Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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6 resultados
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.- 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.
- 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.