System Identification and Adaptive Compensation of Friction in Manufacturing Automation Systems

Industrial demands for more efficient machine tool systems have been significantly increased. In order to obtain high performance machine tool systems, researchers are focused on enhancing functioning of various components of machine tool systems. Feed drives are important component of the most of machine tool systems such as computer numerical control (CNC) machines for achieving desirable performance. An essential research stream of current interest aiming enhancement of feed drive performance is construction of control methods that help to decrease tool positioning errors in the system. An effective approach for mitigation or reduction of positioning errors is modeling, identifying, and compensating friction in appropriate manner. In addition, accurate modeling of feed drive systems is essential in elimination of these positioning errors. In this thesis, the precision control of feed drives is studied using several different control methods. Firstly, the feed drive type that has common use in machine tools is chosen to be main focus for this research, namely ball screw drive. Different dynamic models of ball screw drive are shown in detail. In addition, some of the nonlinearities that affect ball screw dynamics such as friction affects are discussed. Friction modeling needs to be performed realistically and accurately in order to design an effective compensator to cancel friction effects. In general, the friction models are divided into two categories; classic (static) and dynamic friction models. In this thesis, we present details of these models and derive linear parametrization of the key ones. Based on the derived linear parametric models, we design a least-squares on-line friction estimator and adaptive friction compensation scheme. The performance of these designs are verified via simulation and real-time experimental tests. Noting that the parameters of the base rigid body model, i.e., inertia and viscosity constants, need to be known precisely for effective high precision control tasks, including the aforementioned adaptive schemes. The second part of the thesis focuses on off-line identification of these key base model parameters. In this part, we present a real-life case study on identification of plant and built-in controller parameters and a simulator design based on this identification for a grinding CNC machine used in a gear manufacturing company

Dynamic Model Identification and Trajectory Correction for Virtual Process Planning in Multi-Axis Machine Tools

