Browsing by Author "Pragnathilaka, ADKH"

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item: Conference-Full-text
C-jae: 3 dof robotic ankle exoskeleton with compatible joint axes
(IEEE, 2018-05) Weerasingha, AH; Pragnathilaka, ADKH; Withanage, WPK; Ranaweera, RKPS; Gopura, RARC; Chathuranga, D
This paper proposes a three degrees of freedom (DOF) robotic ankle exoskeleton with compatible joint axes, named C-JAE. The device consists of three separate units to achieve triplanar motions. The plantarflexion-dorsiflexion and inversion-eversion are externally powered, whereas internalexternal rotation is passively supported. C-JAE is capable of complying with the functional and ergonomic requirements of the biological ankle joint. This is achieved by accurately mapping exoskeleton axes of rotation with the oblique axes of rotation of talocrural and subtalar joints of ankle. All mechanisms including the drive units are located anterior to shank and foot segments to carry out robotic rehabilitation and/or to provide locomotion assistance for humans having mobility disorders. Control experiments were conducted to assess aptitude of C-JAE to carry out ankle rehabilitation exercises. The results verified potential benefits of the proposed design to generate desired movement patterns of daily activities while providing power-assistance.
item: Conference-Full-text
Effects of restricting ankle joint motions on muscle activity: preliminary investigation with an unpowered exoskeleton
(IEEE, 2022-07) Ranaweera, RKPS; Weerasingha, AH; Withanage, WPK; Pragnathilaka, ADKH; Gopura, RARC; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The human ankle comprises multiple joints and supports triplanar motions to allow the foot to pronate or supinate during walking. However, ankle exoskeletons are mainly designed to assist propulsion whilst inhibiting other degrees of freedom. The kinematic constraints posed by the simplified joint mechanisms may negatively affect the wearer’s performance. In that context, this paper presents a preliminary investigation on the effects of restraining ankle motions during level walking with an unpowered ankle exoskeleton having compatible joint axes. The work investigated the changes in muscle activity in the lower limbs under various constraining conditions. A healthy male subject took part in five tests involving different combinations of kinematic restrictions of the ankle. The electrical activities of key muscles were recorded using a surface electromyography measurement system. The root-mean-square feature of signals was used for comparing results. The analysis confirms that constraining non-sagittal plane motions has caused significant changes to the activities of muscles. The investigation reveals the relative importance of developing ankle mechanisms that promote higher kinematic compliance. In the future, further studies should be conducted to reaffirm the statistical significance of muscle activity across multiple test subjects and assess human comfort to derive specific design guidelines for ankle devices.