Nonlinear Modeling and Control of Driving Interfaces and Continuum Robots for System Performance Gains

With the rise of (semi)autonomous vehicles and continuum robotics technology and applications, there has been an increasing interest in controller and haptic interface designs. The presence of nonlinearities in the vehicle dynamics is the main challenge in the selection of control algorithms for real-time regulation and tracking of (semi)autonomous vehicles. Moreover, control of continuum structures with infinite dimensions proves to be difficult due to their complex dynamics plus the soft and flexible nature of the manipulator body. The trajectory tracking and control of automobile and robotic systems requires control algorithms that can effectively deal with the nonlinearities of the system without the need for approximation, modeling uncertainties, and input disturbances. Control strategies based on a linearized model are often inadequate in meeting precise performance requirements. To cope with these challenges, one must consider nonlinear techniques. Nonlinear control systems provide tools and methodologies for enabling the design and realization of (semi)autonomous vehicle and continuum robots with extended specifications based on the operational mission profiles. This dissertation provides an insight into various nonlinear controllers developed for (semi)autonomous vehicles and continuum robots as a guideline for future applications in the automobile and soft robotics field. A comprehensive assessment of the approaches and control strategies, as well as insight into the future areas of research in this field, are presented.First, two vehicle haptic interfaces, including a robotic grip and a joystick, both of which are accompanied by nonlinear sliding mode control, have been developed and studied on a steer-by-wire platform integrated with a virtual reality driving environment. An operator-in-the-loop evaluation that included 30 human test subjects was used to investigate these haptic steering interfaces over a prescribed series of driving maneuvers through real time data logging and post-test questionnaires. A conventional steering wheel with a robust sliding mode controller was used for all the driving events for comparison. Test subjects operated these interfaces for a given track comprised of a double lane-change maneuver and a country road driving event. Subjective and objective results demonstrate that the driver’s experience can be enhanced up to 75.3% with a robotic steering input when compared to the traditional steering wheel during extreme maneuvers such as high-speed driving and sharp turn (e.g., hairpin turn) passing. Second, a cellphone-inspired portable human-machine-interface (HMI) that incorporated the directional control of the vehicle as well as the brake and throttle functionality into a single holistic device will be presented. A nonlinear adaptive control technique and an optimal control approach based on driver intent were also proposed to accompany the mechatronic system for combined longitudinal and lateral vehicle guidance. Assisting the disabled drivers by excluding extensive arm and leg movements ergonomically, the device has been tested in a driving simulator platform. Human test subjects evaluated the mechatronic system with various control configurations through obstacle avoidance and city road driving test, and a conventional set of steering wheel and pedals were also utilized for comparison. Subjective and objective results from the tests demonstrate that the mobile driving interface with the proposed control scheme can enhance the driver’s performance by up to 55.8% when compared to the traditional driving system during aggressive maneuvers. The system’s superior performance during certain vehicle maneuvers and approval received from the participants demonstrated its potential as an alternative driving adaptation for disabled drivers. Third, a novel strategy is designed for trajectory control of a multi-section continuum robot in three-dimensional space to achieve accurate orientation, curvature, and section length tracking. The formulation connects the continuum manipulator dynamic behavior to a virtual discrete-jointed robot whose degrees of freedom are directly mapped to those of a continuum robot section under the hypothesis of constant curvature. Based on this connection, a computed torque control architecture is developed for the virtual robot, for which inverse kinematics and dynamic equations are constructed and exploited, with appropriate transformations developed for implementation on the continuum robot. The control algorithm is validated in a realistic simulation and implemented on a six degree-of-freedom two-section OctArm continuum manipulator. Both simulation and experimental results show that the proposed method could manage simultaneous extension/contraction, bending, and torsion actions on multi-section continuum robots with decent tracking performance (e.g. steady state arc length and curvature tracking error of 3.3mm and 130mm-1, respectively). Last, semi-autonomous vehicles equipped with assistive control systems may experience degraded lateral behaviors when aggressive driver steering commands compete with high levels of autonomy. This challenge can be mitigated with effective operator intent recognition, which can configure automated systems in context-specific situations where the driver intends to perform a steering maneuver. In this article, an ensemble learning-based driver intent recognition strategy has been developed. A nonlinear model predictive control algorithm has been designed and implemented to generate haptic feedback for lateral vehicle guidance, assisting the drivers in accomplishing their intended action. To validate the framework, operator-in-the-loop testing with 30 human subjects was conducted on a steer-by-wire platform with a virtual reality driving environment. The roadway scenarios included lane change, obstacle avoidance, intersection turns, and highway exit. The automated system with learning-based driver intent recognition was compared to both the automated system with a finite state machine-based driver intent estimator and the automated system without any driver intent prediction for all driving events. Test results demonstrate that semi-autonomous vehicle performance can be enhanced by up to 74.1% with a learning-based intent predictor. The proposed holistic framework that integrates human intelligence, machine learning algorithms, and vehicle control can help solve the driver-system conflict problem leading to safer vehicle operations

