无源下肢助力机器人的结构设计和助力效果分析

Structural design and assistance effect analysis of passive lower limb assistive robot

摘要:

为解决现有无源下肢助力机器人存在的辅助效果欠佳、自重较大,以及人机相容性不足等问题,提出了一种具备更优助力效果、更小自重和更佳人机相容性的无源下肢助力机器人。首先,通过对人体下肢开展逆运动学分析,结合Lagrange方程构建人体下肢动力学模型,为机器人设计提供生物力学依据。其次,结合下肢生物运动特性完成机械结构设计,其中髋关节采用三自由度结构以提升人机相容性,腿部采用镂空设计以减轻自重。然后,在OpenSim中建立人机融合模型进行仿真试验,验证无源下肢助力机器人的助力效果。结果显示:与未穿戴助力机器人相比,穿戴后髋关节、膝关节和踝关节力矩的平均值分别降低19.64%、24.85%和15.39%；人体的总代谢平均值降低16.35%,显著降低了穿戴者的能量消耗,有效减轻了穿戴者的肌肉负担。最后,研制无源下肢助力机器人样机并进行了样机实验。结果表明:与未穿戴助力机器人相比,穿戴后下肢主要肌肉的肌电信号降低率的均方根在5.73%～13.79%之间,实验结果证实了所设计的无源下肢助力机器人在轻量化、高协同性和多场景适应性方面的优势,为下一步样机的优化奠定了基础。

Abstract:

To address the issues of poor assistance effect, heavy weight, and insufficient human-machine compatibility in existing passive lower limb assistive robots, this paper proposed a passive lower limb assistive robot with better assistance effect, lighter weight, and improved human-machine compatibility. Firstly, this paper conducted inverse kinematics analysis of the human lower limbs and constructed a dynamic model of the human lower limbs using the Lagrange equation to provide a biomechanical basis for the robot design. Secondly, the paper designed the mechanical structure by combining the biological movement characteristics of the lower limbs. Specifically, the hip joint adopted a three-degree-of-freedom structure to enhance human-machine compatibility, and the leg structure employed a hollow design to reduce the self-weight. Then, the paper established a human-machine fusion model in OpenSim for simulation experiments to verify the assistance effect of the passive lower limb assistive robot. The results show that compared with those in the unassisted state, the average torques of the hip, knee, and ankle joints after wearing the robot decrease by 19.64%, 24.85%, and 15.39%, respectively; the average total metabolism of the human body decreases by 16.35%. This significantly reduces the energy consumption of the wearer and effectively alleviates muscle burden. Finally, the paper develops a prototype of the passive lower limb assistive robot and conducts prototype experiments. The experimental results indicate that compared with that in the unassisted state, the root mean square of the reduction rate of electromyographic (EMG) signals of the main lower limb muscles ranges from 5.73% to 13.79% after wearing the robot. The experimental results confirm the advantages of the designed passive lower limb assistive robot in terms of light weight, high compatibility, and multi-scenario adaptability, laying the foundation for future optimization of the prototype.