Arquitectura de Control para la Conducción Autónoma de Vehículos en Entornos Urbanos y Autovías

Hoy en día, el desarrollo tecnológico en el campo de los sistemas inteligentes de transporte (ITS por sus siglas en inglés) ha permitido dotar a los vehículos con diversos sistemas de ayuda a la conducción (ADAS, del inglés advanced driver assistance system), mejorando la experiencia y seguridad de los pasajeros, en especial del conductor. La mayor parte de estos sistemas están pensados para advertir al conductor sobre ciertas situaciones de riesgo, como la salida involuntaria del carril o la proximidad de obstáculos en el camino. No obstante, también podemos encontrar sistemas que van un paso más allá y son capaces de cooperar con el conductor en el control del vehículo o incluso relegarlos de algunas tareas tediosas. Es en este último grupo donde se encuentran los sistemas de control electrónico de estabilidad (ESP - Electronic Stability Program), el antibloqueo de frenos (ABS - Anti-lock Braking System), el control de crucero (CC - Cruise Control) y los más recientes sistemas de aparcamiento asistido. Continuando con esta línea de desarrollo, el paso siguiente consiste en la supresión del conductor humano, desarrollando sistemas que sean capaces de conducir un vehículo de forma autónoma y con un rendimiento superior al del conductor. En este trabajo se presenta, en primer lugar, una arquitectura de control para la automatización de vehículos. Esta se compone de distintos componentes de hardware y software, agrupados de acuerdo a su función principal. El diseño de la arquitectura parte del trabajo previo desarrollado por el Programa AUTOPIA, aunque introduce notables aportaciones en cuanto a la eficiencia, robustez y escalabilidad del sistema. Ahondando un poco más en detalle, debemos resaltar el desarrollo de un algoritmo de localización basado en enjambres de partículas. Este está planteado como un método de filtrado y fusión de la información obtenida a partir de los distintos sensores embarcados en el vehículo, entre los que encontramos un receptor GPS (Global Positioning System), unidades de medición inercial (IMU – Inertial Measurement Unit) e información tomada directamente de los sensores embarcados por el fabricante, como la velocidad de las ruedas y posición del volante. Gracias a este método se ha conseguido resolver el problema de la localización, indispensable para el desarrollo de sistemas de conducción autónoma. Continuando con el trabajo de investigación, se ha estudiado la viabilidad de la aplicación de técnicas de aprendizaje y adaptación al diseño de controladores para el vehículo. Como punto de partida se emplea el método de Q-learning para la generación de un controlador borroso lateral sin ningún tipo de conocimiento previo. Posteriormente se presenta un método de ajuste on-line para la adaptación del control longitudinal ante perturbaciones impredecibles del entorno, como lo son los cambios en la inclinación del camino, fricción de las ruedas o peso de los ocupantes. Para finalizar, se presentan los resultados obtenidos durante un experimento de conducción autónoma en carreteras reales, el cual se llevó a cabo en el mes de Junio de 2012 desde la población de San Lorenzo de El Escorial hasta las instalaciones del Centro de Automática y Robótica (CAR) en Arganda del Rey. El principal objetivo tras esta demostración fue validar el funcionamiento, robustez y capacidad de la arquitectura propuesta para afrontar el problema de la conducción autónoma, bajo condiciones mucho más reales a las que se pueden alcanzar en las instalaciones de prueba. ABSTRACT Nowadays, the technological advances in the Intelligent Transportation Systems (ITS) field have led the development of several driving assistance systems (ADAS). These solutions are designed to improve the experience and security of all the passengers, especially the driver. For most of these systems, the main goal is to warn drivers about unexpected circumstances leading to risk situations such as involuntary lane departure or proximity to other vehicles. However, other ADAS go a step further, being able to cooperate with the driver in the control of the vehicle, or even overriding it on some tasks. Examples of this kind of systems are the anti-lock braking system (ABS), cruise control (CC) and the recently commercialised assisted parking systems. Within this research line, the next step is the development of systems able to replace the human drivers, improving the control and therefore, the safety and reliability of the vehicles. First of all, this dissertation presents a control architecture design for autonomous driving. It is made up of several hardware and software components, grouped according to their main function. The design of this architecture is based on the previous works carried out by the AUTOPIA Program, although notable improvements have been made regarding the efficiency, robustness and scalability of the system. It is also remarkable the work made on the development of a location algorithm for vehicles. The proposal is based on the emulation of the behaviour of biological swarms and its performance is similar to the well-known particle filters. The developed method combines information obtained from different sensors, including GPS, inertial measurement unit (IMU), and data from the original vehicle’s sensors on-board. Through this filtering algorithm the localization problem is properly managed, which is critical for the development of autonomous driving systems. The work deals also with the fuzzy control tuning system, a very time consuming task when done manually. An analysis of learning and adaptation techniques for the development of different controllers has been made. First, the Q-learning –a reinforcement learning method– has been applied to the generation of a lateral fuzzy controller from scratch. Subsequently, the development of an adaptation method for longitudinal control is presented. With this proposal, a final cruise control controller is able to deal with unpredictable environment disturbances, such as road slope, wheel’s friction or even occupants’ weight. As a testbed for the system, an autonomous driving experiment on real roads is presented. This experiment was carried out on June 2012, driving from San Lorenzo de El Escorial up to the Center for Automation and Robotics (CAR) facilities in Arganda del Rey. The main goal of the demonstration was validating the performance, robustness and viability of the proposed architecture to deal with the problem of autonomous driving under more demanding conditions than those achieved on closed test tracks.