Generation of Horizontally Curved Driving Lines for Autonomous Vehicles Using Mobile Laser Scanning Data

The development of autonomous vehicle desiderates tremendous advances in three-dimensional (3D) high-definition roadmaps. These roadmaps are capable of providing 3D positioning information with 10-to-20 cm accuracy. With the assistance of 3D high-definition roadmaps, the intractable autonomous driving problem is transformed into a solvable localization issue. The Mobile Laser Scanning (MLS) systems can collect accurate, high-density 3D point clouds in road environments for generating 3D high-definition roadmaps. However, few studies have been concentrated on the driving line generation from 3D MLS point clouds for highly autonomous driving, particularly for accident-prone horizontal curves with the problems of ambiguous traffic situations and unclear visual clues. This thesis attempts to develop an effective method for semi-automated generation of horizontally curved driving lines using MLS data. The framework of research methodology proposed in this thesis consists of three steps, including road surface extraction, road marking extraction, and driving line generation. Firstly, the points covering road surface are extracted using curb-based road surface extraction algorithms depending on both the elevation and slope differences. Then, road markings are identified and extracted according to a sequence of algorithms consisting of geo-referenced intensity image generation, multi-threshold road marking extraction, and statistical outlier removal. Finally, the conditional Euclidean clustering algorithm is employed followed by the nonlinear least-squares curve-fitting algorithm for generating horizontally curved driving lines. A total of six test datasets obtained in Xiamen, China by a RIEGL VMX-450 system were used to evaluate the performance and efficiency of the proposed methodology. The experimental results demonstrate that the proposed road marking extraction algorithms can achieve 90.89% in recall, 93.04% in precision and 91.95% in F1-score, respectively. Moreover, the unmanned aerial vehicle (UAV) imagery with 4 cm was used for validation of the proposed driving line generation algorithms. The validation results demonstrate that the horizontally curved driving lines can be effectively generated within 15 cm-level localization accuracy using MLS point clouds. Finally, a comparative study was conducted both visually and quantitatively to indicate the accuracy and reliability of the generated driving lines

Shared control strategies for automated vehicles

188 p.Los vehículos automatizados (AVs) han surgido como una solución tecnológica para compensar las deficiencias de la conducción manual. Sin embargo, esta tecnología aún no está lo suficientemente madura para reemplazar completamente al conductor, ya que esto plantea problemas técnicos, sociales y legales. Sin embargo, los accidentes siguen ocurriendo y se necesitan nuevas soluciones tecnológicas para mejorar la seguridad vial. En este contexto, el enfoque de control compartido, en el que el conductor permanece en el bucle de control y, junto con la automatización, forma un equipo bien coordinado que colabora continuamente en los niveles táctico y de control de la tarea de conducción, es una solución prometedora para mejorar el rendimiento de la conducción manual aprovechando los últimos avances en tecnología de conducción automatizada. Esta estrategia tiene como objetivo promover el desarrollo de sistemas de asistencia al conductor más avanzados y con mayor grade de cooperatición en comparación con los disponibles en los vehículos comerciales. En este sentido, los vehículos automatizados serán los supervisores que necesitan los conductores, y no al revés. La presente tesis aborda en profundidad el tema del control compartido en vehículos automatizados, tanto desde una perspectiva teórica como práctica. En primer lugar, se proporciona una revisión exhaustiva del estado del arte para brindar una descripción general de los conceptos y aplicaciones en los que los investigadores han estado trabajando durante lasúltimas dos décadas. Luego, se adopta un enfoque práctico mediante el desarrollo de un controlador para ayudar al conductor en el control lateral del vehículo. Este controlador y su sistema de toma de decisiones asociado (Módulo de Arbitraje) se integrarán en el marco general de conducción automatizada y se validarán en una plataforma de simulación con conductores reales. Finalmente, el controlador desarrollado se aplica a dos sistemas. El primero para asistir a un conductor distraído y el otro en la implementación de una función de seguridad para realizar maniobras de adelantamiento en carreteras de doble sentido. Al finalizar, se presentan las conclusiones más relevantes y las perspectivas de investigación futuras para el control compartido en la conducción automatizada

Defining procedures and simulation tools to test high levels of automation for cars in realistic traffic, driving and boundary conditions

