Article

State of the art in tilt-quadrotors, modelling, control and fault recovery

Authors:
  • Dubai Futue Labs
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Abstract

Research studies on quadrotors have recently drawn significant interest from academia and industry. Faults and failures handling are the major weaknesses of conventional quadrotor platforms; therefore, an innovative actuation mechanism was introduced to allow tilting the rotors. Tilting rotors of multirotor platforms provide high dexterity for flying between adjacent obstacles and assist the platforms in dealing with various failure scenarios. This paper reviews the state of the research on tilt-quadrotor platforms. Several platforms, software and hardware architectures, were discussed in the literature. Most of the latest developments were focused on conventional quadrotor modelling, combined with rotor tilting dynamics. On the other hand, controlling such platform was mainly studied using two types of controllers: Feedback Linearisation technique and Control Allocator. Recovery strategy in case of fault or failure has been covered extensively for conventional quadrotors, but very limited known work for tilt-quadrotor. This review concludes that the system dynamic modelling is relatively well covered compared to exploring new control techniques for more stringent requirements. However, recovery strategies as the main advantage of tilt-quadrotor platforms are not explored extensively and require more research attention.

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... The relationship [19] between roll, pitch, yaw and the angular velocities is given in Equation (18). ...
... (19)-(20), respectively. ...
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In this work we present a novel concept of a quadrotor UAV with tilting propellers. Standard quadrotors are limited in their mobility because of their intrinsic underactuation (only 4 independent control inputs vs. their 6-dof pose in space). The quadrotor prototype discussed in this paper, on the other hand, has the ability to also control the orientation of its 4 propellers, thus making it possible to overcome the aforementioned underactuation and behave as a fully-actuated flying vehicle. We first illustrate the hardware/software specifications of our recently developed prototype, and then report the experimental results of some preliminary, but promising, flight tests which show the capabilities of this new UAV concept.
Conference Paper
The use of unmanned aerial vehicles (UAVs) for military, scientific, and civilian sectors are increasing drastically in recent years. The quadrotor platform has been used for many applications and research studies, as well. One of the limiting factors that prevents further implementation of the quadrotor system into applications, is the way quadrotor moves. It needs to tilt along the desired direction of motion. By doing this it can have necessary acceleration towards that direction. But tilting has the undesired effect of moving the onboard cameras' direction of view. This becomes an issue for surveillance and other vision based tasks. This study presents the design and control of a novel quadrotor system. Unlike previous study that uses regular quadrotor, this study proposes an alternative propulsion system formed by tilting rotors. This design eliminates the need of tilting the airframe, and it suggests superior performance with respect to regular quadrotor design. The mathematical model of the tiltable-rotor type quadrotor and designed control algorithms are explained. Various simulations are developed on MATLAB, in which the proposed quadrotor aerial vehicle has been successfully controlled. Comparison of the proposed system to regular quadrotor suggests better performance.
Conference Paper
Standard quadrotor UAVs possess a limited mobility because of their inherent underactuation, i.e., availability of 4 independent control inputs (the 4 propeller spinning velocities) vs. the 6 dofs parameterizing the quadrotor position/ orientation in space. As a consequence, the quadrotor pose cannot track an arbitrary trajectory over time (e.g., it can hover on the spot only when horizontal). In this paper, we propose a novel actuation concept in which the quadrotor propellers are allowed to tilt about their axes w.r.t. the main quadrotor body. This introduces an additional set of 4 control inputs which provides full actuation to the quadrotor position/orientation. After deriving the dynamical model of the proposed quadrotor, we formally discuss its controllability properties and propose a nonlinear trajectory tracking controller based on dynamic feedback linearization techniques. The soundness of our approach is validated by means of simulation results.
Conference Paper
Quadrotors have recently become a focus of research in Unmanned Aerial Vehicle (UAV) and flying robots applications. However, controlling the quadrotor dynamics is noticeably complex as the conventional quadrotor is underactuated. Some of the quadrotor motions are coupled with others which makes it impossible to achieve all the desired maneuvers. In this paper, a novel quadrotor design is proposed. The design increases the number of inputs from four in conventional quadrotors to twelve by allowing each rotor to tilt in two directions about its fixed frames. This addition aims to separate the quadrotor motions and give it more maneuverability and robustness. The model of the new design is introduced and several flights are simulated to show the superiority over conventional design.
Book
Unmanned aerial vehicles (UAVs) offer an incomparable means of gathering intelligence and carrying out missions without needing an onboard human pilot. The benefits are considerable in terms of cost, efficiency, and reduced pilot risk. In order to complete a mission efficiently and with a high level of safety and security, the following key design points must be met: • the flight control system must be robust against the aircraft’s model uncertainties and external disturbances; • an efficient fault detection and isolation (FDI) system should be capable of monitoring the health of the aircraft; and • the flight control and guidance system should be reconfigurable depending on actuator fault occurrence or aircraft damage, and should be able to avoid obstacles. Fault-tolerant Flight Control and Guidance Systems addresses all of these aspects with a practical approach following three main requirements: being applicable in real-time; highly computationally efficient; and modular. The text provides: • an overview of fault-tolerant flight control techniques; • the necessary equations for the modeling of small UAVs; • a complete nonlinear FDI system based on extended Kalman filters; and • a nonlinear flight control and guidance system. The book is written in a didactic style with many figures and diagrams making it suitable not only for academic researchers and practicing engineers but also graduate students working in the fields of fault detection techniques and the automatic control of UAVs.
Book
Supervision, health-monitoring, fault detection, fault diagnosis and fault management play an increasing role for technical processes and vehicles, in order to improve reliability, availability, maintenance and life-time. For safety-related processes fault-tolerant systems with redundancy are required in order to reach comprehensive system integrity. This book gives an introduction into the field of fault detection, fault diagnosis and fault-tolerant systems with methods which have proven their performance in practical applications. It guides the reader in a structured tutorial style: supervision methods, reliability, safety, system integrity and related terminology; fault detection with signal-based methods for periodic and stochastic signals; fault detection with process model-based methods like parameter estimation, state estimation, parity equations and principal component analysis; fault diagnosis with classification and inference methods; fault-tolerant systems with hardware and analytical redundancy; many practical simulation examples and experimental results for processes like electrical motors, pumps, actuators, sensors and automotive components; end-of-chapter exercises for self testing or for practice. The book is dedicated to graduate students of electrical, mechanical, chemical engineering and computer science and for practising engineers.
Article
The report contains a condensed description of the X-19 V/STOL technology. The broad categories discussed include in Section I a review of the developments leading up to the X-19 program. Sections II through VI are devoted entirely to the propellers and the considerations involved in design. The radial force principle is postulated in Section II. Interference effects on the wings due to the propellers are discussed in Section III. The propeller aerodynamic design in hover and cruise is presented in Section IV. Section V is devoted to the structure and control mechanisms of the propeller. Section VI relates to the use of propellers as in airplane control device. The tandem wing principle is discussed in Section VII, covering stability, control, and drag. Section VIII is devoted solely to ground effects. The wind tunnel research activity leading up to the X-19 is presented in Section IX. The structural loads in hover, transition and cruise are discussed in Section X. Section XI presents information pertinent to landing procedures in hover or cruise in the event of power failure. A summary of the flight test program is given in Section XII, including aircraft and hardware performance characteristics. Finally, Section XIII is devoted to a general discussion and assessment of the aircraft's unorthodox features.
Development of a dual axis tilt rotorcraft UAV: modelling, simulation and control
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