Control and measurement delay compensation in bilateral position control

The main aim of this study is the improvement of the previously presented disturbance observer based bilateral control approaches of the authors with a delay regulator and a model tracking control (MTC) that runs on the slave side. These improvements eliminate the problems related to variable time delay inherent to such systems and model mismatch, respectively, and, hence, addressing the control and measurement delay problems in bilateral control applications. The performance is evaluated experimentally on a single-link arm controlled over the internet. The results demonstrate a significant improvement over the previously presented results obtained under load uncertainties and randomly varying network delays both in the control and feedback loop

Experimental Evaluation of Novel Master-Slave Configurations for Position Control under Random Network Delay and Variable Load for Teleoperation

This paper proposes two novel master-slave configurations that provide improvements in both control and communication aspects of teleoperation systems to achieve an overall improved performance in position control. The proposed novel master-slave configurations integrate modular control and communication approaches, consisting of a delay regulator to address problems related to variable network delay common to such systems, and a model tracking control that runs on the slave side for the compensation of uncertainties and model mismatch on the slave side. One of the configurations uses a sliding mode observer and the other one uses a modified Smith predictor scheme on the master side to ensure position transparency between the master and slave, while reference tracking of the slave is ensured by a proportional-differentiator type controller in both configurations. Experiments conducted for the networked position control of a single-link arm under system uncertainties and randomly varying network delays demonstrate significant performance improvements with both configurations over the past literature

Predictive Input Delay Compensation with Grey Predictor for Networked Control System

The performance of networked control systems is affected strictly by time delay. Most of the literature in the area handle the problem from a stability perspective. However, stability optimized algorithms alone are not sufficient to reduce synchronization problems caused by time delay between the action and reaction in geographically distant places, and the effect and performance of other system components should also be taken into account. In teleoperation applications the reference is often provided by a human, known as the operator, and due to the nature of the human system, references provided by the human operator are of a much lower bandwidth when compared to common control reference inputs. This paper focuses on the operator, and proposes an approach to predict the manipulator’s motion (created by the operator) ahead of time with an aim to reduce the time delay between the master and slave manipulator trajectories. To highlight the improvement offered by the developed approach, hereby called Predictive Input Delay Compensator (PIDC), we compare the performance with the only other study in the literature that handles this problem using the Taylor Series approach. The performance of these two approaches is evaluated experimentally for the forward (control) path on a PUMA robot, manipulated by a human operator and it has been demonstrated that the efficient latency in the forward path is decreased by 100ms, on average, reducing the forward latency from 350ms to 250ms

Wavelet packet transform-based compression for teleoperation

This paper introduces a codec scheme for compressing the control and feedback signals in networked control and teleoperation systems. The method makes use of Wavelet Packet Transform (WPT) and Inverse Wavelet Packet Transform (IWPT) for coding and decoding operations, respectively. Data compression is carried out in low-pass filter output by reducing the sampling rate, and in high-pass filter output by truncating the wavelet coefficients. The proposed codec works on both directions of signal transmission between a master robot and a slave robot over a networked motion control architecture. Following the formulation of the compression/decompression methodology, experimental validation is conducted on a single-degree-of-freedom motion control system. In the experiments, responses from different Wavelet structures are analyzed and a comparative study is carried out considering the factors of compression rate, reconstruction power error and real-time computational complexity. It is confirmed that the controller using the proposed compression algorithm performs very close to the uncompressed one while enabling transmission of much less data over the network

Wavelet packet transform based compression for bilateral teleoperation

This paper introduces a codec scheme for compressing the control and feedback signals in bilateral control systems. The method makes use of Wavelet Packet Transform (WPT) and Inverse Wavelet Packet Transform (IWPT) for coding and decoding operations respectively. Data compression is carried out in low pass filter output by reducing the sampling rate; and in high pass filter output by truncating the wavelet coefficients. The proposed codec works on both directions of signal transmission between a master robot and a slave robot over a networked motion control architecture. Following the formulation of the compression/decompression methodology, experimental validation is conducted on a single degree of freedom (DOF) motion control system. In the experiments, responses from different Wavelet structures are analyzed and a comparative study is carried out considering the factors of compression rate, reconstruction power error and real time computational complexity. It is confirmed that the controller using the proposed compression algorithm performs very close to the uncompressed one while enabling transmission of much less data over network

