（3）B757-200aircraft is selected, and benefits such as drag, wingweight and fuel consumption are calculated. Besides, in order to learnmore about benefits of relaxed static stability on aircraft, three differenttypes of civil aircrafts are selected which include B737-2, B757-200andB777-200, and benefits are compared. The results show that increasingrelaxed static stability aircraft size can get a better aircraft performance.（4）In order to improve stability of relaxed static stability aircraft,angle of attack and pitch angular velocity are selected as feedbackvariables, and then, control augmentation system is designed. Besides,three different states of aircraft are chosen to get unit step response, thoseaircraft states include open-loop response of the original aircraft,open-loop response of the relaxed static stability aircraft and closed-loopresponse of the relaxed static stability aircraft with control augmentationsystem, and conclusions are presented.（5）China new civil aircraft and military aircraft are selected, afterthat, qualitative research is made to analysis the influence of relaxed staticstability on china aircraft design, that is to say, the paper is useful toprovide academic research which is prior to practical system design ofrelaxed static stability aircraft.