Browsing by Author "Ranaweera, RKPS"

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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-Abstract
Design and development of an inhalation assist dpi to improve lung deposition
(Faculty of Medicine, University of Moratuwa, 2024) Nayanavee, PMVT; Nethmini, DMDD; Peiris, WAD; Peththanayake, NR; Randeniya, RDDTK; Ranaweera, RKPS; Mangala, KHJ; Samarasinghe, SM; Kottahachhi, J; Peries, WANN; Talagala, I; Samarasinghe, T; Fernando, NS; Pasqual, D; Chandran, T; Shajahan, Z
A dry powder inhaler (DPI) is a small, handheld device that allows breathing in medicine through the mouth directly to the lungs to treat a wide variety of respiratory disorders. These disorders are not well controlled due to inefficient medicine delivery systems, poor treatment compliance, and inaccurate inhaler techniques. In dry powder inhalers, energy is needed for the deagglomeration of the drug and transport it into the lungs. Currently, available DPIs have a low lung drug deposition because deposition depends entirely on the patient’s inspiratory effort. Improvements are being made to introduce an internal energy to improve lung deposition
item: Conference-Abstract
Design of a mobile app to assist post-myocardial infarction patients in adhering to medication and their follow-up
(Faculty of Medicine, University of Moratuwa, 2024) Gunasekara, BAPL; Gunasekara, GBN; Gunathilake, HANH; Gunawardana, WAN; Handugala, HDMA; Ranaweera, RKPS; Wickramage, SP; Kottahachhi, J; Peries, WANN; Talagala, I; Samarasinghe, T; Fernando, NS; Pasqual, D; Chandran, T; Shajahan, Z
Myocardial infarction (MI) can result in irreversible death of heart muscles due to prolonged hypoxia. Recurrent MI significantly increases mortality and morbidity, negatively affecting patients’ quality of life. Our research aims to improve medication adherence and follow-up care for post-MI patients by addressing key issues such as forgetfulness, medication side effects, complex drug regimens, and low health literacy through the proposal of a mobile application with innovative features to support post-MI patients.
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
item: Conference-Abstract
Development of a surface muscle pressure monitoring system for wearable robotic devices
Chandrasiri, MDSD; Ranaweera, RKPS; Gopura, RARC
Monitoring of muscle activities of human limbs is essential for designing controllers of wearable robotic devices such as prosthetics, orthotics and exoskeletons. Human-robot interaction (HRI) is generally studied to control these devices and ascertain comfort levels of the wearer. Cognitive-HRI (cHRI) and physical-HRI (pHRI) are the two main types of HRI methods identified in literature. Surface electromyography (sEMG) signals of skeletal muscles are commonly used in cHRI methods to identify the motion intentions. However, sEMG signals are sensitive to the environmental conditions such as electric and magnetic disturbances. Alternatively, changes to muscle stiffness and volume are measured in pHRI methods. Accordingly, this paper presents a novel sensory system to detect motions of upper or lower limbs by monitoring surface-muscle pressure (SMP). It is comprised of specially designed ’pressurized-air-pouches’ made of silicone. Experiments were carried out with the developed SMP monitoring system to detect muscles activities during biceps curls. The results were compared against sEMG signals to evaluate the validity of the proposed method. The analysis indicated a strong correlation between the signals measured and verifies the potential of using SMP as an effective muscle activity sensing method.
item: Conference-Abstract
Development of temperature prediction model for rubber caster wheels using finite elements
(2017) Wijayasundara, AV; Ranaweera, RKPS; Punchihewa, HKG
Caster wheels made with rubber rings fail during dynamic loading as a result of heat buildup. Temperature inside caster wheel increase gradually due to hysteresis effect of rubber material. Therefore, dynamically testing of rubber caster wheels is critical to evaluate new designs for their successful application. In such tests, caster wheels are rotated on a drum under a predetermined load and speed to evaluate their performance. Alternatively, this paper proposes a temperature prediction model to forecast the failure of the wheel using numerical approach. The objectives were to evaluate the temperature development inside the wheel using finite elements. In this pursuit, temperature inside several caster wheels were measured during dynamic tests. Based on the logged temperature data and raw material tests, finite element simulation of caster wheels was performed. Simulations were carried out in three steps; at first structural simulation, followed by determination of energy conversion factors and finally thermal simulation. The predicted temperature profiles and test data were closely matching with a R2 of 0.9, which eliminates the requirement for iterative dynamic tests. However, further work is needed to predict the failures of caster wheels based on developed model.