The many faces of small B cell lymphomas with plasmacytic differentiation and the contribution of MYD88 testing

Plasmacytic differentiation may occur in almost all small B cell lymphomas (SBLs), although it varies from being uniformly present (as in lymphoplasmacytic lymphoma (LPL)) to very uncommon (as in mantle cell lymphomas (MCLs)). The discovery of MYD88 L265P mutations in the vast majority of LPLs has had a major impact on the study of these lymphomas. Review of the cases contributed to the 2014 European Association for Haematopathology/Society for Hematopathology slide workshop illustrated how mutational testing has helped refine the diagnostic criteria for LPL, emphasizing the importance of identifying a clonal monotonous lymphoplasmacytic population and highlighting how LPL can still be diagnosed with extensive nodal architectural effacement, very subtle plasmacytic differentiation, follicular colonization, or uncommon phenotypes such as CD5 or CD10 expression. MYD88 L265P mutations were found in 11/11 LPL cases versus only 2 of 28 other SBLs included in its differential diagnosis. Mutational testing also helped to exclude other cases that would have been considered LPL in the past. The workshop also highlighted how plasmacytic differentiation can occur in chronic lymphocytic leukemia/small lymphocytic lymphoma, follicular lymphoma, SOX11 negative MCL, and particularly in marginal zone lymphomas, all of which can cause diagnostic confusion with LPL. The cases also highlighted the difficulty in distinguishing lymphomas with marked plasmacytic differentiation from plasma cell neoplasms. Some SBLs with plasmacytic differentiation can be associated with amyloid, other immunoglobulin deposition, or crystal-storing histiocytosis, which may obscure the underlying neoplasm. Finally, although generally indolent, LPL may transform, with the workshop cases suggesting a role for TP53 abnormalities

Ağ üzerinden kontrol sistemlerinin performans iyileştirmesi için yeni kontrol ve haberleşme yaklaşımları

