99 research outputs found

    Handling Qualities Assessment of a Pilot Cueing System for Autorotation Maneuvers

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    This paper details the design and limited flight testing of a preliminary system for visual pilot cueing during autorotation maneuvers. The cueing system is based on a fully-autonomous, multi-phase autorotation control law that has been shown to successfully achieve autonomous autorotation landing in unmanned helicopters. To transition this control law to manned systems, it is employed within a cockpit display to drive visual markers which indicate desired collective pitch and longitudinal cyclic positions throughout the entire maneuver, from autorotation entry to touchdown. A series of simulator flight experiments performed at University of Liverpool’s HELIFLIGHT-R simulator are documented, in which pilots attempt autorotation with and without the pilot cueing system in both good and degraded visual environments. Performance of the pilot cueing system is evaluated based on both subjective pilot feedback and objective measurements of landing survivability metrics, demonstrating suitable preliminary performance of the system

    Design of a DDP controller for autonomous autorotative landing of RW UAV following engine failure

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    A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, April 2016A Rotary Wing Unmanned Aerial Vehicle (RW UAV) as a platform and its payload consisting of sophisticated sensors would be costly items. Hence, a RW UAV in the 500 kg class designed to fulfil a number of missions would represent a considerable capital outlay for any customer. Therefore, in the event of an engine failure, a means should be provided to get the craft safely back on the ground without incurring damage or causing danger to the surrounding area. The aim of the study was to design a controller for autorotative landing of a RW UAV in the event of engine failure. In order to design a controller for autorotative landing, an acceleration model was used obtained from a study by Stanford University. FLTSIM helicopter flight simulation package yielded necessary RW UAV response data for the autorotation regimes. The response data was utilized in identifying the unknown parameters in the acceleration model. A Differential Dynamic Programming (DDP) control algorithm was designed to compute the main and tail rotor collective pitch and the longitudinal and lateral cyclic pitch control inputs to safely land the craft. The results obtained were compared to the FLTSIM flight simulation response data. It was noted that the mathematical model could not accurately model the pitch dynamics. The main rotor dynamics were modelled satisfactorily and which are important in autorotation because without power from the engine, the energy in main rotor is critical in a successful execution of an autorotative landing. Stanford University designed a controller for RC helicopter, XCell Tempest, which was deemed successful. However, the DDP controller was designed for autonomous autorotative landing of RW UAV weighing 560 kg, following engine failure. The DDP controller has the ability to control the RW UAV in an autorotation landing but the study should be taken further to improve certain aspects such as the pitch dynamics and which can possibly be achieved through online parameter estimation.MT 201

    A Flight Dynamics Model for a Small-Scale Flybarless Helicopter

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    Helicopter flight modeling and robust autonomous control with uncertain dynamics

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    Helicopter flight control has gained greater visibility in the last decades due to its characteristics. It is a task of high difficulty due to the system being changeable. Helicopter control is the junction of several variables such as the flying qualities and performance, skill of the pilot, weather conditions, etc. For a given configuration of a helicopter (military, civil, SAR, etc.), we need precise control parameters, and is in flying qualities that we focus our attention. This paper is then dedicated to autonomous modeling and control of conventional rotarywing platforms, so that there is a good balance between robustness and performance of the system, so that when there are disturbances, it can stabilize more quickly and effectively and, to verify this, a particular helicopter is used for the validation of the methods elaborated: DRA research ZD559 Lynx (Lynx Mk7), still serving the UK Army Air Corps. In helicopter flight dynamics, will be focused autorotation phase and different flight speed phase and two specific control systems will be compared: normal LQR and robust LQR. Is then designed the controllers previously mentioned, comparing their results through the dynamic model already linearized in order to verify which one is most appropriate for the platform. When there is a change in the balance of the aircraft, it can return to the same position as quickly as possible. By the obtained results, it’s verified in both cases, success in stabilizing the aircraft and controlling it’s trajectory given different reference speeds, a controller is most evident than the other.O controlo de helicópteros tem vindo a adquirir nas últimas décadas maior visibilidade devido à característica desta aeronave. É uma tarefa de elevada dificuldade devido ao próprio sistema ser, já por si, inconstante. O controlo de helicópteros é a junção de várias variáveis como as qualidades de voo e performance, a perícia do piloto, condições atmosféricas, etc. Seja qual for a missão do helicóptero (militar, civil, SAR, etc), precisaremos de parâmetros de controlo precisos, e é nas qualidades de voo que iremos focar a nossa atenção. O presente trabalho é dedicado então à modelação e controlo autónomo de plataformas de asa rotativa convencional, de forma a que haja uma boa relação entre robustez e performance do sistema para que, quando hajam perturbações, o sistema possa estabilizar eficazmente e, para se verificar isso mesmo, um helicóptero específico é utilizado para a validação dos métodos elaborados: DRA research Lynx ZD559 (Lynx Mk7), ainda ao serviço do UK Army Air Corps. Na dinâmica do voo do helicóptero, irá ser focada a fase de autorrotação e fase de voo para diferentes velocidades e dois sistemas de controlo irão ser comparados: LQR normal e LQR robusto. Projectou-se então os controladores referidos anteriormente comparando os seus resultados através da dinâmica e navegação do modelo já linearizado, para se verificar qual dos dois será mais apropriado para que a plataforma, no momento em que existe uma alteração na dinâmica da aeronave, possa regressar a essa mesma posição o mais brevemente possivel. Através então dos resultados obtidos, verifica-se em ambos os casos, o sucesso em estabilizar a aeronave e controlar o voo dada uma determinada referência para diferentes velocidades, mas um controlador evidencia-se mais que o outro

