Design of a Human Lower Limbs Exoskeleton for Biomechanical Energy Harvesting and Assist Walking

Harvesting human energy currently occurs to power wearable devices or monitor human signs, these applications make the energy harvester less applicable to and seldom used for assisting human motion. However, there is a high demand for using such collected energy with the assistance of human motion. This paper presents a novel energy harvester that is designed to collect negative work, assist human motion, and realize self-powering. An active self-powered human motion assist system (HMAS) is developed. The system consists of a human motion assist device (HMAD), a flexible rack, an electronic circuit module, and a supercapacitor. The HMAS can collect negative work from the human body, provide the user with additional motion assistance, and reduce stamina consumption. A series of experiments verify that HMAS has a high negative work collection power and a high energy conversion efficiency. The average output power is 0.93 W measured by the negative work collection test bed at a simulated knee bend angle of 40° and a frequency of 2 Hz. The energy conversion efficiency is up to 48.2%. Human motion assistance experiments verify that HMAS can provide volunteers with up to 2.57% assisting moment and minimize the metabolic cost of volunteers by 6.07% compared to without wearing HMAS. This research work is proposed to contribute to the development of active self-powered exoskeleton technology. This technology can be practically applied in the fields of rehabilitation therapy, logistics transportation, and military combat.

Section: Modeling and Analysismentioning

confidence: 99%

Active self-powered human motion assist system

Ren,

Zhou,

Zhang

et al. 2024

“…As many researchers have delved into the field of human movement energy harvesting [9,10], an increasing number of energy harvesters that can be worn on the human body are being developed [11,12]. These energy harvesters convert the bioenergy collected from human movement into electricity [13], replacing or extending the life of traditional batteries that are used to power a wide range of wearable devices [14][15][16][17].…”

Section: Literature Reviewmentioning

confidence: 99%

Collecting the energy generated by manual workers to monitor their working status and improve their working conditions by using a flexible rack mechanism

Ren,

Zhou,

et al. 2023

Currently, an increasing quantity of portable energy harvesting modules are being developed to capture the energy generated by human motion. However, the size and weight of a device can affect the smoothness and comfort of a user's normal limb movements in the process of collecting energy generated by human movement. Especially on manual workers, this effect will significantly increase their physical exertion, so the design of energy-harvesting devices for wearing on manual workers has higher requirements. The bend knee energy harvester(BKEH) designed in the work presented in this paper used a laboratory-made flexible rack to harvest the energy generated by manual workers' frequently bent knees during work. It converts the collected energy into electricity for various wearable devices to monitor the working status of manual workers and improve their working conditions. One end of the flexible rack is fixed to the upper thigh. When the user bends the knee, the flexible rack will move downward, causing the gear to rotate, thereby collecting the energy generated by the body's movement.The BKEH was made of many lightweight materials and weighed only 406 g, greatly reducing the impact on the user's normal limb movements and physical exertion. Practical experiments showed that the BKEH output open-circuit voltage is up to 80.3 V, the output power reached as high as 3.16 W, and the power density reached as high as 7.9 W/kg, which can effectively supply sufficient electrical power for wearable devices to work normally. The BKEH has a high practical value and good adaptability to human movement posture and can generate enough voltage and power to allow some wearable devices to work properly. These wearable devices can effectively provide users with the ability to monitor their work status and improve working conditions.

“…During a normal gait cycle, the beginning of a gait cycle is generally recorded as 0% when the heel contacts the ground, and 60% corresponds to the toe off [37,38]. In addition, 100% generally corresponds to the completion of a gait cycle when the same heel contacts the ground again.…”

Section: Operations Of Knee-ankle Exoskeletonmentioning

confidence: 99%

Design and implementation of knee-ankle exoskeleton for energy harvesting and walking assistance

Chen

Zheng²,

Zi³

et al. 2022

The increasing requirement of powering portable electronic devices can be potentially met by recycling the biomechanical energy generated during the human joint motion through a knee-ankle exoskeleton. In this paper, a knee-ankle exoskeleton is designed to recycle the negative work from the wearer’s knee extension and ankle dorsiflexion. The exoskeleton can convert the mechanical energy into electrical energy for energy harvesting and assist the knee flexion and ankle plantarflexion to reduce the wearer’s metabolic cost during walking. It is mainly composed of two torsion springs, two one-way transmission mechanisms, a gear train, and a generator. The torsion springs can store the elastic energy when the wearer’s ankle and knee joints do negative work and release it to assist walking when positive work is required. The one-way transmission mechanisms are employed to filter the knee flexion and ankle plantarflexion and to convert the knee extension and ankle dorsiflexion into the one-way rotation of the generator by symmetrically arranging the gear train. Finally, experiments are conducted to evaluate the performance of the developed knee-ankle exoskeleton. The experimental results indicate that the exoskeleton can generate an average electrical power of 0.49 W and a maximum instantaneous electrical power of 1.8 W at a walking speed of 5.5 km/h during a gait cycle, and reductions of 3.48% ± 0.33%, 9.50% ± 0.29%, and 4.54% ± 0.47% of the average muscle activities of the semitendinosus, soleus, and gastrocnemius during a gait cycle are observed, respectively.