XPED's Reality Check: An evaluation of how human and exoskeleton adapt to each other

XPED's Reality Check: An evaluation of how human and exoskeleton adapt to each other

Maathuis, G.A.

Van der Helm, F.C.T. (mentor)
Van Dijk, W. (mentor)
Wisse, G. (mentor)

Mechanical, Maritime and Materials Engineering

BioMechanical Engineering

BMD

2012-07-12

This thesis presents research done on XPED, a passive walk assisting exoskeleton. It uses exotendons to assist the user, which are elastic elements running over multiple joints which are able to store and redistribute energy over these joints. A computer model predicts that joint powers of the user would decrease when walking with XPED, compared to walking without XPED. Because of these predictions a lower energy consumption for walking with XPED was expected. Previous research shows however that this is not the case, but that the energy consumption of the user increases when walking with XPED. The goal of this research was to find the reasons why XPED does not help the user decrease his energy consumption when walking. Possible mismatches between reality and model were identified and tested on occurrence. Three hypotheses were formulated: A. The user alters his gait pattern B. XPED's hip harness deforms C. XPED moves relative to the user These effects do not occur in the model but they were thought to occur in reality. They all have the potential to decrease the amount of energy storage in the exotendons and thereby decrease the energy efficiency of XPED. Using motion capture measurements on three subjects, the kinematics of XPED as well as those of the human were measured. From these measurements, all three hypotheses were accepted. A: The human alters his gait pattern due to the exotendons by walking on his toes more, thereby relaxing the exotendons. Changes in back orientation were also found. Two of three subjects bend over more, thereby relaxing the exotendons and one subject walked more upright, thereby stressing the exotendons more. The energy stored in the exotendon decreased due to these gait alterations ranging from 9.5 to 32.6 Joule. B: The original hip harness of XPED was found to deform significantly due to the exotendon forces but the stiffening elements added to the hip harness brought down the energy loss from 6.7 Joule for XPED 2.1 to 2.3 Joule or lower for XPED 2.2. C: It was also found that XPED moves relative to the user. The effect of these movements on the stored exotendon forces can range from 0 to 6.7 Joule for XPED 2.2, depending on how the user adapts to less relative movement.

Exoskeleton

http://resolver.tudelft.nl/uuid:feb944d8-98eb-44f7-a576-da35a81fc7ab

2016-07-12

Student theses

master thesis

(c) 2012 Maathuis, G.A.