Il crescente livello di automazione nella guida dei veicoli su gomma rende sempre più complesse e articolate le procedure di testing e validazione dei dispositivi. La tendenza alla realizzazione di sistemi che sostituiscano il guidatore in tutto o in parte, determina un cambiamento paradigmatico nell'ambito della validazione, la quale non può più occuparsi esclusivamente del test del corretto funzionamento del dispositivo da validare, ma dovrà testare le logiche di guida e le "scelte" che opera al variare dei contesti. Come ampiamente evidenziato nella letteratura scientifica di settore1 i processi di validazione rappresenteranno il più grande ostacolo alla realizzazione e messa in produzione dei sistemi di quarto e quinto livello SAE2 di automazione. Numerose ricerche hanno dimostrato3 che il testing su strada non rappresenta una soluzione che possa dare risultati attendibili in tempi sufficientemente brevi, ma a tutt'oggi non esistono software sufficientemente complessi da realizzare simulazioni che tengano conto di tutte le variabili necessarie. La ricerca intende definire le corrette procedure di testing di veicoli ad elevato grado di automazione in condizioni di traffico realistiche, avvalendosi di software di simulazione specifici di ogni settore coinvolto nel processo, realizzando uno strumento di testing integrato sufficientemente efficace

Toward Human-Like Automated Driving: Learning Spacing Profiles From Human Driving Data

For automated driving vehicles to be accepted by their users and safely integrate with traffic involving human drivers, they need to act and behave like human drivers. This not only involves understanding how the human driver or occupant in the automated vehicle expects their vehicle to operate, but also involves how other road users perceive the automated vehicle’s intentions. This research aimed at learning how drivers space themselves while driving around other vehicles. It is shown that an optimized lane change maneuver does create a solution that is much different than what a human would do. There is a need to learn complex driving preferences from studying human drivers. This research fills the gap in terms of learning human driving styles by providing an example of learned behavior (vehicle spacing) and the needed framework for encapsulating the learned data. A complete framework from problem formulation to data gathering and learning from human driving data was formulated as part of this research. On-road vehicle data were gathered while a human driver drove a vehicle. The driver was asked to make lane changes for stationary vehicles in his path with various road curvature conditions and speeds. The gathered data, as well as Learning from Demonstration techniques, were used in formulating the spacing profile as a lane change maneuver. A concise feature set from captured data was identified to strongly represent a driver’s spacing profile and a model was developed. The learned model represented the driver’s spacing profile from stationary vehicles within acceptable statistical tolerance. This work provides a methodology for many other scenarios from which human-like driving style and related parameters can be learned and applied to automated vehicle

Road geometry identification with mobile mapping techniques

Durante il mio dottorato mi sono occupato di Tecniche e Tecnologie innovative per la ricostruzione della geometria dei tracciati stradali esistenti, quali ad esempio Mobile Mapping, analisi immagini e dati GIS; a fronte degli elevatissimi costi oggi richiesti per l’utilizzo di veicoli strumentati già reperibili in commercio per il raggiungimento di tali scopi, il valore aggiunto del lavoro di dottorato riguarda l’uso di strumenti a basso costo che comportano un rilevante lavoro di analisi, trattamento e correzione del dato che risente in maniera decisiva della medio/bassa qualità della strumentazione in uso. L’obiettivo della ricerca è consistito nella realizzazione di un algoritmo di riconoscimento (in ambiente MATLAB) che sia in grado di restituire la geometria as-built di una strada esistente. Parte del lavoro è stata svolta nell’analisi e nell’estrazione delle curvature locali con approcci differenti (successive circonferenze locali, funzioni polinomiali di fitting locale di vario grado e con ampiezza di analisi variabile), nonché sullo studio degli angoli di deviazione locali. Usando questi parametri, nel resto del lavoro, si è prima ricercata una metodologia d’identificazione dei diversi elementi che compongono la geometria stradale, e poi si è lavorato su procedure di fitting con svariate tecniche (minimi quadrati, metodi robusti e altri algoritmi) cercando di estrarre informazioni di carattere geometrico, quali raggi di curvatura e relativi centri, lunghezza e orientamento dei rettifili, fattori di scala delle curve di transizione

Age Differences in the Situation Awareness and Takeover Performance in a Semi-Autonomous Vehicle Simulator

