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The precise control of aircraft pitch angles is critical in aviation for maintaining specific attitudes during flight, including straight and level flight, ascents, and descents. Traditional control strategies face challenges due to the non-linear and uncertain dynamics of flight. To address these issues, this study introduces a novel approach employing the artificial rabbits optimizer (ARO) for tuning a PID controller with a filtering mechanism (PID-F) in aircraft pitch control systems. This combination aims to enhance the stability and performance of the aircraft pitch control system by effectively mitigating the kick effect through the incorporation of a filter coefficient in the derivative gain. The study employs a timedomain-based objective function to guide the optimization process. Simulation results validate the stability and consistency of the proposed ARO/PID-F approach. Comparative analysis with various optimization algorithm-based controllers from the literature demonstrates the effectiveness of the proposed technique. Specifically, the ARO/PID-F controller exhibits a rapid response, zero overshoot, minimal settling time, and precise control during critical phases. The obtained results position the proposed methodology as a promising and innovative solution for optimizing aircraft pitch control systems, offering improved performance and reliability. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles are widely spread and intensively used ones both in governmental and in private applications. The standard arrangements of the commercial-off-the-shelves unmanned aerial vehicles sometimes neglect application of the automatic flight control system onboard. However, there are many initiatives to ensure autonomous flights of the unmanned aerial vehicles via pre-programmed flight paths. Moreover, automatic flight control system can ensure necessary level of the flight safety both in VFR and IFR flights. The aim of this study is to guide UAV users in set up commercial onboard autopilots available on the market. On the contrary, fitness of the autopilot to a given type of the air robot is not guaranteed, and, an extra load on users can appear in controller settings. The proposed pole placement technique is one of the proper methods eliminating difficulties, and, computer aided gain selection using MATLAB will be presented. [ABSTRACT FROM AUTHOR]

In see-through helmet-mounted displays (HMDs), image-intensifier tubes are located on the sides of the helmet. This HMD design increases the effective interpupillary distance and exposes the observer to hyperstereopsis. The modification of three-dimensional space perception by hyperstereopsis in laboratory studies is well known. Little is known, however, about its effects in real, operational conditions. The present study investigated the effects of hyperstereopsis on visual perception in helicopter pilots during the first flight of a night-flight training program using a see-through HMD. Fifteen pilots’ percepts of distance and height under hyperstereoscopic viewing were assessed using a double-distance estimation task in standard flight circuits. In addition, two questionnaires were used to characterize the perceptual effects induced by hyperstereoscopic viewing during the first night flight, and to determine whether any aftereffects were still present during the 24-h period following the flight. Height and distance estimation errors were observed. On average, pilots tended to underestimate the near plane relative to the farther plane in the double-distance estimation task; this is the inverse of what is commonly observed under natural viewing. We ascribed this effect to a non-linear decrease in the hyperstereopsis effect with viewing distance. Six pilots experienced sensory illusions resembling a distortion of apparent visual space: the impression of “sinking into a hole” when landing, of objects appearing closer than they actually were, and reduced in size. Four pilots cited landing as the most difficult situation encountered during the flight. Only minor complaints were reported for the 24-h period following the flight. The results of this field study represent a step towards characterizing the perceptual and operational impact of this display technology in helicopter pilots during initial exposure. [ABSTRACT FROM AUTHOR]

In recent years, multi-rotor unmanned aerial vehicle (UAV) has been widely used in various fields. It has the advantages of multifunctional, reasonable structure, easy operation and convenient for using. In this paper, based on the research results of the helicopter and the dynamic modeling method of rotor, we discuss several problems that need to be overcome in high altitude flight stability control. Combined with the rotor dynamics model, we give the simulation modeling method of multi - rotor UAV in high altitude flight wind field environment. This has laid a solid foundation for the subsequent multirotor UAV project development, control law debugging and flight control system software design. The results show that the control method can effectively improve the stability and flight quality of UAV. In addition, the emergency treatment methods and control strategies that introduced in this paper can improve the safe return rate of UAVs. In the broad sense of the stability control level, it can better guarantee the multi-rotor UAV flight safety. [ABSTRACT FROM AUTHOR]

The paper presents the design of a symmetric, active, gust load alleviation system for a regional transport aircraft, based on a static output feedback with a constrained structure. The design is carried out on a comprehensive finite state aeroservoelastic model, including sensor units and actuator transfer functions, and verified by taking into account saturated control positions, rates, and hinge moments. The controller is designed within a quadratic optimal framework, through a second-order Hessian-based optimization algorithm, exploiting block diagonal Schur transformations of the closed-loop state equations and performance weightings. An accurately chosen worst discrete gust and a reference flight condition provide a baseline design, which is significantly effective in alleviating continuous turbulence loads. Such a reference design proves itself robust enough to alleviate atmospheric loads over the complete flight envelope and is eventually further improved and robustified through a simple bilinear q∞- M∞ algebraic scheduling. [ABSTRACT FROM AUTHOR]

