1,720,960 research outputs found
Automatic control of a multirotor
Get PDFObjective of this thesis is to describe the design and realisation phases of a multirotor to be used for low risk and cost aerial observation. Starting point of this activity was a wide literature study related to the technological evolution of multirotors design and to the state of the art. Firstly the most common multirotor configurations were defined and, according to a size and performance based evaluation, the most suitable one was chosen. A detailed computer aided design model was drawn as basis for the realisation of two prototypes. The realised multirotors were “X-shaped” octorotors with eight coaxially coupled motors. The mathematical model of the multirotor dynamics was studied. “Proportional Integral Derivative” and “Linear Quadratic” algorithms were chosen as techniques to regulate the attitude dynamics of the multirotor. These methods were tested with a nonlinear model simulation developed in the Matlab Simulink environment. In the meanwhile the Arduino board was selected as the best compromise between costs and performance and the above mentioned algorithms were implemented using this platform thanks to its main characteristic of being completely “open source”. Indeed the multirotor was conceived to be a serviceable tool for the public utility and, at the same time, to be an accessible device for research and studies. The behaviour of the physical multirotor was evaluated with a test bench designed to isolate the rotation about one single body axis at a time. The data of the experimental tests were gathered in real time using a custom Matlab code and several indoor tests allowed the “fine tuning” of the controllers gains.
Afterwards a portable “ground station” was conceived and realised in adherence with the real scenarios users needs. Several outdoor experimental flights were executed with successful results and the data gathered during the outdoor tests were used to evaluate some key performance indicators as the endurance and the maximum allowable payload mass. Then the fault tolerance of the control system was evaluated simulating and experimenting the loss of one motor; even in this critical condition the system exhibited an acceptable behaviour.
The reached project readiness allowed to meet some potential users as the “Turin Fire Department” and to cooperate with them in a simulated emergency. During this event the multirotor was used to gather and transmit real time aerial images for an improved “situation awareness”.
Finally the study was extended to more innovative control techniques like the neural networks based ones. Simulations results demonstrated their effectiveness; nevertheless the inherent complexity and the unreliability outside the training ranges could have a catastrophic impact on the airworthiness. This is a factor that cannot be neglected especially in the applications related to flying platforms.
Summarising, this research work was addressed mainly to the operating procedures for implementing automatic control algorithms to real platforms. All the design aspects, from the preliminary multirotor configuration choice to the tests in possible real scenarios, were covered obtaining performances comparable with other commercial of-the-shelf platforms
Design of an U.A.V. controller based on the open source platform Arduino
No full textThis paper focuses on the preliminary implementation and performances assessment of an unmanned aerial vehicles (U.A.V.) controller. Although not showing any innovative technical aspect of the automatic flight control, it underlines the simplicity of building a complete low cost unmanned aerial vehicle starting from a commercially available Ardupilot Mega board, telemetry modules and a G.P.S. sensor. In order to assess the reliability of this product some experimental flights have been performed and the relevant measured and processed data show an acceptable behaviour. The open source nature of this product represents a revolutionary aspect of this technology allowing an impressively fast understanding and developing of these autonomous systems. This approach is especially applicable to research and academic environment
Linear quadratic control for quadrotors UAVs dynamics and formation flight
No full textCooperative control of Unmanned Aerial Vehicles (UAVs) is currently being researched for a wide range of applications. Applicability of aerial unmanned systems might be increased by formation flight. After a necessary overview of quadrotor flight dynamics and linear quadratic control fundamentals, this control technique is applied to the full quadrotor dynamics. Then the more recent and challenging neural networks based control strategy is introduced from a theoretical perspective and applied to the quadrotor vertical dynamics; the results are compared with the relevant linear quadratic controlled behaviour. Finally, based on the developed single-quadrotor control architectures, a practical leader-follower formation concept is simulated, both for the linear quadratic and the neural networks based approac
PID and LQ regulation of a multirotor attitude: mathematical modelling, simulations and experimental results
No full textMultirotors have been recognized to be particularly interesting for surveillance, search and rescue, imaging and more, because of their several advantages as the high maneuverability and the vertical take off and landing capability. This paper presents the experimental results of the application of a Proportional Integral Derivative control law and a Linear Quadratic Regulation technique to the attitude of a multirotor. The reader is driven through all the main steps required to reach this goal, starting from the derivation of the mathematical model and the control laws, to the simulations and the experimental test
Proportional integral derivative and linear quadratic regulation of a multirotor attitude: mathematical modelling, simulations and experimental results
No full textMultirotors have been recognized to be particularly interesting for surveillance, search and rescue, imaging and more, because of their several advantages as the high maneuverability and the vertical take off and landing capability. This paper presents the experimental results of the application of a Proportional Integral Derivative control law and a Linear Quadratic Regulation technique to the attitude of a multirotor. The reader is driven through all the main steps required to reach this goal, starting from the derivation of the mathematical model and the control laws, to the simulations and the experimental test
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Electro-optical and microwave aerospace remote sensing systems data processing and fusion
No full textThe aim of this study is to investigate and evaluate the potential advantages of multi-sensor data fusion in the field of remote sensing, passing through the main theoretical and practical processing steps required to jointly use SAR and optical multi-spectral image
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