In today’s industry, the capability to effectively reduce production time and cost gives a manufacturer a vital advantage against its competitors. Specifically, in the machining industry, the ability to simulate the dynamic performance of machine tools, and the physics of cutting processes, is critical to taking corrective actions, achieving process and productivity improvements, thereby enhancing competitiveness. In this context, being able to estimate mathematical models which describe the dynamic response of machine tools to commanded tool trajectories and external disturbance forces plays a key role in establishing virtual and intelligent manufacturing capability. These models can also be used in virtual simulations for process improvement, such as compensating for dynamic positioning errors by making small corrections to the commanded trajectory. This, in turn, can facilitate further productivity improvement and part quality in multi-axis manufacturing operations, such as machining. This thesis presents new methods for identifying the positioning response and friction characteristics of machine tool servo drives in a nonintrusive manner, and an approach for enhancing dynamic positioning accuracy through commanded trajectory correction via Iterative Learning Control (ILC). As the first contribution, the linear transfer functions correlating the positioning response to the commanded trajectory and friction disturbance inputs are identified using a new pole search method in conjunction with least squares (LS) projection. It is validated that this approach can work with in-process collected data, and demonstrates superior convergence and numerical characteristics, and model prediction accuracy, compared to an earlier ‘rapid identification’ approach based on the application of classical Least Squares for the full model. Effectiveness of the new method is demonstrated in simulations, and in experimental case studies for planar motion on two different machine tools, a gear grinding machine and a 5-axis machining center. Compared to the earlier approach, which could predict servo errors with 10-68% closeness, the new method improves the prediction accuracy to 0.5-2%. In the simulation of feed drives used in multi-axis machines, high fidelity prediction of the nonlinear stick-slip friction plays an important role. Specifically, time-dependent (i.e., dynamic) friction models help to improve the accuracy of virtual predictions. While many elaborate models have been proposed for this purpose, such as the generalized Maxwell-slip (GMS) model, their parameters can be numerous and difficult to identify from limited field data. In this thesis, as the second contribution, a new and highly efficient method of parameterizing the pre-sliding (hysteretic) portion of the GMS friction model is presented. This approach drastically reduces the number of unknown variables to identify, by estimating only the affective breakaway force, breakaway displacement, and ‘shape factor’ describing the shape of the pre-sliding virgin curve. Reduction in the number of unknowns enables this ‘reduced parameter’ GMS model to be identified much more easily from in-process data, compared to the fully parameterized GMS model, and the time-dependent friction dynamics can still be simulated accurately. Having improved the positioning response transfer function estimation and friction modeling, as the third contribution of this thesis, these two elements are combined together in a 3-step process. First, the servo response is estimated considering simplified Coulomb friction dynamics. Then, the friction model is replaced and identified as a reduced parameter GMS model. In the third step, the transfer function poles and zeros, and the reduced parameter GMS model, are concurrently optimized to replicate the observed experimental response with even greater fidelity. This improvement has been quantified as 12-44% in RMS and 28-54% in MAX values. This approach is successful in servo systems with predominantly rigid body behavior. However, its extension to a servo system with vibratory dynamics did not produce an immediately observed improvement. This is attributed to the dominance of vibrations in response to the commanded trajectory, and further investigation is recommended for future research. Having an accurate model of a multi-axis machine’s feed drive response allows for the dynamic positioning errors, which can lead to workpiece inaccuracy or defects, to be predicted and corrected ahead of time. For this purpose, ILC has been investigated. It is shown that through ILC, 1-2 orders of magnitude reduction in the servo errors is possible. While ILC is already available in certain commercial CNC systems, its training cycle (which is performed during the operation of the machine tool) can lead to part defects and wasted productive machining time. The new idea proposed in this thesis is to perform ILC on a virtual model, which is continuously updated via real-time production data using the identification methods developed in this work. This would minimize the amount of trial and error correction needed on the actual machine. In the course of this thesis research, after validating the effectiveness of ILC in simulations, to reliably and safely migrate the virtual modeling and trajectory correction results into industry (such as on a gear grinding machine tool), the author initiated and led the design and fabrication of an industry-scale testing platform, comprising a Siemens 840D SolutionLine CNC with a multi-axis feed drive setup. Majority of this implementation has been completed, and in near future work, the dynamic accuracy and productivity improvements facilitated with ‘virtually’ tuned ILC are expected to be demonstrated experimentally and tested in industry

Molekularno otkrivanje i genomska svojstva psećeg virusa Torque teno u Turskoj

Torque teno virus (TTV) was first detected in humans, and since then it has been reported in many host species, such as monkeys, cats, pigs, seagulls and dogs. The aim of this study was to investigate the presence of Torque teno canis virus (TTCaV) in shelter dogs housed in Sivas Municipal Animal Shelter, Turkey. Faecal specimens, including diarrheic and non-diarrheic (n=202), were collected from dogs of various age groups. In total, 32.18% (65/202) of samples were found positive for TTCaV. Out of the 65 positive samples, 34.64% (44/127) samples were from adult diarrheic dogs and 26.09% (6/23) belonged to diarrheic puppies. On the other hand, 28.84% (15/52) positive samples were detected from clinically healthy dogs. Eight sequences showed close homology among themselves, however, the sequences of two samples (CANEL130 and CANEL140) were genetically distinct from other published sequences. This is the first report on the detection of TTCaV in adult dogs and puppies in Turkey, and provides evidence that TTCaV cannot be considered as the sole cause of diarrhea.Virus Torque teno (TTV) otkriven je najprije u ljudi, no otada je zabilježen i u mnogim drugim domaćinima kao što su majmuni, mačke, svinje, galebovi i psi. Cilj ovoga rada bio je istražiti prisutnost psećeg virusa Torque teno (TTCaV) u pasa u azilu Sivas Municipal Animal Shelter u Turskoj. Uzorci izmeta (n = 202), uključujući one s proljevom i bez proljeva, prikupljeni su od pasa različitih dobnih skupina. Ukupno je 32,18 % (65/202) uzoraka bilo pozitivno na TTCaV. Od 65 pozitivnih uzoraka njih 34,64 % (44/127) potjecalo je od odraslih pasa s proljevom, a 26,09 % (6/23) od štenadi s proljevom. S druge strane, 28,84 % (15/52) pozitivnih uzoraka utvrđeno je u klinički zdravih pasa. Osam je sekvencija pokazalo međusobnu blisku srodnost, no sekvencije dvaju uzoraka (CANEL130 i CANEL140) genetski su se razlikovale od drugih sekvencija. Ovo je prvi nalaz TTCaV u odraslih pasa i štenadi u Turskoj i dokazuje da se TTCaV ne može smatrati jedinim uzročnikom proljeva