This paper proposes a new approach to the derivation of homing guidance laws for interceptor missiles that makes use of linear-quadratic optimal control in a different manner than the traditional approaches. Instead of looking only for the minimization of the miss distance and the integral square of the guidance command, the new criterion penalizes also the "variability" of the guidance command. The solution has the familiar structure of traditional linear-quadratic guidance laws, of a zero-effort-miss term multiplied by a, possibly time-varying, gain. Still it differs in one essential feature: The navigation gain does not only depend on the time to go, but also on the total time of flight. The new guidance law also has an additional design parameter that can be profitably used to avoid acceleration saturation. [ABSTRACT FROM AUTHOR]

The article describes a fractional-order tension control that was developed for the fast and stable deployment of space tethers. Topics covered include the advantages of the fractional-order control, illustration of the in-plane deployment of a space tether system comprising of two satellites, and the steps in discretizing the fractional-order tension control law. Also cited is an issue facing space tether missions.

Abstract. Comparative analysis of the ICAO statistics showed that 35% of the aircraft losses associated with failures and damages of automatic control systems, mainly with failures of drives and external damage of tours and controllers. Classification of approaches to reconfigurable flight control systems is shown. The aim of this work is to develop method of reconfiguration to save the stability and controllability of the aircraft during the collisions with mechanical, biological and electrical elements. [ABSTRACT FROM AUTHOR]

The article analyses new trends in aircraft control under instrument flight rules. It describes the possibilities of using conventional area navigation methods with GNSS devices in approach phase. The authors describe the actual possibilities of using GNSS, especially GPS system, during navigation. In the next part, arrival and departure RNAV routes that are actually in use are described. The article also discusses briefing and preparation for RNAV approaches and describes requirements for the aircrew. [ABSTRACT FROM AUTHOR]

The article highlights model predictive control for air flight, which allows an effective method of controlling multiple-input multiple-output (MIMO) systems that needs significant control coordination to obtain a desired response. Topics discussed include the Algebraic Model Predictive Control (AMPC) algorithm as used in flight control and the effectiveness of the AMPC algorithms in controlling multiple outputs of the linear, longitudinal aircraft model.

Abstract: Japanese Venus Climate Orbiter/AKATSUKI was proposed in 2001 with strong support by international Venus science community and approved as an ISAS (The Institute of Space and Astronautical Science) mission soon after the proposal. The mission life we expected was more than two Earth years in Venus orbit. AKATSUKI was successfully launched at 06:58:22JST on May 21, 2010, by H-IIA F17. After the separation from H-IIA, the telemetry from AKATSUKI was normally detected by DSN Goldstone station (10:00JST) and the solar cell paddles’ deployment was confirmed. After a successful cruise, the malfunction happened on the propulsion system during the Venus orbit insertion (VOI) on Dec. 7, 2010. The engine shut down before the planned reduction in speed to achieve. The spacecraft did not enter the Venus orbit but entered an orbit around the Sun with a period of 203 days. Most of the fuel still had remained, but the orbital maneuvering engine was found to be broken and unusable. However, we have found an alternate way of achieving orbit by using only the reaction control system (RSC). We had adopted the alternate way for orbital maneuver and three minor maneuvers in Nov. 2011 were successfully done so that AKATSUKI would meet Venus in 2015. We are considering several scenarios for VOI using only RCS. [Copyright &y& Elsevier]

Purpose -- The paper aims to detail the educational flight testing activities performed at the Department of Aerospace Science and Technology at the Politecnico di Milano (DSTA-PoliMi), including the development of low-cost, reliable flight testing instrumentation (FTI) and the administration of the graduate course in flight testing. Design/methodology/approach -- The flight testing course program closely adheres to the typical content of an introductory course offered in a professional flight testing school. However, within academic courses, it has a unique feature: each student is required to plan, perform and report on a real flight test experience, acting as a flight test engineer. Educational activities in this framework have been successfully matched to applied research and technical support for private companies. Findings -- At the educational level, several elements arise that are rarely concentrated within a single course, such as multidisciplinary integration, individual conceive-design-implement-operate (CDIO) project, real-life experimental procedures and techniques, teamwork, communication and reporting, relation with non-academic partners. Practical implications -- Based on the development of a FTI system for light aviation and on the flight testing course, DSTA-PoliMi has built a solid capability in flight testing, introducing graduate students to this specific niche of expertise and empowering co-operation with companies in the light aviation environment, while offering capabilities and tools that are typically regarded as a prerogative of major aerospace companies. Originality/value -- The paper discusses an original approach to flight testing education in an academic setting that avoids the high costs and complexity connected to certified aircraft flight operations and instrumentation, nevertheless allowing the achievement of significant results, also in applied engineering research. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to develop an attitude control strategy for the reusable boosted vehicle with large angle of attack, and to remove the cross coupling among roll, pitch and yaw channels. Design/methodology/approach – The coordinated gain scheduling control strategy consists mainly of two parts. First, initially ignoring dynamic coupling, single channel gain scheduling controller is designed based on linearized models, respectively. Second, with respect to main channel gain scheduling controller, coordinated scheduling controller is used to generate intentionally cross coupling to partly cancel inter-channel cross coupling of reusable boosted vehicle. Findings – A coordinated gain scheduling control strategy is presented, and no such analytical solution can be found for the reusable boosted vehicle. Practical implications – The design idea of coordinated gain scheduling strategy is straightforward in physical concepts and has great value for engineering applications. Originality/value – Coordinated gain scheduling control strategy is novel in that single channel gain scheduling design does not involve small perturbation linearization and coordinated channel is scheduled. [ABSTRACT FROM AUTHOR]

