Need for Avionics in Civil, Military and Space Systems
Avionics are advanced electronics used in aircraft, spacecraft and satellites. These systems perform various functions including communication, navigation, flight control, display systems, flight management etc. There is a great need…
Introduction to Tool-Based Design and Evaluation of Resilient Flight Control Systems
A large transport aircraft simulation benchmark (REconfigurable COntrol for Vehicle Emergency Return RECOVER) has been developed within the European GARTEUR Flight Mechanics Action Group 16 (FM-AG(16)) on Fault Tolerant Control (2004-2008) for the integrated evaluation of fault detection, identification (FDI) and reconfigurable flight control systems. The benchmark includes a suitable set of assessment criteria and failure cases, based on reconstructed accident scenarios, to assess the potential of new adaptive control strategies to improve aircraft survivability. The application of reconstruction and modeling techniques, using accident flight data for validation, has resulted in high fidelity non-linear aircraft and fault models to evaluate new Fault Tolerant Flight Control (FTFC) concepts and their real-time performance to accommodate in-flight failures (Edwards et al., 2010). This chapter will give an overview of advanced flight control developments and pilot training related initiatives to reduce the amount of in-flight loss-of-control (LOC-I) accidents. The GARTEUR RECOVER benchmark, validated with accident flight data and used during the GARTEUR FM-AG(16) program, will be described. The modular features of…
Introduction to Effects of Automatic Flight Control
System on Chinook Underslung Load Failures One of the major helicopter attributes is its ability to transport cargo externally in the form of external slung loads (see Fig. 1). Commercial and military operators accept the fact that using a helicopter for external load transportation is usually expensive in terms of both money and time. However, helicopters still have the significant advantage of accessing unreachable sites. Operations of helicopters with external loads impose limitations to the use of the helicopter, as for example: helicopter maximum forward speed is usually severely reduced because of the danger on dynamic instabilities of the load; due to external load the aerodynamic drag can become excessive, resulting in power and control limitations on the helicopter. The problem addressed in this chapter concerns the behaviour of a helicopter following the premature breakdown of one of its cables sustaining the slung load. As a specific example, the Chinook helicopter CH-47B with an external load will be considered. The CH-47 (Chinook) is a twin-engine tandem rotor helicopter (see Fig. 1) designed for all- weather, medium-sized transport type operations. The three bladed rotors are driven in opposite directions (front rotor rotates anticlockwise, rear rotor rotates…
Introduction to Fault Tolerant Flight Control Techniques with Application to a Quadrotor UAV Testbed
Unmanned Aerial Vehicles (UAVs) are gaining more and more attention during the last few years due to their important contributions and cost-effective applications in several tasks such as surveillance, search and rescue missions, geographic studies, as well as various military and security applications. Due to the requirements of autonomous flight under different flight conditions without a pilot onboard, control of UAV flight is much more challenging compared with manned aerial vehicles since all operations have to be carried out by the automated flight control, navigation and guidance algorithms embedded on the onboard flight microcomputer/microcontroller or with limited interference by a ground pilot if needed. As an example of UAV systems, the quadrotor helicopter is relatively a simple, affordable and easy to fly system and thus it has been widely used to develop, implement and test-fly methods in control, fault diagnosis, fault tolerant control as well as multi-agent based technologies in formation flight, cooperative control, distributed control, mobile wireless networks and communications. Some theoretical works consider the problems of control (Dierks & Jagannathan, 2008), formation flight (Dierks & Jagannathan, 2009) and fault diagnosis (Nguyen et al., 2009;…
Introduction to Adaptive Feedforward Control for Gust Loads Alleviation
Active control techniques for the gust loads alleviation/flutter suppression have been investigated extensively in the last decades to control the aeroelastic response, and improve the handling qualities of the aircraft. Nonadaptive feedback control algorithms such as classical single input single output techniques (Schmidt & Chen, 1986), linear quadratic regulator (LQR) theory (Mahesh et al., 1981; Newsom, 1979), eigenspace techniques (Garrard & Liebst, 1985; Leibst et al., 1988), optimal control algorithm (Woods-Vedeler et al., 1995), H∞ robust control synthesis technique (Barker et al., 1999) are efficient methods for the gust loads alleviation/flutter suppression. However, because of the time varying characteristics of the aircraft dynamics due to the varying configurations and operational parameters, such as fuel consumption, air