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.
item: Thesis-Full-text
Fea-based method to predict dynamic test failures of industrial rubber castor wheels
Wijayasundara, AV; Punchihewa, HKG; Ranaweera, RKPS
Castor wheels are used in various applications including industries, hospitals, offices, shopping trollies, air ports and other material handling applications. These applications demand different properties from castor wheels, such as dynamic load capacity, high speed capability, and capability to operate in hot and cold environments. Design of a castor wheel plays a major role to fulfill those various demands while being competitive in the market. Dynamic test of castor wheel is one of the main tests done on new castor wheel designs to evaluate its performance for an application. Due to manual trial and error practice used to test new designs in dynamic test, wheel development cost and lead time for deliver new castor wheel designs for new customer requirements is high. In order to evaluate wheel designs in early stages of development in dynamic test performance, Finite element model was developed to check castor wheel dynamic performance using combination of finite element analysis (FEA) techniques and raw material testing. Initially six samples of castor wheels were selected and dynamic test was carried out on them at various loads to evaluate temperature development inside the wheel and failure modes. Two sets of raw material testing, namely uniaxial tensile test and dynamic mechanical analyze test (DMA), were done on rubber and plastic materials which are used to make castor wheels. One wheel was selected as a case study to develop FEA model. As first step, 3D static loading simulation was done for the selected wheel. Total energy rate was defined for wheel in dynamic motion by data from static test using equations. 2D axisymmetric FEA model was developed as next step to evaluate temperature development of the castor wheel. Calculated energy rate was distributed among rubber elements as heat sources combining with DMA results to predict temperature inside the 2D profile using transient heat. Wheel failure analysis was carried out by combining predicted temperature profile and static loading case with temperature dependent properties of materials used. It was defined as a good design if castor wheel shows higher safety factor in failure simulation. From the case study, step-by-step method was developed to simulated castor wheel designs and evaluated failure. Four castor wheels were simulated according to developed model and predicted temperatures were compared with actual dynamic test temperature to validate the proposed model which showed good match with practical data. As future work, advanced failure analysis of caster wheels can be proposed, which should be carried out considering material chemistry and behavioral changes of materials with heat and fatigue loads.
item: Conference-Extended-Abstract
A feasibility study on developing stirling engines in Sri Lanka
(2006) Wickramaratne, C; Ranaweera, RKPS; Perera, ULIU
Global environment protection has come to be more stringent recently, demanding efficient and environmental friendly engines. Adding to the fact of escalating oil prices, Stirling engine could have a major role to play
item: Conference-Full-text
Hipexo: a hip exoskeleton robot for load lifting with flexible trunk linkage mechanism
(IEEE, 2020-07) Perera, ULS; Dasanayake, NP; Hettiarachchi, HPT; Mannapperuma, MAVA; Ranaweera, RKPS; Gopura, RARC; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
This paper proposes a hip exoskeleton robot named HipExo to provide power assistance for the industrial workers during stoop lifting activities. It introduces a hybrid actuator to power the hip joints. The electric motor and transmission is coupled to a spring system that can store biomechanical energy during the descent phase and release the stored energy during the ascent phase of the lifting cycle. Furthermore, the robot is comprised of flexible upper body linkage mechanism capable of adapting to the lumbar curvature and assuming the shape of the trunk. A mathematical model is formulated to estimate the hip torque profile for the stoop lifting cycle. Moreover, a torque control approach was introduced to control the robot according to the motion intentions of the user. The experimental results reveal that HipExo is effective in reducing muscle activity during stoop lifting and it has the potential of alleviating lift-related musculoskeletal disorders.
item: Conference-Abstract
A Hybrid powering mechanism for a transtibial robotic prosthesis
Sathsara, AKP; Widanage, KND; Nilakshman, S; Ranaweera, RKPS; Gopura, RARC
This paper proposes a hybrid powering mechanism for a unilateral transtibial robotic prosthesis named TRoPHy. The device includes both active and passive actuation methods for plantar flexion/ dorsiflexion while inversion/ eversion is achieved passively. The proposed mechanism uses separate spring systems to vary the ankle stiffness and capture the biomechanical energy for the purpose of controlling plantar flexion and dorsiflexion phases of gait cycle. Here, energy stored during the controlled dorsiflexion phase is released and used for propulsion in the powered plantar flexion phase. The testing of the prosthesis was carried out on an able-bodied person, by using a test-rig to affix the prosthesis in parallel to the shank for mimicking the kinematics of the leg. The resulting ankle kinematic data of the prosthesis provided a 97.3% correlation with the natural human ankle kinematics, implying the viability of applying this mechanism to reproduce the ankle behavior accurately. An analysis of the power balance of the system reveals that 38% of the total power required for the powered plantar flexion phase can be reduced effectively from the proposed energy harvesting mechanism.