Dealing with traffic risk in Latin American toll roads

Análisis de los sistemas de mitigación del riesgo de tráfico en autopistas de peaje en diferentes países de Latinoamérica. This paper presents a cross-country analysis of traffic risk allocation in road concessions of Latin America. It shows that some countries such as Chile, Colombia, and Peru have been greatly concerned with mitigating traffic risk, either by putting into practice public guarantees, implementing flexible term concessions, or through availability payment concessions; whereas other countries such as Mexico and Brazil have assigned traffic risk to the private concessionaire by using fixed-term concession contracts without any traffic guarantees. Based on an analysis of data from 1990 to 2010, the paper finds that shifting traffic risk from the concessionaire to the government or users was not confined to the riskiest projects, as one might expect. The analysis also suggests that the implementation of traffic risk mitigation mechanisms in Latin American toll roads has not been very successful in reducing renegotiation rates or in increasing the number of bidders in the tenders

Probe-based end-to-end overload control for networks of SIP servers

The Session Initiation Protocol (SIP) has been adopted by the IETF as the control protocol for creating, modifying and terminating multimedia sessions. Overload occurs in SIP networks when SIP servers have insufficient resources to handle received messages. Under overload, SIP networks may suffer from congestion collapse due to current ineffective SIP overload control mechanisms. This paper introduces a probe-based end-to-end overload control (PEOC) mechanism, which is deployed at the edge servers of SIP networks and is easy to implement. By probing the SIP network with SIP messages, PEOC estimates the network load and controls the traffic admitted to the network according to the estimated load. Theoretic analysis and extensive simulations verify that PEOC can keep high throughput for SIP networks even when the offered load exceeds the capacity of the network. Besides, it can respond quickly to the sudden variations of the offered load and achieve good fairness.

Sight distance for traffic safety analysis using GIS

Sight distance is of major importance for road safety either when designing new roads or analysing the alignment of existing roads. It is essential that available sight distance in roads is long enough for emergency stops or overtaking manoeuvres. Also, it is vital for engineers/researchers that the tools used for that analysis are both powerful and intuitive. Based on ArcGIS, the application to be presented not only performs an exhaustive sight distance calculation, but allows an accurate analysis of 3D alignment, using all new tools, from a Digital Elevation Model and vehicle trajectory. The software has been successfully utilised to analyse several two-lane rural roads in Spain. In addition, the software produces thematic maps representing sight distance in which supplementary information about crashes, traffic flow, speed or design consistency could be included, allowing traffic safety studies.

