University of Twente Student Theses


Design of a body-weight controlled clutch for the deliverance of assistance with a peadiatric ankle-foot orthosis

Hoorn, Marleen van (2022) Design of a body-weight controlled clutch for the deliverance of assistance with a peadiatric ankle-foot orthosis.

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Abstract:Ankle-foot orthoses (AFOs) greatly improve gait in patients with Cerebral Palsy (CP) by restoring ankle-foot biomechanics and minimising contractures. However, they restrict ankle ROM and poorly adapt to different terrains. This thesis thus aimed to develop an adaptable push-off mechanism to improve gait in children with CP. A survey was conducted among the main stakeholders of CP, based on which a TRIZ analysis was performed to determine the most promising push-off design for the target group. Subsequently, four prototypes of a body weight controlled clutch (BWC) were created. Upon weightbearing, these clutch a slider that is connected to an assistance spring, and thereby store energy during stance while allowing full ankle ROM during swing. The prototypes were technically validated by determining their friction coefficient $\mu$, an indication of successful slider clutching, and mathematically validated with a model to determine if 0.3~Nm/kg ankle torque can be generated. The surveys indicated that future AFOs should better adapt to patients needs and their environment, should be more flexible and allow bigger ankle ROM. TRIZ subsequently concluded a BWC, in combination with a hinged AFO frame, to be most promising for the target group. Technical validation of the corresponding prototypes yielded friction coefficients as high as 0.98, sufficient for the target group, and the mathematical model indicated that 0.3~Nm/kg assistance torque can be reached for target users age 5 to 15, for spring stiffness $K$ = 6 -- 18 N/m and $\mu$ = 0.5 -- 1.0.
Item Type:Essay (Master)
Unknown organization, l
Faculty:TNW: Science and Technology
Subject:50 technical science in general
Programme:Biomedical Engineering MSc (66226)
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