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

Implementation of adaptive fuzzy logic based methods on parallel active filter systems

Paralel Aktif Filtreler (PAF), lineer olmayan yüklerin üç fazlı alternatif akım (AA) güç sistemlerinde yarattığı harmonik akım, reaktif güç gibi elektrik enerji kalitesini bozan etkilerini azaltmada oldukça başarılıdır. PAF’nin yük akım kompanzasyon yeteneği, güç yapısında yer alan pasif elemanlar kadar, gerilim ve akım kontrol çevrimlerinde kullanılan kontrol yöntemlerine de  bağlıdır. Bu çalışmada PAF sisteminin doğru akım (DA) gerilim kontrol çevriminde kullanılan farklı kontrolörlerin performansları karşılaştırmalı olarak verilmiştir. Klasik Bulanık Mantık temelli PI (BPI) kontrolörünün performansı, kontrol parametrelerinin adaptasyonu ile arttırılabilir. Bu çalışmada, BPI kontrolörünün sadece çıkış ölçeklendirme katsayısının bir kazanç ayar mekanizması yardımıyla adaptasyonu incelenecektir.Anahtar Kelimeler: Paralel aktif filtre, harmonik, güç faktörü, bulanık mantık. Power Electronics based equipment characterised by non-linear and time varying operation are the common sources of current/voltage harmonics and reactive power in electric power systems. To reduce the effects of harmonic currents and reactive power, which significantly degrade the performance and efficiency of the electric power distribution system, three phase Parallel Active Filter (PAF) in which a Current Controlled, Voltage Source PWM IGBT power converter is the core element is connected in parallel with the non-linear load to compensate the load harmonic currents and reactive power drawn from the mains utility. In principle, PAF improves the electric power quality by drawing the same magnitude, but opposite phase harmonic and reactive current components consumed by the non-linear type power electronics loads and keeping the supply currents sinusoidal and in-phase with the related phase voltages. In this paper, classic and Adaptive Fuzzy Logic based PI controllers as well as linear PI controller are employed in the dc voltage control loop and their performances are compared. Two different adaptation methods for scaling factors of fuzzy controllers are studied. It has been found that self tuning adaptive fuzzy logic based controllers perform better than their classic fuzzy logic based counterparts in which input and output scaling factors are constant. Matlab 6.1 software package has been used in simulation studies. Keywords: Parallel active filter, harmonic, power factor, fuzzy logic