Analysis of road safety incentives in highway concessions in Spain

Public Private Partnerships (PPPs) are mostly implemented for three reasons: to circumvent budgetary constraints, encourage efficiency and improvement of quality in the provision of public infrastructure. One of the ways of reaching the latter objective is by the introduction of performance-based standards tied to bonuses and penalties to reward or punish the performance of the contractor. These performance based standards often refer to different aspects such as technical, environmental and safety issues. This paper focuses on the implementation of safety based incentives in PPPs. The main aim of this paper is to analyze whether the incentives to improve road safety in PPPs are effective in improving safety ratios in Spain. To this end, negative binomial regression models have been applied using information from the Spanish high capacity network in 2006. The findings indicate that even though road safety is highly influenced by variables that are not much controllable by the contractor such as the Average Annual Daily Traffic and the percentage of heavy vehicles in the highway, the implementation of safety incentives in PPPs has a positive influence in the reduction of fatalities, injuries and accidents.

Self-Tuning PID controller for autonomous car tracking in urban traffic

In this paper an on line self-tuned PID controller is proposed for the control of a car whose goal is to follow another one, at distances and speeds typical in urban traffic. The bestknown tuning mechanism is perhaps the MIT rule, due to its ease of implementation. However, as it is well known, this method does not guarantee the stability of the system, providing good results only for constant or slowly varying reference signals and in the absence of noise, which are unrealistic conditions. When the reference input varies with an appreciable rate or in presence of noise, eventually it could result in system instability. In this paper an alternative method is proposed that significantly improves the robustness of the system for varying inputs or in the presence of noise, as demonstrated by simulation.

Do Public Private Partnerships Improve Road Safety? The Case of Toll Concessions in Spain

El Transportation Research Board es un congreso de reconocido prestigio internacional en el ámbito de la investigación del transporte. Aunque las actas publicadas están en formato digital y sin ISSN ni ISBN, lo consideramos lo suficientemente importante como para que se considere en los indicadores. This paper focuses on the implementation of safety based incentives in Public Private Partnerships (PPPs). The aim of this paper is twofold. First, to evaluate whether PPPs lead to an improvement in road safety, when compared with other infrastructure management systems. Second, is to analyze whether the incentives to improve road safety in PPP contracts in Spain have been effective at improving safety performance. To this end, negative binomial regression models have been applied using information from the Spanish high-capacity network covering years 2007-2009. The results showed that even though road safety is highly influenced by variables that are not manageable by the private concessionaire such as the average annual daily traffic, the implementation of safety incentives in PPPs has a positive influence in the reduction of accidents.

Determinación de la distribución de tamaño y número de partículas provenientes de motores diesel operando en trafico real con equipos embarcados

