Enhancing Mobility for Children with Cerebral Palsy: Artificial Muscle Powered Ankle Orthosis Design and Simulation
Presenter Type
UNO Graduate Student (Doctoral)
Major/Field of Study
Biomechanics
Author ORCID Identifier
https://orcid.org/0009-0001-6840-3127
Advisor Information
Ph.D
Location
CEC RM #201/205/209
Presentation Type
Poster
Start Date
22-3-2024 1:00 PM
End Date
22-3-2024 2:15 PM
Abstract
Cerebral palsy (CP) is the most common pediatric neurological disorder. Ankle control deficiencies frequently manifest in CP and are prominent contributors to gait abnormalities that lead to consequential outcomes, including an elevated risk of falls and injuries, and inefficient gait speeds. The standard of care for ankle control dysfunction associated with CP is an unmechanized, bulky, and uncomfortable L-shaped passive ankle-foot orthosis (AFO). Although successful in providing passive ankle stability, long-term use of conventional AFOs may induce adverse neural adaptations. In the current study, we designed a comfortable smart AFO for children with CP powered by dielectric elastomer (DE)-based artificial muscles; a group of electroactive polymer actuators that are lightweight, compact, soft, noiseless, and contract longitudinally. The characteristics of DE-based artificial muscles closely resemble mammalian skeletal muscle. We call this device the DE (Dielectric Elastomers) -AFO, a biomimetic exoskeleton that drives its artificial muscles in synchrony with lower limb muscles to promote natural ankle motion. The purpose of this study is to investigate the deformity, mechanical properties, and range of motion (ROM) in the sagittal plane of the DE-AFO’s mechanical structure when it is loaded by artificial muscles. In this regard, we designed a DE-AFO prototype in SolidWorks. Then, using Abaqus software, we simulated the structure under load to determine the force profile generated, actuation stretch requirements, and ROM in the sagittal plane (generated by the DE-AFO). The DE-AFO prototypes evaluated in this proposal have two groups of artificial muscle (four muscles): Lateral and Medial plantarflexion, and Lateral and Medial dorsiflexion. Thus, the simulation will be conducted under two conditions: 1) when Medial and Lateral plantarflexion artificial muscles are activated simultaneously, during the stance period of gait; more specifically, the pre-swing phase of stance, i.e., 40% to 60% of the gait cycle. 2) When Medial and Lateral dorsiflexor artificial muscles were activated simultaneously during the swing period of gait, 60-100% of the gait cycle. Our findings indicate that the maximum deformity of the DEA- AFO is obtained in the heel cup when the Medial and Lateral plantarflexion artificial muscles are activated simultaneously. However, when the Medial and Lateral dorsiflexor artificial muscles were activated simultaneously, the maximum deformity was obtained through the back rod of the DEA-AFO. In addition, the maximum principal stress was calculated, and the results showed that our DEA-AFO offers the necessary dorsiflexion support required to lift the foot during the swing period.
Keywords: Cerebral Palsy (CP), Dielectric Elastomer, Artificial Muscle, Structure Analysis, Range of Motion (ROM).
Enhancing Mobility for Children with Cerebral Palsy: Artificial Muscle Powered Ankle Orthosis Design and Simulation
CEC RM #201/205/209
Cerebral palsy (CP) is the most common pediatric neurological disorder. Ankle control deficiencies frequently manifest in CP and are prominent contributors to gait abnormalities that lead to consequential outcomes, including an elevated risk of falls and injuries, and inefficient gait speeds. The standard of care for ankle control dysfunction associated with CP is an unmechanized, bulky, and uncomfortable L-shaped passive ankle-foot orthosis (AFO). Although successful in providing passive ankle stability, long-term use of conventional AFOs may induce adverse neural adaptations. In the current study, we designed a comfortable smart AFO for children with CP powered by dielectric elastomer (DE)-based artificial muscles; a group of electroactive polymer actuators that are lightweight, compact, soft, noiseless, and contract longitudinally. The characteristics of DE-based artificial muscles closely resemble mammalian skeletal muscle. We call this device the DE (Dielectric Elastomers) -AFO, a biomimetic exoskeleton that drives its artificial muscles in synchrony with lower limb muscles to promote natural ankle motion. The purpose of this study is to investigate the deformity, mechanical properties, and range of motion (ROM) in the sagittal plane of the DE-AFO’s mechanical structure when it is loaded by artificial muscles. In this regard, we designed a DE-AFO prototype in SolidWorks. Then, using Abaqus software, we simulated the structure under load to determine the force profile generated, actuation stretch requirements, and ROM in the sagittal plane (generated by the DE-AFO). The DE-AFO prototypes evaluated in this proposal have two groups of artificial muscle (four muscles): Lateral and Medial plantarflexion, and Lateral and Medial dorsiflexion. Thus, the simulation will be conducted under two conditions: 1) when Medial and Lateral plantarflexion artificial muscles are activated simultaneously, during the stance period of gait; more specifically, the pre-swing phase of stance, i.e., 40% to 60% of the gait cycle. 2) When Medial and Lateral dorsiflexor artificial muscles were activated simultaneously during the swing period of gait, 60-100% of the gait cycle. Our findings indicate that the maximum deformity of the DEA- AFO is obtained in the heel cup when the Medial and Lateral plantarflexion artificial muscles are activated simultaneously. However, when the Medial and Lateral dorsiflexor artificial muscles were activated simultaneously, the maximum deformity was obtained through the back rod of the DEA-AFO. In addition, the maximum principal stress was calculated, and the results showed that our DEA-AFO offers the necessary dorsiflexion support required to lift the foot during the swing period.
Keywords: Cerebral Palsy (CP), Dielectric Elastomer, Artificial Muscle, Structure Analysis, Range of Motion (ROM).