Browsing by Author "Chathuranga, DS"

Now showing 1 - 8 of 8

item: Conference-Full-text
Development and characterization of a soft tactile sensor array used for parallel grippers
(IEEE, 2018-05) Weerasinghe, L; Chathuranga, DS; Chathuranga, D
Tactile Sensors play a crucial role in developing robots with human like grasping and manipulation capabilities. Localization, dynamic sensing and good force recognition characteristics are major goals when designing a tactile sensor. However, fulfilling these requirements come at the cost of increased complexity in design, high cost and difficulties in practical implementation due to size. In this research a sensor has been developed that is based on the concept of Hall effect. An array of magnets and hall sensors create a unique combination of outputs for each different deformation of the dual layered silicon membrane which houses the magnets. While allowing the interaction with non-planar surfaces due to the compliant nature of the silicon material, the sensor also facilitates accurate force recognition and localization with super-resolution using sensor readings, geometry and elastic properties of the silicon layer. This paper contains the design, fabrication and calibration of the tactile sensor array.
item: Conference-Full-text
Development of a bicondylar surface for a biomimetic knee joint capable of 3d motion
(IEEE, 2022-07) Senadheera, DS; Kaluarachchi, A; Thilina, P; Kulasekera, AL; Chathuranga, DS; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The knee is a major joint that is capable of 6 degrees of freedom (DoF) motion. In this paper, we present a biomimetic design of a bicondylar knee joint capable of 3D motion. The development of bicondylar surfaces is limited by the absence of accurate condylar surface development methodologies. Hence, this paper proposes a novel methodology, to obtain accurate bicondylar surfaces. The proposed method is used to develop a physical knee joint model. This knee joint model is experimentally evaluated using a model lower limb test setup (replicating the ankle, knee, and hip). The squatting motion of a human is replicated using this test setup. The hip motion of a healthy male test subject is recorded via image capture, and the hip joint of the test setup is actuated to follow this path. The computational model of the knee joint is used to predict the expected motion path during squatting, and the experimental result is compared against it. The results show RMSEs of less than 2.4 mm and 5.78 mm for anterior-posterior and inferior-superior displacements, respectively. Hence, it shows that the proposed bicondylar surface development methodology can be used to develop a biomimetic knee joint capable of 3D motion.
item: Conference-Abstract
Development of wearable fingertip tactile display driven by bowden cables
Premarathna, CP; Kulasekera, AL; Chathuranga, DS; Lalitharatne, TD
This paper presents the development and human interaction evaluation of a Bowden cable based wearable fingertip tactile display. This device is designed to be used in the field of virtual reality and teleoperation to render different types of tactile sensations such as grip force, slipping, roughness and softness through delivering normal force, skin stretch, tangential movement and vibration indication to the user. This paper evaluates the proposed device’s capability in delivering individual taxel actuation through user testing. A four taxel actuation system fixed to a mild steel skeleton is covered in silicone rubber to ensure wearer comfort. A secondary mechanism is developed to provide sliding and lateral skin stretch sensation to the user. In addition, an 8 mm diameter piezo vibration motor is used to deliver vibration to indicate slipping to the user. The force feedback system consist of four independently operable taxels positioned at 2mm center to center distance on the fingertip. Each taxel was actuated via a Bowden cable connected to a geared DC motor, mounted on a lower arm worn sleeve. A taxel discrimination experiment was done to validate human discrimination ability of each taxel and the results showed that a healthy human can distinguish each taxel with 87.45 % mean accuracy.
item: Conference-Full-text
Evaluation of hand tremor frequency among patients in Sri Lanka using a soft glove
(IEEE, 2020-07) Kavindya, P; Awantha, WVI; Wanasinghe, AT; Kulasekera, AL; Chathuranga, DS; Senanayake, B; Weeraddana, C; Edussooriya, CUS; Abeysooriya, RP
Tremors are the involuntary oscillations of a body part which occur due to diseases such as Parkinson’s Disease (PD), Essential tremor (ET) or stroke, which disturbs the activities of daily living (ADL). This paper presents an evaluation of hand tremor frequency among patients in Sri Lanka using a soft glove embedded with inertial measuring units (IMU) and its development and validation. This is a research towards the development of a hand tremor suppression device which requires data on hand tremors. To the best of the authors’ knowledge, no local data is available on hand tremors despite the availability of global studies. The hand tremor was quantitatively analyzed and the dominant frequency for each patient, overall mean and standard deviation of peak frequencies were obtained for this study group. The results show a mean of 5.05 ± 2.03 Hz for peak frequencies for the hand tremor patient sample in Sri Lanka. By the gender 4.62 ± 1.78 Hz and 5.69 Hz ± 2.38 Hz are the mean of peak frequencies for male and female sample respectively. This research will also be useful in disease diagnosing in clinical studies and developing hand tremor assessment tools.