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2015Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 2015Teleoperasyon mobil veya sabit bir manipülatörü coğrafi olarak uzak bir noktanadan kontrol etme anlamına gelmektedir. Tehlikeli bölgelerde arama/tarama, kimyasal madde işleme sistemleri, uzaktan ameliyat sistemleri ve uzay robotiği sistemleri günümüzde teleoperasyon uygulama alanları arasında sayılabilir. Uygulama alanlarının bu kadar geniş ve popüler bir yelpaze olusturması teleoperasyon konusunu aktif bir araştırma alanı haline getirmiştir. Teleoperasyonun en temel problemi coğrafi olarak uzak sistemlerin senkronize edilmesidir. Bu senkronizasyon problemi coğrafi olarak uzakta bulunan bu iki sistemi birleştiren haberleşme kanalı ile doğrudan ilintilidir. Özellikle, günümüzde tüm dünya, Internet üzerinden birbirine bağlı olduğundan, haberleşme kanalı olarak Internet'i tercih etmek ekonomik olarak çok avantajlıdır. Fakat, bununla birlikte Internet'in dezavantajları da yok değildir. Nitekim, Internet üzerinden işaret taşıma, kontrol sistemlerinin kararlılığında ve kontrol performansında bozulmalara neden olabilir. Bu probleme Internet ortamındaki zaman gecikmesi sebep olur. Zaman gecikmesi haricinde, performans band genişliği ve örnekleme hızı arasındaki ters ilişkiden de olumsuz olarak etkilenmektedir. Sistem performansi ayrica efendi taraftaki operatörün köle taraftaki manipülatörün etkileşimde olduğu çevreyi dokunarak algılama başarımına, köle taraftaki manüpülatörün de efendi taraftaki manüpülatörün yörünge takip başarımından da fazlaca etkilenmektedir. Internet üzerinden kontrolü, geleneksel zaman gecikmeli kontrolden ayıran en temel özellik, zamanda gecikme süresinin belli bir kurala bağlı kalmadan değişiyor olmasıdır. Bu özellik sistemde yeni bir bozucu etkisi yaratır. Geliştirilen efendi-kole mimarisi öncelikle bu bozucuyu bastırmalıdır. Bozucunun sadece geribesleme hattında olmasi durumunda olumsuz etki geleneksel bozucu bastırma yöntemleri ile bastırılabilirken, bozucunun kontrol işareti hattında da etkili olmasi haberleşme kaynaklı bozucu bastırma yontemlerinin geliştirilmesini gerektirmektedir. Bu tezde teleoperasyon problemine iki çekirdek mimari önerilmistir. Bu çözümlerin birinde, efendi tarafta kayma kipli bir gözleyici ve köle tarafta model izleyen bir kontrolör bulunmaktadir. Haberleşme gecikmesinin degeri, hem efendi sistemden köle sistem yönüne, hem de köle sistemden efendi sistem yönüne gecikme doğrultucusu ile tasarım sürecinde belirlenen bir maksimum değere sabitlenmiştir. İkinci çözümde ise, efendi sistem tarafında Astrom'un Smith Predictor yapısı, ve köle sistem tarafında yine model izleyen kontrolör bulunmaktadır. Gecikme regülatörleri bu çözümde de kullanılmaktadır. Tezde, yukarida sunulan çekirdek mimari yapısının dayanıklılık, bandgenişliği ve senkronizasyon performansının arttırımını sağlayacak eklentiler de önerilmiştir. Bu eklentilerden birincisi dayanıklılığı garanti altına almak için önerilen kontrol işaret düzeltme yapısıdır. Dayanıklılığın en büyük engeli gecikmenin tasarlanan değerin üstüne çıkması ve gecikme regülatörlerinin gecikmeyi sabitleyememesidir. Bu önerilen yapı ile kontrol işaretinin kendisi değil, sisteme olan etkisi düzeltilebilmektedir. Böylelikle geçici rejim dinamiğinde bozukluklar görülmesine ragmen sürekli halde bu bozukluklar ortadan kalkmaktadır. Ayrıca haberleşme hattının çıktı hızı da çözülmesi gereken başka bir problem kaynağıdır. İkinci eklenti bu problemi çözmektedir. Çıktı hızının limiti kontrol sistemini mekanik sistemin dinamiğinin limitlediğinden daha düşük bir Nyquist frekanında çalışmaya zorlar. Bu nedenle örnekleme hızı belirlenirken sadece mekanik sistem değil, aynı zamanda haberleşme ortamının çıkış hızı da dikkate alınmalıdır. Çıktı hızına uyum sağlamak için örnekleme frekansını düşürmek kontrol sisteminin doğruluğunu da beraberinde düşürecektir. Ayrıca örnekleme hızını düşürme sisteme eklenebilecek olan EKF gibi yüksek örnekleme frekansı gerektiren modern gözleyicilerin de kullanımını kısıtlar. Bu tezde, ayrıca, bu tip problemleri çözebilecek ağ haberleşmesi kaynaklı yaklaşımlar da önerilmektedir. Çıktı hızını en iyileme problemi için tezde Wavelet Paket Ağacı (Wavelet Packet Tree-WPT) dönüşümünü temel alan yeni bir sıkıştırma yapısı önerilmiştir. Bu yapı literatürdeki DFT tabanlı yapı ile karşılaştırılmıştır. Yaptığımız deneyler WPT tabanlı yapınının hemen hemen her sıkıştırma oranında DFT tabalı algoritmadan daha iyi sonuç verdiğini göstermiştir. Üçüncü eklenti, senkronizasyon problemini hedeflemektedir. Efendi ve köle taraf arasındaki senkronizasyonu etkileyen en önemli unsur doğal olarak ağ gecikmesinin büyüklüğüdür. Genelde teleoperasyon problemi hep kararlılık açısından ele alınmıştır. Oysaki sadece kararlılığa odaklanmış algoritmaların çoğrafi olarak uzak mesafedeki sistemlerin