During an operational process, activity is implemented through an ordered sequence of certain actions united by a common motive. Actions can be simple or complex. Simple actions cannot be split into elements having independent objectives. Complex actions can be presented in the form of a set of simple actions. If the logical organisation of this set is open, a complex action can be described as an algorithm consisting of simple actions. That means various kinds of operational activities develop from the same simple and typical actions, but in various sequences. Therefore, human error is always generated by a more elementary error of action. Thus, errors of action are the primary parameter that is universal for any kind of activity of an aviation specialist and can serve as a measure for estimating the negative influence of the human factor (HF) on flight safety. Aviation personnel are various groups of experts having various specialisations and working in various areas of civil aviation. It is obvious that their influence on conditions is also unequal and is defined by their degree of interaction with the performance of flights. In this article, the results of an analysis of air incidents will be presented. [ABSTRACT FROM AUTHOR]

Abstract: Airships provide an attractive solution to many challenges in the aviation industry. The buoyancy force offered by the airship enables to be used for long endurance aero applications. Key objective is to operate the vehicle with a sufficient level of autonomy under extreme range of atmospheric and wind conditions. In order to achieve these goals, a guidance and control system is needed which controls the airship in air at the specified height. The accurate control system first requires an accurate model of the airship dynamics. Based on six degrees of freedom, an airship dynamic model is presented in this paper. The aerodynamic part of the model is taken from the geometrical configuration of the vehicle instead of expensive wind tunnel test setup. The computer simulation algorithm is then derived and the easily available Matlab environment is used to simulate it and its initial validation for YEZ-2A airship is demonstrated. [Copyright &y& Elsevier]

Abstract: Pure gravity orbit is an orbit removed non-gravity disturbances, which can give a more precise relation between gravity and orbit, and can be used to navigation satellite, earth gravity felid measurement, gravity wave detection and other fundamental physical test mission. In this paper, the author propose a system concept of a new pure gravity orbit acquirement method named inner formation flying system, which treats the PM and the outer satellite as a pair of formation flying satellites. The inner formation flying system consists of an outer satellite and an inner satellite. The outer satellite is a small satellite with a cavity in the center. The inner satellite is a PM flying in the housing of the outer satellite''s cavity. So the inner satellite is shielded from non-gravitational forces of atmosphere drag and radiation pressure and flies along a purely gravitational path. From the view of formation flying, the outer satellite can be treated as a formation satellite with zero or small distance to the inner reference satellite. So the analysis of mechanic and dynamics of inner formation is made at first. Then a control architecture including feed forward and feedback strategies is presented and the controller is designed. The simulation is carried out in a high precision formation flying simulation environment at last to validate the inner formation flying methods. [Copyright &y& Elsevier]

Abstract: Three satellites in formation flying have the flexibility to monitor the target on the ground and the vicinity in the space, and can even achieve stereo view for any object. We consider each satellite orbit is slightly different with a daily-repeat circular Sun-synchronous orbit in the inclination, the right ascension of ascending node, the argument of perigee, and the mean anomaly. According to the linearized orbit equation, a formation of a tilted triangle with respect to the equatorial plane can be constructed. A Sun-synchronous formation is then obtained through a rotation. We investigate the maintenance cost through the evaluation of the delta-V for the triangle formation under perturbation by the PID autonomous control of the nonlinear equation of motion. With reference to the relative position with respect to the formation centroid, the formation configuration can be maintained with less delta-V. [Copyright &y& Elsevier]

NextGen aviation will require an even greater reliance on automation than current-day operations. Therefore, systems with problems in human-automation interaction must be identified and resolved early,, well before they are introduced into operation. This paper describes a research and software development effort to build a prototype automation design advisor tool (ADAT) for flight deck, automation. This tool uses models of human performance to identify perceptual, cognitive, and action-related inefficiencies in the design of' flight management systems. Aviation designers can use the tool to evaluate and compare potential flight deck automation designs and to identify potential human-automation interaction concerns. Designers can compare different flight management systems in terms of specific features and their ability to support pilot performance. ADAT provides specific, research-based guidance for resolving problematic design issues. It was specifically designed to be flexible enough for both current-day technologies and revolutionary NextGen designs. [ABSTRACT FROM AUTHOR]

