Faculty of Engineering, Mechanical Engineering

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Browsing Faculty of Engineering, Mechanical Engineering by Author "Amarasinghe, YWR"

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    item: Thesis-Full-text
    Design and development of miniaturizes tactile sensors for tactile imaging
    Thotegodage, DIU; Amarasinghe, YWR
    Tactile sensors are devices which acquire data from the physical world through sense of touch. These acquired data may be related to either, surface roughness, texture, force, or any other tactile parameter. Even though, tactile sensor systems are identified as a feasible method to acquire force feedback in robotics and automation systems, due to the requirement of physical interaction between the sensor and application, development of tactile sensors does not come to the spotlight during the past decades. Rather, researchers were more focused on developing non-contact sensors for various sensing modalities when comparing with the tactile sensors. Currently, importance of tactile sensors has come to the spotlight, as development of robotics, automation and biomedical applications are limited due to lack of tactile feedback. Also, many application areas are identified, where tactile sensors can be incorporated such as robotics, industrial automation, biomedical imaging, biomedical robotics, etc. Tactile imaging is one of the medical imaging technique, which mimic manual palpitation to diagnose diseases such as breast cancer, prostate cancer, etc. Tactile sensor is the foremost element in a tactile imager. Comparing with the other medical imaging techniques, it was found that tactile imaging is the most cost effective method to screen breast cancers. Also it has other advantages such as minimum exposure to radiation, simple and easy operation, etc. Hence, main aim of this research is to develop miniaturized tactile sensors for tactile imaging applications. Working with that aim, miniaturized tactile sensors were developed during this research. In these developed sensors, Quantum Tunnelling Composite (QTCTM), which is a conductive polymer composite, has been used as the sensing element. A novel structure was proposed to be incorporated with the sensing elements and analysis of the structure discussed. Proposed sensor was developed and calibrated. In the next stage of this research, a novel enclosed tactile sensor was designed and developed utilizing the same sensing and working principle as the developed 1-DOF tactile sensor. Main motive of developing this sensor is to include the proposed improvements for the 1-DOF tactile sensor based on its experimental results. An enclosed novel structure was proposed so that the sensing element and spring will be omitted from the environmental effects. Sensor was developed and calibrated so that it could be integrate with tactile imaging applications. Sensitivity of this developed tactile sensor, calculated to be 0.02 V/N and sensor displayed repeatability of ±3 N. An experiment was carried out to evaluate the usability of developed sensors in tactile imaging applications. Using the developed sensor pressure variation of a human left hand was mapped and visual images were constructed. Applicability of sensor arrays instead of a single sensor in tactile imaging applications and miniaturization techniques to be used to construct tactile sensor arrays with high Taxel density is discussed. A MEMS based tactile sensor design was proposed to be developed to construct tactile sensor arrays with good performance for tactile imaging applications. Proposed sensor design analysed and simulated to validate the proposed working and sensing principles. Fabrication steps for the designed MEMS sensor was proposed.
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    item: Thesis-Abstract
    Development and clinical testing of a negative pressure wound therapy device
    (2015-09-16) Welgama, WPD; Gray, HA; Amarasinghe, YWR; Sugathapala, AGT
    Negative Pressure Wound Therapy (NPWT) is a type of treatment in which suction is applied to a wound bed in combined with a specialized dressing to increase the wound healing rate. This study aims to develop a fully automated, portable and user friendly NPWT device and it is capable of increasing the healing rate of wounds, which cannot be healed by only using conventional wound treating methods. The pressure of the developed device can be controlled within the range of -25 mmHg to -250 mmHg with an accuracy of ± 3 mmHg. Pressure controlling is done by controlling rpm of the motor in the vacuum of the device. Dimensions of the developed device are 30 cm x 20 em x 15cm, voltage is 12 V and power consumption range is 4 W to lOW. The satisfactory level of user friendliness of the device was shown when it was being clinically tested by non-technical medical staff. To evaluate the performance of the device, it was clinically tested and validation was done by analyzing the clinical results. It was proved that this device has the same performance as previously validated NPWT devices, during the clinically testing. Reliability of the device was validated by longer period clinical testing at hospital. Portability, size reduction and possibility to operate using battery power supply are the other advantages of the device compared to other NPWT devices developed in Sri Lanka.
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    item: Thesis-Full-text
    Development of a vision aided reach-to-grasp path planning and controlling method for trans-humeral robotic prostheses
    Madusanka, DGK; Gopura, RARC; Amarasinghe, YWR; Mann, GKI
    This study proposes a reach-to-grasp path planning and controlling method for trans- humeral prostheses. Trans-humeral prostheses are used to replace the missing body part after the loss of upper limb (UL) above elbow. Reach-to-grasp paths refers to the paths taken by the human UL to reach towards an object with the intention of grasping. A trans-humeral prosthesis has been designed and fabricated with 5DOF. A simulation environment has been proposed using the design. Simulation environment consists of a virtual shoulder joint which can be actuated according to a natural human shoulder using an Inertial Measurement Unit (IMU). Prosthesis and the simulation environment has been used to experimentally evaluate the proposed path planning method. A reach-to-grasp path planning method combining Electromyography (EMG) signals and vision signals has been proposed. EMG Based Module (EBM) is capable of con- trolling prosthesis elbow motion e ectively with an accuracy of 92%. Visual Servoing Module (VSM) consists of a 2-1/2D visual servoing system to center the object of in- terest to the hand of the prosthesis and to correct the orientation. An object reaching algorithm has been proposed to reach towards the object. Later, the EBM and the VSM has been fused using an fusion lter. An improvement to the above method has been proposed to make the paths straight. It consists of a path generation module and a path tracking module. Path generation module is capable of generating a path towards the object. The object position is located and a path is generated from the current position of the prosthetic hand to the object position with the aid of vision. Path tracking module takes the prosthetic hand on the generated path considering shoulder motions. Two path tracking methods has been proposed: spatial path following method and Model Predictive Controller (MPC) based path tracking method. Proposed path planning method has been experimentally evaluated.