density, velocity, air turbulence, it is difficult to synthesize a unique control law to work effectively throughout the whole flight envelope. Therefore, a gain scheduling technique is necessary to account for the time varying aircraft dynamics. An alternative methodology is the feedforward and/or feedback adaptive control algorithms by which the control law can be updated at every time step (Andrighettoni & Mantegazza, 1998; Eversman & Roy, 1996; Wildschek et al., 2006). With the novel development of the airborne LIght Detection and Ranging (LIDAR) turbulence sensor available for an accurate vertical gust velocity measurement at a considerable distance ahead of the aircraft (Schmitt, Pistner, Zeller, Diehl & Navé, 2007), it becomes feasible to design an adaptive feedforward control to alleviate the structural loads induced by any turbulence and extend the life of the structure. The adaptive feedforward control algorithm developed in (Wildschek et al., 2006) showed promising results for vibration suppression of the first wing bending mode. However, an unavoidable constraint for the application of this methodology is the usage of a high order Finite Impulse Response (FIR) filter. As a result, an overwhelming computation effort was needed to suppress the structural vibration of the aircraft. In this chapter, an adaptive feedforward control algorithm where the feedforward filter is parameterized using orthonormal basis expansions along with a recursive least square algorithm with a variable forgetting factor is proposed for the feedforward compensation of gust loads. With the use of the orthonormal basis expansion, the prior flexible modes information of the aircraft dynamics can be incorporated to build the structure of the feedforward controller. With this strategy, the order of the feedforward filter to be estimated can be largely reduced. As a result, the computation effort is greatly decreased, and the performance of the feedforward controller for gust loads alleviation will be enhanced. Furthermore, an FFT based PolyMAX identification method and the stabilization diagram program (Baldelli et al., 2009) are proposed to estimate the flexible modes of the aircraft dynamics. The need for an integrated model of flight dynamics and aeroelasticity is brought about by the emerging design requirements for slender, more flexible and/or sizable aircraft such as the Oblique Flying Wing (OFW), HALE, Sensorcraft and morphing vehicles, etc. Furthermore, a desirable unified nonlinear simulator should be formulated in principle by using commonly agreeable terms from both the flight dynamics and aeroelasticity fields in a consistent manner. A unified integration framework that blends flight dynamics and aeroelastic modeling approaches with wind-tunnel or flight-test data derived aerodynamic models has been developed in (Baldelli & Zeng, 2007). This framework considers innovative model updating techniques to upgrade the aerodynamic model with data coming from CFD/wind-tunnel tests for a rigid configuration or data estimated from actual flight tests when flexible configurations are considered. Closely following the unified integration framework developed in (Baldelli & Zeng, 2007), an F/A-18 Active Aeroelastic Wing (AAW) aeroelastic model with gust perturbation is developed in this chapter, and this F/A-18 AAW aeroelastic model can be implemented as a test-bed…
Introduction to Gain Tuning of Flight Control Laws for Satisfying Trajectory Tracking Requirements
The present chapter is concerned with presenting an approach for the synthesis of a gain- scheduled flight control law that assures compliance to trajectory tracking requirements. More precisely, a strategy is proposed for improving the tracking performances of a baseline controller, obtained by conventional synthesis techniques, by tuning its gains. The approach is specifically designed for atmospheric re-entry applications, in which gain scheduled flight control laws are typically used. Gain-scheduling design approaches conventionally construct a nonlinear controller by combining the members of an appropriate family of linear time-invariant (LTI) controllers (Leith & Leithead, 2000). The time-invariant feedback laws usually share the same structure, and differ only for the values of some tunable parameters, most notably the controller’s gains. These gains are generally determined taking advantage of well-assessed LTI-based design techniques, such as pole placement and gain/phase margin methods. However, once a set of LTI feedback laws is specified, the nonlinear controller must be synthesized, which requires an additional design step. This step is of considerable importance since the choice of nonlinear controller realization can greatly influence the closed loop performance (Leith…
Introduction to Quantitative Feedback Theory and Its Application in UAV’s Flight Control
