Development of physical interfaces to promote kinematic compatibility for agora lower-limb Exoskeleton
Ballén Moreno, Felipe | 2020
Over the years, exoskeletons are included in clinical, industrial, and military applications to enhance and assist the human body. Regarding lower-limb exoskeletons in clinical applications are intended to provide aid during daily living activities. Lower-limb exoskeletons are equipped with a mechanical structure, actuators, sensors, attachments, and interfaces that interact physically with the user. These features are focused on being adequately designed for suitable human-robot interaction. However, the features' design has multiple complexities and limitations to solve and assess. On one hand, the human hip joint has intricacy behavior due to the three degrees of freedom that are not resolved by commercial exoskeletons. On the other hand, there is a lack of robotic devices’ performance indicators that properly assess the physical interfaces.
In this sense, this master's thesis presents the design and modeling of a passive hip joint intended to assist the hip ab/adduction motion. Besides, it also presents a novel three-dimensional relative motion methodology to assess the human-robot interaction of the AGoRA lower-limb exoskeleton. The passive hip joint presents the design principles used to estimate the interaction torque allowing the understanding of energy provided to the user. Moreover, it also raises the three-dimensional relative motion methodology's theoretical concepts and the implementation in a pilot study. The principal outcomes are aimed to improve the AGoRA lower-limb exoskeleton's understanding of the Physical Human-Robot Interaction. On the one hand, the passive hip joint is characterized along different preloads, giving the user a maximum torque of 15.8 $Nm$ at a preload of 472.43 $N$. Likewise, the joint's stiffness provided a maximum of 4.24 $Nm/deg$. On the other hand, the proposed three-dimensional relative motion methodology demonstrated the exoskeleton's interaction among the three principal planes of motion, identifying undesirable motions in the secondary planes. The proposed joint's results revealed multiple improvements for the user's assistance. Similarly, the three-dimensional relative motion's results suggested a physical interfaces' enhancement to reduce the undesirable motions and improve AGoRA lower-limb exoskeleton's human-robot interaction and its kinematic compatibility.