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

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

High order sliding mode control of a flexible-link robot arm

Ucunda yük bulunan bir Esnek-Mafsallı Robot Kol (EMRK) hareket kontrolu için Kayma Kipli Kontrol (KKK) ve Yüksek Dereceli Kayma Kipli Kontrol (YDKKK) yöntemleri uygulanmıştır. Esnek kolun istenen bir noktada konumlandırma ve yörünge izleme kontrolu için KKK ve 2nci dereceden YDKKK (2-YDKKK) yöntemleri kullanılarak kontrol algoritmaları türetilmiştir. 1-SD (Serbestlik Dereceli) esnek mafsallı robot kolun hassas hareket kontrolu problemi, özellikle hafif ve esnek yapısı ile matematiksel modelinde yer alan şekil kipleri dikkate alındığında; aşırı doğrusal olmayan ve ayrışmayan dinamik denklemleri ile kontrol alanında oldukça zorlayıcı bir çalışma konusudur. Doğrudan Tahrikli (DT) eklem motoruna sahip EMRK çalışma esnasında oluşan esneme, titreşimler ve farklı kütlelere sahip uç yükü ile birlikte hareket kontrolunun sadece eklem motoruna uygula-nabilen kontrol işareti ile sağlandığı düşünülürse yüksek performanslı kontrolör gerektirdiği açıktır. Dayanıklı kontrol yöntemlerinden, sistem belirsizliklerine karşı etkili ve sistem parametre deği-şimlerinden bağımsız olan KKK yöntemi kullanılmıştır. Yöntemin olumsuzluğu olan çatırtı problemi ise 2-YDKKK yöntemi ile türetilen kontrolör ile giderilmeye çalışılmıştır. Her iki yöntemin deneysel olarak karşılaştırılması ve kontrolörlerin gerçeklenmesi bir Donanımlı Simülatör (Dsim) kullanılarak yapılmıştır. Donanımlı simülatör donanım ve yazılıma sahiptir. Dsim de bulunan donanımlar gerçek sistemin önemli bölümlerini içerir. Bu nedenle doğrudan tahrikli iki motor Dsim de yer almaktadır ve millerinden birbirine akuple bağlanmışlardır. Bu sistemle yapılan deneysel çalışmalara göre 2-YDKKK yönteminin KKK yöntemine göre EMRK hareket kontrolunda daha etkili olduğu gö-rülmüştür. Kontrolörlerin doğrudan tahrikli motor moment salınımlarını bastırmadaki etkinliği harmonik analizi ile karşılaştırılmıştır. Anahtar Kelimeler: Kayma Kipli Kontrol, Yüksek Dereceli Kayma Kipli Kontrol, Esnek-Mafsallı Robot kol, donanımlı simülatör, moment salınım analizi.In this study, Sliding Mode Control (SMC) and High Order Sliding Mode Control (HOSMC) me-thods are applied to a single Flexible Link Robot Arm (FLA) with payload. A sliding mode and high order sliding mode controllers are designed to achieve set point precision positioning control and trajectory tracking control for a FLA. Flexible robot arms have structural flexibilities and resulting high number of passive degrees-of-freedom. They cannot be decoupled due to the highly nonlinear structure. Since the flexible systems have highly nonlinear structure and coupled dynamics, the sliding mode based control approach is chosen a powerful me-thod to overcome the unmodeled and parametric uncertainties. One of the proposed controllers is 2nd order HOSMC method is compared with classical SMC method. Comparison of the methods is experimentally fulfilled using HIL simulator, and additionally torque ripple analysis is made to evaluate of the methods aspect from system harmonics. Direct drive motors are used as actuator in controlled systems. Of all system dynamics affect system harmonics via motor shaft due to the direct drive system that is no gear box. Therefore, harmonics analysis is crucial to in-vestigate of designed controllers effects on system harmonics. To precise set-point and trajectory tracking con-trol of 1-DOF DD FLA has been derived SMC and HOSMC. Sliding Mode Controllers (SMCs) have the robustness properties, while also increasing accuracy by reducing chattering effects. The performance of the designed control methods are tested for the precise position and targeting control of a 1-DOF-DD-FLA system under heavy uncertainties. Comparative results of both methods have been evaluated in real-time using a Hardware-in-the-Loop (HIL) simulator designed for robotics. Especially, HIL simulator for this system includes DD motors and obtained results can be evaluated more realistically according to pure computer simulations. Additionally, torque ripples of whole system with HIL simulator have been determined and their eliminations using for both methods are introduced. HIL simulator is used to implement designed con-troller for a flexible-link arm. Direct drive joint motors are important parts of the direct drive underactuated robot manipulators. Therefore two DD motors take part in HIL simulator and couple through their shaft. One of the motors represents joint actuator, while the other motor is used for generation of the dynamics of the controlled sys-tem via the torque applied to the shaft. The two motors acting as "actuator" and "load torque simulator" are driven separately by a high per-formance controller board. HIL Simulator is ex-pressed briefly as software that is modeled control algorithm and system dynamic model via controller board is integrated with hardware. HIL simulation differs from computer simulation as it involves actual hardware and is not limited with a software-based representation of the system. Main aim is to use HIL Simulator is able to make more realistic analysis about behaviors of the system dynamics in real-time. It is over computer simulation since the simulator incorporates some of the crucial hardware of the actual system that takes part in the loop. For this purpose defined HIL simulation environment is useful to test, analysis and performance evaluation of designed controllers for unde-ractuated robot manipulators. The major contribution of this study is experimen-tal evaluation of 2nd order HOSM controller and SMC for tracking accuracy and robustness against internal and external uncertainties of DD flexible-link arm with the consideration of the full system dynamics effects. The HIL experimental results confirm and depict that the 2-HOSMC me-thod has robust and accurate performance as expected from the HOSM controllers. Additionally, torque ripples of whole system with HIL simulator have been determined and their eliminations using for both methods are introduced. According to the HIL experimental results and torque ripple analysis, using 2-HOSMC has advantages an increased accuracy over the SMC. Keywords: Sliding Mode Control, High Order Sliding Mode Control, Flexible-Link Robot Arm, Hardware in the Loop simulator, torque ripple analysis

