Platooning-based control techniques in transportation and logistic

This thesis explores the integration of autonomous vehicle technology with smart manufacturing systems. At first, essential control methods for autonomous vehicles, including Linear Matrix Inequalities (LMIs), Linear Quadratic Regulation (LQR)/Linear Quadratic Tracking (LQT), PID controllers, and dynamic control logic via flowcharts, are examined. These techniques are adapted for platooning to enhance coordination, safety, and efficiency within vehicle fleets, and various scenarios are analyzed to confirm their effectiveness in achieving predetermined performance goals such as inter-vehicle distance and fuel consumption. A first approach on simplified hardware, yet realistic to model the vehicle's behavior, is treated to further prove the theoretical results. Subsequently, performance improvement in smart manufacturing systems (SMS) is treated. The focus is placed on offline and online scheduling techniques exploiting Mixed Integer Linear Programming (MILP) to model the shop floor and Model Predictive Control (MPC) to adapt scheduling to unforeseen events, in order to understand how optimization algorithms and decision-making frameworks can transform resource allocation and production processes, ultimately improving manufacturing efficiency. In the final part of the work, platooning techniques are employed within SMS. Autonomous Guided Vehicles (AGVs) are reimagined as autonomous vehicles, grouping them within platoon formations according to different criteria, and controlled to avoid collisions while carrying out production orders. This strategic integration applies platooning principles to transform AGV logistics within the SMS. The impact of AGV platooning on key performance metrics, such as makespan, is devised, providing insights into optimizing manufacturing processes. Throughout this work, various research fields are examined, with intersecting future technologies from precise control in autonomous vehicles to the coordination of manufacturing resources. This thesis provides a comprehensive view of how optimization and automation can reshape efficiency and productivity not only in the domain of autonomous vehicles but also in manufacturing

A CHARACTERIZATION OF NETWORK PERFORMANCE: THE ROLE OF COMMUNICATION DIRECTIONALITY AND SYSTEM HETEROGENEITY

Networked dynamical systems’ ability to preserve the system equilibrium in the face of disruptive events or persistent disturbances can be an indication of the convergence efficiency and quantified as a measure of system performance. The performance analysis is usually facilitated by simplifications overlooking certain structural properties of the network that can potentially be significant to actual system behavior. We characterize the performance of networks in relation to these properties, such as communication directionality and system heterogeneity, and unravel their influence on overall performance. We examine performance metrics that quantify an aggregate system effort to maintain and/or restore a network equilibrium; formulated by a general quadratic function (L2 norm) of the system output. Using this approach, which builds on the widely-used H2 norm based analysis, we obtain novel closed-form solutions to the performance metrics. We then use them to identify the role of communication directionality and system heterogeneity in network performance. Particularly, we show that the effect of communication directionality on performance can be characterized by the spectral properties of the weighted Laplacian matrix describing the network interconnection and the output performance matrix. Our results indicate that while this directionality can degrade performance, well-designed feedback can also exploit directionality in certain cases to mitigate this degradation or even lead to improved performance. We also demonstrate that performance is sensitive to the degree of connectivity in networks with directed interconnection, however it does not necessarily improve by increasing this degree of connectivity. We then derive the asymptotic behavior of performance with respect to network size, and identify additional performance trade-offs associated with large-scale networks with communication directionality. In addition, we investigate system heterogeneity in droop-controlled inverter-based power systems, by relaxing the common assumption of uniformity of inverter control gains. This heterogeneity, which can result from the distribution of power demand between the inverters, can lead to performance limitations. Numerical examples verify and support our theoretical findings. Our results highlight the performance capabilities and limitations due to the structural properties of the network, and can inform judicious feedback design

Proof-of-concept of a single-point Time-of-Flight LiDAR system and guidelines towards integrated high-accuracy timing, advanced polarization sensing and scanning with a MEMS micromirror

