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- Intelligent transportation systemsPublication . Figueiredo, Lino; Jesus, Isabel S.; Tenreiro Machado, J. A.; Ferreira, José RuiThis paper presents a review of the state of the art on Intelligent Transportation Systems and discuss the problem of modelling and simulation. ITS involves a large number of research ares and, therefore, this paper focus on those we believe to be the most relevant.
- Application of Fractional Order Concepts in the Study of Electrical PotentialPublication . Jesus, Isabel S.; Machado, J. A. TenreiroThe Maxwell equations, expressing the fundamental laws of electricity and magnetism, only involve the integer-order calculus. However, several effects present in electromagnetism, motivated recently an analysis under the fractional calculus (FC) perspective. In fact, this mathematical concept allows a deeper insight into many phenomena that classical models overlook. On the other hand, genetic algorithms (GA) are an important tool to solve optmization problems that occur in engineering. In this work we use FC and GA to implement the electrical potencial of fractional order. The performance of the GA scheme and the convergence of the resulting approximations are analyzed.
- Fractional order electrical impedance of fruits and vegetablesPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.; Cunha, J. Boaventura; Silva, ManuelThe idea of fractional calculus is not new. Fractional derivatives are almost as old as integer-order definition. In 1695 Leibniz discussed this problem with L’Hospital, but many other contributions are due to investigators such as Liouville, Abel, Heaviside and Riemann, that formalized the theory of the non-integer order systems. The area of fractional calculus has primarily been the domain of mathematicians, and only had the theoretical foundation. Nowadays, this concept is employed in physics, engineering, biology, economy and other scientific fields. In our work, we apply the concepts of fractional calculus and the theory of electrical impedance to botanical elements. The fractional order behaviour of these type of systems are studied and the relation with the electrical impedance is formulated.
- Fractional order capacitorsPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.; Silva, ManuelThe performance of electrical devices, depending on the processes of the electrolytes, have been fully described and the physical origin of each parameter is well established. However, the influence of the irregularity of the electrodes was not a subject of study and only recently, this problem became relevant in the viewpoint of fractional calculus. This paper describes an electrolytic process in the perspective of fractional order capacitors. In this line of thought, are developed several experiments for measuring the electrical impedance of the devices. The results are analyzed through the frequency response, revealing capacitances of fractional order that can constitute an alternative to the classical integer order elements.
- On the Fractional PID Control of a Laboratory Servo SystemPublication . Barbosa, Ramiro; Tenreiro Machado, J. A.; Jesus, Isabel S.In this paper are investigated several types of fractional-order PID controllers in the velocity control of a servo system. The fractional controller is more flexible and gives the possibility of adjusting carefully the dynamical properties of a control system. The servo system is controlled by using a real-time digital control system based on MATLAB/Simulink. Results are compared with those obtained from classical PID controllers. Experimental responses are presented and analyzed, showing the effectiveness of the proposed fractional-order algorithms.
- Modeling and simulation of walking robots with 3 dof legsPublication . Silva, Manuel; Tenreiro Machado, J. A.; Jesus, Isabel S.This paper describes a simulation model for a multilegged locomotion system with 3 dof legs and leg joint actuators having saturation. For that objective the robot prescribed motion is characterized in terms of several locomotion variables. Moreover, the robot body is divided into several segments in order to emulate the behavior of an animal spine. A non-linear spring-dashpot system models the foot-ground interaction, being its parameters computed from studies on soil mechanics. To conclude, the performance of the developed model is evaluated through a set of experiments while the robot leg joints are controlled using a proportional and derivative algorithm.
- Some Applications of Fractional Calculus in EngineeringPublication . Tenreiro Machado, J. A.; Silva, Manuel; Barbosa, Ramiro; Jesus, Isabel S.; Reis, Cecília; Marcos, Maria G.; Galhano, AlexandraFractional Calculus (FC) goes back to the beginning of the theory of differential calculus. Nevertheless, the application of FC just emerged in the last two decades, due to the progress in the area of chaos that revealed subtle relationships with the FC concepts. In the field of dynamical systems theory some work has been carried out but the proposed models and algorithms are still in a preliminary stage of establishment. Having these ideas in mind, the paper discusses FC in the study of system dynamics and control. In this perspective, this paper investigates the use of FC in the fields of controller tuning, legged robots, redundant robots, heat diffusion, and digital circuit synthesis.
- Comparing Integer and Fractional Models in some Electrical SystemsPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.The Fractional Calculus (FC) is a mathematical tool applied in scientific areas such as electricity, magnetism, fluid dynamics and biology. This paper describes the use of integer and fractional electrical elements, for modelling several diffusion systems. Experimental and theoretical results are analyzed in the frequency domain and the pros and cons of adopting fractional order electrical components for modelling these systems are compared.
- Application of Genetic Algorithms to the Implementation of Fractional Electromagnetic PotentialsPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.; Cunha, J. BoaventuraA genetic algorithm (GA) is a search technique based on the natural selection process. The GAs provide further flexibility and robustness that are unique for signal process. Recently, a closer look of some phenomena present in electrical systems, such as motors, transformers and lines, and the motivation towards the development of comprehensive models, seem to point out the requirement for a fractional calculus approach. Bearing these ideas in mind, we address the analysis and the synthesis of fractional-order multipoles, based in a GA optimization scheme.
- Implementation of fractional electric potential using genetic algorithmsPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.A fresh look of several phenomena present in electrical systems induced an approach based in the fractional calculus (FC) viewpoint. The problem of point multipoles with electrical charges is an important subject in the field of electromagnetism. In this work, it is applied the concept of FC to implement the electrical potential of fractional order through a genetic algorithm (GA) optimization scheme. The work is complemented by analyzing the locus of charge versus position distribution of the required electrical charges.