In this paper, we explore the mechanical behavior of the knee during the weight acceptance stage of stance during normal walking. We show that the torque/angle behavior of the knee during this stage can be approximated by a linear torsional spring. The mechanical parameters completely specifying this spring are identified, including stiffness, amount of rotation, and angle of engagement, and the effect of gait speed and body/load mass on those parameters are discussed. We discuss how the findings of this paper can be applied to the design of leg orthoses, prostheses and exoskeletons, and bipedal robots in general, allowing the implementation of human-like leg compliance during stance with a relatively simple latched-spring mechanism.

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Symmetric ankle propulsion is the cornerstone of efficient human walking. The ankle plantar flexors provide the majority of the mechanical work for the step-to-step transition and much of this work is delivered via elastic recoil from the Achilles’ tendon — making it highly efficient. Even though the plantar flexors play a central role in propulsion, body-weight support and swing initiation during walking, very few assistive devices have focused on aiding ankle plantarflexion. Our goal was to develop a portable ankleexoskeleton taking inspiration from the passive elastic mechanisms at play in the human triceps surae-Achilles’ tendon complex during walking. The challenge was to use parallel springs to provide ankle joint mechanical assistance during stance phase but allow free ankle rotation during swing phase. To do this we developed a novel `smart-clutch’ that can engage and disengage a parallel spring based only on ankle kinematic state. The system is purely passive — containing no motors, electronics or external power supply. This `energy-neutral’ ankle exoskeleton could be used to restore symmetry and reduce metabolic energy expenditure of walking in populations with weak ankle plantar flexors (e.g. stroke, spinal cord injury, normal aging).

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This paper presents an analysis of the human biomechanical considerations related to the development of lower limbexoskeletons. Factors such as kinematic alignment and compatibility, joint range of motion, maximum torque, and joint bandwidth are discussed in the framework of a review of the design specifications for exoskeleton prototypes discussed in the literature. From this analysis, we discuss major gaps in the research related to the topic and how those might be filled.

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Stroke patients often have flexor hypertonia and finger extensor weakness, which makes it difficult to open their affected hand for functional grasp. Because of this impairment, hand rehabilitation after stroke is essential for restoring functional independent lifestyles. The goal of this study is to develop a passive, lightweight, wearable device to assist with hand function during performance of activities of daily living. The device, Hand Spring Operated Movement Enhancer (HandSOME), assists with opening the patient’s hand using a series of elastic cords that apply extension torques to the finger joints and compensates for the flexor hypertonia. Device design and calibration are described as well as functional and usability testing with stroke subjects with a wide range of hand impairments. In initial testing with eight stroke subjects with finger flexor hypertonia, use of the HandSOME significantly increased range of motion (p <; 0.001) and functional ability (p=0.002) . There was some decrease in grip strength with the HandSOME device at the subject’s ideal setting, however this was not statistically significant (p=0.167) and did not seem to have a significant effect on function. Overall HandSOME shows promise as a training tool to facilitate repetitive task practice for improving hand function in stroke patients. HandSOME can be used as part of a home-based therapy program, or as an orthotic for replacing lost function.

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This paper introduces a bimanual haptic interface robot and presents results from its trial operation. Our aim in developing a bimanual haptic interface is to display high-precision three-directional forces at all 10 fingertips of both hands of the operator. By installing two five-fingered robot hands and two robot arms, we construct a bimanual haptic interface. A haptic interface that consists of robot hands and robot arms can provide multi-point contact between the operator and a virtual environment. However, there is the risk that robot hands and robot arms will collide while an operator is manipulating the haptic interface. To solve this problem, we also propose a collision avoidance control law for the multi-fingered bimanual haptic interface. Finally, to determine the validity of the proposed interface, we carry out several experiments. These results show the validity and great potential of the proposed bimanual haptic interface.

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