Dissertação de mestrado integrado em Engenharia Física (área de especialização em Dispositivos, Microssistemas e Nanotecnologias)The core focus of the work reported herein is the fulfillment of a functional Light Detection and Ranging (LiDAR) sensor to validate the direct Time-of-Flight (ToF) ranging concept and the acquisition of critical knowledge regarding pivotal aspects jeopardizing the sensor’s performance, for forthcoming improvements aiming a realistic sensor targeted towards automotive applications. Hereupon, the ToF LiDAR system is implemented through an architecture encompassing both optical and electronical functions and is subsequently characterized under a sequence of test procedures usually applied in benchmarking of LiDAR sensors. The design employs a hybrid edge-emitting laser diode (pulsed at 6kHz, 46ns temporal FWHM, 7ns rise-time; 919nm wavelength with 5nm FWHM), a PIN photodiode to detect the back-reflected radiation, a transamplification stage and two Time-to-Digital Converters (TDCs), with leading-edge discrimination electronics to mark the transit time between emission and detection events. Furthermore, a flexible modular design is adopted using two separate Printed Circuit Boards (PCBs), comprising the transmitter (TX) and the receiver (RX), i.e. detection and signal processing. The overall output beam divergence is 0.4º×1º and an optical peak power of 60W (87% overall throughput) is realized. The sensor is tested indoors from 0.56 to 4.42 meters, and the distance is directly estimated from the pulses transit time. The precision within these working distances ranges from 4cm to 7cm, reflected in a Signal-to-Noise Ratio (SNR) between 12dB and 18dB. The design requires a calibration procedure to correct systematic errors in the range measurements, induced by two sources: the timing offset due to architecture-inherent differences in the optoelectronic paths and a supplementary bias resulting from the design, which renders an intensity dependence and is denoted time-walk. The calibrated system achieves a mean accuracy of 1cm. Two distinct target materials are used for characterization and performance evaluation: a metallic automotive paint and a diffuse material. This selection is representative of two extremes of actual LiDAR applications. The optical and electronic characterization is thoroughly detailed, including the recognition of a good agreement between empirical observations and simulations in ZEMAX, for optical design, and in a SPICE software, for the electrical subsystem. The foremost meaningful limitation of the implemented design is identified as an outcome of the leading-edge discrimination. A proposal for a Constant Fraction Discriminator addressing sub-millimetric accuracy is provided to replace the previous signal processing element. This modification is mandatory to virtually eliminate the aforementioned systematic bias in range sensing due to the intensity dependency. A further crucial addition is a scanning mechanism to supply the required Field-of-View (FOV) for automotive usage. The opto-electromechanical guidelines to interface a MEMS micromirror scanner, achieving a 46º×17º FOV, with the LiDAR sensor are furnished. Ultimately, a proof-of-principle to the use of polarization in material classification for advanced processing is carried out, aiming to complement the ToF measurements. The original design is modified to include a variable wave retarder, allowing the simultaneous detection of orthogonal linear polarization states using a single detector. The material classification with polarization sensing is tested with the previously referred materials culminating in an 87% and 11% degree of linear polarization retention from the metallic paint and the diffuse material, respectively, computed by Stokes parameters calculus. The procedure was independently validated under the same conditions with a micro-polarizer camera (92% and 13% polarization retention).O intuito primordial do trabalho reportado no presente documento é o desenvolvimento de um sensor LiDAR funcional, que permita validar o conceito de medição direta do tempo de voo de pulsos óticos para a estimativa de distância, e a aquisição de conhecimento crítico respeitante a aspetos fundamentais que prejudicam a performance do sensor, ambicionando melhorias futuras para um sensor endereçado para aplicações automóveis. Destarte, o sistema LiDAR é implementado através de uma arquitetura que engloba tanto funções óticas como eletrónicas, sendo posteriormente caracterizado através de uma sequência de testes experimentais comumente aplicáveis em benchmarking de sensores LiDAR. O design tira partido de um díodo de laser híbrido (pulsado a 6kHz, largura temporal de 46ns; comprimento de onda de pico de 919nm e largura espetral de 5nm), um fotodíodo PIN para detetar a radiação refletida, um andar de transamplificação e dois conversores tempo-digital, com discriminação temporal com threshold constante para marcar o tempo de trânsito entre emissão e receção. Ademais, um design modular flexível é adotado através de duas PCBs independentes, compondo o transmissor e o recetor (deteção e processamento de sinal). A divergência global do feixe emitido para o ambiente circundante é 0.4º×1º, apresentando uma potência ótica de pico de 60W (eficiência de 87% na transmissão). O sensor é testado em ambiente fechado, entre 0.56 e 4.42 metros. A precisão dentro das distâncias de trabalho varia entre 4cm e 7cm, o que se reflete numa razão sinal-ruído entre 12dB e 18dB. O design requer calibração para corrigir erros sistemáticos nas distâncias adquiridas devido a duas fontes: o desvio no ToF devido a diferenças nos percursos optoeletrónicos, inerentes à arquitetura, e uma dependência adicional da intensidade do sinal refletido, induzida pela técnica de discriminação implementada e denotada time-walk. A exatidão do sistema pós-calibração perfaz um valor médio de 1cm. Dois alvos distintos são utilizados durante a fase de caraterização e avaliação performativa: uma tinta metálica aplicada em revestimentos de automóveis e um material difusor. Esta seleção é representativa de dois cenários extremos em aplicações reais do LiDAR. A caraterização dos subsistemas ótico e eletrónico é minuciosamente detalhada, incluindo a constatação de uma boa concordância entre observações empíricas e simulações óticas em ZEMAX e elétricas num software SPICE. O principal elemento limitante do design implementado é identificado como sendo a técnica de discriminação adotada. Por conseguinte, é proposta a substituição do anterior bloco por uma técnica de discriminação a uma fração constante do pulso de retorno, com exatidões da ordem sub-milimétrica. Esta modificação é imperativa para eliminar o offset sistemático nas medidas de distância, decorrente da dependência da intensidade do sinal. Uma outra inclusão de extrema relevância é um mecanismo de varrimento que assegura o cumprimento dos requisitos de campo de visão para aplicações automóveis. As diretrizes para a integração de um micro-espelho no sensor concebido são providenciadas, permitindo atingir um campo de visão de 46º×17º. Conclusivamente, é feita uma prova de princípio para a utilização da polarização como complemento das medições do tempo de voo, de modo a suportar a classificação de materiais em processamento avançado. A arquitetura original é modificada para incluir uma lâmina de atraso variável, permitindo a deteção de estados de polarização ortogonais com um único fotodetetor. A classificação de materiais através da aferição do estado de polarização da luz refletida é testada para os materiais supramencionados, culminando numa retenção de polarização de 87% (tinta metálica) e 11% (difusor), calculados através dos parâmetros de Stokes. O procedimento é independentemente validado com uma câmara polarimétrica nas mesmas condições (retenção de 92% e 13%)

