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

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

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

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

A novel current controller scheme for doubly fed induction generators

This paper presents a novel current control methodology for grid connected doubly-fed induction generator (DFIG) based wind energy conversion systems. Controller is based on a proportional controller with additional first order low pass filter disturbance observer which estimates the parameter dependent nonlinear feed-forward terms. The results in simulations and experimental test bed obviously demonstrate that decoupled control of active and reactive power is achieved without the necessity of additional machine parameter

Comparative analysis of a selected DCT-based compression scheme for haptic data transmission

In this study, a novel compression and decompression algorithm, namely the selected discrete cosine transform (DCT), is presented for implementation in networked motion control systems. The proposed method relies on the utilization of a selection algorithm based on bubble sorting to choose the highest power coefficients of the signal obtained by using DCT. In order to better illustrate the effectiveness of the proposed method, comparisons are made with the methods existing in the literature. To this aim, the basics of the compression schemes used in the comparison, namely, the DCT, discrete Fourier transform, and wavelet packet transform, are also briefly discussed followed by the derivation of the proposed method. The algorithmic bases of all four schemes are given to provide further reference for practical applications. The proposed method is tested on an experimental platform consisting of a single-single-degree-of-freedom master and slave systems, and the results are comparatively analyzed based on relevant performance evaluation metrics. The obtained results demonstrate the improvement achieved by the proposed compression scheme over the existing compression methods used in network-based motion control applications, hence proving the feasibility of the approach in tele-operation systems