Abstract：Lower limb exoskeletons (LLEs) can assist paraplegic or hemiplegic patients to regain movement. However, different physiological structures and assembly errors create undesirable forces between the human and the exoskeleton, which result in undesired loadings on the joints and soft tissues of the user. Traditional physical human-robot interfaces of LLEs are unable to solve this problem. This study developed a physical human-robot interface for LLEs that focused on the internal joint forces through comparisons with traditional physical human-robot interfaces. A statics analysis of the forces on the human lower limb during the swing phase showed that this device stabilizes the internal joint forces. The device reduces the internal joint force on the human hip by 2.45% on average when there is vertical difference in the sagittal plane between the human hip joint and the exoskeleton hip joint and by 11.23% on average when there is horizontal difference in the sagittal plane between the human hip joint and the exoskeleton hip joint. The device also reduces the force on the human knee by 13.68% when there is vertical difference in the sagittal plane between the human knee joint and the exoskeleton knee joint, but increases the force on the human knee by 23.48% when there is horizontal difference in the sagittal plane between the human knee joint and the exoskeleton knee joint. This paper shows that this device can reduce the wear on the human hip and knee cartilage and soft tissues; thereby improving the exoskeleton experience for patients.
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