senkronizasyon problemlerini de çözdüğünü söylemek pek mümkün değildir. Bu senkronizasyonu iyileştirmek için performansı belirleyen diğer bileşenleri de dikkate almak gerekir. Teleoperasyonda, referans işareti genel olarak operatör diye adlandırılan bir insan tarafından oluşturulmaktadır. İnsanın doğasını düşündüğümüzde, band genişliği entegre sisteme oranla çok küçüktür. Senkronizasyon probleminin çözümü için tezde Grey Teori tabanlı bir kestrici önerilmiş, ve efendi maniplatörde gerçek referans yörüngesi oluşmadan bir kestrim yörüngesi oluşturulmuştur. Böylelikle efendiden köleye etki süresinin kısaltılması hedeflenmiştir. Bizim buradaki felsefemiz, ağ kaynaklı gecikmelerin kaçınılmaz ve rastgele olduğunu bilip, imkanlar dahilinde diğer tüm gecikmeleri azaltmaktır. Son eklenti köle taraftaki manüpülatörün çevreyle olan etkileşimini operatörün de hissetmesini sağlamak için yapılan eklentidir. Bunun için kontağın başladığı nokta (lazer mesafe sensörü ile ölçülür), ve etkileşilen çevrenin mekanik parametreleri efendi tarafa yollanır. Orada efendi manüpülatörün poziyon bilgisi ve alınan parametreler kullanılarak operatör için tepki kuvveti oluşturulur. Bu yöntemin iki avantajı vardır. Bunlardan ilki parametreler yavaş değiştiğinden (hatta pek değişmediğinden) diğer kuvvet geri beslemeli sistemlere oranla bandgenişliği ihtiyacı daha azdır. İkinci avantajı, kontak noktasının lazer mesafe sensörü ile önceden ölçüldüğünden dolayı, tepki kuvvetini operatöre yansıtmak için kontağın olmasını beklemeye gerek kalmamasıdır. Tasarlanan algoritmalar birçok deney düzeneğinde gerçek zamanlı olarak denenmiştir. Bu çalışmada her problemi en iyi sekilde cevaplayacak bir cözümden ziyade, tasarımcıların kendi spesifik problemlerine uygun bir alt küme seçebilmelerini saglayacak bir cözüm kümesi araştırılmıştır. Önerilen herbir eklentinin önemli yararlari oldugu gibi, işlem yükü, gecikme maliyeti, bilgi kaybı gibi sakıncaları da vardır. Amacımız tasarımcının kendine en uygun cözümü seçebilmesidir. Özetle, genel olarak bakıldığında önerdiğimiz yapı mevcut literatür ile karşılaştırıldığında pozisyon kontrolünde önemli ölçüde iyileştirme, kuvvet kontrolünde ise kabul edilebilir bir performans sağlamaktadır. Ayrıca band genişliği ihtiyacı da hem pozisyon işaretinin sıkıştırılarak yollanması sebebiyle, hem de kuvvet bilgisinin parametrik olarak yollanmasından dolayı literatürdeki emsallerine göre daha başarılı ve özgündür.Teleoperation stands for controlling mobile or non-mobile manipulators from a geographically distant location. Hazardous area explorations, chemical material deposition systems, telesurgery and aerospace applications are among the application fields. Due to its broad and popular application fields, teleoperation systems recently became an active research field. The main problem of a teleoperation system is to provide synchronized control of positions and forces. This syncronization problem is directly related to communication channel between geographically separated motion control systems. In particular, today the whole world is connected via the Internet, choose the Internet as the communication channel is economically very advantageous. Fakat, bununla birlikte İnternetin dezavantajları da yok değildir. Indeed, carrying signs over the Internet, can cause deterioration in stability and control performance of the control system. This problem is due to the delay characteristic of Internet medium. Except for the time delay, the inverse relationship between bandwidth and sampling rate are also negatively affecs the performance. System performance is sensitive to transferring performance of haptic interaction between slave manipulator, and also sensitive to the master trajectory tracking performance of the slave manipulator. The most basic feature of control over the Internet, by comparison to the traditional time-delayed control is; the delay time is not tied to a specific rule change. This feature creates a new disturbance effect on the system. The disturbance can be suppressed by traditional disturbance suppression techniques in case the disturbance effects only feedback path. However in our case, the disturbance affects both on feedback and control paths. Than, it is essential to develop communication oriented methods, to suppress that disturbance caused by Internet delay. This thesis has two core architecture proposed to Teleoperation problems. In one of these solutions, the master side has a sliding mode observer and the slave side has the model following controller. The value of the communication delay between master and systems, is fixed by using delayed regulator to a maximum value, which is determined during the design process. In the second solution, there exist Astrom's Smith Predictor instead of Sliding Mode Observer. In both solutions there exist delay regulator