Towards Long-endurance Flight: Design and Implementation of a Variable-pitch Gasoline-engine Quadrotor

Majority of today's fixed-pitch, electric-power quadrotors have short flight endurance ($<$ 1 hour) which greatly limits their applications. This paper presents a design methodology for the construction of a long-endurance quadrotor using variable-pitch rotors and a gasoline-engine. The methodology consists of three aspects. Firstly, the rotor blades and gasoline engine are selected as a pair, so that sufficient lift can be comfortably provided by the engine. Secondly, drivetrain and airframe are designed. Major challenges include airframe vibration minimization and power transmission from one engine to four rotors while keeping alternate rotors contra-rotating. Lastly, a PD controller is tuned to facilitate preliminary flight tests. The methodology has been verified by the construction and successful flight of our gasoline quadrotor prototype, which is designed to have a flight time of 2 to 3 hours and a maximum take-off weight of 10 kg.Comment: 6 page

Comparison of Fixed and Variable Pitch Actuators for Agile Quadrotors

This paper presents the design, analysis and experimental testing of a variable- pitch quadrotor. A custom in-lab built quadrotor with on-board attitude stabi- lization is developed and tested. An analysis of the dynamic di erences in thrust output between a xed-pitch and variable-pitch propeller is given and validated with simulation and experimental results. It is shown that variable-pitch actuation has signi cant advantages over the conventional xed-pitch con guration, includ- ing increased thrust rate of change, decreased control saturation, and the ability to quickly and e ciently reverse thrust. These advantages result in improved quadro-tor tracking of linear and angular acceleration command inputs in both simulation and hardware testing. The bene ts should enable more aggressive and aerobatic ying with the variable-pitch quadrotor than with standard xed-pitch actuation, while retaining much of the mechanical simplicity and robustness of the xed-pitch quadrotor.Aurora Flight Sciences Corp.National Science Foundation (U.S.) (Graduate Research Fellowship Grant 0645960

A new concept

Nowadays, airships are generating a growing interest. The development of new technologies has allowed hybrid airships to become a reality, leading to a significant number of new research projects. In this way, numerous lines of research are opened in all areas of airship designs and, especially, this will allow the development of stability and control systems that are truly efficient. To overcome this limitation in the stability and control there are numerous possible solutions for hybrid airships. This thesis’ objective is to analyze the feasibility and performance of a new concept of stability and control system. This system is a combination of two elements: a distribution of six control surfaces and a set of four variable pitch rotors. For that, four different prototypes were built. Two of them are a scale model of the airship aimed to test the stability and control of all surfaces. The third one is a quad rotor to analyze the behavior of a variable pitch solution. Finally, the last prototype is a scale model again, but this time aimed to test the performance of a quad rotor airship with fixed pitch control. The results from the different tests showed this concept is a promising way to stabilize and control a hybrid airship. Tests of the first prototype validated a new mode of control which solves different problems related to the stability and control. The results from the tests of prototype 1.5 confirmed that a six surfaces configuration allows full control for different types of performance, being necessary to continue investigating this concept as well as its implementation along with a system of rotors. Prototype 2 results showed that a variable pitch rotor solution for a quad rotor provides an effective and feasible control, among other advantages. The results from prototype 2.5 showed that because the airship model does not have an internal or external structure, it has vibration problems at high rotor power settings. In addition, the airship was uncontrollable when utilizing a system of fixed pitch rotors, so it is necessary to study the implementation of the variable pitch ones. Finally, one can conclude that the combination of a system of six control surfaces with a system of four rotors with variable pitch is a promising way to stabilize and control a hybrid airship.Hoje em dia, os dirigíveis estão gerando um crescente interesse. O desenvolvimento de novas tecnologias tem permitido aos dirigíveis híbridos tornar-se uma realidade, multiplicando o número de investigações sobre eles. Desta forma, inúmeras linhas de investigação são abertas em todas as áreas de desenho dos dirigíveis e, especialmente, isso permitirá que o desenvolvimento de sistemas de controlo e de estabilidade que são verdadeiramente eficientes. Para superar essa limitação na estabilidade e no controlo existem numerosas soluções possíveis para os dirigíveis híbridos. O objetivo desta tese é analisar a viabilidade e o desempenho dum novo conceito de sistema de estabilidade e controlo. Este sistema é uma combinação de dois elementos: uma distribuição de seis superfícies de controlo e um conjunto de quatro rotores de passo variável. Para isso, foram construídos quatro protótipos diferentes. Dois deles são um modelo em escala do dirigível com o objetivo de testar a estabilidade e controlo de todas as superfícies. O terceiro é um quad rotor para analisar o comportamento de uma solução de passo variável. Finalmente, o último protótipo é novamente um modelo em escala, mas desta vez tem como objetivo testar o desempenho de um dirigível quad-rotor com controlo de passo fixo. Os resultados dos diferentes ensaios mostram que este conceito é um caminho promissor para estabilizar e controlar um dirigível híbrido. Os testes do primeiro protótipo validaram um novo modo de controlo que resolve diversos problemas relacionados com a estabilidade e o controlo. Os resultados dos ensaios do segundo protótipo confirmaram que uma configuração de seis superfícies de controlo permite um controlo total para diferentes atuações, sendo necessário continuar a investigação deste conceito e a sua implementação em conjunto com um sistema de rotores. Os resultados do protótipo 2 mostraram que uma solução de passo variável proporcionará um controlo eficiente e fiável para um quad rotor, entre outras vantagens. Os resultados do protótipo 2.5 mostraram que ao não ter uma estrutura interna ou externa, o dirigível têm problemas de vibrações para grandes potências nos rotores. Além disso, o dirigível foi incontrolável quando se utilizou um sistema de rotores de passo fixo, por isso é necessário estudar a implementação de passo um sistema de passo variável. Finalmente, pode-se concluir que a combinação de um sistema de seis superfícies de controlo com um sistema de quatro rotores com passo variável é um caminho promissor para estabilizar e controlar um dirigível híbrido