We describe a novel quadrotor Micro Air Vehicle (MAV) system that is designed to use computer vision algorithms within the flight control loop. The main contribution is a MAV system that is able to run both the vision-based flight control and stereo-vision-based obstacle detection parallelly on an embedded computer onboard the MAV. The system design features the integration of a powerful onboard computer and the synchronization of IMU-Vision measurements by hardware timestamping which allows tight integration of IMU measurements into the computer vision pipeline. We evaluate the accuracy of marker-based visual pose estimation for flight control and demonstrate marker-based autonomous flight including obstacle detection using stereo vision. We also show the benefits of our IMU-Vision synchronization for egomotion estimation in additional experiments where we use the synchronized measurements for pose estimation using the 2pt+gravity formulation of the PnP problem. [ABSTRACT FROM AUTHOR]

Communication, information and air navigation support for coordinator and control of all the activities concerning preparation, execution and the ending of the flight operation is one of the most important factor for the flight mission. For an air flotilla communication, information and air navigation support is represented by a communication, information and air navigation system provided by communication and information compartments involved in planning, organizing, exploiting and controlling the system which have the task to plan, organize, exploit and control the system. The communication, information and air navigation support is active provided in all flight stages from starting the preparation until the ending of the flight operation. The communication, information and air navigation system, as a board technical support, is the main tool of the communication, information and air navigation support for the acquisition, dissemination, protection and diffusion of information regarding the flight. [ABSTRACT FROM AUTHOR]

Abstract: Stratospheric airship is a typical stratospheric platform, and has attracted worldwide research interests for its broad application prospect. In order to design the flight control software of a stratospheric airship, an introduction of realtime software and stratospheric airship is proposed in this paper. The development of real-time software has undergone the historical change which was from the process-oriented design methods to the object-oriented design methods, and all of these methods are prospected in detail. Moreover, a bus structure of flight control system for the stratospheric airship is described, which is the basis for the later flight control software design. [Copyright &y& Elsevier]

The objective of this paper is to analyze the role of helicopter rotor, to classify them by type, and to imagine new types of helicopter rotors that can equip future helicopters. Finally, the author shows a coaxial rotor 3D model such a best alternative to equip the new helicopters. [ABSTRACT FROM AUTHOR]

The paper briefly overviews the application of membrane and jet pneumatic devices in control systems. The most promising lines of development in the field are discussed. [ABSTRACT FROM AUTHOR]

This paper describes calculations and computer simulations concerning handling qualities of general aviation aircraft equipped with an indirect (fly-by-wire) control system. The main idea of this proposal is shaping small aircraft dynamic characteristics in a way that enables all general aviation aircraft to exhibit similar user-friendly properties from the pilot's point of view. The natural solution of this problem is modifying aircraft dynamic properties to comply with the 'ideal model' of a safe and easily controllable airplane. We can improve the handling qualities of an aircraft using the indirect flight control system. In this paper, the model following method was used for controller synthesis, with the purpose of obtaining qualitatively new handling properties and simplifying the control system for pilots with limited professional training. However, a control system designer has to assume responsibility for proper functioning of complex flight control systems. The properties of the optimal controller were calculated applying the indirect (implicit) model following method. In particular, the modified version based on the computer simulations was used. Model following method allows shaping properties of the flight control systems that satisfactorily approximate those of the desired model of controlled aircraft. In this way, the expected handling qualities can be reached. [ABSTRACT FROM AUTHOR]

A concept for lift modification on a conventional aircraft wing flow roll control at low angle of attack with dielectric barrier discharge plasma actuators is proposed and assessed through computational fluid dynamics simulations and preliminary wind-tunnel experiments. The concept consists of placing plasma actuators around the wing tip to add momentum in the direction opposite to that of the flow forming the tip vortex. Because of the limited strength of existing plasma actuators, the assessment is carried out for a relatively small two-dimensional wing (NACA 4418) with a rounded tip at zero angle of attack and 15 m/s for a Reynolds number in the range of 1.5 x 105. Computational fluid dynamics simulations show a significant alteration of the vorticity field downstream of the trailing edge characterized by a more diffused vortex surrounded by zones of negative vorticity induced by the actuators and, but not necessarily, outboard displacement of the tip vortex. This leads to a reduced downwash that results in a change in lift of up to almost 20% for actuator strength levels that should be achievable in the short term with a new generation of dielectric barrier discharge actuators. The actuator placed on the suction side contributes the most to the lift increase, with its induced jet blocking the flow around the wind tip at the origin of the formation of the tip vortex. Wind-tunnel experimental results support the computational fluid dynamics predictions in both magnitude and trend. Furthermore, preliminary computational fluid dynamics simulations are carried out for a symmetric nonlifting wing (NACA 0018), representative of aircraft tail surfaces at zero angle of attack to generate lift for pitch and yaw control. Results indicate lift generation that increases and becomes larger than drag at higher actuator strengths. These promising results show a potential for the proposed concept to replace movable flight control surfaces on future aircraft wings and empennages. [ABSTRACT FROM AUTHOR]

