Engenharia Mecânica
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/23
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3 resultados
Resultados da Pesquisa
- Performance of Impedance Control-Based Strategies in Power-Assisted Wheelchairs: A Predictive Simulation Study(2022-03-05) CUERVA, V. I.; Marko Ackermann; Fabrizio LeonardiCopyright © 2022 Cuerva, Ackermann and Leonardi.Manual wheelchair propulsion is known to be inefficient and causes upper extremity pain, fatigue, and injury. Power-assisted wheelchairs can mitigate these effects through motors that reduce users' effort and load during propulsion. Among the different control strategies proposed to govern the user-wheelchair interaction, impedance control-based ones appear to be the most natural and effective. It can change the apparent dynamical properties of the wheelchair, particularly mass and friction, and automatically compensate for external disturbances such as terrain conditions. This study investigates the advantages and disadvantages of this control strategy employing predictive simulations of locomotion with power-assisted wheelchairs in different scenarios. The simulations are generated using a biomechanically realistic model of the upper extremities and their interaction with the power-assisted wheelchair by solving an optimal control problem. Investigated scenarios include steady-state locomotion vs. a transient maneuver starting from rest, movement on a ramp vs. a level surface, and different choices of reference model parameters. The results reveal that the investigated impedance control-based strategy can effectively reproduce the reference model and reduce the user's effort, with a more significant effect of inertia in the transient maneuver and of friction in steady-state locomotion. However, the simulations also show that imposing a first-order, linear reference model with constant parameters can produce disadvantageous locomotion patterns, particularly in the recovery phase, leading to unnecessary energy dissipation and consequent increase in energy consumption from the batteries. These observations indicate there is room for improvement, for instance, by exploring energy regeneration in the recovery phase or by switching reference model nature or parameters along the cycle. To the best of our knowledge, this is the first investigation of impedance control-based strategies for power-assisted wheelchairs using predictive simulations and a realistic, nonlinear model of the user-wheelchair system.
- 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 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.