Force-Canceling Mixer Algorithm for Vehicles with Fully-Articulated Radially Symmetric Thruster Arrays

A new type of fully-holonomic aerial vehicle is identified and developed that can optionally utilize automatic cancellation of excessive thruster forces to maintain precise control despite little or no throttle authority. After defining the physical attributes of the new vehicle, a flight control mixer algorithm is defined and presented. This mixer is an input/output abstraction that grants a flight control system (or pilot) full authority of the vehicle\u27s position and orientation by means of an input translation vector and input torque vector. The mixer is shown to be general with respect to the number of thrusters in the system provided that they are distributed in a radially symmetric array. As the mixer is designed to operate independently of the chosen flight control system, it is completely agnostic to the type of control methodology implemented. Validation of both the vehicle\u27s holonomic capabilities and efficacy of the flight control mixing algorithm are provided by a custom MATLAB-based rigid body simulation environment

Optimasi Topologi pada Geometri Frame “Impulse RC Alien 4 Inch”Racing Quadcopter dengan Material Polylactic Acid Hasil 3D Printing

Racing quadcopter adalah UAV jenis quadcopter yang didesain memiliki kecepatan sangat tinggi. Sehingga frame racing quadcopter umumnya dari material karbon fiber yang terkenal ringan dan sangat kaku. Tapi sangat mahal harganya, sehingga perlu adanya alternatif material lain seperti polylactic acid (PLA). Namun frame dari PLA harus melalui proses optimasi untuk mendapatkan keringanan dan kekakuan yang relatif sama dengan frame dari karbon fiber. Salah satu metode optimasi struktural yang dapat digunakan adalah optimasi topologi. Meskipun metode ini menghasilkan detail geometri yang cukup kompleks sehingga sulit untuk manufaktur konvensional, tapi dengan berkembangnya teknologi addictive manufacturing atau 3D printing, geometri yang kompleks tidak lagi menjadi masalah. Tujuan dari penelitian ini untuk mengetahui hasil simulasi tegangan dan deformasi total dari racing quadcopter dengan frame karbon fiber, frame PLA, frame PLA setelah dioptimasi topologi, dan juga hasil realisasi desain akhir dengan 3D printing. Tahapan pada penelitian ini terdiri dari proses pemodelan quadcopter, simulasi tahap awal menggunakan simulasi static structural dengan software elemen hingga yang meliputi pendefinisian model, meshing, set up constaint, dan analisis hasil. Lalu dilanjutkan dengan simulasi optimasi topologi terhadap frame dengan massa retain 50%, 60%, 70%, dan 80% untuk kemudian dilakukan desain ulang pada keempat model tersebut. Setelah itu simulasi tahap akhir dengan metode yang sama dengan simulasi tahap awal untuk keempat model frame hasil desain ulang, dan kemudian analisis hasil akhir dilakukan untuk menentukan “desain terbaik”. Selanjutnya realisasi model dengan menggunakan 3D printer, uji coba model secara langsung di lapangan, dan evaluasi hasil. Simulasi tahap awal didapatkan bahwa existing frame memiliki massa total dan deformasi total maksimum standar berturut-turut 74,13 gram dan 0,14678 mm. Jika mengganti material existing frame dengan PLA, maka ketebalan tiap komponen frame harus diperbesar hingga dua kali untuk mencapai deformasi total maksimum standar. Topologi dengan massa retain 80%,70%, 60%, dan 50% menghasilkan massa berturut-turut 87,88, 82,27, 74,11, 67,85 gram dengan deformasi total maksimum berturut-turut 0,13318, 0,14106, 0,1463, 0,20839 mm sehingga desain “terbaik” adalah desain ulang dengan massa retain 60%. Realisasi terhadap desain ini dapat dilakukan dan berhasil diuji coba meski dengan beberapa evaluasi. ================================================================================================== The racing quadcopter is kind of UAV which is designed for high speed. Frame of racing quadcopter is generally manufactured from carbon fiber material because of its light-weightiness and stiffness, however, it is very expensive. So alternative material, like polylactic acid (PLA) is significantly considered. However polylactic acid frame needs some optimization process to reach relatively same mass and stiffness with the carbon fiber one. One of the structural optimization methods that can be used to solve this case is topology optimization. Although this method will devise very complex details in geometry which is difficult for conventional manufacturing, however, the development of additive manufacturing technology nowadays has changed the complex-geometry structures models as a piece of cake. The purposes of this research are obtaining stress and total deformation simulation result of the racing quadcopter with carbon fiber frame, PLA frame, PLA frame after optimization and also manufacturing “best design” frame using the 3D printer. Stages of the research are started from the quadcopter modeling process, initial simulation using the static structural simulation of finite element software which is consists of model defining, meshing, setting up constraint, and analysis of results. Continued by topology optimization simulation with varying retain mass on 50%, 60%, 70%, and 80% then redesigning those four models. The next stage is the final simulation on the after-redesigning models using the same method as the initial simulation, then the final analysis is established to achieve “The best design”. The last stage is model manufacturing using 3D printer, field testing, and result evaluation. The initial simulation show that the existing frame has standard total mass and maximum total deformation 74.13 gram and 0,14678 mm respectively. If the material is changed to polylactic acid, doubling the thickness of each frame component is needed to reach the standard maximum total deformation. Topology optimization for retain mass 80%, 70%, 60%, and 50% produce total mass 87.88, 82.27, 74.11, 67.85 gram respectively and maximum total deformation 0.13318, 0.14106, 0.1463, 0.20839 mm respectively, so “The best design” is achieved from establishing redesign of 60% retain mass. Then both “The best design” manufacturing and field testing are done well although with some evaluations

