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- Analysis of Systems with Backlash and Impacts through the Describing FunctionPublication . Barbosa, Ramiro S.; Machado, J. A. TenreiroThis paper analyses the dynamical properties of systems with backlash and impact phenomena based on the describing function method. The dynamics is illustrated using the Nyquist and Bode plots and the results are compared with those of standard models.
- Neural control of an autonomous robotPublication . Pinto, Adriano; Barbosa, Ramiro S.; Silva, Manuel SantosThis article aims to apply the concepts associated with artificial neural networks (ANN) in the control of an autonomous robot system that is intended to be used in competitions of robots. The robot was tested in several arbitrary paths in order to verify its effectiveness. The results show that the robot performed the tasks with success. Moreover, in the case of arbitrary paths the ANN control outperforms other methodologies, such as fuzzy logic control (FLC).
- 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.
- 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.
- Fractional describing function analysis of systems with backlash and impact phenomenaPublication . Barbosa, Ramiro; Tenreiro Machado, J. A.This paper analyses the dynamical properties of systems with backlash and impact phenomena based on the describing function method. It is shown that this type of nonlinearity can be analyzed in the perspective of the fractional calculus theory. The fractional-order dynamics is illustrated using the Nyquist plot and the results are compared with those of standard models.
- Performance of fractional PID algorithms controlling nonlinear systems with saturation and backlash phenomenaPublication . Barbosa, Ramiro S.; Machado, J. A. Tenreiro; Galhano, AlexandraThe development of fractional-order controllers is currently one of the most promising fields of research. However, most of the work in this area addresses the case of linear systems. This paper reports on the analysis of fractional-order control of nonlinear systems. The performance of discrete fractional-order PID controllers in the presence of several nonlinearities is discussed. Some results are provided that indicate the superior robustness of such algorithms.
- Fractional Order Nonlinear Control of Heat SystemPublication . Jesus, Isabel S.; Tenreiro Machado, J. A.; Barbosa, RamiroIn the last decade, the interest in the area of fractional calculus and its applications has increased significantly. In this paper, we study a heat diffusion system in a fractional calculus perspective. A fractional order nonlinear controller is proposed, and its tuning, in the viewpoint of several performance indices, is analyzed. The simulations demonstrate the good performance of the proposed fractional-order structure.
- Comparison of Different Fractional Order PD0.5 Control Algorithm Implementations for Legged RobotsPublication . Silva, Manuel; Tenreiro Machado, J. A.; Barbosa, RamiroThis paper studies different Fractional Order (FO) PD0.5 algorithms applied to the leg joint control of a hexapod robot with two dof legs. For the implementation of the FO PD0.5 joint controllers both the Padé and the series approximations are considered, being compared their performance. For simulation purposes the robot prescribed motion is characterized through several locomotion variables and parameters and for the walking performance evaluation two indices are used, one of them based on the mean absolute density of energy per travelled distance and the other one on the hip trajectory errors. A set of simulation experiments reveals the influence of the different approximations and the order of the PD0.5 controllers tuning upon the proposed indices.
- Fractional modelling of the electrical conduction in nacl electrolytePublication . Jesus, Isabel S.; Tenreiro Machado, J. A.; Barbosa, RamiroThe fractional calculus (FC) constitutes a mathematical tool that presently is being applied in many emerging scientific areas, such as electricity, magnetism, mechanics, fluid dynamics and medicine. This paper describes the use of an electrolytic process for developing fractional order capacitors. The study includes several experiments for measuring the electrical impedance of the devices. The results are analyzed through the frequency response revealing capacitances of fractional order.
- Tuning and application of integer and fractional order PID controllersPublication . Barbosa, Ramiro S.; Silva, Manuel F.; Machado, J. A. TenreiroFractional calculus (FC) is widely used in most areas of science and engineering, being recognized its ability to yield a superior modeling and control in many dynamical systems. In this perspective, this article illustrates two applications of FC in the area of control systems. Firstly, is presented a methodology of tuning PID controllers that gives closed-loop systems robust to gain variations. After, a fractional-order PID controller is proposed for the control of an hexapod robot with three dof legs. In both cases, it is demonstrated the system's superior performance by using the FC concepts.