Dynamic Modeling and Analysis of a Small Solid Launch Vehicle

Rotorcraft flight control systems present design challenges which often exceed those associated with fixed-wing aircraft. First, large variations in the response characteristics of rotorcraft result from the wide range of airspeeds of typical operation (hover to over 100 kts). Second, the assumption of vehicle rigidity often employed in the design of fixed-wing flight control systems is rarely justified in rotorcraft where rotor degrees of freedom can have a significant impact on the system performance and stability. Proposed herein is a methodology for the design of robust rotorcraft flight control systems utilizing Quantitative Feedback Theory (QFI'), a technique which accounts for variability in the dynamic response of the controlled element in the design of robust control systems. It was developed to address a Multiple-Input-Single-Output (MISO) design problem, but was extended to the address the Multiple-Input-Multiple-Output (MIMO) flight control system (FCS) design problem of a UH-60 Black Hawk Helicopter. Inherent conservatism in this design technique leads to limitations in its utility. A modified QFI' approach proved a viable method for designing robust MIMO flight control systems. An analysis of the two flight control system design methodologies is presented.

A direct methodology for the design of flight control systems is introduced. The design approach uses a control selector and an inner/outer loop structure to achieve robustness and performance across the flight envelope. A control selector normalizes control effectiveness with respect to generalized inputs. An inner loop uses dynamic inversion to equalize plant dynamics across the flight envelope. An outer loop is designed around this equalized plant using μ-synthesis to achieve performance and robustness goals. The methodology is applied in the design of a manual flight control system for the lateral axis of a fighter aircraft. Analysis shows that the inner/outer loop approach produces designs which exhibit excellent performance and robustness for a broad range of operating conditions. The direct incorporation of design goals such as flying qualities requirements and the elimination of gain scheduling make this direct methodology an effective and efficient alternative to traditional flight control design approaches.

This book provides information covering the fundamentals of control theory and optimization applied to real-world flight control systems. Covers the following topics: the challenges inherent in flight control system design; an overview of their core approach to flight control system design utilizing multiobjective parametric optimization; the specific software developed called Control Designer’s Unified Interface (CONDUIT); detailed explanations of the tools, plots, language, and four key components involved in defining the problem using CONDUIT; the XV-15 hover/forward flight case study is discussed in sufficient detail for even seasoned veterans to find the presentation informative and useful. Here the authors have done an excellent job of demonstrating many flight control concepts; proprietary specifications; methodologies for developing simulation models of model-based flight control system designs; design of flight control systems; the inner workings of the design optimization approach. The coverage includes specifics of various algorithms, along with their relative advantages and disadvantages. This chapter also provides insights into sequential loop closure strategies, with emphasis on their effectiveness and practical use; nested versus simultaneous multiloop strategies; and design considerations for real-world applications. This book serves as an excellent reference for senior undergraduate and/or graduate students, and it provides a wellbalanced perspective covering the theory, implementation, and practical applications of flight control design.

Nonlinear Flight Control Systems Design for Hypersonic Vehicles: Results and Open Problems

In the modern aviation field, flight control systems’ reliability and safety are paramount. This paper presents a triplex redundant flight control system based on the M1394B bus and designs several key algorithms to enhance system performance. Firstly, a triplex redundant flight control system with a redundant bus structure is constructed based on the characteristics of the M1394B bus. Secondly, a periodic synchronization algorithm with automatic adjustment capabilities is designed to achieve periodic synchronization among the Vehicle Management Computers. An improved voting algorithm based on a sliding window is proposed to enhance the decision-making accuracy and reliability of the control commands output by the flight control system. Additionally, a system reconstruction algorithm is designed to promptly identify and isolate faults, enabling the recovery and reallocation of system resources. Finally, experiments validate the effectiveness of the synchronization algorithm, voting algorithm, and system reconstruction algorithm. The results indicate that the system can effectively address practical engineering challenges and significantly improve reliability and stability. This research provides an essential theoretical foundation and practical reference for the design of future flight control systems for unmanned aerial vehicles and aircraft, holding significant relevance to application.

In order to realize excellent flight control system design and simulation, it is indispensable to establish a more realistic and more integrated aircraft model, so a scheme for an integrated aircraft model which consists of flight dynamics, propulsion system and flight environment is proposed in this research. Three parts of the integrated aircraft model are closely connected and interacted with each other. Furthermore, the aero engine model can reflect the engine thrust changes in the full real flight envelope and gains great parsimoniousness, which is designed based on K-means clustering algorithm and recursive reduced least squared vector regression. Simulation results confirm the effectiveness and preciseness of the integrated aircraft model. It also indicate to the control system designers that flight control system should be integrated with propulsion control, and the robustness and adaptivity of the flight control system should be paid much more attention to, so as to overcome the adverse effects of the flight environment.

