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- Development of a genetic algorithm for the optimization of hexapod robot parametersPublication . Silva, Manuel; Barbosa, Ramiro; Tenreiro Machado, J. A.Legged robots allow the locomotion on terrains inaccessible to other type of vehicles because they do not need a continuous support surface. Different strategies have been adopted for the optimization of these systems, during their design and construction phases, and during their operation. Among the different optimization criteria followed by different authors, it is possible to find issues related to energy efficiency, stability, speed, comfort, mobility and environmental impact. Evolutionary strategies are a way to ”imitate nature” replicating the process that nature designed for the generation and evolution of species. The objective of this paper is to present a genetic algorithm, running over a simulation application of legged robots, which allows the optimization of several parameters of the robot model and of its gaits, for different locomotion speeds.
- Application of Fractional Calculus in Control and ElectromagnetismPublication . Tenreiro Machado, J. A.; Barbosa, Ramiro; Jesus, Isabel S.; Silva, Manuel; Reis, Cecília; Figueiredo, LinoThis article illustrates two applications of fractional calculus (FC) in engineering. It has been recognized the advantageous use of this mathematical tool in the modeling and control of many dynamical systems. In this perspective, this paper investigates the use of FC in PID tuning and electrical potential.
- Comparison of different orders padé fractional order PD0.5 control algorithm implementationsPublication . Silva, Manuel; Tenreiro Machado, J. A.; Barbosa, RamiroThis paper studies the performance of different order Padé Fractional Order (FO) PD0.5 controllers applied to the leg joint control of a hexapod robot with two dof legs and joint actuators with saturation. For simulation purposes the robot prescribed motion is characterized through several locomotion variables and for the walking performance evaluation are used two indices, one based on the mean absolute density of energy per travelled distance and the other on the hip trajectory errors. A set of simulation experiments reveals the influence of the different order Padé PD0.5 controllers tuning upon the proposed indices.
- Applications of fractional calculus in electrical and computer engineeringPublication . Tenreiro Machado, J. A.; Silva, Manuel; Barbosa, Ramiro; Jesus, Isabel S.; Reis, Cecília; Marcos, Maria da Graça; M. Afonso, Luís; Lima, Miguel F. M.; Pires, E. J. Solteiro; Ferreira, N. M. FonsecaFractional 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 a FC perspective in the study of the dynamics and control of several systems. This article illustrates several applications of fractional calculus in science and engineering. It has been recognized the advantageous use of this mathematical tool in the modeling and control of many dynamical systems. In this perspective, this paper investigates the use of FC in the fields of controller tuning, electrical systems, digital circuit synthesis, evolutionary computing, redundant robots, legged robots, robotic manipulators, nonlinear friction and financial modeling.
- Comparison of fractional and integer order control of an hexapod robotPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, António M.This paper studies the dynamics of foot-ground interaction and the performance of integer and fractional order controllers in multi-legged locomotion systems. For that objective the robot precribed motion is characterized in terms of several locomotion variables. Moreover, to compare the system performance, we formulate six performance measures of the walking robot namely, the mean absolute power, the mean power dispersion, the mean power lost in the joint actuators, the mean force of the interface body-legs per walking distance and mean square error of the hip and foot trajectories. A set of model-based experiments reveals the influence of the different controller implemantations in the proposed indices.
- Energy Efficiency of Quadruped GaitsPublication . Silva, Manuel F.; Machado, J. A. TenreiroThis paper studies periodic gaits of quadruped locomotion systems. The purpose is to determinate the best set of gait and locomotion variables during walking, for different robot velocities, based on two formulated performance measures. A set of experiments reveals the influence of the gait and locomotion variables upon the prposed indices, namely that the gait and the locomotion parameters should be adapted to the robot foward velocity.
- Fractional Order Control of a Hexapod RobotPublication . Silva, Manuel; Tenreiro Machado, J. A.; Lopes, A. M.This paper studies the performance of integer and fractional order controllers in a hexapod robot with joints at the legs having viscous friction and flexibility. For that objective the robot prescribed motion is characterized in terms of several locomotion variables. The walking performance is analysed through the Nyquist stability criterion and several indices that reflect the system dynamical properties. A set of model-based experiments reveals the influence of the different controller implementations upon the proposed metrics.
- Fractional Order PDα Joint Control of Legged RobotsPublication . Silva, Manuel; Tenreiro Machado, J. A.This paper studies a fractional order proportional and derivative controller for a hexapod robot, having legs with three DoF and joint actuators with saturation, when walking over ground with varying properties. A simulation model is developed and the robot motion is characterized in terms of several locomotion variables. Two indices measure the walking performance based on the mean absolute density of energy per unit distance travelled and on the hip trajectory errors. A set of experiments reveal the influence of different controller tunings on the proposed indices, for different locomotion conditions.
- New Technologies for Climbing Robots Adhesion to SurfacesPublication . Silva, Manuel F.; Tenreiro Machado, J. A.The interest in the development of climbing robots is growing steadily. The main motivations are to increase the operation e ciency, by eliminating the costly assembly of sca olding, or to protect human health and safety in hazardous tasks. Climbing robots have already been developed for applications ranging from cleaning to inspection of constructions di cult to reach. These robots should be capable of travelling over di erent types of surfaces, with di erent inclinations, such as oors, walls, ceilings, and to walk between such surfaces. Furthermore, they should be able of adapting and recon guring for di erent environment conditions and to be self-contained. Regarding the adhesion to the surface, the robots should be able to produce a secure gripping force using a light-weight mechanism. This paper presents a survey of di erent technologies proposed and adopted for climbing robots adhesion to surfaces, focusing on the new technologies that are recently being developed to ful ll these objectives.
- Energy analysis of Multi-legged Locomotion SystemsPublication . Silva, Manuel F.; Machado, J. A. TenreiroThis paper presents the energy analysis of periodic gaits for multi-legged locomotion systems. The main purpose is to determine the system performance during walking and the best set of locomotion variables that minimizes a cost function related to energy. For that objective, the prescribed motion of the robot is completely characterized in terms of several locomotion variables such as gait, duty factor, body height, step lengh, stroke pitch, maximum foot clearance, link lengths, body and legs mass and cycle time. In this work, we formulate three indices to quanitatively measure the performance of the walking robot namely the mean absolute power, the mean power dispersion and the mean power lost in the joint actuators. A set of experiments reveals the influence of the locomotion variables in the proposed indices.