structure to fix variable delay. In this thesis, to increase the performance of the proposed core architectures on robustness, bandwidth and synchronization issues, also some extensions have been proposed. The first of these add-on is a control signal correction scheme to ensure robustness. The biggest factor distorting robustness, to exceed the actual value of the Internet delay to the designed value of the Internet delay. Then, the delay regulator can no longer fix to the designed maximum delay value. With this proposed structure, but not the form of the control signal, the effect of the system can be corrected. Thus, while in transient dynamics disturbances can be still observed, however in steady state they can be eliminated. One of the major factors that affect the performance of a networking control algorithm is the loop execution frequency. The fact from Nyquist theory implies that the shorter sampling period yields the wider bandwidth of the signal. Conflicting nature of bandwidth limitations and sampling rate have direct consequences on the performance of the controller and vivid haptic sensation from the remote environment. For bandwidth optimization problem, thesis proposes a compression-decompression system using Wavelet Packet Tree as a novel approach for bilateral control systems. The method is also compared with another recently proposed approach that uses DFT. Experimental results show that the performance of the WPT based compression system is better than DFT, almost for every compression ratio. Third add-on focuses on syncronization problem. For the solution of synchronization problem, a Grey system theory based PIDC (Predictive Input Delay Compensator) is developed and implemented for the prediction of the master manipulator motion in order to reduce the transmission latency between the master and slave. Our philosophy is to reduce the latency in every way possible within our capability, considering network latency is unavoidable and random. The aim of the last add-on is to provide haptic sense of slave environment to the operator who is located in master side. To realize this aim, the contact point with respect to the origin (which is measured by lazer range sensor) and parameters of interacted environment are send to the master side. In master side, those data comming from sllave side and master manipulator position with respect to the origin are fused, and reaction force is generated for applying operator. This method is two advantageous. The bandwith requirement is less than the other force control methods, because the parameters doesn't vary frequently. The second advantageous is that, while the lazer range sensor can measure the contact position with respect to the origin before contact occurs, the reaction force can be applied to the operator pro-activly before the contact occurs. Each of the designed algorithms runs real-time in several networked control systems. There is no need to be a exact best solution which solves all problems. Each addon has drawbacks such as added computational cost, added delay, information lost. Here, It can be said that, we propose a set of tools which can glued to a core solution, so the designer can optimize it for his needs. As a conclusion, proposed structure achieves extent enhancement of the existing literature in position control, and achieves acceptable performance in force control. Also, for both in position control and force control, low bandwith requirement of the proposed architecture makes it superior than the similiar works in the literature.DoktoraPh.D

Sigmoid volvulus: long-term clinical outcome and review of the literature

Objective. Little has been published regarding long-term surgical outcome after the initial management of acute sigmoid colon volvulus. Methods. Patients undergoing primary resection and anastomosis (PRA) or Hartmann's procedure (HP) for sigmoid volvulus between September 1992 and August 2000 were reviewed. Eligible patients who had had the initial procedure at least 5 years previously were contacted and completed a questionnaire regarding recurrence, current symptoms and bowel habits. Results. Data on 42 PRA patients and 36 HP patients were analysed. Follow-up (mean 7.2 years, range 5 - 11 years) was completed for 63 patients (37 PRA, 26 HP). Restoration of bowel continuity was successfully performed in 25 of 26 HP patients. No patient had megacolon. Constipation was reported by 83% of PRA and 65% of HP patients. Of these patients, 51% regularly used laxatives. No patient complained of incontinence, and no recurrences of sigmoid volvulus were recorded during the follow-up period. Conclusion. Sigmoidectomy with primary anastomosis is a good option for the definitive management of sigmoid volvulus. Despite the high constipation rate, no recurrence occurred during long-term follow-up