Engenharia Mecânica

URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23

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Agora exibindo 1 - 10 de 12

Incremental root locus and pid tuning
(2006-10-04) GOMES, S. C. P.; Fabrizio Leonardi; DA CRUZ, J. J.
This work discusses the Incremental Root Locus property and one application of it to PID controllers tuning. It is shown that using that property it is easy do determine the departure angle from the real axis, which is a not a trivial task using the classical root locus rules. As an application, a procedure for tuning PID controllers in two steps is shown. Firstly it is necessary to perform a step response test using a proportional controller in order to stabilize the system. In a second step the PID design is performed by a zero-pole canceling. The controller obtained is a two-degree-of-freedom PID controller. Simulations carried out indicate that the controller associated with the setpoint tracking exhibits an almost first-order response whereas the one associated with the disturbance rejection exhibits a more oscillatory response. As illustrations, a real application for a position servo control system and some design projects tested by simulation were done.
Integrated manufacturing laboratory and software tools applied to an industrial engineering undergraduate course
(2009-03-23) Fabio Lima; PRADO, A. C.; Alexandre Augusto Massote; Fabrizio Leonardi
This paper describes the experience of using software tools associated with an integrated manufacturing laboratory in an industrial engineering undergraduate course at FEI (Fundacao Educacional Inaciana, Brazil). The integrated manufacturing laboratory has got three complete manufacturing cells integrated by computer. The aim of the laboratory is to provide to the industrial engineering student a powerful analysis capability of how to use these kinds of systems to improve product quality and production performance. To do that, computational models are implemented using software tools like Visual Object Net++, Promodel® and WEB support. Finally, the models are validated in laboratory experiments. It was observed that such strategy has been given excellent learning results.
Using linear programming for the optimal control of a cartpendulum system
(2011-01-05) PUGLIA, L. V.; Fabrizio Leonardi; Marko Ackermann
This paper discusses the use of linear programming for the optimal control of a cart pendulum system. The objective function and the constraints are designed to minimize the control effort and the time duration of the operation. Simulations and experimental tests were performed. Restrictions of null angle and angular velocity at the extremes were incorporated in the design specification as well as other physical constraints. In order to compensate for the modeling errors and disturbances, the optimal trajectory was kept within a prescribed precision by means of a closed loop system. The obtained results illustrate that the technique is simple, powerful and always conclusive.
Using linear programming for the optimal control of a cartpendulum system
(2011) PUGLIA, L. V.; Fabrizio Leonardi; Marko Ackermann
This paper discusses the use of linear programming for the optimal control of a cart pendulum system. The objective function and the constraints are designed to minimize the control effort and the time duration of the operation. Simulations and experimental tests were performed. Restrictions of null angle and angular velocity at the extremes were incorporated in the design specification as well as other physical constraints. In order to compensate for the modeling errors and disturbances, the optimal trajectory was kept within a prescribed precision by means of a closed loop system. The obtained results illustrate that the technique is simple, powerful and always conclusive.
Automation course for industrial engineers: An approach based on Petri Nets, software tools and laboratory experiments
(2014-01-05) Fabio Lima; PRADO, A. C.; Alexandre Augusto Massote; Fabrizio Leonardi
© 2014 TEMPUS Publications.This paper proposes a methodology for teaching industrial automation to Brazilian industrial engineering undergraduate students, based on analysing a computational solution associated with an integrated manufacturing laboratory. As a first approach an analytical analysis of the automated process is carried out. Then the manufacturing laboratory is combined with software tools, to provide the industrial engineering student with a powerful analysis for using these kinds of systems to improve product quality and production performance. For the computational analysis, we have inserted Petri Nets to evaluate the production system performance with a good acceptance from the students. This is the highlight of this work since using Petri Nets for Industrial Engineering undergraduate students is not a common approach. Finally, an assessment proved that such a strategy has been producing excellent learning results.
Design of a hydraulic turbine control system by numerical optimization
(2015-09-21) CANONICO, R.; Renato Aguiar; Fabrizio Leonardi
© 2015 Dime universita di genova, dimeg university of calabria. All rights reserved.This work proposes the use of numerical optimization based on Direct Transcription as a method for the design of the control system for hydroelectric turbines. The control design for this application involves constraints but the usual control techniques do not allow explicitly to incorporate constraints in its formulation or are very sensitive to initial estimates of the optimization problem implying in convergence issues. The Direct Transcription is an alternative optimization-based design where the dynamics are discretized and included as constraints of the optimization problem causing the errors due to the quality of the initial estimate to be diluted over the discretization nodes. The constraints considered are related to the actuator and other operating limits during a change maneuver of operating point.