The maximum performance of a supersonic inlet will be achieved when operating as close as possible to its buzz boundary. In order to maintain high performance without crossing the buzz boundary, an active buzz margin predictor and controller is necessary. The goal of a control system is to acquire inlet buzz margin and maintain it as the designated value and predict inlet buzz before it occurs and then take some measures to buzz mitigation or inlet restart. The inlet buzz boundary and the margin of ducted rockets were first discussed and analysed. Then the dynamic mathematical model of a gas flow control system was established. Lastly, the inlet buzz margin controller of a ducted rocket was designed. Simulation results show that there exist anti-regulation characteristics for gas flow control for ducted rockets, and it leads to the particularity of inlet buzz margin control for ducted rockets in contrast to liquid ramjet. The designed inlet buzz margin has to be bigger to avoid the appearing of inlet buzz because of anti-regulation characteristics; otherwise, the inlet buzz phenomenon probably appears. If the inlet buzz of the ducted rocket appears, the command of decreasing fuel flow could not be given immediately; otherwise, the inlet buzz will aggravate. [ABSTRACT FROM AUTHOR]

One of the aims of air data systems is the determination of flight parameters angles of attack and angle of sideslip from measurements of local pressures and of local flow angles on wings or fuselage using a proper set of sensors. The active and integrated use of flight parameters in a full-authority flight control system imposes requirements for accurate and reliable air data, which are critical to maintain control. In this paper, a methodology based on the data fusion using Extended Kalman Filter technique is applied to dynamic maneuvers with rapid variations in the aircraft motion to calibrate angle of attack and angle of sideslip. The main goal of the investigations reported in this paper is to obtain online accurate flow angles from the measured vane deflection and difference pressures from probes sensitive to flow angles even in the adverse effect of wind or turbulence. The investigations are initially made on simulated flight data with wind and turbulence effects and it is showed that both alpha and beta estimates are accurate. The same procedure is then extended to flight test data of a high performance fighter aircraft. It has been shown using these results that sensor data fusion approach proposed in this paper is of great value in online implementation. [ABSTRACT FROM AUTHOR]

This paper presents the vertical takeoff, landing and transition between level flight and hovering of a tail-sitter vertical takeoff and landing (VTOL) aerial robot. The tail-sitter is suitable for micro aerial vehicles because it does not need any extra equipment for the VTOL maneuver. The developed tail-sitter aerial robot is equipped with four actuators for controlling ailerons, an elevator, a rudder and a propeller. A micro computer, various sensors and a battery are mounted on the aerial robot for autonomous flight without any support from a ground system. A transition flight strategy is constructed so that the transition finishes in the shortest time restricting an altitude change. In order to achieve the transition strategy, the reference trajectory of the pitch angle is computed offline by using an optimization technique. In the transition flight control system, a PID feedback controller is applied to attitude control, while a feedforward controller is applied to altitude control. The gain scheduling is applied to the control of the rudder and aileron. The experimental results on the transition between level flight and hovering, takeoff, and landing are presented. [ABSTRACT FROM AUTHOR]

In this article, the multi-objective design of a fuzzy logic augmented flight controller for a high performance fighter jet (the Lockheed-Martin F16) is described. A fuzzy logic controller is designed and its membership functions tuned by genetic algorithms in order to design a roll, pitch, and yaw flight controller with enhanced manoeuverability which still retains safety critical operation when combined with a standard inner-loop stabilizing controller. The controller is assessed in terms of pilot effort and thus reduction of pilot fatigue. The controller is incorporated into a six degree of freedom motion base real-time flight simulator, and flight tested by a qualified pilot instructor. [ABSTRACT FROM AUTHOR]

Research studies have indicated that the optical flow parameter, time to close tau, is the basis of purposeful control in the animal world, and used by both fixed wing and helicopter pilots during manoeuvring. This parameter is defined as the instantaneous time to close a gap (spatial or force) at the current closing rate. A novel automatic flight control strategy has been developed that makes use of optical flow theory and in particular, the parameter tau. This strategy has been applied to two distinct problems; (1) the landing of a helicopter on a ship and (2) the lateral repositioning of a helicopter. The first is a challenging case because the landing of a helicopter on a ship is one of the most dangerous of all helicopter flight operations. Furthermore, helicopters are often subject to torque oscillations during rapid collective control, which increases pilot workload significantly when operating with low power margins and/or whilst performing tasks that require accurate heave control. The second case demonstrates the generality of the teclmique. Both automatic manoeuvres were simulated successfully within desired limits, with the novel control strategy creating a 'natural', smooth, tau motion. [ABSTRACT FROM AUTHOR]

For a significant improvement in the fuel efficiency of long-range transport aircraft, a transition to blended-wing-body (BWB) configurations will be required in the long term. Further efficiency improvements are expected from an all-composite primary structure, all-electric actuation, as well as from seamless control surfaces that provide reduced drag compared to conventional control surfaces. BWB configurations feature specific demands on the control system because of the high coupling between flap deflections and aircraft movements in all three axes. Thus, multi-objective control surfaces are required for flight control, as well as for active gust and manoeuvre load alleviation. A major challenge therefore is to provide sufficient yaw control and stability in the absence of a vertical tail. Generally, one engine inoperative poses an important sizing case for the control system design, especially for the control surfaces. In this article, the sizing of winglet flaps and crocodile flaps is performed for the preliminary design of an all-composite, all-electric BWB airliner. For further improvement in efficiency, a seamless morphing trailing edge device is designed that provides both crocodile flap and aileron modes at the same time. Based on these results, a composite morphing trailing edge demonstrator with an all-electric actuation system is investigated. Some open issues remain for investigation. Still, the proposed design provides a promising approach for further efficiency improvement on BWB aircraft configurations. [ABSTRACT FROM AUTHOR]

