Doctor of Philosophy (Ph.D.)

Permanent URI for this collectionhttp://192.248.9.226/handle/123/2055

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Browsing Doctor of Philosophy (Ph.D.) by Author "Gopura RARC"

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    item: Thesis-Abstract
    Development of a bio-inspired lower extremity exoskeleton with a passive-powering system
    (2023) Ranaweera, RKPS; Gopura RARC; Jayawardena TSS; Mann GKI
    Manual handling is an indispensable activity in any occupational setting. It is any activity that requires the use of human force for lifting, carrying or moving an object. Such repetitive and tiring tasks may cause work-related musculoskeletal disorders and adversely affect productivity of manual workers. In that context, the goal of this research was to develop a wearable device or exoskeleton for providing lift assistance during squat lifting. The outcome of the research was to reduce human effort and improve human comfort. The objectives or contributions of the work include conceptualization of a biomechanical energy management approach for squat lifting, development of an anthropomorphic passively powered multi-joint lower extremity exoskeleton for lift assistance, and investigation of the effectiveness of the proposed lift-assist system. Initially, a literature review was conducted on lower extremity exoskeletons to identify the research gap. The analysis on the state-of-the-art of exoskeletons revealed the need for introducing sustainable powering systems and minimizing interference issues at the human robot interface. Next, the biomechanical energy management approaches were conceptualized. The work includes the biomechanical modelling of squat lifting activity and the investigation of feasibility of proposed energy recycling strategies. Subsequently, design of anthropomorphic mechanical structure for the exoskeleton, design of bio-inspired passive-dynamic powering system for ankle and knee joints, and design of passive and active controlling systems were carried out. Thereafter, prototype of the ankle knee exoskeleton was fabricated as per the design specifications. Finally, performance with the proposed lift-assist system was experimentally evaluated. Results from the biomechanical analysis show that, when wearing the exoskeleton, energetic consumption at ankle and knee got reduced by 23-24% and 38-40%, respectively. The effectiveness of proposed system was also verified by evaluating muscle activities of lower and upper leg. All in all, the ankle knee exoskeleton with proposed passive actuators made a positive influence on the lower limb’s muscular system. Therefore, the proposed exoskeleton has proven to be an effective solution for industrial use. Keywords: Bio-inspired Design, Biomechanical Energy Harvesting, Lower Extremity Exoskeleton, Leg/Squat Lifting, Motion Analysis, Passive Actuator, Power Assistance, Surface Electromyography
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    item: Thesis-Full-text
    Development of a soft linear actuator to use in wearable assistive exosuits
    (2023) Kulasekera AL; Chathuranga KVDS; Gopura RARC; Lalitharatne SWHMTD
    Wearable exosuits require flexible, linearly contractile, and lightweight actuators to provide sufficient force to move the respective limb. This thesis presents the concept, design, fabrication, experimental performance characterization, and numerical modeling of two types of respectively thin and low-profile vacuum-driven, soft, linearly contractile actuators. The proposed soft actuators are made of an inextensible yet flexible thin-skinned pouch supported by a collapsible skeleton that orients the collapse of the actuator in the longitudinal axis upon the evacuation of the air within the pouch. The proposed novel soft, lightweight, contractile actuators are thin (ThinVAc) and lowprofile (LPVAc). Both these actuators are lightweight (ThinVAc: 0.75 g; LPVAc: 14 g), provide high maximum blocked forces (ThinVAc: 5.2 N; LPVAc: 39 N), provide maximum stresses similar to that expected from biological muscles (ThinVAc: 184 kPa; LPVAc: 117 kPa) and have high force-to-weight ratios (ThinVAc: 477; LPVAc: 285). The ThinVAc can combine to create multifilament actuators for force scaling. Combining 15 units of 500 mm ThinVAcs generates a maximum blocked force of 54 N (Max. stress: 62 kPa), 290 times the self-weight. The LPVAc integrates a position sensor based on an inductive sensor allowing closed-loop control with minimal error at 0.25 Hz. Numerical models for the contraction and blocked force of mono- and multifilament actuators allow for predicting their behavior independent of external sensors. The proposed actuators are tested in wearable applications to check their suitability. The ThinVAc is integrated into a knee rehabilitation assist device, and the LPVAc is incorporated into a novel mono-articular sit-to-stand transition (StSt) assist exosuit, helping to reduce muscle activity by 45%. These actuators have the potential to be integrated into a wide range of assistive devices and orthoses, such as knee or ankle braces, exoskeletons, and prosthetics, to provide the necessary support for people with mobility impairments.