item: Article-Full-text
A Low-Profile vacuum actuator (LPVAc) with integrated inductive displacement sensing for a novel sit-to-stand assist exosuit
(IEEE, 2021) Kulasekera, AL; Arumathanthri, RB; Chathuranga, DS; Chathuranga, RARC; Lalitharatne, TD
Muscle weakness owing to stroke, spinal cord injuries, or aging can make a person's life sedentary, temporarily as well as permanently. Such persons need to be motivated to break their sedentary postures and attempt independent motion. A key motivator in this aspect is the ability to easily transition from seated to standing posture. If this sit-to-stand transition (STSt) is easy, it will encourage further mobility. A soft wearable device that can assist the STSt, would ll this need perfectly. Such a device should be able to seamlessly assist during STSt and be unobtrusive during sitting. A major limitation that is currently holding back the development of soft exosuits in STSt-assist is the lack of low-pro le soft actuators with high strain rate and force-to-weight ratio. Hence, we propose a novel low-pro le vacuum actuator (LPVAc) with an integrated inductive displacement sensor that, can be rapidly fabricated, is lightweight (14 g), and can provide high strain (65%) and a high force-to-weight ratio (285 times self-weight). The proposed actuator comprises a low-pro le spring encased within a low-density polyethylene lm with rapid vacuum actuation and passive quick return. The proposed inductive sensor has a sensitivity of 0.0022 H=mm and the hysteresis is below 1.5% with an overall absolute average error percentage of 5.24%. The performance of the proposed integrated sensor in displacement control of the LPVAc is experimentally evaluated. The proposed actuator is integrated into a novel mono-articular STSt-assist exosuit for preliminary testing. Surface electromyography measurements of the gluteus maximus muscles during STSt indicate a mean muscle activity reduction of 45%. This supports the potential use of the proposed actuator in STSt-assist.
item: Conference-Abstract
A Novel fabrication method for rapid prototyping of soft structures with embedded pneumatic channels
Premarathna, CP; Kulasekera, AL; Chathuranga, DS; Lalitharatne, TD
Soft robotics is a major disruptive technology that is rapidly revolutionizing the world of robotics. As the design optimization of these soft robotic structures are still in its infancy, their designers have to resort to prototype testing. This paper describes how a novel casting method based on a 2D layered approach and thermal programming of pneumatic tubing can be used to simplify soft structure prototyping. The proposed casting method is based on the sequential stacking of laser-cut pre-fabricated plates, i.e. PMMA (acrylic) sheets, to create a 3D mold, instead of the traditional methods of fabricating 3D molds, such as CNC machining or 3D printing. Contemporary soft robotic applications are more interested in pneumatic actuation and thus require pneumatic channels embedded within their structure. Creation of channels is a critical factor that limit the fabrication scope of most such soft structures. A simple solution is using Polyurethane (PU) tubing to create channels within soft structures. A limitation of PU tubes is that, they cannot be directly embedded as any twist added to obtain the required path of the tube adds a strain on the soft structure from within, which can affect the desired operation. Hence, the authors propose removing the strain on the PU tubes by thermally programming the required shape onto the PU tube. PU tubes reinforced with copper cores are bent in to the desired shape and are heat treated to program the desired shape. After placing the programmed tubes within the mold, silicon rubber can be simply poured into the mold; and the finished structure can be taken out of the mold once cured. Main purpose of this paper is to present these two novel fabrication methods to simplify soft robotic prototyping, without the need for advanced, costly, complex equipment.
item: Article-Full-text
A robotic platform for aircraft composite structure inspection using thermography
(MDPI, 2022) Samarathunga, AI; Piyasundara, N; Wanigasooriya, AI; Kumara, BS; Vithanage, VP; Chathuranga, DS
Water ingression is a critical issue in honeycomb composite structures, which could result in catastrophic structural failure. In the aviation industry, they are widely used to manufacture critical aircraft structural components including fuselage, wings, and flight control surfaces. Catastrophic failure of these structures would be disastrous, thus identifying water accumulation in earlier stages of the defect is necessary. The conventional non-destructive testing method is thermography which is performed using handheld thermography cameras by manually accessing the specific areas. This method of inspection has been identified to be a risky, costly, time-consuming, and inspector-dependent technique. This paper describes using a wall-climbing robotic platform that can be controlled remotely to access and perform the inspection on a targeted structural area replacing the manual process. The designed wall-climbing inspection robot onboard a heat pump to stimulate the composite surface to an adequate temperature and, an infrared sensor to feed the real-time temperature data via Bluetooth serial communication to a remote computer system to be processed into a thermal image and evaluated to determine the presence of water. The results obtained from the thermographic sensor are validated with the comparison of the Fluke thermography camera.
item: Conference-Full-text
Variable stiffness soft actuator using layer jamming for food handling
(IEEE, 2022-07) Tennakoon, CL; Kulasekera, AL; Chathuranga, DS; Gopura, RARC; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
This study proposes a novel hybrid actuator combining PneuNet with layer jamming actuation to address the problems with conventional soft pneumatic actuators such as stability and lack of integrated locking mechanisms. The introduction of sandpaper-based layer jamming element is made as a solution. A set of experiments were conducted to identify suitable sandpaper grit-level and possible layering arrangement for the jamming section. P220 grit sandpaper showed the best flexural strength change which was suitable for the jamming element. The hybrid actuator was tested to identify the deviation from the typical PneuNet actuator in the performance of bending angle and generated tip force. The novel actuator showed a 25% reduction in bending angle while producing a 30° maximum bending angle at 160 kPa pressure. Tip force of the novel actuator didn’t show a significant difference and it produced 2.3 N force at 160 kPa. The integrated jamming element can act as a locking mechanism for the novel actuator. Due to the relaxation of the PneuNet, actuating locking mechanism shows an average 30% bending angle reduction compared to the initial bending angle. A two-finger gripper was produced using the hybrid actuator and it was successfully tested on soft food handling with the integrated locking feature.