The operations of Cassini optical remote sensing instruments require a high level of spacecraft-pointing stability to minimize image distortion during an exposure window. This paper summarizes the flight performance of the Cassini spacecraft's pointing stability with respect to mission requirements. Sources of spacecraft jitter, the Cassini spacecraft control modes, and pointing-stability metrics are discussed to provide a context for the results. In designing the Cassini attitude-control system, a pointing-stability performance metric that considered the frequency contents of the disturbance sources was employed. Cassini pointing-stability results using the root-mean-square stability metric are provided for both spacecraft control modes, using the reaction-wheel assembly or the reaction control system composed of eight thrusters. The pointing-stability results are then related to characteristics of the spacecraft and operations. For thruster-based control, the pointing-stability results are analyzed with respect to the per-axis dead band. Results from the scientific instruments onboard the Cassini spacecraft confirm that the pointing-stability results in either control mode have achieved high accuracy pointing capabilities critical to the success of the mission and have resulted in data to improve our understanding of Saturn. [ABSTRACT FROM AUTHOR]

In this brief, we consider the problem of 3-D path generation and tracking for unmanned air vehicles (UAVs). The proposed path generation algorithm allows us to find a path satisfying arbitrary initial and final conditions, specified in terms of position and velocity. Our method assumes that aircraft structural and dynamic limitations can be translated in a turn radius constraint; therefore, the generated paths satisfy a constraint on the minimum admissible turning radius. The proposed algorithm for the path tracking guarantees, under specified assumptions, that the tracking error, both in position and in attitude, asymptotically tends to zero. The work has been carried out with reference to the UAV of the Italian Aerospace Research Center (CIRA). Simulation results for both the path generation and the tracking algorithms are presented; the latter have been obtained using a detailed 6-degree-of-freedom model of the CIRA UAV in the presence of wind and turbulence. [ABSTRACT FROM AUTHOR]

Reusable launch vehicles are a promising business for the future because of their flexibility, reliability, low cost, and good operability. There are two takeoff styles: the vertical takeoff and the horizontal takeoff. Compared to the horizontal takeoff vehicle, the vertical takeoff reusable launch vehicle has advantages, such as a shorter down-range landing, a quicker recovery system (wherein takeoff and landing happen in approximately the same location), and a lighter weight. A vertical profile is used for vertical takeoff and vertical landing (VTVL) vehicles to achieve a recovery at the launch site. However, the first stage of the vertical takeoff reusable launch vehicle (RLV) typically can provide a very small or even zero velocity to its second or upper stage, if the upper stage is released at the peak altitude. Therefore, primarily, this type of launch vehicle is used to achieve hundreds of seconds in a microgravity environment. The upper stage payload delivery capabilities of a vertical takeoff RLV and its potential applications are described from a trajectory point of view. A modified optimal control methodology and an intuitive method of the trajectory control, called energy for altitude and time, are used to determine the maximum throw distance, maximum flight time, and orbital insertion capabilities for certain payloads, separately. The results from this investigation show the possibilities of expanding the applications for the VTVL suborbital RLV. [ABSTRACT FROM AUTHOR]

The main factor in design and operation of aircraft is safety of an airplane. The “safety culture” developed in aeronautics results in detailed regulations and certification procedures in all phases of aircraft design and operation. But despite that, aircraft safety depends on several unpredictable factors, such as the hostile actions both inside and outside of the aircraft. When failures occur during the flight, the most important actions are aimed at maintaining the aircraft controllability. The aircraft control system should be fault tolerant and ensure aircraft controllability in the event of the failure of a part of the flight control system. In this paper the influence of control surface failures on autopilot operation has been investigated. The autopilot is designed for business jet airplanes and fulfills the main functions of the real autopilot system in longitudinal and lateral directions. The autopilot structure allows implementation of various methods of reconfiguration for aircraft protection. [ABSTRACT FROM AUTHOR]

The research team from Control and Avionics Department of Rzeszow University of Technology (RUT) has been working on control systems for many types of flying objects for years. Experiences the team has had during their activity have helped create the control algorithms for a medium-size flying target (MSFT). Researchers from RUT, together with the small aviation company EUROTECH, have been working on a flying target for artillery. This paper gives a generic view of the system, including airborne and on-ground parts. But this paper mainly presents the control system that is mounted on the MSFT. The paper describes the generic conception of the control system of the flying target, including control laws used in the control system of the MSFT. Results of simulations and real flight data are also presented. [ABSTRACT FROM AUTHOR]

