Cuerva Vinicius Ishimoto, Ackermann Marko, Leonardi Fabrizio
Department of Mechanical Engineering, Centro Universitário FEI, São Bernardo do Campo, Brazil.
Front Neurorobot. 2022 Mar 4;16:805835. doi: 10.3389/fnbot.2022.805835. eCollection 2022.
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.
众所周知，手动轮椅推进效率低下，会导致上肢疼痛、疲劳和受伤。电动助力轮椅可以通过电机减轻这些影响，电机可在推进过程中减轻使用者的用力和负荷。在为控制用户与轮椅的交互而提出的不同控制策略中，基于阻抗控制的策略似乎是最自然、最有效的。它可以改变轮椅的表观动力学特性，特别是质量和摩擦力，并自动补偿外部干扰，如地形条件。本研究通过对电动助力轮椅在不同场景下的运动进行预测模拟，研究了这种控制策略的优缺点。模拟是通过求解一个最优控制问题，使用上肢及其与电动助力轮椅相互作用的生物力学逼真模型生成的。研究的场景包括稳态运动与从静止开始的瞬态机动、在斜坡上与在水平面上的运动，以及参考模型参数的不同选择。结果表明，所研究的基于阻抗控制的策略可以有效地再现参考模型并减少使用者的用力，在瞬态机动中惯性的影响更显著，在稳态运动中摩擦力的影响更显著。然而，模拟还表明，采用具有恒定参数的一阶线性参考模型可能会产生不利的运动模式，特别是在恢复阶段，导致不必要的能量耗散，从而增加电池的能量消耗。这些观察结果表明仍有改进的空间，例如，通过探索恢复阶段的能量再生，或通过在整个周期内切换参考模型的性质或参数。据我们所知，这是首次使用预测模拟和用户-轮椅系统的逼真非线性模型，对电动助力轮椅基于阻抗控制的策略进行研究。