Quantitative feedback theory (hereafter referred as QFT), developed by Isaac Horowitz (Horowitz, 1963; Horowitz and Sidi, 1972), is a frequency domain technique utilizing the Nichols chart in order to achieve a desired robust design over a specified region of plant uncertainty. Desired time-domain responses are transformed into frequency domain tolerances, which lead to bounds (or constraints) on the loop transmission function. The design process is highly transparent, allowing a designer to see what trade-offs are necessary to achieve a desired performance level. QFT is also a unified theory that emphasizes the use of feedback for achieving the desired system performance tolerances despite plant uncertainty and plant disturbances. QFT quantitatively formulates these two factors in the form of (a) the set R {TR } of acceptable D D command or tracking input-output relationships and the set {T } of acceptable disturbance input-output relationships, and (b) a set {P} of possible plants which…
Introduction to Fundamentals of GNSS-Aided Inertial Navigation
GNSS-aided inertial navigation is a core technology in aerospace applications from military to civilian. It is the product of a confluence of disciplines, from those in engineering to the geodetic sciences and it requires a familiarity with numerous concepts within each field in order for its application to be understood and used effectively. Aided inertial navigation systems require the use of kinematic, dynamic and stochastic modeling, combined with optimal estimation techniques to ascertain a vehicle’s navigation state (position, velocity and attitude). Moreover, these models are employed within different frames of reference, depending on the application. The goal of this chapter is to familiarize the reader with the relevant fundamental concepts. Background Modeling motion The goal of a navigation system is to determine the state of the vehicle’s trajectory in space relevant to guidance and control. These are namely its position, velocity and attitude at any time. In inertial navigation, a vehicle’s path is modeled kinematically rather than dynamically, as the full relationship of forces acting on the body to its motion is quite complex. The kinematic model incorporates accelerations and turn rates from an inertial measurement unit (IMU) and accounts for effects on the measurements of the reference frame in which the model is formalized. The kinematic model relies solely on measurements and known physical properties of the reference frame, without regard to vehicle dynamic characteristics.…
Introduction to ATM systems and Wind Farms
Air safety includes all the rules and processes that enable commercial and cargo aeroplanes to fly safely across the European Union. It includes rules on aircraft construction and use, infrastructure safety, data management and analysis, flying operations, and cargo. Air safety management aims to spot potential accidents and incidents before they occur. It is not the same as air security, which seeks to prevent voluntary illegal and harmful acts in the field of aviation. The wind is an increasingly important source of energy, but negative impact on air transport is in area of Air Traffic Services. Communication Navigation and Surveillance systems are endangered with big wind farms. Primary problem is in radar system and is detailed described in my text. The potential impacts of wind farms on air traffic management include the cumulative effects on the Slovak republic airspace management and surveillance infrastructure and affect the following systems: Primary Radar, Secondary Surveillance Radar (SSR), Microwave links associated with a) and …
Introduction to Legal aspects of Air traffic management based on satellite navigation
“Air Traffic Control’s primary objective is to ensure flight safety: pilots in their cockpit are to a large extent « blind » to the exterior world and, given the aircraft speed and trajectory complexity, it is necessary to control them from the ground in order to make sure that of course there are no accidents, but also to ensure the overall fluidity and efficiency of traffic flows. Air Traffic Control (ATC) is based on two main pillars: “surveillance”, which enables ground operators to know precisely where the aircraft are, and the “controller”, who manages the safety of flights .Ever since the implementation of radars in the 70s-80s as surveillance means, air traffic control has not evolved much: ATC is essentially “craftsmanship”, and relies entirely on the controllers’ individual capability to handle always more traffic. Even though air transport has exceptionally good reliability and safety records, to a large extent thanks to the high quality of work performed by air traffic controllers, this craftsmanship is becoming anachronistic: in the information society era, communications between controllers and pilots are still using the voice-radioiii!” The current Air Traffic Management (ATM) is based on ground navigational system such as radar and voice communications experience difficulty in meeting growing demand of air traffic. Despite economic recession ICAOiv expects moderate growth of air traffic of 3.3 percent to 5 percent during 2010-11v.According to aircraft manufacturer Airbus, global air passenger traffic is set to increase by over 150% over the next 20 years, representing an annual growth of 4.7%. The size of the world’s passenger aircraft fleet will double in number from 14,016 in 2008 to 28,111. The fastest growing regions will be India, China and Africa, driven by deregulation, economic growth, …