The flight envelope states the conditions where an aircraft is safe to fly and those conditions must be carefully determined for every configuration. That is why, even today, the numerical tools have become more and more precise, flight test is the only reliable method to define the flight envelope, especially in the conditions where the numerical model reaches a great degree of complexity (non-linearities). However, flight test is expensive and different procedures must arise in order to match reliability (safety) and cost (flight hours). This dilemma is even worse when free-flutter conditions must be provided for a new aircraft or a new external configuration, because the envelope expansion is done by increasing the flight test hours. The present article shows a procedure to predict the flutter speed based on real-time tuning of a quasi non-linear aeroelastic model. A two-dimensional non-linear (freeplay) aeroeslastic model is implemented in MatLab/Simulink with incompressible aerodynamic conditions. A comparison with real compressible conditions is provided. Once the numerical validation is accomplished, a parametric aeroelastic model is built in order to describe the proposed procedure and contribute to reduce the number of flight hours needed to expand the flutter envelope. [ABSTRACT FROM AUTHOR]

The recent period has been tilled with exceptionally interesting developments and advances, resulting in high-performance conventional and non-conventional manned and unmanned aircraft. Although those vehicles seem to comply well with specific mission performance requirements, one is still confronted with an apparent weakness to reliably stabilise and control throughout the flight envelope. Since the provision of satisfactory stability and control characteristics invariably compromises flight performance, it becomes essential to identify and integrate performance-optimal stability and control design solutions early during the flight vehicle definition phase. In particular, the conceptual design of integrated control effectors for advanced aircraft is far from being trivial. Never before have we been presented with such tremendous wealth of specialised data and information suitable for detail design of controls. In contrast, never before has it been necessary to approach any one of the primary design disciplines still as entirely ad hoc and inconsistent as in the case of designing controls during the conceptual design phase. This need initiated the development of a configuration independent (generic) stability and control methodology capable of sizing primary control effectors of fixed wing subsonic to hypersonic designs of conventional and unconventional, symmetric and asymmetric configuration layouts. This paper summarises the methodology concept and demonstrates its versatility and validity by analyzing selected stability and control characteristics of the Northrop YB-49 flying wing. [ABSTRACT FROM AUTHOR]

The collective behaviour observed in many social insects and animals provides the inspiration for the development of multi-vehicle control systems. The distributed nature of the multi-vehicle control problem enhances the performance of the collective system along the dimensions of scalability, robustness, and fault tolerance. The distributed/decentralized nature of the cooperative control task introduces many sub-problems often associated with network control design. In this paper, a survey of recent results in the field of cooperative control for multi-vehicle systems is presented. Various applications are discussed and presented in a mathematical framework to illustrate the major features of the cooperative control problem. Theoretical results for various cooperative control strategies are presented by topic and applied to the multi-vehicle applications. [ABSTRACT FROM AUTHOR]

A mathematical model was developed for the reversible longitudinal control system of a regional commuter aircraft using the available geometry, mass property and kinematics. The model was incorporated into a general multi-body dynamics code and validated using existing manufacturer's data as well as recorded data from several flights. Analysis of the flight data revealed light atmosphere turbulence level. To investigate the effect of higher turbulence intensity on the reversible flight control system, a sever turbulence level was generated using Von Karman model for the same flight level and velocity. The result was used as a random input to the dynamic model for computation of the frequency response of control column. It was shown that turbulence could act as a random input through the hinge moment during the flight and introduced a new mode in the lower end of power spectral density curve. The energy induced by this low frequency input resulted in large displacement of control column in simulation which surpassed the existing limits. Therefore it should be taken into account when dealing with handling quality as well as autopilot design. [ABSTRACT FROM AUTHOR]

The effect of actuator damage on a helicopter rotor with an IBC based primary control system is studied. Such a system eliminates the swashplate and can be accomplished by trailing-edge flaps, active twist or full authority IBC, especially with smart material actuators. Damage to the collective, longitudinal and lateral cyclic are simulated for one blade, both individually and in combinations ranging from partial damage to complete failure. Numerical results are obtained using a dissimilar blade aeroelastic analysis based on finite elements in space and time for hover and forward speed conditions. It is found that the helicopter can be trimmed for all cases with all three controls having failed on the blade with actuator damage thereby showing that the IBC actuated rotor can survive an actuator failure and can be reconfigured by the pilot using the controls on the other blades. However, in case the collective fails and the longitudinal cyclic is present, there are problems in achieving trim at high damage levels at high forward speeds. Physical explanations of this phenomenon are given. The response (especially flap) for the damaged rotor blades can become high and 1/rev and 2/rev are transmitted by the reconfigured rotor to the hub. Results show that IBC based primary controls provide redundancy which can improve the survivability of a helicopter in case of actuator failure in one blade. [ABSTRACT FROM AUTHOR]