item: Article-Full-text
iGrasp Robotic prosthetic hand
(2021) Widanage, KND; Perera, ULS; Dasanayake, NP; Viduranga, RKP; Siyambalagoda, SAPK; Cooray, TMGCSP; Fernando, KRT; Ranaweera, RKPS; Gopura, RARC
e are living in an era in which technology is shaping the world at an incredible speed. In this wake, the Bionics laboratory of the Department of Mechanical Engineering of the University of Moratuwa is doing inspiring research to improve the quality of life of differently-abled people.
item: Conference-Full-text
Machine learning-based approach for modelling elastic modulus of woven fabrics
(IEEE, 2020-07) Kularatne, SDMW; Ranawaka, RAHS; Fernando, EASK; Niles, SN; Jayawardane, TSS; Ranaweera, RKPS; Edussooriya, C; Weeraddana, CUS; Abeysooriya, RP
There has been a shift of focus from aesthetic properties to mechanical and functional properties of textiles with the recent developments in technical textiles and wearable technology. Therefore, understanding how various fabric parameters influence the mechanical properties of fabrics is paramount. In applications where compression and stretching of fabrics are important, the elastic modulus is a key fabric property that needed to be controlled precisely. Woven fabrics are capable of providing superior elastic properties, but how various fabric parameters affect elastic modulus is not well understood. In this study, two machine learning techniques were implemented to model the elastic modulus of woven fabrics and were compared with multivariable regressions. The two machine learning techniques used are Artificial Neural Network (ANN) and Random Forest Regression. As input variables; weave factor (numerical representation of weave structure), warp yarn count and pick density were used. Both ANN and Random Forest Regression were able to generate reasonably accurate results with Random Forest Regression been the better of the two methods. Using Random Forest Regression, feature importance of the input variables was obtained, and it proved that the weave structure has a notable impact on the elastic modulus of woven fabrics.
item: Conference-Extended-Abstract
Mathematical model and prototype design of an electro-hydraulic camless valvetrain
(2006) Perera, ULIU; Ranaweera, RKPS; Weerasinghe, WMSR
Presented within is a synopsis of the mathematical model and prototype design & manufacture of an electro-hydraulic camless valvetrain. This valvetrain system was developed for use as a replacement for the conventional camshaft operated valvetrain in an internal combustion engine.
item: Conference-Full-text
A robotic hand for rehabilitation of wrist and fingers
(Information Technology Research Unit, Faculty of Information Technology, University of Moratuwa., 2023-12-07) Weerasoory, WAKC; Kumasaru, URE; Nipun, HMW; De Silva, HHMJ; Ranaweera, RKPS; Gopura, RARC; Piyatilake, ITS; Thalagala, PD; Ganegoda, GU; Thanuja, ALARR; Dharmarathna, P
Carpal Tunnel Syndrome is a common neural disease among people with repetitive wrist movements. It affects the sensation and movement of the thumb, index finger, middle finger, and half of the ring finger. The syndrome can be treated effectively through therapeutic exercises in the early stages of diagnosis or through surgery in more severe cases. However, the lack of physiotherapists poses a significant challenge in hospitals where thorough observation is required. The proposed rehabilitation robot focuses on wrist and finger exercises designed explicitly for Carpal Tunnel Syndrome and intended for clinical use. The sensors detect the patient’s range of motion and display the data for the therapist, who can then determine the appropriate exercises. Finger exercises include flexion-extension, mimicking grasping patterns, while wrist exercises include flexion-extension and hyperextension. The rehabilitation program consists of three stages and several iterations, progressing according to the patient’s recovery, which can be observed through the data collected from the sensors. The rehabilitation robot utilizes an under-actuation method that drives proximal interphalangeal, and distal interphalangeal joints of the four fingers using two servo motors for finger rehabilitation. The thumb is actuated using a separate servo motor. A stepper motor actuates wrist movement. A mathematical model was developed to simulate the movements of the linkage system, which is deployed in the sagittal plane of the fingers. The effectiveness of the rehabilitation robot has been verified through simulations and experiments.
