This thesis describes an all-in-one flight control system (FCS) that was designed for unmanned aerial vehicles (UAVs). The project focuses on the embedded hardware aspect of a stand-alone system with low-cost and reliability in mind.

The development and testing for a UAV testbed to be used in academic research and undergraduate education is proposed in this thesis. Analysis on commercial off-the-shelf UAV systems and autopilots lead to the development of a custom, open-architecture and modular UAV testbed. The main focus is to support research in UAV control field and education of the undergraduate students. The integration and use of commercial-off-the-shelf avionics and air vehicle are described in detail. System performance is examined both in flight and on the ground. Results of the system tests show that the developed system is a functional UAV testbed to be used in research of different flight control algorithms.

The primary objective of this thesis was to study, implement, and test low-cost electronic flight control systems (FCS) in remotely piloted subscale research aircraft with relaxed static longitudinal stability. Even though this implementation was carried out in small, simplified test-bed aircraft, it was designed with the aim of being installed later in more complex demonstrator aircraft such as the Generic Future Fighter concept demonstrator project. The recent boom of the unmanned aircraft market has led to the appearance of numerous electronic FCS designed for small-scale vehicles and even hobbyist-type model aircraft. Therefore, the purpose was not to develop a new FCS from scratch, but rather to take advantage of the available technology and to examine the performance of different commercial off-the-shelf (COTS) low-cost systems in statically unstable aircraft models. Two different systems were integrated, calibrated and tested: a simple, gyroscope-based, single-axis controller, and an advanced flight controller with a complete suite of sensors, including a specifically manufactured angle-of-attack transducer. A flight testing methodology and appropriate flight-test data analysis tools were also developed. The satisfactory results are discussed for different flight control laws, and the controller tuning procedure is described. On the other hand, the different test-bed aircraft were analysed from a theoretical point of view by using common aircraft-design methods and conventional preliminary-design tools. The theoretical models were integrated into a flight dynamics simulator, which was compared with flight-test data obtaining a reasonable qualitative correlation. Possible FCS modifications are discussed and some future implementations are proposed, such as the integration of the angle-of-attack in the control laws.

This thesis work presents a parametrized integration of the flight control system within RAPID by means of the automation in CATIA V5, using Knowledge Pattern. Nowadays aircraft’s design and development processes are not only time-consuming but also incur high economic cost. In addition, system integration is highly a multi-disciplinary design process which often involves a large number of different discipline teams working at the same time and space. The main objective of this thesis is to investigate how CAD (Computer Aided Design) software can be used in the early design stages to define the flight control system integration. The purpose of this work to improve the functionality of an in house produced aircraft conceptual design tool carried out at the Division of Fluid and Mechatronic Systems, Linköping University. The work consists of preliminary integration of the RAPID flight control system and the hydraulics associated to it. By defining several reusable templates, the automatic definition of a flight control system within the RAPID aircraft has been achieved. Moreover it is a parametrical model which allows the user to modify a high number of features as desired to enhance the design process. For this, a user interface in Microsoft Excel connected to CATIA has also been attained.

The objective of this work is to adopt and further expand the type design of the SONG motor glider. The study will result in the basic aerodynamic calculation and the design of lateral control system including structural strength inspection of selected parts. Subsequently, the proposal will allow for further calculation to be made (of flight mechanics, wings strength or fuselage and empennage firmness) and for more specific constructional design of individual components of the glider.

A modern ghter aircraft has an advanced ight control system which highly augmentsthe control inputs from the pilot. To verify a new iteration of the control system is a timeconsuming and expensive task. It is desired to nd qualities that is not satisfactory to thepilot as early as possible in the verication process to reduce the cost for design changes.The primary objective of this thesis is to develop methods that can be used for automaticalevaluation of aircraft ying qualities from the data provided by a desktop simulator. A desktopsimulator is cheap to use compared to ight tests and tests with a pilot in a simulator.Only ghter aircraft in the precision ight phase are studied however the methods developedcould easily be extended to include other types of aircraft and other phases of ight.To evaluate the ying qualities two sets of criteria are used the MIL-F-8785C standardand the Gibson criteria. The MIL-F-8785C standard uses a second order linear system toevaluate the aircraft's ying qualities. The linear system is estimated from the nonlineardata and evaluated against the MIL-F-8785C standard. The Gibson criteria studies the timeand frequency domain directly and are designed to work with highly augmented aircraft.The set of Gibson criteria used in this thesis primary evaluates data from the time domainhowever one criterion from the frequency domain is studied.The methods developed to evaluate the ying qualities from the MIL-F-8785C standardonly works for a small part of the ight envelope furthermore they show a large dierencefor what is considered acceptable ying qualities. Because of this the methods developed forthe MIL-F-8785C standard are considered not to be suited for evaluating ying qualities forhighly augmented aircraft. The methods developed to evaluate the ying qualities againstthe Gibson criteria works for a large part of the ight and also show a high accuracy. Thismakes the methods suited for evaluation of the ying qualities.