Radar deception through phantom track generation using multiple electronic combat air vehicles is addressed, which serves as a motivating example for cooperative control of autonomous multiagent systems. A general framework to derive sufficient conditions for the existence of feasible solutions for an affine nonlinear control system comprising of a team of nonholonomic mobile agents having to satisfy actuator and interagent constraints is presented. Based on this feasibility analysis, an algorithm capable of generating trajectories online and in real time, for the phantom track generation problem, is developed. A rigorous treatment of the phantom track generation problem, which includes results on its accessibility, feasibility, local asymptotic straightening of trajectories, and a limited result on system controllability, is given. The basic approach to the algorithm based on the results developed here is presented along with simulation results, validating the proposed approach. [ABSTRACT FROM AUTHOR]

The article reports on dynamic gain scheduled control of a Hawk scale model. It is posed that when designing flight control laws employing linearisations of an aircraft model about various flight conditions, some form of scheduling of the resultant gains will often be mandated to implement the controller over wide operating areas. Moreover, the dynamic gain schedule is reflected to enhance significantly the transient response of the aircraft model during rapid maneuvering and to lessen the chances of control surface actuator position limit saturation.

Abstract: The technique of inverse simulation is finding application in many and varied fields. As the name implies this technique is used to calculate the control action required to achieve a specified system response. The field of aircraft flight dynamics is particularly suited to this form of simulation as the question of what control actions must the pilot (or automatic flight control system) take for the aircraft to fly along a particular trajectory (a landing approach, for example) is often asked. This paper looks specifically at the application of inverse simulation in flight dynamics. The aim is not only to give an overview of the various techniques and applications but also to provide guidance to potential users of the technique on several of the physical and numerical features often observed in the results. An extensive review of the methodologies used within the family of inverse simulations is presented followed by a formal treatment of the theoretical development of inverse simulation as an established technique. A case study involving the inverse simulation of a helicopter flying a slalom manoeuvre is presented to demonstrate the application of inverse simulation in a flight dynamics analysis. An important feature of the use of inverse simulation is that it is necessary to define the output response required—in the case of flight dynamics the required flight path has to be modelled. Some of the methods used are documented, and their validity discussed. The paper also gives an insight into the types of problem which can be addressed by inverse simulation by detailing some of the many applications to which it has been put in the past. These include studies of rotorcraft handling qualities, performance and design, and pilot modelling as well as model validation. An important element of this paper is the formal, theoretical analysis of some of the numerical and physical features exhibited by inverse simulation which should aid potential users to interpret their results. The work presented in this paper shows a clear evolution of inverse simulation from its initial days when the mathematical models used were relatively simple into a mature analytical technique able to incorporate state of the art mathematical models and be applied to real flight dynamics problems. [Copyright &y& Elsevier]

This paper describes the design of a switching scheme for integrated flight and propulsion control of a vehicle/short take-off land (V/STOL) aircraft throughout the hover and transition regions of its flight envelope. The approach adopted makes use of a recently introduced bumpless transfer technique and presents a methodology for switching between multiple controllers while limiting on-line computational overheads. The success of the switching scheme in maintaining desirable flying qualities as the aircraft accelerates from hover to wing-borne flight is demonstrated in non-linear simulation. Simulation results for the switched system clearly show the effectiveness of the bumpless transfer scheme in preserving closed-loop performance during switching. [ABSTRACT FROM AUTHOR]

The dynamic growth of general aviation as a mean of transport over medium distances means that people having no extraordinary qualifications or extraordinary physical or mental abilities more often pilot such types of airplanes. This phenomenon creates the necessity of giving planes flying qualities that allow them to be safely piloted by ordinary people. One way of solving this problem is equipping airplanes with fly-by-wire control systems that modify their handling qualities. Then the computer included into such control systems modifies the actions taken by the pilot, making the airplane both easier and more comfortable to control. This paper presents sample software tools — control algorithms that allowing an airplane's handling qualities to be improved. They are prepared by the authors and tested on board an experimental plane. That plane was equipped with a prototypical fly-by-wire control system, which can modify a plane's responses to a pilot's actions. Selected results of flying tests of this control system that modifies handling qualities are presented in this paper. Those results were a starting point for investigations to rate and compare the handling qualities of a plane equipped with a control system working according to the algorithms tested. [ABSTRACT FROM AUTHOR]

The objective of this study is to demonstrate the concept of active trailing-edge flaps as primary flight control and vibration reduction devices for a typical full-scale helicopter. A comprehensive rotorcraft analysis based on UMARC was developed to analyze the swashplateless rotor. A parametric study of various key design variables involved in the trailing-edge flap design was carried out. An optimal design of a trailing-edge flap system that provides effective control authority within the complete range of advance ratios as well as minimum actuation requirements was achieved. Trailing-edge flaps demonstrated the capability of performing both primary flight control and active vibration control functions. At a high forward speed (advance ratio of 0.32), the 4/rev vertical force and roll and pitch moments at hub ate successfully eliminated (by 90%), and the 4/rev in-plane hub forces are reduced by more than 40%. The half peak-to-peak value of the trailing-edge flap deflection for primary flight control is 7.1 deg, and an additional 4.7 deg is required for active vibration control. [ABSTRACT FROM AUTHOR]