Monthly Trend Investıgatıon of the Dıscharge of a Stream in Cache County. Utah.

Discharge values of streams are critical for planning the water resources of basins. Discharge values of streams may change due to many reasons such as climatological effects or human-related issues. It is essential to make estimations about the discharge values’ trends for more feasible constructions on streams. In this study, discharge monitoring station records of USGS were used to determine the trends over 50 years. The data set is belonging to the Logan River Above State Dam, Near Logan. UT station and it starts in 1971 and ends in 2020. Traditional Mann Kendall Spearman’s Rho and Sen’s slope statistical tests were used to determine the monthly trends. Additionally, a yearly investigation was performed by using the same statistical approaches. According to the obtained results, any significant trends were not detected in the yearly evaluation. However, in the monthly evaluation trends were detected for August and September

Rectus sheath hematoma: three case reports

<p>Abstract</p> <p>Introduction</p> <p>Rectus sheath hematoma is an uncommon cause of acute abdominal pain. It is an accumulation of blood in the sheath of the rectus abdominis, secondary to rupture of an epigastric vessel or muscle tear. It could occur spontaneously or after trauma. They are usually located infraumblically and often misdiagnosed as acute abdomen, inflammatory diseases or tumours of the abdomen.</p> <p>Case presentation</p> <p>We reported three cases of rectus sheath hematoma presenting with a mass in the abdomen and diagnosed by computerized tomography. The patients recovered uneventfully after bed rest, intravenous fluid replacement, blood transfusion and analgesic treatment.</p> <p>Conclusion</p> <p>Rectus sheath hematoma is a rarely seen pathology often misdiagnosed as acute abdomen that may lead to unnecessary laparotomies. Computerized tomography must be chosen for definitive diagnosis since ultrasonography is subject to error due to misinterpretation of the images. Main therapy is conservative management.</p

GENETIC DIVERSITY of OVINE HERPESVIRUS 2 STRAINS OBTAINED FROM MALIGNANT CATARRHAL FEVER CASES in EASTERN TURKEY

Malignant Catarrhal Fever (MCF) is a generalized, definitive lethal disease affecting the epithelial and lymphoid tissues of the respiratory and digestive tract, mainly cattle and some wild ruminants such as deer, buffalo or antelope. The sheep-related form of MCF is known to be present in Turkey and is caused by ovine herpesvirus 2 (OvHV-2). The aim of this study was to reveal the genetic diversity of OvHV-2 strains obtained from MCF cases in Eastern Turkey where the livestock industry has an important impact on economic activities. For this purpose, RTA (Replication and transcription activator), FGARAT (formylglycineamide ribotide amidotransferase) and some of glycoprotein genes (0v7, Ov8 ex2, ORF27 and Ov9.5) were investigated in blood samples from 24 cattles, clinically diagnosed with MCF. Genomic data of chosen samples were furthermore used to characterize and undergo combined phylogenetic analysis to determine possible alleles and subvariants. The results showed that high level of OvHV-2 diversity existed in selected genes and strains carrying allelic variants might circulate both in two geographically distinct regions and in a region itself. Moreover, three different OvHV-2 types and various subtypes were identified based on multi locus approach. This study provides important data to epidemiological research and thereby helps to determine the source of the virus and understand the spread of the disease

