Dynamics Modeling andL1Adaptive Control of a Transport Aircraft for Heavyweight Airdrop

Abstract

The longitudinal nonlinear aircraft model with cargo extraction is derived using theoretical mechanics and flight mechanics. Furthermore, the nonlinear model is approximated by a semilinear time-varying system with the cargo disturbances viewed as unknown nonlinearities, both matched and unmatched types. On this basis, a novel autopilot inner-loop based on the LQR andL1adaptive theory is developed to reject the unknown nonlinear disturbances caused by the cargo and also to accommodate uncertainties. Analysis shows that the controller can guarantee robustness in the presence of fast adaptation, without exciting control signal oscillations and gain scheduling. The overall control system is completed with the outer-loop altitude-hold control based on a PID controller. Simulations are conducted under the condition that one transport aircraft performs maximum load airdrop mission at the height of 82 ft, using single row single platform mode. The results show the good performance of the control scheme, which can meet the airdrop mission performance indexes well, even in the presence of±20% aerodynamic uncertainties.

Active disturbance rejection control for heavy cargo airdrop operations

“…The desired pitch angle can be obtained from the PID controller of the external loop [12][13]. In the inner loop, the airspeed and pitch angle are tracked by first-order and second-order ADRC controller, respectively, and we can obtain the desired instructions c V , c  through the decoupling control.…”

Adaptive backstepping sliding mode control for heavy-weight airdrop operations

“…Over recent years, some achievements have been reported in developing advanced flight control laws that are compatible with the heavyweight cargo airdrop. Based on the linear system at a given trimming position, [6] investigated the L 1 adaptive control approach subject to system uncertainties, [7] and [8] made a research on the use of active disturbance rejection control technique, and [9] proposed a robust control approach to achieve specified handing qualities. A key problem is that thus linear design controllers may cause unsatisfactory performance in the event that the cargo becomes increasingly heavy.…”

“…However, precise knowledge of the plant model must be known for achieving perfect feedback linearization. It is generally not the case for the airdrop flight controller design, as the complex nonlinear aerodynamic characteristics are very difficult to ascertain and model precisely [5,6,11]. Moreover, aerodynamic data obtained from wind tunnel tests always contain a certain degree of uncertainty.…”

An Adaptive Dynamic Surface Controller for Ultralow Altitude Airdrop Flight Path Angle with Actuator Input Nonlinearity

“…Over recent years, quite a few meaningful achievements have been made in developing advanced aircraft controllers to ensure the accuracy and aircraft safety of airdrop [1,2,7]. For example, it is proposed that a remarkable robustness of double ring mixed with iterative sliding-mode controller can reject constant uncertainties and uncertain atmospheric disturbances [1].…”

“…Meanwhile, a nonlinear function in the second level is designed to constitute an integral sliding manifold, which weakens the overcompensation of the integral term to big errors effectively [2]. Recently, a novel autopilot inner-loop based on LQR and 1 adaptive approach that employs a semilinear time-varying system with cargo disturbances to approximate the model nonlinearities is presented to suppress the unknown disturbances caused by cargo movements [7]. However, it is worth noting that when designing the controller, the above references do not consider actuator input nonlinearities such as dead-zone and backlash and ignore the actuator dynamic characteristics and nonlinear factors; instead, they consider that the actual deflection angle is equal to the rudder angle instruction [8].…”