Mechatronic and biomechanical considerations toward the design of an ankle clonus simulator

Clonus is a rhythmic, involuntary reflex response often seen in individuals with lesions in their descending motor neurons. These lesions can be the result of spinal cord injury or diseases like multiple sclerosis, Parkinson’s disease and cerebral palsy. During clinical evaluation of an individual suspected of having lesions in their descending motor neurons, an ankle clonus test is often employed. Clinical evaluation of clonus is currently reported using qualitative rating scales and therefore accurate diagnosis is largely dependent on the clinician’s experience. Clinician trainees may not be able to obtain sufficient training time with patients to understand and diagnose clonus effectively. Thus, we, at the Human Dynamics and Controls Lab, designed an electromechanical ankle clonus simulator, based on a series elastic actuator mechanism, that is capable of providing training for administration of an ankle clonus test and therefore substituting the need of human patients. The ankle clonus simulator is intended to accurately mimic the behavior of the ankle joint of a patient demonstrating ankle clonus. However, to obtain confidence in the performance of the ankle clonus simulator, clonus has to be academically explored after which, biomechanical and mechatronic requirements of the simulator must be investigated. This thesis first presents an overview of ankle clonus and subsequently establishes specific research questions that needed to be answered, based upon which biomechanical targets, anthropomorphic designs, and sensor subassemblies are constructed. Biomechanical models of passive ankle torque to be mimicked by the simulator were developed and preliminary evaluation of sensors designed to be included in the first-generation ankle clonus simulator was conducted. To determine the optimal model for passive joint moment, in both healthy individual case and clonus’s case, two different ankle passive stiffness models, derived from literature, were computed and compared. Double exponential functions were consequently selected as the appropriate models for passive stiffness for healthy and clonus cases. Sensor systems were designed to provide appropriate force readings, joint angle measurements and estimates of clinical learner’s hand position on the foot structure of the simulator. Off-device testing stations/fixtures for these sensors were built to evaluate the selected sensor’s efficacies and also to inform us of the final torque error margins (<5%) and ankle angle margins (<1%) that the clonus simulator would operate in. Overall, enough confidence was established in selected sensors such that an ankle clonus simulator that is manufactured based on the designs presented in this thesis would be able to perform as intended.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2020

Author dc:creator

• Garag, Prateek

Contributors dc:contributor

• Hsiao-Wecksler, Elizabeth T

• Clonus
• Medical Devices

Statement dc:rights

• Copyright 2019 Prateek Garag

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/106403

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/106403