Design and control of an autonomous variable-pitch quadrotor helicopter

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012.Cataloged from department-submitted PDF version of thesis. This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 101-106).The aerospace community, particularly in academia, has seen a recent rise in the popularity of fixed-pitch quadrotor helicopters. The fixed-pitch quadrotor is popular largely because of its mechanical simplicity relative to other hovering aircraft. This simplicity, however, places fundamental limits on the achievable actuator bandwidth and the types of maneuvers possible to fly. This thesis explores the extent to which the addition of variable-pitch propellers to a quadrotor helicopter overcomes these limitations. A detailed analysis of the potential benefits of variable-pitch propellers over fixed-pitch propellers for a quadrotor is presented. This analysis is supported with experimental testing to show that variable-pitch propellers, in addition to allowing for efficient generation of negative thrust, substantially increase the maximum rate of thrust change. A nonlinear, quaternion-based control algorithm is presented for controlling the quadrotor. An accompanying trajectory generation method is detailed with an optimization routine for finding minimum-time paths through waypoints. The control law and trajectory generation algorithms are implemented in simulation and on a custom variable-pitch quadrotor. The quadrotor attitude control is performed on the vehicle using a custom autopilot. Position and attitude measurements are made with an off-board motion capture system. Several flight tests are shown with a particular emphasis on the benefits of a variable-pitch qaudrotor over a standard fixed-pitch quadrotor for performing aggressive and aerobatics maneuvers. To the best of the author's knowledge, this work marks the first documented, autonomous variable-pitch quadrotor built for agile and aggressive flight.by Mark Johnson Cutler.S.M