item: Conference-Extended-Abstract
A study on the technological requirement of the small and medium scale footwear industry in Sri Lanka
(2006) Muthunayaka, APK; Manthilake, MMID; Ranaweera, RKPS; Punchihewa, HKG
The Small and Medium scale Enterprise (SME) footwear industry of Sri Lanka has a long history. However, the technology used in designing has hardly changed over the years. Around the world, research and development is being carried out on developing new technologies for designing and manufacturing footwear for different applications (Fernando et. al., 2005). These high quality products at a low cost inadvertently attract consumers and surpass the local footwear market. Thus, the local SME footwear industry has come to a juncture; either prosper by adopting new technology to compete against the imported products or to ignore the competitors and get perished from the industry.
item: Thesis-Full-text
Topology optimisation of 5000 LB over-center buckle
Prabuddha, BGC; Ranaweera, RKPS
Topology optimisation has for a considerable time been applied successfully in the automotive industry, but still has not commonly become a mainstream technology in the aerospace industry. The aircraft manufactures have already been achieving benefits with optimisation for some areas where as the bottom layer suppliers in the aerospace industry are still following conventional design techniques. Most of metal fittings which are widely used in the aerospace industry with safety nets and straps are identified as bulky and heavy as they are based on conventional designing techniques. 5000 lb over-center buckle (OCB) is one of the most frequently used tightening devices having the aforementioned characteristics. The purpose of this study is to formulate a mechanism for a strength-based weight reduction on standard 5000 lb OCB which is used in the aerospace industry and consequently, to propose a light-weight design. First objective was to identify the relevant design considerations of existing 5000 lb OCB. Design specifications and standards related to 5000 lb OCB and 5000 lb safety strap were collected and reviewed for collecting necessary strength, functionality and other requirements of 5000 lb OCB. Second objective was to develop a finite element methodology for static structural analysis of 5000 lb OCB. 5000 lb OCB samples were carefully examined to identify the functionality and other necessary requirements of the OCB. OCBs were then subjected to a detail measurement check and the dimensions were used to build a computer aided design (CAD) model for the study. Engineering drawings were also created from the model for future reference. Then OCB samples with polyester webbing parts were subjected to various kind of strength tests using tensile testing machine. Purposes of these tests were to identify the failure loads and failure modes of the OCB itself and the OCB with safety strap in the operational conditions. These experimental results showed that the 5000 lb OCB used in the aerospace industry is an over-design. Last objective was to optimise the 5000 lb OCB using an effective optimisation scheme. Having reviewed on optimisation procedures and current trends in the aerospace industry, Altair HyperMesh software was selected as the numerical simulation tool to setup the finite element model and ‘Topology Optimisation’ was selected as optimisation method for the study. The finite element model was validated using simulation results and experimental results and the validated methodology was used to setup optimisation problem with aim of reducing weight. In formulating the topology optimisation problem, the minimum averaged compliance of the buckle was taken as the objective, and element density was used as the design variable. Topology optimisation results were analysed and the elements in the critical regions were derived as geometries to compare those with original OCB model. Considering other functionality requirements with the topology optimisation results, a light-weight design was proposed with step-by-step modifications. Subsequently, FE simulations were repeated for the proposed light-weight design. Comparing the results of the light-weight design with the original model results, the proposed light-weight design can be noted as a better alternative. Nearly 7% (41g) weight reduction could be achieved for 5000 lb OCB using the proposed optimisation procedure.
item: Conference-Full-text
Topology optimization to improve structural efficiency of 5000 lb over-center buckle
(IEEE, 2016-04) Prabuddha, BGC; Ranaweera, RKPS; Mangala, KHJ; Jayasekara, AGBP; Bandara, HMND; Amarasinghe, YWR
Topology optimization for a considerable time has been successfully applied in the field of design for the development of light-weight structures. Especially in the aerospace sector, topology / topography optimization techniques are gaining recognition as effective tools for improving structural efficiency of newly designed aerospace vehicles. In that context, a study has been conducted on 5000 lb Over Center Buckle (OCB), which is one of the most commonly used tie down hardware to strap cargo in aircrafts. The aim of the research was to arrive at a light-weight design of the OCB without compromising on its strength and functional requirements. Key objective was to formulate a generally applicable methodology to assess and improve conventional designs of OCBs having different styles and capacities. Initially, various types of mechanical tests were conducted in accordance with SAE standard to identify the performance of commonly used 5000 lb OCB. Then a finite element model was developed and model validation was performed using experimental results. The tuned model served as a platform to carry out topology optimization where several design parameters were tested to assess their sensitivity and degree of influence for achieving higher structural efficiency. Finally, an alternative design was proposed for the existing 5000 lb OCB where 7% weight reduction could be achieved.