El presente trabajo se propone determinar la distribución de tamaño y número de partículas nanométricas provenientes de motores diésel con equipos embarcados en tráfico extraurbano. Para ello, se utilizaron equipos de medición de última generación en condiciones promedio de conducción en tráfico extraurbano por más de 800 km a lo largo del trayecto Madrid-Badajoz-Madrid mediante un vehículo característico del parque automotor español y se implementaron métodos novedosos y pioneros en el registro de este tipo de emisiones. Todo ello abre el camino para líneas de investigación y desarrollo que contribuirán a entender, dimensionar y cualificar el comportamiento de las partículas, así como su impacto en la calidad de vida de la población. El estudio hace dos grandes aportes al campo. Primero, permite registrar las emisiones en condiciones transitorias propias del tráfico real. Segundo, permite mantener controladas las condiciones de medición y evita la formación aleatoria de partículas provenientes de material volátil, gracias al sistema de adecuación de la muestra de gases de escape incorporado. Como resultado, se obtuvo una muestra abundante y confiable que permitió construir modelos matemáticos para calcular la emisión de partículas nanométricas, ultrafinas, finas y totales sobre las bases volumétrica, espacial y temporal en función de la pendiente del perfil orográfico de la carretera, siempre y cuando esté dentro del intervalo ±5.0%. Estos modelos de cálculo de emisiones reducen tanto los costos de experimentación como la complejidad de los equipos necesarios, y fundamentaron el desarrollo de la primera versión de una aplicación informática que calcula las partículas emitidas por un motor diésel en condiciones de tráfico extraurbano ("Partículas Emitidas por Motores Diésel, PEMDI). ABSTRACT The purpose of this research is to determine the distribution of size and number of nanometric particles that come from diesel engines by means of on-board equipment in extra-urban traffic. In order to do this, cutting-edge measuring equipment was used under average driving conditions in extra-urban traffic for more than 800 km along the Madrid-Badajoz-Madrid route using a typical vehicle from Spain's automotive population and innovative, groundbreaking registering methods for this type of emissions were used. All this paves the way for lines of research and development which should help understand, measure and characterize the behavior of such particles, as well as their impact in the quality of life of the general population. The study makes two important contributions to the field. First, it makes it possible to register emissions under transient conditions, which are characteristic to real traffic. Secondly, it provides a means to keep the measuring conditions under control and prevents the random formation of particles of volatile origin through the built-in adjustment system of the exhaust gas sample. As a result, an abundant and reliable sample was gathered, which enabled the building of mathematical models to estimate the emission of nanometric, ultrafine, fine and total particles on volumetric, spatial and temporal bases as a function of the orographic outline of the road within a ±5.0% range. These emission estimating models lower both the experimentation costs and the required equipment's complexity, and they provided the basis for the development of a first software application version that estimates the particles emitted from diesel engines under extra-urban traffic conditions (Partículas Emitidas por Motores Diésel, PEMDI).

Multi-resolution model-based traffic sign detection and tracking

In this paper we propose an innovative approach to tackle the problem of traffic sign detection using a computer vision algorithm and taking into account real-time operation constraints, trying to establish intelligent strategies to simplify as much as possible the algorithm complexity and to speed up the process. Firstly, a set of candidates is generated according to a color segmentation stage, followed by a region analysis strategy, where spatial characteristic of previously detected objects are taken into account. Finally, temporal coherence is introduced by means of a tracking scheme, performed using a Kalman filter for each potential candidate. Taking into consideration time constraints, efficiency is achieved two-fold: on the one side, a multi-resolution strategy is adopted for segmentation, where global operation will be applied only to low-resolution images, increasing the resolution to the maximum only when a potential road sign is being tracked. On the other side, we take advantage of the expected spacing between traffic signs. Namely, the tracking of objects of interest allows to generate inhibition areas, which are those ones where no new traffic signs are expected to appear due to the existence of a TS in the neighborhood. The proposed solution has been tested with real sequences in both urban areas and highways, and proved to achieve higher computational efficiency, especially as a result of the multi-resolution approach.

Traffic sign detection and tracking using robust 3D analysis

In this paper we present an innovative technique to tackle the problem of automatic road sign detection and tracking using an on-board stereo camera. It involves a continuous 3D analysis of the road sign during the whole tracking process. Firstly, a color and appearance based model is applied to generate road sign candidates in both stereo images. A sparse disparity map between the left and right images is then created for each candidate by using contour-based and SURF-based matching in the far and short range, respectively. Once the map has been computed, the correspondences are back-projected to generate a cloud of 3D points, and the best-fit plane is computed through RANSAC, ensuring robustness to outliers. Temporal consistency is enforced by means of a Kalman filter, which exploits the intrinsic smoothness of the 3D camera motion in traffic environments. Additionally, the estimation of the plane allows to correct deformations due to perspective, thus easing further sign classification.