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This thesis investigates the possibility of using reinforcement learning (RL) techniques to create a flight controller for a quadrotor Micro Aerial Vehicle (MAV). A capable flight control system is a core requirement of any unmanned aerial vehicle. The challenging and diverse applications in which MAVs are destined to be used, mean that considerable time and effort need to be put into designing and commissioning suitable flight controllers. It is proposed that reinforcement learning, a subset of machine learning, could be used to address some of the practical difficulties. While much research has delved into RL in unmanned aerial vehicle applications, this work has tended to ignore low level motion control, or been concerned only in off-line learning regimes. This thesis addresses an area in which accessible information is scarce: the performance of RL when used for on-policy motion control. Trying out a candidate algorithm on a real MAV is a simple but expensive proposition. In place of such an approach, this research details the development of a suitable simulator environment, in which a prototype controller might be evaluated. Then inquiry then proposes a possible RL-based control system, utilising the Q-learning algorithm, with an adaptive RBF-network providing function approximation. The operation of this prototypical control system is then tested in detail, to determine both the absolute level of performance which can be expected, and the effect which tuning critical parameters of the algorithm has on the functioning of the controller. Performance is compared against a conventional PID controller to maximise the usability of the results by a wide audience. Testing considers behaviour in the presence of disturbances, and run-time changes in plant dynamics. Results show that given sufficient learning opportunity, a RL-based control system performs as well as a simple PID controller. However, unstable behaviour during learning is an issue for future analysis. Additionally, preliminary testing is performed to evaluate the feasibility of implementing RL algorithms in an embedded computing environment, as a general requirement for a MAV flight controller. Whilst the algorithm runs successfully in an embedded context, observation reveals further development would be necessary to reduce computation time to a level where a controller was able to update sufficiently quickly for a real-time motion control application. In summary, the study provides a critical assessment of the feasibility of using RL algorithms for motion control tasks, such as MAV flight control. Advantages which merit interest are exposed, though practical considerations suggest at this stage, that such a control system is not a realistic proposition. There is a discussion of avenues which may uncover possibilities to surmount these challenges. This investigation will prove useful for engineers interested in the opportunities which reinforcement learning techniques represent.

This thesis considers the problem of designing gain scheduled flight control system (FCS) for large transport aircraft that satisfy handling qualities criteria. The goal is to design a set of local Linear Time Invariant (LTI) controllers to cover the wide non- linear aircraft operation flight envelope from the viewpoint of the handling qualities assessment. The global gain scheduler is then designed that interpolates between the gains of the local controllers in order to transfer smoothly between different equilibrium points, and more importantly to satisfy the handling qualities over the entire flight envelope. The mathematical model of the Boeing 747-100/200 aircraft is selected for the purpose of the flight controller design and handling qualities as- sessment. In order to achieve an attitude hold characteristic, and also improve the dynamic tracking behavior of the aircraft, longitudinal pitch Rate Command-Attitude Hold (RCAH) controllers are designed as the local flight controllers at the specific equilib- rium points in the flight envelope by means of a state space pole placement design procedure. The handling qualities assessment of the aircraft is presented, based on which the scheduler is designed. A number of existing criteria are employed to assess the han- dling qualities of the aircraft, including the Control Anticipation Parameter (CAP), Neal and Smith, and C∗ criteria. The gain scheduled flight controller is found to have satisfactory handling qualities. The global gain scheduler is designed by interpolating the gains of the local flight controllers in order to transfer smoothly between different equilibrium points, and more importantly to satisfy the handling qualities over the flight envelope. The main contribution of this research is the combination of the gain scheduling technique based on the local controller design approach and handling qualities as- sessment. The controllers are designed based at a number of operating points and the interpolation between them (scheduling) takes place through the scheduling scheme functions. The aircraft augmented with gain-scheduled controller performs satisfactorily and meets the requirement of handling qualities. Moreover, the per- formance using the gain-scheduled controller is considerably improved compared to the performance using the fixed one.

This thesis describes the automatic flight control systems designed for a conventional and an over actuated unmanned air vehicle (UAV). A nonlinear simulation model including the flight mechanics equations together with the interpolated nonlinear aerodynamics, environmental effects, mass-inertia properties, thrust calculations and actuator dynamics is created / trim and linearization codes are developed. Automatic flight control system of the conventional UAV is designed by using both classical and robust control methods. Performances of the designs for full autonomous flight are tested through nonlinear simulations for different maneuvers in the presence of uncertainties and disturbances in the aircraft model. The fault tolerant control of an over actuated UAV is the main concern of the thesis. The flight control system is designed using classical control techniques. Two static control allocation methods are examined: Moore-Penrose pseudo inverse and blended inverse. For this purpose, an aircraft with three sets of ailerons is employed. It is shown that with redundant control surfaces, fault tolerant control is possible. Although both of the static control allocation methods are found to be quite successful to realize the maneuvers, the new blended inverse algorithm is shown to be more effective in controlling the aircraft when some of the control surfaces are lost. It is also demonstrated that, with redundant control surfaces it is possible to recover the aircraft during a maneuver even some of the control surfaces are damaged or got stuck at a particular deflection.