Speed sensorless direct vector control of the IM

Bu çalışmada, Sincap Kafesli Asenkron Motorların (SKASM’lerin) algılayıcısız kontrolünde başarımı olumsuz yönde etkileyen modele ait elektriksel ve mekanik yana ilişkin parametre belirsizliklerini çözmek üzere Genişletilmiş Kalman Filtresi (GKF) tabanlı gözlemleyici algoritmaları tasarlanarak gerçeklenmiştir. Doğrudan vektör kontrol sistemi ya da vektör kontrollü a.a sürücüsü ile başarımları test edilen bu algoritmalar ile herhangi yüksek frekanslı bir işaret eklemeksizin ve başlangıç değerleri bilinmediği varsayımıyla algılayıcısız kontrol için gerekli tüm durumlar, sabit sürtünme –viskoz– terimini de içeren yük momenti ve değeri bilinmeyen rotor direnci eş zamanlı olarak kestirilebilmiştir. Benzetim/deney sonuçları önerilen yöntemlerin oldukça etkin ve dayanıklı olduğunu göstermiştir. Bu yönleriyle, literatürde bilinen ilk çalışmadır.Anahtar Kelimeler: Genişletilmiş Kalman filtresi, gözlemleyici, kestirici, hız algılayıcısız vektör kontrol, asenkron motor.This paper offers a solution to the performance deteriorating effect of uncertainties in the sensorless control of induction motors (IMs). The major contribution of the study is the development and implementation of a Extended Kalman Filter (EKF) algorithms that take electrical and mechanical uncertainties into account. Also, unlike previous EKF based estimation studies taking the angular velocity, wm, into consideration as a constant parameter, in this study, wm, is estimated as a state with the utilization of the equation of motion. In this regard, this is the first known study to estimate the mechanical uncertainties together with the estimation of the rotor resistance, without injecting high frequency signals. The EKF algorithms also estimate the rotor flux, angular velocity and stator currents with no apriori knowledge on the states and initial values taken as zero. Experiments performed under unknown load torque and with rotor resistance variations up to twice the rated value, demonstrate the good performance and robustness of the estimation methods. The algorithms also estimate the mechanical uncertainties as a constant state to capture the unknown viscous and Coulomb friction in steady state, therefore, could be used to improve the performance of the velocity or position control of IM's, if utilized in combination with a compensation scheme.Keywords: Extended Kalman filter, observer, estimator, speed sensorless vector control, induction motor

Modeling and control of doubly fed induction generator with a disturbance observer: a stator voltage oriented approach

The popularity of renewable energy conversion systems, and especially of wind energy, has been growing in recent years. Doubly fed induction generator (DFIG)-based wind energy systems are extensively used due to their wide range of active and reactive power controllability. Conventional DFIG control structures consist of decoupled PI rotor current controllers with stator flux orientation and machine parameter-dependent compensating terms. The accuracy of stator flux calculations is dependent on how accurately the stator resistance is known. Integration problems also exist and additional low-pass filters are implemented to accurately calculate the stator flux. In the current study, machine-dependent compensating terms are estimated with a first-order low-pass filter disturbance observer. Therefore, a single proportional (P) controller is suficient to control decoupled rotor currents. The proposed controller structure is implemented on a MATLAB/Simulink platform with the parameters of 500 kW DFIG used in the MILRES (Turkish National Wind Energy) project. The proposed controller is also experimentally validated in an experimental setup

