This thesis is a study of modelling and control of a multirotor unmanned aerial vehicle(UAV). On behalf of Intuitive Aerial, a model of their hexarotor aircraft has been developedas a tool in further development and testing of their product. The potential of using ModelPredictive Control (MPC) as control method for multirotor UAV:s has also been evaluated.The model was successfully implemented in MATLAB/Simulink, as was the Model Predic-tive Controller. Quaternion angle representation has been used to avoid singularities in themodel and non-linear dynamics have been included in the simulation model. Unknownmodel parameters have been estimated with data acquired from testing. Model validity hasalso been evaluated with flight data gathered from flights using a test vehicle. A basic MPCformulation has been expanded to include reference tracking, integral action and to ensurestability.Assessment proved the model to be feasible but in need of more rigorous evaluation to guar-antee good performance. The MPC controller showed promising performance compared toa linear feedback controller.

The aim of this thesis is to improve understanding of the effects of rotor-rotor interference on small scale rotor systems used on Micro Air Vehicles (MAVs). Previous research on rotor-rotor interactions has focused primarily on planar co-axial and tandem rotors of large scale rotorcraft. The work presented is distinct from prior research not only in its consideration of non-planar rotor systems, but also because of the lower Reynolds numbers and the use of fixed-pitch variable-speed propulsion systems. A design for a novel adjustable rotor interaction test-rig is presented along with a methodology for acquiring accurate and repeatable steady state performance data for two interacting rotor systems. Two six-axis force balances are used to acquire instantaneous and time averaged force and torque data and PIV is used to derive instantaneous and time-averaged flow field data for single and interacting rotor cases. The resulting performance and flow field data represents a unique dataset that can be used in the analysis of small scale rotor interactions, and in the validation of CFD investigations. Results show that for disc angles of between 180 degrees and 90 degrees interactions between rotors are negligible. As the disc angle is reduced from the orthogonal case to the coaxial case interactions significantly effect thrust, pitching moment, and efficiency. It is recommended that in the design of non-planar multirotor vehicles disc angles greater than 75 degrees are utilised to avoid the strong rotor-rotor interactions seen at lower disc angles. A review of existing and future non-planar multirotor concepts shows that the majority avoid significant rotor interactions by virtue of large disc angles.

Teknikens utveckling går i en rasande fart och idag kan man köpa en avancerad obemannad luftfarkost i butik. De obemannade luftfarkosterna kallas för multirotorfarkoster, eller i folkmun för drönare. Dessa multirotorfarkoster kan leverera en dödlig last med stor precision av någon utan större tekniskt kunnande. I stadsmiljö vid stora folkansamlingar skulle det idag vara svårt att stoppa en sådan inkommande attack utan att riskera ytterligare skador. Det här arbetet går ut på att belysa problemet och studera tekniken. Eftersom tekniken bara blir mer och mer avancerad så gäller det att vara vaksam för att förebygga en terrorattack. Ibland kanske det inte räcker att vara vaksam och då måste man söka andra lösningar. Från studien har ett antal krav på en försvarande lösning sammanställts. Från de utarbetade kraven så har också ett koncept tagits fram i form av en försvarande multirotor. / The developments in technology are at a furious pace and today you can buy an advanced unmanned aerial vehicle at hobby retail stores. These unmanned aerial vehicles are called multi-rotorcrafts or in the vernacular for drones. These multi-rotorcrafts can deliver a lethal payload with great precision by someone without much technical knowledge. In the urban environment at large public gatherings, it is currently difficult to stop an incoming attack without risking collateral damage. This papers purpose is to highlight the problem and study the technology. As the technology is just becoming more and more advanced you have to be vigilant to prevent a terrorist attack. It may not be enough and then you have to look for other solutions. From the study a number of requirements for a defending solution have been compiled. Also a concept has been developed from the elaborated requirements in shape of a defending multi-rotorcraft.

