Longitudinal Control Law Design Research Articles

Parameter Adaptive Terminal Sliding Mode Control of Flexible Coupling Air-Breathing Hypersonic Vehicle

The highly nonlinear and coupling characteristics of a flexible air-breathing hypersonic vehicle create great challenges to its flight control design. A unique parameter adaptive nonsingular terminal sliding mode method is proposed for longitudinal control law design of a flexible coupling air-breathing hypersonic vehicle. This method uses adaptive reaching law gain instead of the additional adaptive compensation term to handle the uncertainty to improve robustness. The stability of the close loop system is proved via a Lyapunov way. The longitudinal tracking control law for velocity and angle of attack is designed based on a rigid dynamic model of a flexible air-breathing hypersonic vehicle. A strong coupling model of the same vehicle, considering aerodynamic-scramjet engine-flight dynamic-elastic couplings, is established as the verification platform of the designed control law. The remarkable differences of flight dynamic characteristics between this strong coupling model and the rigid body model can be seen, which mean the controller needs to endure very great uncertainty, unmodeled dynamics, and other types of internal disturbance. Simulation results based on the coupling model demonstrate that the designed control law has good performance and acceptable robustness.

Development of a control law to improve the handling qualities for short-range air-to-air combat maneuvers

Modern fighter aircraft have been designed to have high maneuverability in order to preoccupy strategic superiority in short-range air-to-air combat between fighter aircraft in warfare. Digital fly-by-wire flight control system design is aimed at providing good handling qualities for all mission task elements over the entire flight envelope. To provide both excellent gross acquisition and fine tracking compatibility, simultaneously for air-to-air combat maneuvers, this article presents a common longitudinal control law design of a task-dependent self-adjusting command-path pilot prefilter gain scheduler within the same control law design architecture and response type based on nonlinear dynamic inversion control. We perform the frequency- and time-domain analyses based on the mathematical model of T-50 advanced trainer aircraft to evaluate the basic flying qualities of the proposed control method. Furthermore, the pilot evaluation is performed to evaluate the gross acquisition and fine tracking capability for air-to-air tracking maneuvers in a handling quality simulator. The evaluation results reveal that the proposed control method improves the fine tracking capability without the degradation of gross acquisition.

Longitudinal Control Law Design and Simulation of Fixed-Wing UAV

Taken some fixed-wing UAV as the study object, the aircraft movement was broken down into the longitudinal movement and lateral movement according to the linearized small perturbation principle, the longitudinal control law design method was discussed using root locus which belonged to classical control theory. The six degrees of freedom nonlinear model simulation result shows that: the control parameters designed are reasonable, the simulation profile is fully consistent with the setting profile, the control effect of pitch angle loop and altitude loop meets with the indices requirements, the method is mature and reliable, easy to realize in engineering.

Design of automatic climbing controller for large civil aircraft

This paper focuses on automatic climbing control methods for large civil aircraft. The key technique is how to design automatic flight control laws that meet the requirements of flight performance indexes and have good characteristics of restraining various disturbances. The classical engineering methods are used to solve the above problem. Based on the aerodynamic data of Boeing707, a nonlinear model of large civil aircraft is established. Linear models which are divided into longitudinal and lateral equations are obtained by trim and linearization. The design of longitudinal control laws uses C⁎ criterion, three climbing schemes including pitch control mode, vertical velocity control mode and altitude control mode are designed and mutually compared. For lateral control problem, by the feedback angle of sideslip, the bank attitude control with good effect is achieved. The simulation results indicate the designed control laws can meet the requirements of performance indexes, and have satisfied characteristics of anti-gust disturbance.

T-50 정밀추적 성능 향상을 위한 세로축 제어법칙에 관한 연구

An advanced method of Relaxed Static Stability (RSS) is utilized for improving the aerodynamic performance of modern version supersonic jet fighter aircraft. The laws of flight control system utilize RSS criteria in both longitudinal and lateral-directional axes to achieve performance enhancements. Particularly, the design of longitudinal control laws for utilizing RSS methods greatly affects the performance of the aircraft in Air-to-Air Tracking and Air-to-Ground modes, which improves weapon delivery. In the area of Air-to-Air Tracking, the development of longitudinal control laws aids in the fine tracking and gross acquisition of other aircraft. This paper proposes that new concept of longitudinal control law introduce in order to improve fine tracking performance in air-to-air tracking maneuver. Result of HQS pilot simulation and flight test, fine tracking performance improve without degradation of gross acquisition when new concept of control law is applied.

Regulation layer controller design for automated highway systems

In [1], Varaiya outlines a fully automated highway system (AHS), which promises a threefold increase in traffic capacity. The core of this protocol to achieve a fully automated highway system is a four-layer hierarchical control architecture. Starting from the bottom, the layers are called the regulation, planning, link and network layers. In this paper, our emphasis is on the design of longitudinal control laws for the regulation layer operation. Longitudinal control laws are proposed for a vehicle to execute different maneuvers requested from its planning layer. The maneuvers include leader tracking target speed, platoon merge, platoon split, lane change, and follower spacing control. In particular, the novelty of the proposed follower spacing control law is that the controller uses the information not only from vehicles in front but also from vehicles behind. It is proven that, with the proposed approach, the platoon is theoretically stable and free of slinky-type effects.