Alocação de controle desacoplada rápida em sistemas de controle superatuados

Over-actuated systems usually require nonlinear control allocation methods to map Virtual Control Actions (VCAs) into Real Control Actions (RCAs). This process requires computational efforts sometimes not available on embedded robotic platforms. It is in this context that this work presents the design of an Quadrotor Tilt-Rotor (QTR) through a new concept of control allocation with uncoupled RCAs, where the initial nonlinear system is divided into partially dependent linear subsystems with fast and robust convergence. For this purpose, the RCAs are divided into smaller sets, used sequentially to linearize and solve the system. The reduction of the initial nonlinear control effectiveness matrix is improved by selecting each subset in a different arrangement of VCAs. However, the choice of this arrangement may lead to absence, partial or full superposition of VCAs in the subsystems. The technique was validated through mathematical tutorial cases, QTR simulation tests and open field flight and gyroscopic test bench experimental tests. Finally, the control allocation technique proved to be reliable, robust, efficient and applicable in the QTR when there is full superposition of VCAs between the subsystems.Sistemas superatuados geralmente requerem métodos de alocação de controle não lineares para mapear as Ações de Controle Virtuais (ACVs) em Ações de ControleReais (ACRs). Esse processo exige esforços computacionais que, as vezes, são limitados em plataformas robóticas embarcadas. E neste contexto que este trabalho apresenta o projeto de um Veículo Aéreo Não-Tripulado (VANT) do tipo Quadrotor Tilt-Rotor (QTR) superatuado, utilizando de um novo conceito de alocação de controle com ACRs desacopladas, onde o sistema não-linear inicial é dividido em subsistemas lineares parcialmente dependentes. Para esse propósito, as ACRs são divididas em conjuntos menores, usados sequencialmente para linearizar e resolver o sistema. Para melhorar a redução da matriz de eficácia de controle não-linear inicial, é possível selecionar para cada subconjunto um arranjo diferente de ACVs. Contudo, a escolha deste arranjo pode gerar ausência, parcial ou completa superposição das ACVs nos subsistemas. A validação da técnica foi realizada através de exemplos matemáticos tutoriais, testes de simulação e experimentais do QTR em uma bancada giroscópica e em campo aberto. Por fim, a técnica de alocação de controle se mostrou confiável, robusta, eficiente e aplicável no QTR quando se tem superposição completa das ACVs entre os subsistemas

Aerodynamic force interactions and measurements for micro quadrotors

Unmanned Aerial Vehicles (UAVs) have become mainstream through the success of several large commercial drone manufacturers. Quadrotors have been widely adopted due to their mechanical simplicity, ability to take off from a small area and hover at a fixed location. As these aircraft are increasingly being used in urban environments and indoors their ability to maintain stable flight in the presence of disturbances and nearby obstacles is of growing importance.Understanding the aerodynamics acting in these environments is the first step to improving quadrotor behaviour. This presents a challenge, as to characterise and verify models of the aerodynamic phenomena it is essential to collect numerous consistent experimental data points. On a typical quadrotor the motor response changes as the battery discharges, leading to variation in flight performance. Typically, this is addressed through the use high gain feedback control regulating attitude and position. To overcome this a unique voltage regulator for quadrotor power was developed to maintain constant supply voltage over the quadrotors flight. This enables the quadrotor to produce consistent and repeatable behaviour as the battery discharges.One way to improve the performance of quadrotors flying in constrained environments with limited sensing is to exploit aerodynamic effects for passive control and stability. Ground effect and rotor inflow damping are two effects of interest: ground effect provides a quadratic increase in thrust as a rotor moves closer to the ground; rotor inflow damping acts to resist axial motion by causing a change thrust opposing the movement. By canting the rotors of a quadrotor these effects were brought from the vertical axis into the lateral axis as well. A canted quadrotor flying over a v-shaped channel was modeled and found to exhibit passive stability in position. A demonstrator aircraft and v-shaped channel were tested in a number of configurations and shown to be stable for a channel slope of 10, 15 or 20 degrees with a rotor cant of 15 or 20 degrees.In order to observe more subtle aerodynamic effects, such as wall effect, it is necessary to have a method to measure rotor forces directly during quadrotor flight. Existing force torque sensors are too bulky, heavy, expensive or insensitive. To overcome these limitations a novel force torque sensor was developed that costs less than $50, weighs 3g and is capable of measuring sub mN forces. These sensors utilise an array of micro-electro-mechanical system (MEMS) barometers encapsulated in rubber to measure the strain field imparted by forces acting on the attached load plate. Mounting force torque sensors under the motors of a quadrotor allows the lateral rotor forces to be transmitted through the motor body and measured as torques at the base.Closely related to this, one of the key limitations faced by quadrotors is their inability to directly measure the airspeed of the aircraft. Providing an oncoming wind speed measurement will allow them to compensate for disturbances improving trajectory tracking and gust rejection. Blade flapping and induced drag are aerodynamic phenomena which relate lateral motion to a force acting in opposition to the rotors motion. By measuring this force using a rotor force sensor the airspeed of the aircraft is computed directly using induced drag and rotor blade flapping models. It was found that lateral velocity could be measured for the velocities tested, up to 1.5m/s, and showed a strong linear relationship to ground truth measurements.The work of this thesis has led to the development of: a quadrotor platform for consistent flight behaviour; a passive position-keeping quadrotor; and a novel rotor force sensor for direct measurement of quadrotor airspeed. These technologies open up avenues to improve the flight performance of quadrotors and better understand subtle aerodynamic interactions in flight