Modeling of an Overactuated Vehicle in Simscape Multibody for the Characterization of Suspension and Steering Actuation Systems.

Overactuated systems are increasingly among us. They are used for applications in vehicles, aeronautics and robotics, among others [1, 2]. These systems have a number of advantages, among which we can mention that there are multiple (or infinite) solutions for a given problem. More specifically, in the case of overactuated vehicles, similar states of the system can be achieved in many different ways. These systems are still under development, especially in the field of vehicle dynamics. For example, there are various steer-by-wire algorithms, when the steering of the vehicles is independent, or brake blending strategies. In this work, a part of an overactuated vehicle is designed and validated. This multiphysics model allows to know the plant of the system in much more depth in order to develop control algorithms. More specifically, by modeling the delay of the systems and the nonlinear relationships inherent to multibody systems, much more accurate predictive control can be performed. These results allow a previous validation of the control algorithms in the test platform vehicle being manufactured and developed by the research group, greatly accelerating the control process of each of the overactuated systems of the vehicle.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

On-line learning applied to spiking neural network for antilock braking systems

Computationally replicating the behaviour of the cerebral cortex to perform the control tasks of daily life in a human being is a challenge today. First, … Finally, a suitable learning model that allows adapting neural network response to changing conditions in the environment is also required. Spiking Neural Networks (SNN) are currently the closest approximation to biological neural networks. SNNs make use of temporal spike trains to deal with inputs and outputs, thus allowing a faster and more complex computation. In this paper, a controller based on an SNN is proposed to perform the control of an anti-lock braking system (ABS) in vehicles. To this end, two neural networks are used to regulate the braking force. The first one is devoted to estimating the optimal slip while the second one is in charge of setting the optimal braking pressure. The latter resembles biological reflex arcs to ensure stability during operation. This neural structure is used to control the fast regulation cycles that occur during ABS operation. Furthermore, an algorithm has been developed to train the network while driving. On-line learning is proposed to update the response of the controller. Hence, to cope with real conditions, a control algorithm based on neural networks that learn by making use of neural plasticity, similar to what occurs in biological systems, has been implemented. Neural connections are modulated using Spike-Timing-Dependent Plasticity (STDP) by means of a supervised learning structure using the slip error as input. Road-type detection has been included in the same neural structure. To validate and to evaluate the performance of the proposed algorithm, simulations as well as experiments in a real vehicle were carried out. The algorithm proved to be able to adapt to changes in adhesion conditions rapidly. This way, the capability of spiking neural networks to perform the full control logic of the ABS has been verified.Funding for open access charge: Universidad de Málaga / CBUA This work was partly supported by the Ministry of Science and Innovation under grant PID2019-105572RB-I00, partly by the Regional Government of Andalusia under grant UMA18-FEDERJA-109, and partly by the University of Malaga as well as the KTH Royal Institute of Technology and its initiative, TRENoP

Influencia de la temperatura y la velocidad en la dinámica del contacto neumático carretera

En el contexto de los sistemas de seguridad activa en vehículos, los neumáticos juegan un papel fundamental. Un conocimiento más preciso del comportamiento del neumático conlleva directamente una mejora de la seguridad activa en vehículos, y más concretamente en los sistemas de control de tracción y frenada. En este trabajo se ha analizado la influencia de la temperatura y la velocidad en la generación de fuerzas longitudinales y laterales entre el neumático y la carretera. Para ello, se ha empleado un banco de ensayo de neumáticos y una llanta dinamométrica. Se ha determinado la temperatura óptima de trabajo, así como se observa un comportamiento anómalo en el caso del neumático frío. También se ha observado una disminución drástica de la adherencia conforme aumenta la velocidad.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Estimación de la resistencia a la rodadura en neumáticos mediante banco de ensayos de tracción-compresión

La resistencia a la rodadura constituye alrededor del 20 % del consumo energético en automóviles. Más del 90 % del impacto medioambiental de los neumáticos se atribuye a la energía perdida en la rodadura. Cada vez más, los fabricantes de vehículos y de neumáticos invierten recursos para minimizar esta energía desaprovechada. Actualmente, con objeto de maximizar la autonomía en los vehículos eléctricos, se impone el uso de los conocidos “green tire”, que son neumáticos con una resistencia a la rodadura muy inferior a la convencional. En el sector de los camiones, las cifras son aún mayores, pues la resistencia a la rodadura supera el 30 % del consumo energético. El origen de esta pérdida de energía es debido, fundamentalmente, al comportamiento viscoelástico que presenta la goma de los neumáticos. En este trabajo, se propone una metodología novedosa para estimar la resistencia a la rodadura en neumáticos, empleando para ello un banco de ensayo de tracción-compresión.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Assembling the Dead, Gathering the Living: Radiocarbon Dating and Bayesian Modelling for Copper Age Valencina de la Concepción (Seville, Spain)

The great site of Valencina de la Concepción, near Seville in the lower Guadalquivir valley of southwest Spain, is presented in the context of debate about the nature of Copper Age society in southern Iberia as a whole. Many aspects of the layout, use, character and development of Valencina remain unclear, just as there are major unresolved questions about the kind of society represented there and in southern Iberia, from the late fourth to the late third millennium cal BC. This paper discusses 178 radiocarbon dates, from 17 excavated sectors within the c. 450 ha site, making it the best dated in later Iberian prehistory as a whole. Dates are modelled in a Bayesian statistical framework. The resulting formal date estimates provide the basis for both a new epistemological approach to the site and a much more detailed narrative of its development than previously available. Beginning in the 32nd century cal BC, a long-lasting tradition of simple, mainly collective and often successive burial was established at the site. Mud-vaulted tholoi appear to belong to the 29th or 28th centuries cal BC; large stone-vaulted tholoi such as La Pastora appear to date later in the sequence. There is plenty of evidence for a wide range of other activity, but no clear sign of permanent, large-scale residence or public buildings or spaces. Results in general support a model of increasingly competitive but ultimately unstable social relations, through various phases of emergence, social competition, display and hierarchisation, and eventual decline, over a period of c. 900 years