João Maurício Rosário

Multi-objective optimization of Stewart-Gough manipulator using global indices

The paper addresses the optimal design of parallel manipulators based on multi-objective optimization. The objective functions used are: Global Conditioning Index (GCI), Global Payload Index (GPI), and Global Gradient Index (GGI). These indices are evaluated over a required workspace which is contained in the complete workspace of the parallel manipulator. The objective functions are optimized simultaneously to improve dexterity over a required workspace, since single optimization of an objective function may not ensure an acceptable design. A Multi-Objective Evolution Algorithm (MOEA) based on the Control Elitist Non-dominated Sorting Genetic Algorithm (CENSGA) is used to find the Pareto front.

Robust generalized predictive control of the Orthoglide robot

The purpose of this paper is to address the synthesis and experimental application of a generalized predictive control (GPC) technique on an Orthoglide robot.Design/methodology/approach– The control strategy is composed of two control loops. The inner loop aims at linearizing the nonlinear robot dynamics using feedback linearization. The outer loop tracks the desired trajectory based on GPC strategy, which is robustified against measurement noise and neglected dynamics using Youla parameterization.Findings– The experimental results show the benefits of the robustified predictive control strategy on the dynamical performance of the Orthoglide robot in terms of tracking accuracy, disturbance rejection, attenuation of noise acting on the control signal and parameter variation without increasing the computational complexity.Originality/value– The paper shows the implementation of the robustified predictive control strategy in real time with low computational complexity on the Orthoglide robot.

Robot axis dynamics control using a virtual robotics environment

Robots are complex electromechanical systems where several electric drives are employed to control the movement of articulated structures. In industrial environments they must perform tasks with rapidity and accuracy in order to produce goods and services with minimal production time. These procedures require the use of flexible robots which can act in a large workspace, thus subject to important parameters variations, with efficient control algorithms. The progress of technology and the close relationships among several sciences, such as micro-electronic, software engineering and communications, open space for a great development in the robotics area and automation process. Generalized predictive control (GPC) has shown to be an effective strategy in many fields of applications, with good time-domain and frequency properties (small overshoot, improved tracking accuracy and disturbance rejection ability, good stability and robustness margins), able to cope with important parameters variations. This paper presents an application of GPC to a robot trajectory control with a comparison between classical PID and GPC controllers within an original virtual environment

Robust generalized predictive control of Stewart-Gough platform

This paper addresses the position tracking control application of a Stewart-Gough platform using robust generalized predictive control. The robustification of GPC against measurement noise using Youla parameterization is performed. The simulation of the complete model of the Stewart-Gough platform is performed on a circular trajectory. The robustified GPC controller is compared with the classical Computed Torque Control (CTC). The robustified GPC controller shows a better performance reducing the effect of the noise in the control signal of the Stewart-Gough Platform.

Condition-based diagnosis of mechatronic systems using a fractional calculus approach

While fractional calculus (FC) is as old as integer calculus, its application has been mainly restricted to mathematics. However, many real systems are better described using FC equations than with integer models. FC is a suitable tool for describing systems characterised by their fractal nature, long-term memory and chaotic behaviour. It is a promising methodology for failure analysis and modelling, since the behaviour of a failing system depends on factors that increase the model’s complexity. This paper explores the proficiency of FC in modelling complex behaviour by tuning only a few parameters. This work proposes a novel two-step strategy for diagnosis, first modelling common failure conditions and, second, by comparing these models with real machine signals and using the difference to feed a computational classifier. Our proposal is validated using an electrical motor coupled with a mechanical gear reducer.

APPLICATION OF PREDICTIVE CONTROL TECHNIQUES WITHIN PARALLEL ROBOT

This paper addresses the position tracking control application of a parallel robot using predictive control techniques. A Generalized Predictive Control strategy (GPC), which considers the linear dynamic model, is used to enhance the tracking position accuracy. The robustification of GPC against measurement noise and neglected dynamics using Youla parameterization is performed. A simulation of the orthoglide robot considering uncertainties related to geometrical and dynamic parameters, sensors noise and frictions is performed on two different trajectories. Finally, it is compared the ro-bustified GPC controller with the classical Computed Torque Control (CTC). The robustified GPC controller shows a better performance for high accelerations and it also reduces the effect of the noise in the control signal of the parallel robot.

Conceptual Bases of Robot Navigation Modeling, Control and Applications

The advancements of the research on Mobile Robots with high degree of autonomy is possible, on one hand, due to its broad perspective of applications and, on other hand, due to the development and reduction of costs on computer, electronic and mechanic systems. Together with the research in Artificial Intelligence and Cognitive Science, this scenario currently enables the proposition of ambitious and complex robotic projects. Most of the applications were developed outside the structured environment of industry assembly lines and have complex goals, such as planets exploration, transportation of parts in factories, manufacturing, cleaning and monitoring of households, handling of radioactive materials in nuclear power plants, inspection of volcanoes, and many other activities. This chapter presents and discusses the main topics involved on the design or adoption of a mobile robot system and focus on the control and navigation systems for autonomous mobile robots. Thus, this chapter is organized as follows: • The Section 2 introduces the main aspects of the Robot design, such as: the conceptualization of the mobile robot physical structure and its relation to the world; the state of art of navigation methods and systems; and the control architectures which enables high degree of autonomy. • The Section 3 presents the dynamic and control analysis for navigation robots with kinematic and dynamic model of the differential and omnidirectional robots. • And finally, Section 4 presents applications for a robotic platform of Automation, Simulation, Control and Supervision of Navegation Robots, with studies of dynamic and kinematic modeling, control algorithms, mechanisms for mapping and localization, trajectory planning and the platform simulator.

Scientific Collaboration and Knowledge Sharing in the Virtual Manufacturing Network

Abstract Most of past research efforts on Collaborative Work Support adopt tool-centric approaches to define cooperation. These approaches are often related to a single category of communication (synchronous or asynchronous) and support only a single type of collaboration (planned or open). In this paper, vc describe our view for successful collaboration in Virtual Manet. Our aim is to extend the classical asynchronous computer-supported scientific collaboration by introducing and integrating collaborative work support tools with knowledge management approaches. We are starting by effective requirements analysis, and we will continue by identifying the associated collaboration technologies, and finally defining the Cooperative e-Space integration architecture. The idea can be generalized to encompass the manufacturing business or the collaborative production in virtual enterprises.

Proposal of educational environments with mobile robots

This paper describes an initiative which uses low-cost mobile robots to create robotics courses and learning environment to support the teaching of computing and many other related disciplines. The pursued principle is that lower cost alternatives that can meet the educational needs, since it is accompanied by an environment with friendly software interface. In this sense, the hardware interface was developed to allow the computer to process data from the sensors and actuators of the mobile robot. This architecture is adequate because of the acceptance of students in their use, since the environment is unrolled within a familiar platform to them.

ANALYSIS OF FRACTIONAL - ORDER ROBOT AXIS DYNAMICS

Abstract Robots are complex mechatronics systems where several electric drives are employed to control the movement of articulated structures. In industrial environments they must perform tasks with rapidity and accuracy in order to produce goods and services with minimal production time. These procedures require the use of flexible robots which can act in a large workspace, thus subjected to important parameters variations and nonlinear dynamics effects. This paper investigates the fractional order dynamics during the evolution of trajectories of three robotic joints, considering the complete system dynamics.