Control Using Local Distance Measurements Cannot Prevent Incoherence in Platoons

When local control strategies are used to arrange a platoon into a string like formation, there is mounting evidence that a poorly regulated accordion like motion will emerge. In this paper we prove that this is an inevitable consequence of using local distance measurements to design the control. More specifically we demonstrate that no controller, irrespective of its dynamical complexity, sparsity, or linearity, can prevent the appearance of macroscopic behaviours in the platoon if only noisy measurements of the distances between neighbouring vehicles are available

Oakeshott és a XX. századi antiracionalizmus = Oakeshott and the antirationalism in the 20th century

Oakeshott életműve a szabadság és a hagyomány, a szkepticizmus és a nyugati hagyományba vetett bizalom, a konzervatív gondolkodás és a jelen élvezete összekapcsolásával írható le. Nem akart rendet minden áron. El tudta viselni a zűrzavart, és úgy gondolta a politikai gondolkodás egyik feladata az, hogy képessé tegye az embereket a kaotikus világ elfogadására és élvezetére. A kérdés Oakeshott kapcsolata a modernitáshoz és a posztmodernhez. Noha láthatóak közös elemek a posztmodern és a premodern gondolkodásban, nyilvánvaló eltérések is vannak. Az egyik bizonyosan, legalábbis Oakeshott esetében, a törvény uralma. És az autoritás szerepe. A politikai modernizmus igyekszik átalakítani a politikát manager tudománnyá, amely folytonosan harcolna a létezővel, mert tökéletlen, és egy utópikus, harmonikus végállapotra törekszik a nép átnevelése vagy manipulálása révén. Felismerte a modernitás ellentmondásait, de el akarta a kerülni a modernitás utópikus kísértését is (történelem vége). A modernitás ellentétekből áll, és ezek egyensúlyozzák ki. A modernista hiba, ha valaki az egyik szélsőséget választja. A feladat az ellentétek megőrzése és nem a megoldása. A conditio humana lényege az ellentétek egysége. A modern gondolkodás megpróbálta az ellentétek e bonyolult világát leegyszerűsíteni egy egyszerű alapelvre, egyetlen magyarázatra. E paradox felismerése határozza meg a konzervatív gondolkodót. A politika dilemmái végső soron a conditio humana dilemmái. Mindkettő örök. | Oakeshott’s work is a negotiation of freedom and tradition; “skepticism” and confidence in the resources of the Western tradition; conservatism and the celebration of the present. He were never engaged in an irritable search for order. He could accept confusion and he thought that one task of political and moral thinking is to make the people able and enjoy the chaotic world as it is. One aspect of this issue is his relation to modernism and postmodernism. Whilst one may see common points in the pre-modern and post-modern thinking, there are obvious differences, as well. One of them, at least in case of Oakeshott is rule of law and the role of authority. Modernism in politics means the continuous effort to transform politics into a managerial science that struggles against present as imperfect, and aiming an utopical, harmonious end state by means of re-education or managerial manipulation of people, based on hedonistic calculus. He realized the ambivalences within modernity, but he also was keen to avoid the modernist seduction of utopical hope. Modernity is divided yet balanced. Modernist political thought has tried to reduce this incongruous complex in modern order to a single principle, a single explanation. The core of human condition is a fusion of opposites. To realize this paradox of order defines the conservative thinker. The dilemmas of politics are ultimately dilemmas of the human condition