Recent miniaturization of computer hardware, MEMs sensors, and high energy density batteries have enabled highly capable mobile robots to become available at low cost. This has driven the rapid expansion of interest in multi-rotor unmanned aerial vehicles. Another area which has expanded simultaneously is small powerful computers, in the form of smartphones, which nearly always have a camera attached, many of which now contain a OpenCL compatible graphics processing units. By combining the results of those two developments a low-cost multi-rotor UAV can be produced with a low-power onboard computer capable of real-time computer vision. The system should also use general purpose computer vision software to facilitate a variety of experiments. To demonstrate this I have built a quadrotor UAV based on control hardware from the Pixhawk project, and paired it with an ARM based single board computer, similar those in high-end smartphones. The quadrotor weights 980 g and has a flight time of 10 minutes. The onboard computer capable of running a pose estimation algorithm above the 10 Hz requirement for stable visual control of a quadrotor. A feature tracking algorithm was developed for efficient pose estimation, which relaxed the requirement for outlier rejection during matching. Compared with a RANSAC- only algorithm the pose estimates were less variable with a Z-axis standard deviation 0.2 cm compared with 2.4 cm for RANSAC. Processing time per frame was also faster with tracking, with 95 % confidence that tracking would process the frame within 50 ms, while for RANSAC the 95 % confidence time was 73 ms. The onboard computer ran the algorithm with a total system load of less than 25 %. All computer vision software uses the OpenCV library for common computer vision algorithms, fulfilling the requirement for running general purpose software. The tracking algorithm was used to demonstrate the capability of the system by per- forming visual servoing of the quadrotor (after manual takeoff). Response to external perturbations was poor however, requiring manual intervention to avoid crashing. This was due to poor visual controller tuning, and to variations in image acquisition and attitude estimate timing due to using free running image acquisition. The system, and the tracking algorithm, serve as proof of concept that visual control of a quadrotor is possible using small low-power computers and general purpose computer vision software.

This master's thesis has been on modeling, identification and control of a hexarotor system. It has been carried out on behalf of UAS Europe in Link\"{o}ping. A set of non-linear dynamic equations describing the motion of the hexarotor were derived. These equations were then implemented in Matlab/Simulink, which became a good simulation environment for further studies. A decentralized control system using P-PD controllers was successfully implemented in both simulation and on a hexarotor platform. The non-linear simulation model and the hexarotor platform were then identified using black box identification between virtual controls and angular rates. The result from identification of the hexarotor platform was not bad at all, but left some room for improvements. These linear models ware then used to tune the parameters of the inner PD controllers using a method called placement of dominant poles. This method worked well in simulation environment but unfortunately not as well on the real platform.

No description available.

This thesis presents some existing gimbal and UAV control algorithms as well as novel algorithms developed as the extensions of the existing ones. The existing image-based visual servoing algorithms for both gimbal and UAV require the depth information to the object of interest. The depth information is not measurable when only a monocular camera is used for tracking. This thesis is the result of contemplation to the question: how can the necessity for a depth measurement be removed? A novel gimbal algorithm using adaptive control is developed and presented with simulation and hardware results. Although the estimated depth using the algorithm cannot be used as reliable depth information, the target tracking objective is met. Also, a new UAV control algorithm for target following is developed and presented with simulation results. This algorithm does not require the depth to the target or the UAV altitude to be measured because it exploits the unit vectors to the target and to the optical axis.

A multirotor is a type of aerial vehicle that has attracted a lot of attention in recent years. Multirotors have found applications in a variety of different fields and they are used by scientists and researchers, commercial UAV companies and radio control enthusiasts alike. In this thesis a multirotor with eight rotors, also called an octorotor, is used. A physical model of the octorotor has been developed using theory from rigid body mechanics and aerodynamics. The unknown parameters in this model have been found using several identification experiments. The model has been used for controller design and comparison in a simulation environment. An attitude estimation algorithm has been designed and implemented on the target hardware. The algorithm is referred to as a nonlinear complementary filter and it uses a quaternion rotation representation and onboard measurements to compute an estimate of the current aircraft attitude. Two different attitude controllers have been designed and evaluated. The first controller is based on PID techniques which are commonly used in multirotor flight stabilization systems. The second controller uses a novel control structure based on L1 adaptive control techniques. A baseline attitude PD controller is augmented with an L1 adaptive controller in the rate feedback loop. The two controller structures are compared using a simulation environment based on the developed model of the octorotor. The results show that the proposed structure gives a notable performance increase with respect to robustness against modeling errors and input disturbance rejection compared to the PID controller. However, the L1 adaptive controller is more complex to implement and gives less noise attenuation. The PID controller has been implemented on the platform's hardware and initial flight tests have been performed with promising results. / En multirotor är en typ av flygande farkost som har fått mycket uppmärksamhet under senare år. Multirotorer tillämpas inom flertalet områden och de används av bland annat forskare och vetenskapsmän, kommersiella UAV- företag samt hobbyentusiaster. I detta examensarbete används en multirotor med åtta rotorer, en så kallad oktakopter. En fysikalisk modell av oktakoptern har tagits fram med hjälp av teori från stelkroppsmekanik och aerodynamik. De okända parametrarna i modellen har skattats med hjälp av ett flertal identifieringsexperiment. Modellen har använts för att designa och jämföra regulatorer i en simuleringsmiljö. En algoritm för att skatta farkostens attityd har designats och implementerats på oktakopterns hårdvara. Algoritmen är en variant av ett olinjärt komplementärt filter och använder en kvaternionrepresentation av attitydvinklar och uppmätt sensordata för att skatta farkostens nuvarande attityd. Två olika attitydregulatorer har designats och utvärderats. Den första regulatorn är baserad på PID-teknik vilket är vanligt för stabilisering av multirotorsystem. Den andra regulatorn använder en ny regulatorstruktur baserad på L1-adaptiv teknik. En grundregulator av PD-typ utökas med en L1-adaptiv regulator i vinkelhastighetsloopen. De två regulatorstrukturerna jämförs i en simuleringsmiljö baserad på den framtagna modellen av oktakoptern. Resultaten visar att den föreslagna regulatorstrukturen ger en betydande prestandaökning gällande robusthet mot modellfel och undertryckning av ingångsstörningar jämfört med PID-regulatorn. Dock är L1-regulatorn mer komplex att implementera och den ger mindre brusundertryckning. PID-regulatorn har implementerats på plattformens hårdvara och inledande flygtester har genomförts med lovande resultat.

