Suggested closed-loop response characteristics for tanker in aerial refueling via mission-oriented evaluation

The flight control law design for tanker should ensure that the closed-loop response can meet the aerial refueling mission requirements. In order to reveal the movement characteristics of the tanker and the handling characteristics of the pilot in aerial refueling, the flight path capture and hold under gust disturbance task is designed as the demonstration maneuver mission to evaluate the flying qualities for tanker in aerial refueling task, which is based on the design requirements of maneuvering tasks used in mission-oriented flying qualities assessment. By analyzing the flight path tracking and holding requirements of the tanker in aerial refueling mission, the relevant parameters that reflect the response characteristics of the tanker in pitch and roll axes are put forward. The ground flight simulation test based on mission-oriented flight quality assessment is conducted, and the test pilot's assessment results based on Cooper-Harper rating and PIO scales are obtained for different flight control law configurations. The suggested requirements of the closed-loop response characteristics of the pitch and roll axes of the tanker are put forward, which can be specifications for the aerial refueling mode flight control design of tanker.

Pilot multi-axis control behavior modeling of receivers in probe-and-drogue aerial refueling

The probe-and-drogue aerial refueling(PDR)task is seriously disturbed by the wind field,so it is difficult to obtain accurate visual information of the probe and drogue position.Additionally,the pilot needs to control the vertical,lateral and forwardbackward positions of the receiver through the stick and throttle lever,and the pitch and roll manipulation actions of the stick should be reasonably distributed.To simulate the behavior of the pilot’s visual perception and the stick manipulation allocation in the PDR task,three modules are designed,including the visual information acquisition module(VIAM),strategy switching module(SSM)and pilot control and action module(CAM).Based on the coherence function analysis of the flight simulation test data,it is proven that the pilot’s multi-axis control behavior can be decoupled,and the flight states to be controlled are determined.Finally,the established multi-axis receiver pilot model(EPM)is developed.Combined with the motion models of the receiver,the tanker and the refueling equipment,a PDR flight task simulation model is established,and the evaluation indicators for the receiver’s flight performance during the PDR task,such as capture time and settling time,are proposed.The PDR flight simulation model was used to build the ground-based flight simulation test platform,and the flight simulation test of the PDR task was carried out.A comparison between the flight simulation test data and the numerical simulation results shows that the calculation error is less than 10%,which verifies the correctness of the established pilot model.The pilot model can be used to evaluate the design scheme of the refueling equipment and the receiver flight control law and provide a theoretical reference for the flight test design of the PDR task.

Icing tolerance envelope protection based on variable-weighted multiple-model predictive control

Multiple-model predictive control(MMPC) is a fundamental icing tolerance envelope protection(ITEP) design method that can systematically handle nonlinear and time-varying constraints. However, few studies have addressed the envelope protection failure that results from the inaccurate prediction of multiple linear predictive models when actual conditions deviate from design conditions. In this study, weights that vary with icing conditions and flight parameters are considered to develop an effective and reliable envelope protection control strategy. First, an ITEP structure based on variable-weighted MMPC was implemented to improve the protection performance with condition departure information. Then, a variable-weighted rule was proposed to guarantee the stability of variable-weighted MMPC. A design approach involving a variable-weighted function that uses icing conditions and flight parameters as arguments was also developed with the proposed rules. Finally, a systematic ITEP design method on variable-weighted MMPC was constructed with additional design criteria for other normal control parameters.Simulations were conducted, and the results show that the proposed method can effectively enhance ITEP performance.