Gongzhang Shen

Modeling and attitude control of aircraft with variations in mass and center of gravity

Large scale variations in the mass or center of gravity (C.G.) pose serious problems for the control of aircraft in situations as heavy load airdrop on cargo aircraft, the airliners which employ the active C.G. control technology, aircraft with structural damages during the flight. To solve the problem of attitude control of such aircraft, a general model for the aircraft is established and a disturbance rejection attitude controller is proposed. The proposed model comprises of a 6-DOF dynamics model and the mass and C.G. variation model, which can handle various mass or C.G. variations and can reflect the dynamic couplings introduced by such variations. For the attitude control of such aircraft, based on the framework of observation and compensation, an explicit model following controller with the extension of extended state observer (ESO) is established. Real-time simulations demonstrate that the proposed model can accurately reflect the aircrafts dynamic responses during the variations, and with the compensation from the ESO, the model following controller can improve the performance and meet the requirements of precision attitude control.

Modeling and attitude control of aircraft with center of gravity variations

Active center of gravity (C.G.) control is a key technology of vehicle management system, which has been extensively used in various types of aircraft. With active C.G. control system, aircraft may deviate from its known dynamics due to the C.G. offset, thus bringing new problems to the existing flight control system. A new design approach of the attitude control system of aircraft with C.G. variations is proposed in this paper.

Control allocation and management for aircraft with multiple effectors

This paper focuses on the control redundancy problem due to the increase of control effectors of advanced aircrafts. Based on the current control allocation research, this paper further puts forward the concept of control allocation and management system. The bases sequenced control allocation method is proposed firstly, and then some management strategies are introduced to the control allocation process of bases sequenced method. The candidate effectors and optimal indexes are managed according to the information of flight conditions, mission requirements and effectors working conditions, and engineering experience is also considered in this system. The key aspects of the proposed system are illustrated by a 6DOF nonlinear aircraft model. The simulation results show that the functions of control allocation system are extended and the system adaptability to the flight status, mission requirements and effectors failure conditions are improved.

Control Allocation Based Reconfigurable Flight Control for Aircraft with Multiple Control Effectors

A control allocation based reconfigurable flight controller is presented for aircraft with multiple control effectors because of the redundancy effectors feature. The main idea is to use the remaining control effectors to cancel or compensate the effects of the failure effectors. The control law was designed by trajectory linearization control method, which can provides robust performance at all stages of flight. And the desired moments are the outputs of the trajectory linearization controller. A novel optimal control allocation method, named bases sequence optimal control allocation (BSOCA) method, is proposed to distribute the deflections of control effectors of the aircraft to generate desired moments. A control effectors management system based on BSOCA method is presented to achieve flight reconfiguration under effector failures. The simulation results show that the control allocation based reconfigurable flight controller can adapt the effector failures and maintain stability and acceptable handling qualities.

Research on robust control allocation for the advanced configuration aircraft

The accuracy of control allocation algorithms relies on control effectiveness matrix. To address this issue, this paper focuses on the robustness of control allocation. Several existing robust control allocation algorithms are analyzed at first. Then performance evaluation criteria for robust control allocation, which are designed for flight control, are proposed based on performance requirements of flight control system. Comparisons among existing robust control allocation algorithms are conducted via simulations. Finally, robustness of existing robust control allocation algorithms is evaluated according to the proposed robustness evaluation criteria.

Predictor-corrector guidance based on optimization

A new guidance algorithm based on a predictor-corrector approach is presented. The algorithm was designed for the re-entry guidance of the axisymmetric hypersonic vehicle. For this purpose, the angle-of-attack was considered to be the only input. We cast the re-entry guidance problem as a constrained optimization problem, then translated the constrained optimization problem into an unconstrained optimization problem using exterior point penalty function method and solved the unconstrained optimization problem using the steepest decent method. Altitude and range errors computed from the desired and achieved state at the terminal point were used to correct the angle-of-attack variables. Simulation results show that the algorithm developed in the paper is able to solve the re-entry guidance problem of the axisymmetric hypersonic vehicle and satisfies both terminal and path constraints.

Control capability evaluation based reconfigurable flight control for aircraft with failures

This paper focuses on the reconfigurable flight control problem of aircraft with control effectors failures and damages. The architecture of the reconfigurable control system based on control capability evaluating and reference model adapting is presented firstly. And the baseline control law is designed by the dynamic inversion method. Based on the concept of attainable moments, the control capability function under failures is defined. The control capability evaluating results are used to modify the reference model by fuzzy reasoning when the performance of aircraft is undergoing a severe degradation. The key aspects of the proposed system are tested in a 6-DOF nonlinear aircraft model. The simulation results show that the control capability evaluation based reconfigurable flight control system can improve the control performance and enhance the flight safety of the aircraft with failures and damages of control effectors.