"Stapler" ile yapılan akciğer rezeksiyonlarındaki hava kaçağının azaltılmasında yeni bir yöntem

Air leaking after stapled pulmonary parenchymal resections is one of the causes of postoperative morbidity. In this clinical trial, a synthetic material, polytetrafluoroethylene (PTFE), was used for buttressing staple lines, in an attempt to evaluate its efficacy on postoperative air leaks. 71 patients who underwent pulmonary parenchymal resections were divided into two groups. Control group consisted 28 patients in which resections were accomplished with a stapler, whereas in the study group (43 patients), PTFE sleeves were used that fit over the arms of the stapler. The time of cessation of air leaks were assessed statistically in both groups. The averages of the duration of air leaks were 52.9 ;plusmn; 14.5 and 41.3 ;plusmn; 12.5, respectively. The study showed a significant difference (p;lt; 0.05) by the use of PTFE sleeves to buttress the staple lines in pulmonary parenchymal resections, for reducing the incidence of air leaks. There was, however, a considerable cost increasing, thus limiting the overuse of this material, except for the resections performed in emphysematous lungs."Stapler" (STP) ile yapılan akciğer rezeksiyonlarından sonra gözlenen hava kaçağı, postoperatif morbidite nedenlerinden biridir. Bu klinik çalışmada, STP hattının takviyesi için kullanılan, sentetik yapıdaki politetrafloroetilen (PTFE) kılıfın postoperatif hava kaçağı üzerine olan etkisi araştırıldı. Pulmoner parankim rezeksiyonu uygulanan 71 hasta çalışmaya alındı. İki gruba ayrılan olgulardan kontrol grubunda yer alan 28'ine sadece STP ile rezeksiyon yapıldı. Çalışma grubundaki 43 hastada ise, STP kollarına geçirilen PTFE kılıf kullanılarak rezeksiyon gerçekleştirildi. İki grup, postoperatif hava kaçağı süresi açısından değerlendirildi. Kontrol ve çalışma gruplarındaki postoperatif hava kaçağı süresinin ortalamaları sırasıyla 52.9 ± 14.5 ve 41.3 ± 12.5 saat olarak kaydedildi. PTFE kılıf ile STP hattının takviye edildiği akciğer parankim rezeksiyonlarında postoperatif hava kaçağı süresi, PTFE kullanılmayan olgulara göre istatistiksel olarak anlamlı derecede kısa bulundu (p 0.05). Ancak ameliyat maliyetini arttırması, bu ürünün amfizemli akciğere uygulanacak rezeksiyonlar dışında aşırı kullanımını sınırlamaktadır

Dysfunctional Attitudes in Alcohol Dependents: A Comparative Study

Objective: Cognitive behavioral theory provides a theoretical framework for understanding the etiology and persistence of pathological drinking, and a conceptual basis for developing clinical techniques to treat the disorder. In line with this scope, we aimed to investigate the cognitive properties of alcohol dependence. Method: Two groups composed of seventy-nine inpatients with a diagnosis of alcohol dependence and thirty one healthy controls who were using alcohol, but not filling the requirements of alcohol dependence diagnosis were included in this study. Dysfunctional attitudes scale (DAS) was given to both groups for detection of dysfunctional cognition. At the same time, alcohol dependent group was evaluated using Structured Clinical Interview for DSM-III-R-Axis-I and Axis-II (SCID I and II). The data was evaluated using SPSS 17. Results: DAS total scores and perfectionist attitudes, need for approval and independent attitudes subscores were significantly higher in patients than healthy controls. In addition, a significant correlation was detected between DAS total scores, and the age of emergence of alcohol dependence. Conclusion: As a result of the study, it can be concluded that concluded with literature, alcohol dependent patients have dysfunctional beliefs. In particular, a relation was detected between alcohol dependence and perfectionist attitude, need for approval and independent attitudes. [JCBPR 2012; 1(2.000): 113-120