A Novel Lightweight Wearable Soft Exosuit for Reducing the Metabolic Rate and Muscle Fatigue

Wearable robotic devices have been proved to considerably reduce the energy expenditure of human walking. It is not only suitable for healthy people, but also for some patients who require rehabilitation exercises. However, in many cases, the weight of soft exosuits are relatively large, which makes it difficult for the assistant effect of the system to offset the metabolic consumption caused by the extra weight, and the heavy weight will make people uncomfortable. Therefore, reducing the weight of the whole system as much as possible and keeping the soft exosuit output power unchanged, may improve the comfort of users and further reduce the metabolic consumption. In this paper, we show that a novel lightweight soft exosuit which is currently the lightest among all known powered exoskeletons, which assists hip flexion. Indicated from the result of experiment, the novel lightweight soft exosuit reduces the metabolic consumption rate of wearers when walking on the treadmill at 5 km per hour by 11.52% compared with locomotion without the exosuit. Additionally, it can reduce more metabolic consumption than the hip extension assisted (HEA) and hip flexion assisted (HFA) soft exosuit which our team designed previously, which has a large weight. The muscle fatigue experiments show that using the lightweight soft exosuit can also reduce muscle fatigue by about 10.7%, 40.5% and 5.9% for rectus femoris, vastus lateralis and gastrocnemius respectively compared with locomotion without the exosuit. It is demonstrated that decreasing the weight of soft exosuit while maintaining the output almost unchanged can further reduce metabolic consumption and muscle fatigue, and appropriately improve the users’ comfort.

IMU-based Optimization Control of a Soft Exosuit for Hip Extension and Flexion Assistance

The optimization of the assistive force for soft exosuits is crucial to the improvement of their assistive efficiency. In this paper, an inertial measurement unit (IMU)-based optimization controller was proposed to provide effective hip extension and flexion assistance for soft hip-assistive exosuits during outdoor walking. Initially, the optimal parameters of the assistive profiles defined by two functions were determined based on an analysis of biological hip power. Secondly, the assistive profiles were optimized in real time based on the detected information of hip angles from two IMUs bound to both thighs. Specifically, the peak and offset timings of the assistive profiles were estimated from the previous gait cycle, while the start and stop timings were estimated using current gait information. Lastly, the experiments including four subjects were scheduled to evaluate the performance of proposed controller. Each subject carried a 15kg load to walk on a treadmill at a constant speed, and two of them completed the outdoor walking tests at a self-determined pace while carried a 15kg load. The results show that the assistive profiles can be reliably and orderly delivered across the subjects. In particular, during outdoor self-paced walking, the wearer's natural gait can be maintained by optimizing the assistive profiles. During walking on a treadmill at a constant speed of 1.53 m/s, metabolic rate wearing the soft exosuit with assistance turned on was reduced by 8.53 ± 2.65% (average ± SEM), compared with wearing the soft exosuit with assistance turned off.

A soft exosuit for hip extension assistance of the elderly

BACKGROUND: Population aging is now a universal trend. Many elderly persons can only conduct limited and short time walking because of age-related skeletal muscle decline of the lower limbs. The wearable device for walking assistance is beneficial to improve the life quality of the elderly. OBJECTIVE: This study aimed to propose a soft exosuit for walking assistance of the elderly and verify its feasibility. METHODS: The wearable structure and control strategy were presented. The performance of the soft exosuit was tested by force tracking evaluation and metabolic cost test. RESULTS: The mean error of the measured and target peak force was 1.1%. The metabolic cost with assistance on while wearing the exosuit was reduced by 9.2% compared with that in locomotion assistance off. The reduction of assistance on was 7.1% compared with no exosuit. CONCLUSIONS: The proposed soft exosuit has the potential to improve the walking efficiency of the elderly.