L1 Adaptive Control For Aircraft Longitudinal Trajectory

1L adaptive control for aircraft longitudinal trajectory was researchd in this topic. First the mathematical model of aircraft longitudinal motion was bulid, which transform the mathematical model of aircraft longitudinal motion under varying flight states into a transfer function whos paramaters are uncertain but varying in known range. Then we make use of 1L adaptive theory to dealing with the transfer function and simulation for it. Comparing with the traditional root locus technique, its control law parameters are global convergenced and have a good response when parameter of system shakes. Besides, nonlinearity model of longitudinal motion was bulid and preliminary research was done.The task of longitudinal automatic flight control system is achiving the control of aircraft track and velocity, the control system contains several models, including the model of pitch control and hold, vertical velocity control and hold, height control and hold, velocity control and hold, vertical navigation, and GS glide-path localizer. The models about pitch, vertical velocity, height and vertical navigation were mainly discussed in this paper. In logitidinal movement, pitch control system was considered as the inner loop while the outer loops are vertical velocity control system and height control system. When aircraft change its cruise flight model, it contains three parts, in these parts the aircraft was controlled in height control model or vertical velocity control model, this was called the vertical navigation control model if we make choice on which control model to use and this control model enable aircraft track and hold various flight heights.In traditional longitudinal automatic flight control system, design principles for each control models was list below: in pitch control inner loop, linearity feedback was taken to ensure the dynamic performance of control system; in outer loop such as height control and vertical velocity control, PI or PD control method was taken for gain orders of system by using the feedback of height or vertical velocity; in vertical navigation control loop, height control or vertical velocity control was selected for the correspondent flight phase, and this was decided by a selection controller depends on height. Each design of control of control model above was depending on determined under controlled dynamic model. But the flight state was changing along as the pilot aviate, and the dynamic of aircraft varies, so the stability of undercontrolled dynamic could not be ensure by using the control law parameters we get above.1L adaptive control theory can deal with a kind of systems whos parameters are uncertain, the mathematical model of aircraft longitudinal motion under varying flight state can be transformed into transfer functions whos parameters are uncertain but bounded. So the stability of undercontrolled dynamic could be ensure by building 1L adaptive control law, and the transient performance could be uniform for each flight state.In the longitidunal movement, if attitude is no longer small enough, then the lineary model of longitidunal movement failed, cause it can not acturely describe the dynamic character of attitude in longitidunal movement. In this paper, a nonlinearity model of longitudinal movement was bulid under the state of high angle-of-attack flying, then the control law using 1L adaptive control theory was designed for it. At last, a simulation was done and the result show that 1L adaptive control is reasonable for nonlinear system.