Zhang Longbin, Liu Yixing, Wang Ruoli, Smith Christian, Gutierrez-Farewik Elena M
KTH MoveAbility Lab, Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm, Sweden.
KTH BioMEx Center, KTH Royal Institute of Technology, Stockholm, Sweden.
Front Neurorobot. 2021 Mar 8;15:620928. doi: 10.3389/fnbot.2021.620928. eCollection 2021.
Exoskeletons are increasingly used in rehabilitation and daily life in patients with motor disorders after neurological injuries. In this paper, a realistic human knee exoskeleton model based on a physical system was generated, a human-machine system was created in a musculoskeletal modeling software, and human-machine interactions based on different assistive strategies were simulated. The developed human-machine system makes it possible to compute torques, muscle impulse, contact forces, and interactive forces involved in simulated movements. Assistive strategies modeled as a rotational actuator, a simple pendulum model, and a damped pendulum model were applied to the knee exoskeleton during simulated normal and fast gait. We found that the rotational actuator-based assistive controller could reduce the user's required physiological knee extensor torque and muscle impulse by a small amount, which suggests that joint rotational direction should be considered when developing an assistive strategy. Compared to the simple pendulum model, the damped pendulum model based controller made little difference during swing, but further decreased the user's required knee flexor torque during late stance. The trade-off that we identified between interaction forces and physiological torque, of which muscle impulse is the main contributor, should be considered when designing controllers for a physical exoskeleton system. Detailed information at joint and muscle levels provided in this human-machine system can contribute to the controller design optimization of assistive exoskeletons for rehabilitation and movement assistance.
外骨骼越来越多地应用于神经损伤后运动障碍患者的康复和日常生活中。本文生成了一个基于物理系统的逼真的人体膝关节外骨骼模型，在肌肉骨骼建模软件中创建了人机系统，并模拟了基于不同辅助策略的人机交互。所开发的人机系统能够计算模拟运动中涉及的扭矩、肌肉冲动、接触力和相互作用力。在模拟正常和快速步态期间，将建模为旋转执行器、简单摆模型和阻尼摆模型的辅助策略应用于膝关节外骨骼。我们发现，基于旋转执行器的辅助控制器可以少量降低用户所需的生理膝关节伸肌扭矩和肌肉冲动，这表明在制定辅助策略时应考虑关节旋转方向。与简单摆模型相比，基于阻尼摆模型的控制器在摆动期间影响不大，但在站立后期进一步降低了用户所需的膝关节屈肌扭矩。在设计物理外骨骼系统的控制器时，应考虑我们所确定的相互作用力与生理扭矩之间的权衡，其中肌肉冲动是主要因素。该人机系统提供的关节和肌肉水平的详细信息有助于辅助外骨骼康复和运动辅助控制器设计的优化。
