This paper presents a portable stand-alone pneumatic knee exoskeleton that operates in both passive and active modes. The system can store and recover energy by means of compressed air in passive mode, leading to energy savings. In active mode, a small air pump inflates the pneumatic artificial muscle (PAM), which stores the compressed air, that can be then released into a pneumatic cylinder to generate torque. All electronic and pneumatic components are integrated into the system, and the exoskeleton weighs only 3.9 kg with a maximum torque of 20 Nm in the knee joint. Further, the system is modular, allowing wearability on one or both legs. The paper describes the mechatronic design, mathematical model and includes a validation study with an able-bodied subject performing sit-to-stand and squat-hold exercises. The results show that the exoskeleton can harvest energy while assisting the subject and reduce muscle activity, without compromising transparency. These results suggest that the presented exoskeleton could be a useful low-energy consumption device for individuals with low to moderate lower limb mobility impairments and improve endurance in both clinical and industrial settings.

翻译：本文介绍了一种可在被动和主动模式下运行的便携式独立气动膝关节外骨骼。在被动模式下，系统通过压缩空气储存和回收能量，从而实现节能。在主动模式下，小型气泵为储存压缩空气的气动人工肌肉（PAM）充气，随后压缩空气可被释放至气动气缸以产生扭矩。所有电子和气动组件均集成于系统内，外骨骼仅重3.9千克，膝关节可提供最大20牛米的扭矩。此外，系统采用模块化设计，可单腿或双腿穿戴。本文阐述了机电设计、数学模型，并开展了一项由健康受试者执行坐-站和深蹲保持动作的验证研究。结果表明，该外骨骼在辅助受试者的同时可进行能量收集，并能减少肌肉活动，且不影响透明度。这些结果提示，所提出的外骨骼可作为一种低能耗设备，适用于轻中度下肢运动障碍患者，并能在临床和工业环境中提升耐力。