Image based visual servoing using bitangent points applied to planar shape alignment

We present visual servoing strategies based on bitangents for aligning planar shapes. In order to acquire bitangents we use convex-hull of a curve. Bitangent points are employed in the construction of a feature vector to be used in visual control. Experimental results obtained on a 7 DOF Mitsubishi PA10 robot, verifies the proposed method

Positioning and trajectory following tasks in microsystems using model free visual servoing

In this paper, we explore model free visual servoing algorithms by experimentally evaluating their performances for various tasks performed on a microassembly workstation developed in our lab. Model free or so called uncalibrated visual servoing does not need the system calibration (microscope-camera-micromanipulator) and the model of the observed scene. It is robust to parameter changes and disturbances. We tested its performance in point-to-point positioning and various trajectory following tasks. Experimental results validate the utility of model free visual servoing in microassembly tasks

A fast algorithm for vision-based hand gesture recognition for robot control

We propose a fast algorithm for automatically recognizing a limited set of gestures from hand images for a robot control application. Hand gesture recognition is a challenging problem in its general form. We consider a fixed set of manual commands and a reasonably structured environment, and develop a simple, yet effective, procedure for gesture recognition. Our approach contains steps for segmenting the hand region, locating the fingers, and finally classifying the gesture. The algorithm is invariant to translation, rotation, and scale of the hand. We demonstrate the effectiveness of the technique on real imagery

İki noktada teğetler kullanarak görüntü tabanlı görsel geri beslemeli kontrol ile düzlemsel şekil hizalama

Bu bildiride, düzlemsel şekilleri hizalamak için iki noktada teğetlerden (bitangent) faydalanan görsel geri beslemeli kontrol stratejileri sunulmuştur. Bitangentları elde etmek ic¸in bir eğrinin dışbükey zarfından (convex-hull) yararlanılmıştır. İmge nitelik vektörü bitangent noktalarından oluşturularak görsel kontrolde kullanılmıştır. 7 serbestlik dereceli Mitsubishi PA10 robotu üzerinde gerçekleştirilen deneyler önerilen metodun geçerliliğini göstermiştir

Model-based vs. model-free visual servoing: A Performance evaluation in microsystems

In this paper, model-based and model-free image based visual servoing (VS) approaches are implemented on a microassembly workstation, and their regulation and tracking performances are evaluated. A precise image based VS relies on computation of the image jacobian. In the model-based visual servoing, the image Jacobian is computed via calibrating the optical system. Precisely calibrated model based VS promises better positioning and tracking performance than the model-free approach. However, in the model-free approach, optical system calibration is not required due to the dynamic Jacobian estimation, thus it has the advantage of adapting to the different operating modes

Konservatif tedavi edilen bir izole kapitatum kırığı: Olgu sunumu

Kapitatum kırıkları karpal kemik kırıklarının %1'ini oluşturmaktadır. İzole kapitatum kırığı nadir olarak görülür ve literatürde olgu sunumları olarak yer almaktadır. Kapitatum kırıklarının tanısındaki gecikmeler kaynamama, avasküler nekroz ve sekonder artroza neden olabilir. Bu yazımızda tanısında gecikme olan ve konservatif tedavi ettiğimiz bir izole kapitatum kırığının erken dönem sonuçlarını bildirerek nadir görülen bu kırığın tanı ve tedavisinin önemini vurgulamak istedikCapitatum fractures contributes 1% of all carpal bone fractures. Isolated fracture of capitatum is a rare entity which is seen in the literature as case reports. Any delay in diagnosis can cause complications such as nonunion, avascular necrosis, malunion and secondary arthrosis. We present in this paper the early result of the conservative treatment of an isolated nondisplaced capitatum fracture which was diagnosed late and emphasize the importance of the diagnosis and treatment of capitatum fracture

A new point of view for mosaicplasty in the treatment of focal cartilage defects of knee joint: honeycomb pattern