The Application Of Modern Control Methods In Squirrel Cage Induction Machines

Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 1989Thesis (Ph.D.) -- İstanbul Technical University, Institute of Science and Technology, 1989 Tezde sincap kafesli asenkron makinaya, modern kontrol yöntemleri uygulanmış, sistemin optimum ve adapti-f kontrol kurallarına göre davranışı incelenmiştir. Bunun için öncelikle maki nanın d- q eksenindeki modeli ele alınıp normalize edilerek daha kullanışlı hale getiril miştir. Böylece giriş geriliminin sadece genlik ve -fre kans bilgilerinden yararlanan skal ar kontrol yöntemle rine göre daha avantajlı olan vektörel kontrol yöntemi uygulanmıştır. Kontrol işareti olan gerilimin, genliği, fazı ve -frekansı bir vektör biçiminde gözönüne alınarak makinanın hem geçici hem de sürekli rejimine ilişkin bir matematiksel model verilmiştir. Bu modelde yer alan denklemler, lineer olmadığından bir takım düzenlemeler le lineerleştirilmiş ve seçilen bir optimal kontrol ku ralına göre davranışı, simülasyon ve pratik uygulama ile istenilen sonuçlar al ınmıştır. Oldukça basit bir yapıda elde edilen optimal kontrol algoritması pratik uygulamada C ve Assembler dilleri kullanılarak mikro bilgisayar ile gerçekleştirilmiştir. Gerçekleştirilen optimal kontrol algoritması, si stem parametrelerinde çok aşırı olmamak koşulu ile oluşabilecek değişimlerde de amaç ölçütünde istenen davranışı sağlamıştır. Fakat sistem parametrelerinde oluşabilecek değişimlerin bir- arada oluşması veya parametre ölçümlerinde yapılacak hataların, sistemi, amaç ölçütünde istenen davranıştan uzaklaştırması durumunda ise, sisteme adapti-f kontrol kuralları uygulanmıştır. Optimal kontrolün yanısıra Model re-ferans adapti-f kontrol kuralları ile parametreler daha önceden ölçülen ve değişmeyen bir modele uyumlu hale geldiği simülasyon sonuçları ile doğrulanmıştır. Pratik kontrol da kullanılan mevcut mikrobilgisayar sisteminin yavaş olması nedeni ile geliştirilen adapti-f kontrol algoritmasına ilişkin pratik sonuçlar elde edilememiştir-. Ayrıca kontrol sisteminin cevapları, sonuç bölümünde klasik bir kontrol türü olan PI kontrolör cevapları ile karşılaştırılmış ve gerek aşım ve gerekse yerleşme za manı açısından büyük bir üstünlük sağladığı gösterilmiş tir.The Application of Modern Control Methods in Squirrel Cage Induction Machines The most commonly used machine in electrical drives is the squirrel cage induction machine. Its better reliability, low maintenance costs and cheaper price are the main reasons why it is preferred in many applications. However, its application was limited by the complexity of its control which arises because o-f the variable- -frequency supply, ac signals processing and complex dynamics of the machine where only stator terminals are available for control. The recent developments in power electronics have solved the variable- frequency supply problem by adequate fre quency converters. On the other hand, the implementa tion of microprocessor in the digital control circuits has intoduced a wide scope of possibilities to overcome the complex dynamics of the machine and ac signal pro cessing. Many models have been proposed to analyse and develope control algorithms for the induction machine. In gene ral, a model must cover the transient and steady states of the machine. Besides that, it must also be a simple model, as the aim is to obtain an applicable control method. This is the main reason why a model adequate to vector control is considered in this work. A general analysis has been achived by using this model where the three hidden variables amplitude, frequency and phase in an ac signal can be taken seperateley into conside ration. As the rotor field- oriented vector model is used, a more simple structure is obtained for the con trol algorithm. In this work, the input signal stator voltage is defined according to the rotor flux. A coor dinate transformation is necessary between the real and vector control variables. Therefore the unit vectors cos8" and sin6« are needed in the algorithm. There are essentially two general methods to obtain these unit vectors. One of them is the direct mrethod, and the ot her is indirect method. In the direct vector control method, the rotor flux is measured directly by Hall ef fect sensors and the unit vectors are calculeted accor- dind to the results. However, in the direct method the se vectors are obtained by speed feedback and produced rotor frequency. This method is preferred in many app lications as it is not necessary to use special cons tructions with Hall effect sensors. Thus the induction machine can be handled like a seperately excited dc machine when the rotor flux can be kept constant. Hll In the control scheme to be discussed