How lowering speed limits in an urban highway affects traffics performance and emissions: the case of Madrid M-30 ring-road

The city of Madrid keeps not meeting the GHG and air pollutant limits set by the European legislation. A broad range of strategies have being taken into account to reduce both types of emissions; however traffic management meas ures are usually consigned to the sidelines. In 2004, Madrid City Council launched a plan to re-design its inner ring-road supported by a socioeconomic study that evaluated the environmental and operational benefits of the project. For safety reasons the planned speed limit for the tunnel section was finally reduced from 90km/h to 70km/h. Using a Macroscopic Traffic Model and the European Air Pollutant and Emissions Inventory Guidebook (EMEP/EEA), this paper examines the environmental and traffic performance consequences of this decision. Results support the thesis that reduced speed limits leads to GHG and air pollution reductions in the area affected by the measure without substantially altering traffic performance. The implementation of the new speed limit policy brings about a 15% and 16% reduction in both CO2 and NOx emissions respectively. Emissions’ reduction during off-peak hours is larger than during peak hours.

Impact of introducing longer and heavier vehicles on regional consumer price index and Spanish road freight transport system

This paper applies an integrated modeling approach to the case of Spain; the approach is based on a random utility-based multiregional input-output model and a road transport network model for assessing the effect of introducing longer and heavier vehicles (LHVs) on the regional consumer price index (CPI) and on the transportation system. The approach strongly supports the concept that changes in transport costs derived from the LHV allowance as well as the economic structure of regions have direct and indirect effects on the economy and on the transportation system. Results show that the introduction of LHVs might reduce prices paid by consumers for a representative basket of goods and services in the regions of Spain and would also lead to a reduction in the regional CPI. In addition, the magnitude and extent of changes in the transportation system are estimated by using the commodity-based structure of the approach to identify the effect of traffic changes on traffic flows and on pollutant emissions over the whole network.

Road fright transport decoupling: A comparative analysis between the United Kingdom and Spain

Economic growth has traditionally been linked to road freight transport demand, leading to a steady rise in social and environmental impacts. Concern about this problem has caused the EU to promote a decoupling strategy aimed at boosting sustainable development in European countries by improving the efficiency of transport systems without curbing economic growth. Over the last few years empirical evidence in some countries such as the United Kingdom has shown an increase in GDP while the volume of road freight traffic has remained stable or even decreased. This paper compares recent decoupling trends by analyzing the evolution of road tonne-kms/GDP relationship in the United Kingdom and Spain from 1999 to 2007. This comparison seeks to identify the main differences and key drivers of decoupling in both countries. We first provide an overview of the divergences between both economic structures and levels of road transport intensity. Then we conduct a decomposition analysis in order to identify the variables that explain the evolution of truck traffic per unit of GDP in each country. The results show that the increasing share of services in GDP has substantially contributed to decreasing road transport demand in both cases. Changes in road transport intensity due to improvements in logistic and supply chain management have been more successful in the UK than in Spain.

On-line learning of a fuzzy controller for a precise vehicle cruise control system

Usually, vehicle applications require the use of artificial intelligent techniques to implement control methods, due to noise provided by sensors or the impossibility of full knowledge about dynamics of the vehicle (engine state, wheel pressure or occupiers weight). This work presents a method to on-line evolve a fuzzy controller for commanding vehicles? pedals at low speeds; in this scenario, the slightest alteration in the vehicle or road conditions can vary controller?s behavior in a non predictable way. The proposal adapts singletons positions in real time, and trapezoids used to codify the input variables are modified according with historical data. Experimentation in both simulated and real vehicles are provided to show how fast and precise the method is, even compared with a human driver or using different vehicles.

Experimental analysis of energy savings and hygrothermal conditions improvement by means of air curtaines in stores with intensive pedestrian traffic

Current worldwide building legislation requirements aim to the design and construction of technical services that reduce energy consumption and improve indoor hygrothermal conditions. The retail sector in Spain, with a lot of outdated technical systems, demands energy conservation measures in order to reduce the increasingly electrical consumption for cooling. Climatic separation with modern air curtains and advanced hygrothermal control systems enables energy savings and can keep suitable indoor air temperature and humidity of stores with intense pedestrian traffic, especially when located in hot humid climates. As stated in the article, the energy savings in commercial buildings with these systems exceeds 30%