Analysis of the human interaction with a wearable lower-limb exoskeleton

Abstract

The design of a wearable robotic exoskeleton needs to consider the interaction, either physical or cognitive, between the human user and the robotic device. This paper presents a method to analyse the interaction between the human user and a unilateral, wearable lower-limb exoskeleton. The lower-limb exoskeleton function was to compensate for muscle weakness around the knee joint. It is shown that the cognitive interaction is bidirectional; on the one hand, the robot gathered information from the sensors in order to detect human actions, such as the gait phases, but the subjects also modified their gait patterns to obtain the desired responses from the exoskeleton. The results of the two-phase evaluation of learning with healthy subjects and experiments with a patient case are presented, regarding the analysis of the interaction, assessed in terms of kinematics, kinetics and/or muscle recruitment. Human-driven response of the exoskeleton after training revealed the improvements in the use of the device, while particular modifications of motion patterns were observed in healthy subjects. Also, endurance (mechanical) tests provided criteria to perform experiments with one post-polio patient. The results with the post-polio patient demonstrate the feasibility of providing gait compensation by means of the presented wearable exoskeleton, designed with a testing procedure that involves the human users to assess the human–robot interaction.

Keywords:

• biological motor systems
• man–machine systems
• robots
• exoskeletons

Acknowledgements

The authors thank Ossur hf and IB Valencia for their contributions in materials and experimentation. We also acknowledge the enormous contributions and support from J.M. Baydal in testing and data analysis. The work presented in this paper has been partially founded through grants IST-2001-37751 (GAIT, intelligent knee and ankle orthosis for biomechanical evaluation and functional compensation of joint disorders) and IST-61-045301-STP (ESBIRRO, Biomimetic actuation, sensing and control technology for limit cycle bipedal walkers) of the European Commission.