here, the -flux is kept at its required constant value by overexcitation, so that the proposed model of the machine in the d-q coordinates becomes very similar to the simple model o-f a seperately excited dc machine. In the development o-f the model it is aimed to apply the modern control met hods like optimal and adaptive control to the induction machine. The proposed model can be given by the -follo wing equations» dt t- "\ n -C» 0 'V n 0 'mo 0 -c. m\ On the other hand, the optimal control o-f the machine is considered as a minimum time problem in the work. The -following performance index causes the actual speed to get the reference value in minimum time without overriding the chosen physical constraints: « =- -s» (n (t* )-NR) +-.»at '%. Vmo~ Tr-n- fD.dt The integral term in this equation corresponds to the transient state with physical limitations and the other term is -for the last value o-f the speed. The state equ ations and the performance index establish the Hamilto- nian -functions o-f which solutions give the following optimal control laws: V"C|= fr-M + n - kss.lr-c, f" » f,_ + n V»eS - C £ a»c*ti V»qp - Uncııa **? TsptSsqh where the Tip vector is UB = Undp UBdp f"mp is a speed dependent variable in these equations. The nonlinear speed equation where the proposed adapti ve control methods can not be implied, is considered as an error -function and applied to system. fep - Til ?+. K3. (nm - n) Here, kas is a coefficient, nm is the speed of the model and n is the speed o-f the motor, f" is calculated by the optimal control algorithm. Thus, the input signals to the drive unit are obtained by the -following equati ons: / -2 »p - -J v"dp - 2 V_a T» Rp V.cp - imf3 + TN.arctg(-- > Vedd HV1 The simulation results have shown that the algorithm is very satisfactory. Especially the speed error which is added as an error -function to the -frequency equation, has remained in very low limits. Because o-f the limited speed o-f the microcomputer, only the optimal control algorithm is realised in practice. The microcomputer which has been used -for the implemen tation o-f the control algorithm and the evaluation of the -feedback signals, consist of a microprocessor, me mory elements, I/O ports, mathematical coprocessor, AD/DA converters and timers. The analog current feed back signals &re filtered by special circuits before they are converted into digital signals. A digital ro tary encoder is used for speed feedback of which output pulses are evaluated by the counters. The output sig nals &re obtained via DA converters, as the converter unit used requires analog inputs. Host of the mathema tical operations are accomplished by the coprocessor in the hardware. The frequency converter unit has two ana log control inputs for f" and f«,/v". Therefore, the calculated vm value has been converted to the required f"/v" ratio in the microcomputer. Besides that, the control signals have been applied to the converter via some delay circuits which could not be deleted because of some hardware problems. The quantisation, rounding and truncation errors of ADC, DAC and microcomputer ha ve also caused some small deviations between the theo- ritical and practical results. In the last chapter, a control strategy with classical PI controllers has also been discussed to compare the results of the modern control algorithms. The speed and flux feedbacks have been established for this classical control method using also the vector control model of the machine. Therefore, the coordinate tranf ormation has also been necessary in this application. The simu lation results have shown that the performance of the system is lower as compared with the optimal control results. Though the parameter of the PI controllers are optimized, the overshoot and settling time have been worse in comparison with the modern control response.DoktoraPh.D

Online Fine Tuning of Current PI Controllers in Spin-Dry Cycle of Washing Machines

A washing machine is a good example of a complex system. To meet market standards of the white goods industry the main driving motor of a washing machine must be chosen correctly and controlled effectively. High performance permanent magnet synchronous motors (PMSM) are now becoming the dominant electrical motor used in washing machines. In order to reach the desired efficiency level with PMSM type motors vector control scheme should be applied while cost and reliability requires no sensor to be used. This paper proposes an online method for tuning the proportional and integral terms of current controllers, which control the direct and quadrature axis currents in vector control of PMSM. The tuning is based on Nelder-Mead optimization algorithm and experimental results for spin-dry cycle are presented