Vicente Díaz López

Active roll control using reinforcement learning for a single unit heavy vehicle

In this paper, a reinforcement learning algorithm using neural networks to improve the roll stability in a single unit heavy vehicle is proposed. The controller, consisting of active anti-roll bars, provides the adequate roll moments to the vehicle to improve its performance. The main advantages of the implemented neuro control are its good performance to control non-linear systems, it is a free-model control and it learns online, so that the system can adapt to changes produced in the environment. In this case, it is only necessary to measure a unique variable (the sprung mass roll angle) to control the vehicle so both the number of sensors and vehicle cost are reduced. Simulation results show the effectiveness of the proposed control system during different manoeuvres such as J-turn and lane-change.

Simplified dynamic torsional model of an urban bus

Nowadays, one of the concerns of vehicle safety is the bus rollover due to the great number of injured and deaths. The torsion stiffness of the bus structure is a parameter of security against rollover. The torsion behaviour of the bus structure is studied from a dynamic point of view. In this paper, a dynamic free vibration model, based on the Holzer method, of a bus body is proposed. Modes and natural vibration frequencies have been obtained applying the proposed model and compared with those calculated by means of a Finite Element Model (FEM) of the bus structure, which has been validated by experimental static torsion tests. Results show that the natural frequencies and modes using the proposed dynamic model agree with those obtained with the FEM.

AUTOMATH: MATLAB‐based educational software for vehicle's performance and longitudinal dynamics

In this article, we present an educational software called AUTOMATH, developed to allow the engineering students to learn easily and rapidly about the vehicles performance and longitudinal dynamics. This software uses the graphical user interface (GUI) capabilities of MATLAB which has shown to be a good choice if the teacher wishes to collaborate with students on a GUI because engineering students are typically familiar.

A Contact Model Between Tyre and Pavement at Low Speed for Periodic Motor Vehicle Inspection

The behaviour of the tyre plays an important role in the vehicle handling. Thus for the analysis of vehicles and road safety it is necessary to take into account the forces and moments generated at contact patch. An accurate tyre model that estimates these forces and moments is highly essential for the studies of vehicle dynamics and control. Most of the tyre models have been developed for high speed, combined forces, etc. But, usually, automobile vehicles run at low speeds during an important part of their operating life (less than 60 km/h) and in steady state conditions. Furthermore, during vehicle inspection and maintenance of the steering and brake system, by means of sideslip tester and roller brake tester respectively, the forces transmitted by the tyres are measured, all of these inspections are carried out at low speeds. Therefore, it is particularly interesting to develop a model of the contact patch tyre-pavement for low speeds without the complexity of models that cover a wide speed range but with a bigger precision at low speeds. The dynamometer plate has proved to be an appropriate test equipment to characterise the tyre-pavement contact at low speed and the steering geometry and wheel alignment. It has the feature of being able to carry out tests for any type of tyre allowing to test with a great flexibility and operating speed. For this reason, the dynamometer plate has been chosen as test equipment. The main aim of this research is to set up a contact model between tyre and pavement at low speed, based on the measurement of longitudinal and lateral forces. The experimental tests carried out by means of the dynamometer plate have allowed to establish a relationship between influence variables and the longitudinal and lateral forces in the contact patch for steady state low speeds. A sensibility study has shown that the most influential variables in the forces of the contact patch are the pressure, the vertical force and the toe angle. However, the influence of temperature and camber angle is lower for the defined model conditions. A test methodology that allows carrying out the experimental tests in a systematic and controlled way in the dynamometer plate has also been developed.Copyright

Enhanced Steering System Inspection for Improving Road Safety

Three new criteria have been developed with the purpose of improving road safety, through an enhanced wheel alignment inspection in the context of the Periodic Motor Vehicle Inspection (PMVI). Nowadays, the result of the inspection in Spain is not determined directly from an objective measurement. It depends greatly on the inspector criterion. The three developed criteria provide the inspectors with an objective procedure, based on the measuring device that is nowadays installed in the PMVI stations: the sideslip tester. The first proposed criterion checks if the toe-in angle is set according to the manufacturer’s specifications, using a model that has been specifically developed to estimate this angle from the sideslip measurement. The second one evaluates if there is an excessive permanent side force when driving in straight line, thanks to a model expressly developed for this purpose. A third criterion establishes a limit for the sideslip measurement, common for all the vehicles, with a non-symmetrical range from the zero sideslip. An extensive program of validation tests has been carried out for the three proposed methods. According to them, the third proposal has been chosen as the preferred one. Previously, a comprehensive study of the sideslip measurement fundamentals and the different factors that may have an influence on the results was done.© 2011 ASME