    Experimental implementation controlled SPWM inverter based harmony search algorithm

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    An optimum PI controller using harmony search optimization algorithm (HS) is utilized in this research for the single-phase bipolar SPWM inverter. The aim of this algorithm is to avoid the conventional trial and error procedure which is usually applied in finding the PI coefficients in order to obtain the desired performance. Then, the control algorithm of the inverter prototype is experimentally implemented using the eZdsp F28355 board along with the bipolar sinusoidal pulse width modulation (SPWM) to control the output voltage drop under different load conditions. The proposed overall inverter design and the control algorithm are modelled using MATLAB environment (Simulink/m-file Code). The mean absolute error (MAE) formula is used as an objective function with the HS algorithm in finding the adaptive values of  and  parameters to minimize the error of the inverter output voltage. Based on the output results, the proposed voltage controller using HS algorithm based PI (HS-PI) showed that the inverter output performance is improved in terms of voltage amplitude, robustness, and convergence rate speed as compared to PSO algorithm based PI (PSO-PI). This is to say that the proposed controller provides a good dynamic responses in both cases; transient and steady-state. Finally, the experimental setup result of the inverter controller is verified to validate the simulation results

    Time-to-Contact-Based Control Laws for Flare Trajectory Generation and Landing Point Tracking in Autorotation

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    For many rotorcraft platforms, incorrect timing of the autorotation flare and deceleration maneuvers may result in significant aircraft damage and injury to the crew, or worse. There is a clear need for new pilot cueing and control augmentation technologies that lead to a higher probability of a successful autorotation landing. This paper describes a recent effort to develop two different Tau (time-to-contact)-based autorotation controllers from two different approaches that can be used to drive visual aids to help guide a pilot to apply the required control inputs to complete a safe autorotative landing

    Rotary-Wing Decelerators for Probe Descent Through the Atmosphere of Venus

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    An innovative concept is proposed for atmospheric entry probe deceleration, wherein one or more deployed rotors (in autorotation or wind-turbine flow states) on the aft end of the probe effect controlled descent. This concept is particularly oriented toward probes intended to land safely on the surface of Venus. Initial work on design trade studies is discussed

    Design and Analysis of Stop-Rotor Multimode Unmanned Aerial Vehicle (UAV)

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    abstract: The objective of this work is to develop a Stop-Rotor Multimode UAV. This UAV is capable of vertical take-off and landing like a helicopter and can convert from a helicopter mode to an airplane mode in mid-flight. Thus, this UAV can hover as a helicopter and achieve high mission range of an airplane. The stop-rotor concept implies that in mid-flight the lift generating helicopter rotor stops and rotates the blades into airplane wings. The thrust in airplane mode is then provided by a pusher propeller. The aircraft configuration presents unique challenges in flight dynamics, modeling and control. In this thesis a mathematical model along with the design and simulations of a hover control will be presented. In addition, the discussion of the performance in fixed-wing flight, and the autopilot architecture of the UAV will be presented. Also presented, are some experimental "conversion" results where the Stop-Rotor aircraft was dropped from a hot air balloon and performed a successful conversion from helicopter to airplane mode.Dissertation/ThesisM.S.Tech Mechanical Engineering 201
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