In this thesis a quadrotor is studied and a linear model is derived using grey-box estimation, a discipline in system identification where a model structure based on physical relations is used and the parameters are estimated using input-output measurements. From IMU measurements and measured PWM signals to the four motors, a direct approach using the prediction-error method is applied. To investigate the impact of the unknown controller the two-stage method, a closed-loop approach in system identification,  is applied as well. The direct approach was enough for estimating the model parameters. The resulting model manages to simulate the major dynamics for the vertical acceleration and the angular rates well enough  for future control design.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-02T12:49:22Z No. of bitstreams: 1 AlyssonNascimentoDeLucena_DISSERT.pdf: 4569473 bytes, checksum: 34d0b14b7d7d70819c4d05eb81951a77 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-04T14:25:01Z (GMT) No. of bitstreams: 1 AlyssonNascimentoDeLucena_DISSERT.pdf: 4569473 bytes, checksum: 34d0b14b7d7d70819c4d05eb81951a77 (MD5) / Made available in DSpace on 2018-04-04T14:25:01Z (GMT). No. of bitstreams: 1 AlyssonNascimentoDeLucena_DISSERT.pdf: 4569473 bytes, checksum: 34d0b14b7d7d70819c4d05eb81951a77 (MD5) Previous issue date: 2018-01-31 / Este trabalho busca apresentar o desenvolvimento de um Ve?culo A?reo n?o Tripulado (VANT) duplamente h?brido, capaz de conciliar as vantagens de dois tipos de aeronaves (asa fixa e multirotor), utilizando motores a combust?o e el?tricos para a propuls?o e para a sustenta??o em voo a asa e o multirotor, capaz de decolar e pousar verticalmente, executar voos lentos ou parados, tamb?m executar voo horizontal com sustenta??o pela asa e propuls?o por motor a combust?o que garante maior autonomia. Para a realiza??o desse estudo foram desenvolvidas tr?s aeronaves, inicialmente uma asa voadora e um multirotor tric?ptero com objetivo de analisar separadamente cada tipo de aeronave, ap?s os testes e an?lises foi desenvolvido um VANT duplamente h?brido, uma asa voadora e um hexac?ptero, propuls?o por motores el?tricos e ? combust?o. A partir dos testes e c?lculos te?ricos da aeronave h?brida observou-se a viabilidade de um novo tipo de aeronave, com caracter?sticas pr?prias, capaz de conciliar as vantagens de dois tipos de aeronaves. / This work aims to present the development of a double hybrid unmanned aerial vehicle (UAV), capable of reconciling the advantages of two types of aircraft (fixed wing and multirotor), using combustion and electric motors for propulsion and in flight support the wing and the multirotor, able to take off and land vertically, to perform slow or stopped flights, also to execute horizontal flight with support by the wing and propulsion by combustion engine that guarantees greater autonomy. In order to carry out this study, three aircraft were developed, initially a flying wing and a tricopter multirotor with the objective of analyzing separately each type of aircraft, after the tests and analyzes a double hybrid VANT was developed, a flying wing and a hexacopter, motor propulsion electrical and combustion. From the theoretical tests and calculations of the hybrid aircraft, the viability of a new type of aircraft, with its own characteristics, was able to reconcile the advantages of two types of aircraft.