: New handling qualities specifications are currently being developed for attack helicopters. Most unaugmented helicopters will not meet these specifications and feedback control is necessary to improve handling qualities so that safe operation close to the earth in poor weather conditions and/or at night is possible. In this paper a methodology for the direct design of helicopter flight control systems which meet handling qualities specifications is presented. This methodology uses full state feedback to place closed loop eigenvalues to achieve bandwidth specifications and to shape closed loop eigenvectors to decouple lateral and longitudinal responses to control inputs. Full state feedback requires that all state variables be known; however, only angular rates and normal acceleration are measured by sensors. Thus, a state estimator is required in the feedback loop in order to convert sensor outputs to control inputs. This estimator is designed using eigenstructure assignment so as to achieve loop transfer recovery. Design of a feedback system for use in precise hovering control for a modern attack helicopter is used to illustrate the method. Control law synthesis is accomplished using an eighth order model which includes only rigid body modes. Control law performance is evaluated using a 37th order model which includes rigid body, actuator, rotor, sensor, and flexure dynamics. It is found that a notch filter must be added to the design in order to eliminate a high frequency instability. Once this is accomplished, both the time and frequency response characteristics of the augmented helicopter are much improved compared with the unaugmented helicopter.

Research on a Safety-Critical Architecture of Large Commercial Aircraft Fly-by-Wire Flight Control System

This paper reports on the experience gained when a multivariable helicopter flight control law was tested on the Large Motion Simulator (LMS) at DRA Bedford. This was part of a study into the application of multivariable control theory to the design of full-authority flight control systems for high-performance helicopters. Results are presented that were obtained during the piloted simulation trial. The performance provided by the control law led to level 1 handling quality ratings for all of the mission task elements assessed, both during the real-time and off-line analysis.

In this paper, some problems concerning with eigenstructure assignment of state feed-back systems have been studied. An important result about the freedoms in assigning closed-loop system eigenstructure is given and two kinds of new algorithms to assign the eigenstructure with complex conjugate eigenvalues and/or with repeat eigenvalues are presented, which is the development of the algorithm given by B. Porter & J.J. D'Azzo [2] [3] to assign the eigenstructure with distinct real eigenvalues. An extensive flight control system example with practical application background is also presented which might give directions to the application of eigenstructure assignment in diverse areas.

The evolution of modern day aircraft increases the interaction between aeroelastic dynamics and control laws, known as aeroservoelasticity. An integrated flight control system without structural filters is proposed in order to achieve good handling qualities and increase structural mode damping. In the first step sensor and actuator location is studied, and in a second step the use of the linear quadratic regulator with output feedback for the synthesis of the control law.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The Variable Forward-Swept Wing (VFSW) Tailless configuration UAV can well satisfy multipurpose demands. However, this kind of unconventional morphing aircraft lacks tail, which brings great challenge to stability analysis. The connatural aero-elasticity divergence and the strong aerodynamic coupling as well as many uncertain factors in mechanical environment, give the VFSW Tailless configuration UAV complicated dynamic characteristics. During the process of transformation, the variation of dynamic shape will inevitably lead to the variation about aerodynamic center and barycentre positions of airplane, then make the angle of attack static stability margin variable, and directly influence stability of aircraft. On the basis of introduction of the VFSW Tailless configuration UAV, according to its geometric shape, positions of aerodynamic center and barycentre, in different states with different forward-swept angle, were calculated, so as to obtain variation curve of longitudinal static stability margin, which provided preferences for dynamics analysis, position of barycentre adjustment and design of flight control system (FCS).

Results are presented from an application of the H/sup /spl infin// loop-shaping design methodology to the problem of integrated flight and propulsion control (IFPC) system design for the vectored thrust advanced aircraft control (VAAC) Harrier STOVL aircraft. The suitability of the method of H/sup /spl infin// loop-shaping for centralised IFPC design is considered. The effectiveness of balanced residualisation as a tool for controller order reduction is demonstrated. Nominal and robust performance characteristics of the resultant reduced order controller are evaluated in nonlinear simulation.

Investigation of different strategies for access to space of small satellites on a defined LEO orbit

The design of an advanced flight control system (FCS) is a technically challenging task for which a range of engineering disciplines have to align their skills and efforts in order to achieve a successful system design. This paper presents an overview of some of the factors which need to be considered and is intended to serve as an introduction to this stimulating subject. Specific aspects covered are: flight dynamics and handling qualities, mechanical and fly-by-wire systems, control laws and air data systems, stores carriage, actuation systems, flight control computer implementation, flexible airframe dynamics, and ground and flight testing. The flight control system challenges and expected future developments are reviewed and a comprehensive set of references is provided for further reading.