Background: A focal full thickness cartilage lesion of knee joint is one of the commonly seen intraarticular pathologies among the joint cartilage problems. Osteochondral autograft transfer mosaicplasty is a method which has satisfactory outcomes among the treatment preferences of cartilage defects. In spite of the favorable clinical results there are some pitfalls of mosaicplasty treatment especially in cases of large defects. One of the major problems of the classical OAT mosaicplasty is the gap spaces between the plugs. The objective of the present study is to report the early clinical and radiological outcomes and to evaluate the clinical application of a new hexagonal osteochondral graft system (HOGS) with the hypothesis of improvement of the OAT mosaicplasty method with the use of hexagonally shaped plugs. The study has intended to answer two questions. (1) Does mosaicplasty with the new HOGS has favorable early clinical outcomes? (2) Is it possible to arrange the osteochondral autografts without leaving gap spaces by using hexagonal pattern in OAT mosaicplasty? Patients and methods: We designed a retrospective study to report analysis of early outcomes of the initial case series of OAT mosaicplasty by using a new HOGS. Six male individuals with the diagnosis of osteochondral defect and treated with HOGS and reached sixth month follow-up formed the basis of the study. The clinical status of the patients were evaluated with IKDC score. The radiological evaluations were carried out with direct X-rays and magnetic resonance imaging (MRI) studies. The mosaicplasty procedures were carried out via standard surgical method of classical OAT mosaicplasty by using the HOGS following a diagnostic arthroscopy in the same session. The inclusion criteria was a full thickness osteochondral lesion of femoral condyle between 1.5 and 6 cm(2) and completion of 6 month follow-ups. The patients having deformities around the knee or major ligament lesions were excluded. MOCART scoring system was used for the evaluation of follow-up MRI findings. The clinical status of the patients were evaluated with IKDC scores. Results: The mean age of the patients was 40.8 (+/- 5.2) years and the mean duration of the symptoms on presentation was 16 (+/- 4.3) months. On the initial MRI studies mean defect area was measured 3.7 cm(2) (+/- 0.9) which was compatible with arthroscopic findings. During the surgical procedures it was possible to fill the defect area completely. The mean number of plugs in this series was 4.8 (+/- 1.1). We did not faced with insufficient donor reserve problem in any of the cases. On the sixth month follow-up physical examination there was no limitation of the knee joint range of motion in the cases. All patients were able to bear weight on to their operated extremities without pain. The mean postoperative IKDC score improvement was 70.2 (+/- 3.5) which shows significant improvement compared to preoperative scores. On the control MRI studies the bone integration of the hexagonal plugs were complete the cartilage continuity of the articular surfaces were intact and the grafts were well incorporated in all cases. The mean MOCART score on the 6th month MRI studies was 65.8 (+/- 4.1). Conclusion: The early outcomes of OAT mosaicplasty with HOGS are comparable to studies on the classical mosaicplasty. According to our observations in this study we can say that the gap space left between the cylindrical plugs can be solved by using hexagonal prism shaped plugs

Model free visual servoing in macro and micro domain robotic applications

This thesis explores model free visual servoing algorithms by experimentally evaluating their performances for various tasks performed both in macro and micro domains. Model free or so called uncalibrated visual servoing does not need the system (vision system + robotic system) calibration and the model of the observed scene, since it provides an online estimation of the composite (image + robot) Jacobian. It is robust to parameter changes and disturbances. A model free visual servoing scheme is tested on a 7 DOF Mitsubishi PA10 robotic arm and on a microassembly workstation which is developed in our lab. In macro domain, a new approach for planar shape alignment is presented. The alignment task is performed based on bitangent points which are acquired using convex-hull of a curve. Both calibrated and uncalibrated visual servoing schemes are employed and compared. Furthermore, model free visual servoing is used for various trajectory following tasks such as square, circle, sine etc. and these reference trajectories are generated by a linear interpolator which produces midway targets along them. Model free visual servoing can provide more exibility in microsystems, since the calibration of the optical system is a tedious and error prone process, and recalibration is required at each focusing level of the optical system. Therefore, micropositioning and three di erent trajectory following tasks are also performed in micro world. Experimental results validate the utility of model free visual servoing algorithms in both domains

Design and development of novel large scale applications in micro/nanophotonics and nanobiotechnology

Ankara : The Materials Science and Nanotechnology Program and the Graduate School of Engineering and Science of Bilkent University, 2014.Thesis (Ph. D.) -- Bilkent University, 2014.Includes bibliographical references leaves 91-101.Developments in micro/nanophotonics and nanobiotechnology creates new opportunities regarding development of devices with unprecedented capabilities, which could improve human civilization substantially. On the other hand, a certain level of maturity in transforming these possibilities into reality still requires considerable efforts. One of the main problems of these novel technologies is that their practical know-how is so scarce that they could only be utilized within strictly determined laboratory conditions, and by highly sophisticated scientists. This thesis focuses on large scale applications at the intersection of microphotonics and nanobiotechnology, and also in nanophotonics. On microphotonics side, optical microresonators with toroidal shape were successfully fabricated and optically integrated. Having an extremely high sensitivity towards perturbations in their environments, these microcavities could be used as biological sensors; however, they are also very sensitive for nonspecific interactions. Thus, a novel surface chemistry enabling bioconjugation of molecular probes without compromising their sensitivity and enhancing their selectivity was developed, based on methylphosphonate containing silane modification of the microtoroid surface. After this functionalization, microtoroids were used in biodetection in complex media. Also, a macroscopic photodetection device composed on intrinsically aligned semiconducting selenium nanowires were demonstrated. This device could be considered as a novel and efficient demonstration of nanowire integration to the macroscopic world. Together with the research on biosensors, these are important large scale applications of emergent science of our age.Özgür, ErolPh.D