Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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Resultados da Pesquisa
Artigo 2 Citação(ões) na Scopus Using linear programming for the optimal control of a cartpendulum system(2011-01-05) PUGLIA, L. V.; Fabrizio Leonardi; Marko AckermannThis 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.Artigo de evento 0 Citação(ões) na Scopus Using linear programming for the optimal control of a cartpendulum system(2011) PUGLIA, L. V.; Fabrizio Leonardi; Marko AckermannThis 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.Artigo 0 Citação(ões) na Scopus Reducing vibrations on flexible rotating arms through the movement of sliding masses: Modeling, optimal control and simulation(2012-01-05) TERCEIRO, E.; FLEURY, A. T.This paper brings contributions on the proposal of use of translational motions of sliding masses to minimize vibrations induced by the rotational motion of a light flexible manipulator (rotating arm). This system is inspired by rotating cranes used to transport loads. Optimal control methods have been used to generate the slider trajectories while the flexible manipulator performs a rotational maneuver from a fixed to other fixed configuration. This approach has led to good solutions even in case of quite quick maneuvers, as, for example, a 90° beam rotation in just 1 second, using 1 or 2 sliders (Terceiro, 2002). In the present paper, the complete motion equations for any number of masses are firstly presented, in order to emphasize the complexity of the coupled elastic-rotational-translational motions. Simplifying assumptions are pointed out and the corresponding optimal control problems (OCP) are obtained. Optimal trajectories, generated according to different Indexes of Performance and different problem parameters, are analysed and compared in order to get feasible movements for the set.Artigo de evento 0 Citação(ões) na Scopus Reducing vibrations on flexible rotating arms through the movement of sliding masses: Modeling, optimal control and simulation(2012-09-19) TERCEIRO, E.; FLEURY, A. DE. T.This paper brings contributions on the proposal of use of translational motions of sliding masses to minimize vibrations induced by the rotational motion of a light flexible manipulator (rotating arm). This system is inspired by rotating cranes used to transport loads. Optimal control methods have been used to generate the slider trajectories while the flexible manipulator performs a rotational maneuver from a fixed to other fixed configuration. This approach has led to good solutions even in case of quite quick maneuvers, as, for example, a 90o beam rotation in just 1 second, using 1 or 2 sliders (Terceiro, 2002). In the present paper, the complete motion equations for any number of masses are firstly presented, in order to emphasize the complexity of the coupled elastic-rotational-translational motions. Simplifying assumptions are pointed out and the corresponding optimal control problems (OCP) are obtained. Optimal trajectories, generated according to different Indexes of Performance and different problem parameters, are analysed and compared in order to get feasible movements for the set.- A comparison of different assistance strategies in power assisted wheelchairs using an optimal control formulation(2016-08-18) CUERVA, V. I.; Marko Ackermann; Fabrizio LeonardiPower 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 AckermannThe 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.
- An optimal control framework to predict gait patterns resulting from changes in musculoskeletal properties(2016-08-18) SANTOS, G. F.; GOMES, A. A.; SACCO, I. C. N.; Marco AckermannA musculoskeletal model allows the analysis of the human gait and may aid the investigation of different strategies employed by the human body to perform this important task. This study presents a planar multibody model of the musculoskeletal system and an optimal control approach to obtain the time history of motion and muscle activation during the gait. Passive joint moments and muscle properties of the model are modified to represent potential changes caused by different diseases, such as diabetic neuropathy. The system adaptation is predicted on the basis of an optimal control framework and the results show many global adaptations as a response to local changes in the properties of the musculoskeletal system and evidences the great potential of this framework to predict patient adaptations to disease, assistive devices or surgical interventions.
- EFFECTS OF A CLOSED-LOOP PARTIAL POWER ASSISTANCE ON MANUAL WHEELCHAIR LOCOMOTION(2018-12-12) MARTINS, M. A. DE A.; Marko Ackermann; Fabrizio LeonardiIn manual wheelchair locomotion, the large upper extremity loads and the repetitions of the propulsion movement increase the incidence of upper limbs injuries, pain and muscle fatigue. The main goal of this study was to investigate the influence of a closed-loop partial power assistance for manual wheelchairs through predictive simulations of a dynamic four-bar model. The applied control law applied can be seen as an impedance-like control, but it does not require force measurement. The simulation results indicate that this strategy can reduce joint torques without significantly altering the typical kinematic pattern of manual wheelchair locomotion.
- Predictive simulation of gait at low gravity reveals skipping as the preferred locomotion strategy(2012) Marko Ackermann; Van den Bogert A.J.The investigation of gait strategies at low gravity environments gained momentum recently as manned missions to the Moon and to Mars are reconsidered. Although reports by astronauts of the Apollo missions indicate alternative gait strategies might be favored on the Moon, computational simulations and experimental investigations have been almost exclusively limited to the study of either walking or running, the locomotion modes preferred under Earth's gravity. In order to investigate the gait strategies likely to be favored at low gravity a series of predictive, computational simulations of gait are performed using a physiological model of the musculoskeletal system, without assuming any particular type of gait. A computationally efficient optimization strategy is utilized allowing for multiple simulations. The results reveal skipping as more efficient and less fatiguing than walking or running and suggest the existence of a walk-skip rather than a walk-run transition at low gravity. The results are expected to serve as a background to the design of experimental investigations of gait under simulated low gravity. © 2012 Elsevier Ltd.