Modeling and optimal control formulation for manual wheelchair locomotion: The influence of mass and slope on performance
(2014-08-15) Marko Ackermann; Fabrizio Leonardi; COSTA, H. R.; FLEURY, A. T.
A framework to generate predictive simulations is proposed to investigate the influence of system's mass on manual wheelchair locomotion. The approach is based on a model of wheelchair propulsion dynamics and an optimal control formulation. In this study, predictive simulations of steady-state wheelchair locomotion are generated for different combinations of model mass and uphill slope inclination angle. The results show that the influence of system's mass is negligible in level surfaces in steady-state, a finding which agrees with experimental observations in the literature. On the other hand, the results show that the influence of mass on slopes is critical, with large increases in propulsion effort with system's mass, even for slight inclination angles. This shows the importance of reducing wheelchair mass for improving locomotion performance, particularly in overcoming obstacles and ramps. Decreasing the wheelchair's mass may not be sufficient. Therefore, and on the light of these findings, we propose the reduction of system's apparent mass through the implementation of an impedance control scheme in powerassisted wheelchairs.
A modeling framework to investigate the radial component of the pushrim force in manual wheelchair propulsion
(2015-11-25) Marko Ackermann; COSTA, H. R.; Fabrizio Leonardi
© Owned by the authors, published by EDP Sciences, 2015.The ratio of tangential to total pushrim force, the so-called Fraction Effective Force (FEF), has been used to evaluate wheelchair propulsion efficiency based on the fact that only the tangential component of the force on the pushrim contributes to actual wheelchair propulsion. Experimental studies, however, consistently show low FEF values and recent experimental as well as modelling investigations have conclusively shown that a more tangential pushrim force direction can lead to a decrease and not increase in propulsion efficiency. This study aims at quantifying the contributions of active, inertial and gravitational forces to the normal pushrim component. In order to achieve this goal, an inverse dynamics-based framework is proposed to estimate individual contributions to the pushrim forces using a model of the wheelchair-user system. The results show that the radial pushrim force component arise to a great extent due to purely mechanical effects, including inertial and gravitational forces. These results corroborate previous findings according to which radial pushrim force components are not necessarily a result of inefficient propulsion strategies or hand-rim friction requirements. This study proposes a novel framework to quantify the individual contributions of active, inertial and gravitational forces to pushrim forces during wheelchair propulsion.
A comparison of different assistance strategies in power assisted wheelchairs using an optimal control formulation
(2016-08-18) CUERVA, V. I.; Marko Ackermann; Fabrizio Leonardi
Power assisted wheelchairs are a promising solution to overcome problems associated with manual wheelchair propulsion, such as the incidence of upper limbs injuries and muscle fatigue. However, there are still open questions regarding the most appropriate assistance strategy. The main goal of this paper is to compare three different types of assistance in power assisted wheelchairs: constant force, proportional force and a novel type of assistance inspired on the impedance control theory. The comparison was performed using a simple model and an optimal control formulation that searched for optimal user actuation and controller parameters so as to minimize the user effort. The fairness of the comparison was ensured by imposing an upper bound on the energy consumption by the motors. The results show that the proportional and impedance controlbased strategies are the most appropriate steady state conditions. In typical daily activities such as obstacle avoidance, the impedance control has advantage as it permits a faster system's response.
Optimal control of the wheelchair wheelie
(2016-08-18) DOS SANTOS, E. G.; Fabrizio Leonardi; Marko Ackermann
The wheelchair wheelie is a maneuver employed to overcome obstacles and descend ramps, for instance. The task is similar to the stabilization problem of an inverted pendulum that is extensively described in the control theory literature. However, in this case, the goal is to maintain the user and the wheelchair in equilibrium on wheels, which is achieved when the center of mass of the system is aligned with the rear axle in the vertical direction. This work investigates a controller to perform the wheelie in power-assisted wheelchairs using optimal control theory and a model of the user and wheelchair system. The proposed approach leads to a controller capable of rising the wheelchair, which is able to reject perturbations and which is robust to typical parameter uncertainties.

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