Objective: Active exoskeletons can handle different walking conditions, but require bulky components (e.g., motors) that need a significant source of power to do so. Purely passive exoskeletons are lightweight and energy-neutral, containing energy-recycling mechanisms that capture energy loss during negative power phases and return it as walking assistance. However, they are usually designed for stereotyped gaits (e.g., walking at fixed speed) and thus show poor adaptivity for variable conditions. This study is aimed to overcome these issues. Methods: A quasi-passive ankle exoskeleton is designed to integrate the merits of both active and passive exoskeletons, which captures the heel-strike energy loss and recycles it into propulsion. A novel, lightweight, energy-saving clutch and a heel-strike energy-storage mechanism are developed. They are coupled by a series spring that assists user's calf muscles. Six healthy subjects walked with the device on level ground and inclined surfaces to validate its functionality. Results: Level ground studies indicate that the energy-storage mechanism enhances the assistance by increasing the output torque of the exoskeleton. Reductions in metabolic cost (6.4 ± 1.3%, p < 0.05) were observed. During uphill walking, the assistance torque decreased compared with that on level ground, but it still reduced overall metabolic cost compared with baseline walking. During downhill walking, the assistance torque increased, but metabolic cost also slightly increased. Conclusion: These results demonstrate the functionality of the prototype on level ground and its limitations on inclined surfaces. Significance: The proposed device highlights the possibility of widening the potential applications of exoskeletons.

The engineering design of robotic grippers presents an ample design space for optimization towards robust grasping. In this paper, we adopt the reconfigurable design of the robotic gripper using a novel soft finger structure with omni-directional adaptation, which generates a large number of possible gripper configurations by rearranging these fingers. Such reconfigurable design with these omni-adaptive fingers enables us to systematically investigate the optimal arrangement of the fingers towards robust grasping. Furthermore, we adopt a learning-based method as the baseline to benchmark the effectiveness of each design configuration. As a result, we found that a 3-finger and 4-finger radial configuration is the most effective one achieving an average 96% grasp success rate on seen and novel objects selected from the YCB dataset. We also discussed the influence of the frictional surface on the finger to improve the grasp robustness.

Stroke rehabilitation with the assistance of exoskeleton robots has the potential to facilitate the recovery of motor skills by guiding, supporting, and encouraging movement in the affected limbs. In this work, an upper-extremity exoskeleton actuated by the cable transmission mechanism, was developed for rehabilitation training of stroke patients. The exoskeleton is designed with three DOFs, including shoulder abduction/adduction, shoulder flexion/extension, and elbow flexion/extension. The main body of exoskeleton is comprised of three links and two cuffs, with a total weight of approximately 1.7 kg. Based on the mechanical design and cable arrangement, the kinematics and dynamics of the actuation cables are analyzed. In addition, a PID-based position control strategy and an impedance control strategy are designed based on the cable kinematics and dynamics. To investigate the application performance in passive motion assistance, a prototype of the cable-driven exoskeleton system was established, and the corresponding experiments were conducted with five subjects. In position control experiments, the measured joint trajectories exhibit similar variation trends and close peek angles to the demonstration trajectory, which is the main emphasis in rehabilitation scenarios. Meanwhile, it can be inferred that the time lag is the primary reason for the tracking error between the expected and measured trajectories. As to the impedance control experiments, the statistical results indicate that the employment of lower impedance parameters tends to protect the human-robot interaction safety by sacrificing the tracking accuracy of joint position.

Traditional soft crawling robots have many disadvantages, including their complex structure, difficulty in manufacturing, and low load capacity. Inspired by the art form of kirigami, we opted to design a soft, flat crawling robot using only simple, fast laser cutting technology and a weaving method in this study. The robot mainly consists of two components: a piece of skin with scales and a flat balloon, which are weaved orthogonally to each other. The fully formed robot weighs only 5g, and the scales can tilt up after the balloon inflates. All the scales are distributed on one side of the robot, increasing the load capacity. The expansion of the balloon ensures that the robot becomes contract coupled. With the anisotropic friction provided by the scales, the robot can now crawl forward. This experimental work demonstrates that the crawling efficiency can be improved by choosing the appropriate pressure waveform. By shortening the period of the pressure waveform, the crawling speed can also be significantly improved. In terms of loading, the robot still has a high crawling ability when carrying a load over 400 times its weight.

Carrying a load can affect human locomotion and increase the risk of musculoskeletal injuries. In this letter, we proposed a method inspired by the running posture of ungulate species to reduce metabolic energy by controlling load motion. We developed an energy-saving exoskeleton with an active load CoM adjustment system, which enables accurate control of load CoM acceleration using active disturbance rejection control (ADRC) technology. Finally, we tested the energy-saving exoskeleton system, and the results showed an $8.82 \pm 4.19\%$ decrease in the integrated EMG signals of rectus femoris, as well as an $8.21 \pm 3.85\%$ reduction in net metabolic rate. These findings validate the effectiveness of our energy-saving exoskeleton.

Passive back-support exoskeletons commonly employ elastic components to assist users during dynamic tasks. However, these designs are ineffective in providing sustained assistance for prolonged static bending postures, such as those required in surgery, assembly, and farming, where users experience continuous lumbar flexion. To address this limitation, a novel passive back-support exoskeleton inspired by the human spine is proposed in this work. The exoskeleton integrates a five-bar linkage mechanism with vertebrae-mimicking units, allowing for both dynamic flexion–extension movements and rigid support at various flexion angles. During the experiments, subjects are instructed to perform a 30-min forward-bending assembly task under two conditions: with and without wearing the exoskeleton. Compared to the free condition, the electromyography results indicate a 10.1% reduction in integrated EMG (IEMG) and a 9.78% decrease in root mean square (RMS) values of the erector spinae with the exoskeleton. Meanwhile, the metabolic rate is decreased by 11.1%, highlighting the effectiveness of the exoskeleton in mitigating muscle fatigue during prolonged static work. This work provides a promising solution for reducing musculoskeletal strain in occupations requiring sustained forward bending, making it a valuable advancement in passive exoskeleton technology.