Research on young and elderly drivers indicates a high crash risk amongst these drivers in comparison to other age groups of drivers. Young drivers have a greater propensity to adopt a risky driving style and behaviors associated with poor road safety. On the other hand, age-related declines can negatively impact the performance of older drivers on the road leading to crashes and risky maneuvers. Thus, autonomous vehicles have been suggested to improve the road safety and mobility of younger and older drivers. However, the difficulty of manually taking over control from semi-autonomous vehicles might vary in different driving conditions, particularly in those that are more challenging. Hence, the present study aims to examine the effect of road geometry and scenario, by investigating young, middle-aged and older drivers' situation awareness (SA) and takeover performance when driving a semi-autonomous vehicle simulator on a straight versus a curved road on a highway and an urban non-highway road when engaged in a secondary distracting task. Due to the impact of COVID-19, data from only the young (n=24) and middle-aged (n=24) adults were collected and analyzed. Participants drove a Level 3 semi-autonomous simulator vehicle and performed a secondary non-driving related task in the distracted conditions. The results indicated that the participants had significantly longer hazard perception times on the curved roads and autopilot drives, but there was no significant effect of driver age and road type. Their Situation Awareness Global Assessment Technique (SAGAT) scores were higher in the highway scenarios, on the straight roads, and in the manual drive compared to the autopilot with distraction drive. Young drivers were also found to have significantly higher SAGAT scores than middle-aged drivers. While there was a significant interaction effect between road type and road geometry on takeover time, there was no significant main effect of road geometry, drive type and driver’s age. For the takeover quality metrics, road geometry and drive type had an effect on takeover performance. The resulting acceleration was higher for the straight road and in the autopilot drives, and the lane deviation was higher on the curved road and autopilot only drive compared to the autopilot with distraction drive. There was no significant main effect of road type and driver’s age on resulting acceleration and lane deviation. Overall, while there were age differences in some aspects of SA, young and middle-aged drivers did not differ in their takeover performance. The participants' SA was impacted by the road type and geometry and their takeover quality varied according to the road geometry and drive type. The outcomes of this research will aid vehicle manufacturing companies that are developing Level 3 semi-autonomous vehicles with appropriately designing the lead time of the takeover request to meet the driving style and abilities of younger and middle-aged drivers. This will also help to improve road safety by reducing the crash rate of younger drivers

Arquitetura multi-câmara e multi-algoritmo para perceção visual a bordo do ATLASCAR2

Road detection is a crucial concern in Autonomous Navigation and Driving Assistance. Despite the multiple existing algorithms to detect the road, the literature does not offer a single effective algorithm for all situations. A global more robust set-up would count on multiple distinct algorithms running in parallel, or even from multiple cameras. Then, all these algorithms’ outputs should be merged or combined to produce a more robust and informed detection of the road lane, so that it works in more situations than each algorithm by itself. This dissertation integrated in the ATLAS-CAR2 project, developed at the University of Aveiro, proposes a ROS-based architecture to manage and combine multiple sources of lane detection algorithms ranging from the algorithms that return the spatial localization of the road lane lines and those whose results are the navigable zone represented as a polygon. The architecture is fully scalable and has proved to be a valuable tool to test and parametrise individual algorithms. The combination of the algorithms’ results used in this work uses a confidence based merging of individual detections.A deteção de estradas é uma questão crucial na Navegação Autónoma e na Assistência à Condução. Apesar de os múltiplos algoritmos existentes para detetar a estrada, a literatura não oferece um único algoritmo eficaz para todas as situações. Uma configuração global mais robusta incorporaria vários algoritmos distintos e executados em paralelo, ou mesmo baseado em múltiplas câmaras. Então, todos os resultados destes algoritmos devem ser fundidos ou combinados para produzir uma deteção mais robusta e informada da via da estrada, para que funcione em mais situações do que cada algoritmo funcionando individualmente. Esta dissertação integrada no projeto ATLASCAR2, desenvolvido na Universidade de Aveiro, propõe uma arquitetura baseada em ROS para gerir e combinar múltiplas fontes de algoritmos de deteção de vias da estrada, desde algoritmos que devolvem a localização espacial da faixa de rodagem até àqueles cujos resultados são a zona navegável representada como um polı́gono. A arquitetura é totalmente escalável e provou ser uma ferramenta valiosa para testar e parametrizar algoritmos individuais. A combinação dos resultados dos algoritmos utilizados neste trabalho utiliza uma combinação de deteções individuais baseada na confiança.Mestrado em Engenharia Mecânic

Fully automated urban traffic system

The replacement of the driver with an automatic system which could perform the functions of guiding and routing a vehicle with a human's capability of responding to changing traffic demands was discussed. The problem was divided into four technological areas; guidance, routing, computing, and communications. It was determined that the latter three areas being developed independent of any need for fully automated urban traffic. A guidance system that would meet system requirements was not being developed but was technically feasible