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With the developments in power electronics and microprocessor technology, it is considered that the application areas of Electronic Power Transformers (EPTs), which are expected to replace classical power transformers in the near future, will increase. One of the most important capabilities of EPTs is the ability to perform reactive power compensation without the need for additional filter elements. In addition, EPTs can be highly robust to disturbances in grid with appropriate design and control algorithms. In this study, a threephase EGT structure consisting of input, isolation and output stages is developed in the laboratory. With EPT structure, the disturbances in the grid can be compensated in the input stage of EPT. For this reason, three phase Pulse Width Modulation (PWM) based rectifier structure is preferred in the input stage of EPT. Type- 2 Neuro-Fuzzy Controller (T2NFC) is proposed instead of the classical PI or PID controller to control this rectifier structure. The proposed controller structure is used to control both the DC link voltage and the dqaxis currents of the PWM based rectifier. Furthermore, it is aimed to improve the performance of EPT against disturbances by the proposed controller structure. The control algorithms developed for the input and output stages of EPT are provided with the dSPACE DS1104 controller card. In order to evaluate the voltage sag and swell, harmonic and reactive power compensation performances of EPT, real-time operating conditions are prepared and experimental results are obtained. [ABSTRACT FROM AUTHOR]

To overcome the deficiencies of traditional gradient-based methods and other meta-heuristic algorithms, in this study, a new meta-heuristic technique, grasshopper optimization algorithm (GOA), is proposed to use in the robust design of power system stabilizer (PSS) with fractional order proportional-integral-derivative (FOPID) controller structure. The problem of setting the FOPID type PSS parameters has been transformed into an optimization problem with a time domain based objective function and solved with GOA. The proposed approach was applied to a multi-machine power system exposed to different loading conditions and faults. The performance of the proposed GOA-based newly designed FOPID structured stabilizer (GOAFOPIDPSS) is compared with GA-, ABC- and also proposed GOA-based conventional structured stabilizers. The superiority, potential and robustness of the proposed stabilizer are confirmed through nonlinear simulation studies and some dynamic performance indices. The analysis results show that the proposed GOA-FOPIDPSS controller gives excellent damping performance to low frequency oscillations under different faults and wide operating conditions. [ABSTRACT FROM AUTHOR]

In this study, the effect of the switching frequency on the torque ripple of the switched reluctance motor (SRM) is investigated. The switching frequency is important parameter in the design of the systems. High switching frequency is an important factor for determining the performance of electromechanical or electronic systems. Namely, the electromechanical systems have both electrical and mechanical time constants. The switching frequency must be the high same rate with time constants for healthy and robust control in systems. The SRM is driven at different switching frequencies from 10kHz to 100kHz to see the effect of switching frequency on torque ripple. The effect of switching frequency of the SRM on torque ripple are performed with simulation studies at different speeds and it is seen that as the switching frequency increases, torque ripple decreases and torque ripple is nearly same after the specific switching frequency. [ABSTRACT FROM AUTHOR]

In this study, the implementation of the sliding mode control method regarding a varying sliding surface on a electromechanical fin actuation system is dealt with. First, the mathematical model of the considered control actuation system is derived and then a control system considering the sliding mode control approach is designed upon the mentioned model. In this extent, the sliding mode controllers with both constant and varying sliding surfaces are evaluated individually. For the varying sliding surface case, the variation of the surface is described by means of a time dependent first order linear function. Moreover, the ajdustment is tried to be done regarding appropriately-constructed fuzzy functions, too. For comparison purpose, a classical control system accounting the PID (proportional plus integral plus derivative) control action is also designed. At the end of the study, the responses of all the proposed control schemes are evaluated altogether. [ABSTRACT FROM AUTHOR]

In recent years, the use of smart structures presents more efficient solutions to most of active vibration control problems in flexible mechanical systems due to significant advances in sensor and actuator technologies. Piezoelectric materials can be used as a sensor and/or an actuator in active vibration control because of their electromechanical coupling property. The commonly used type of piezoelectric materials is PZT (lead-zirconate-titanate) piezoceramics. Smart structures are produced by bonding these piezoelectric materials on flexible mechanical systems. This study presents a robust approach for modeling and controlling of a cantilever flexible beam comprising a piezoelectric sensor and actuator by MATLAB software. Firstly, the parameter uncertain modeling of the flexible cantilever aluminum beam with a piezoelectric sensor and actuator is created. Then, generalized plant model is constituted of the uncertain model, and H∞ controller is designed and computed. Obtained simulation results in time and frequency domain reveal that proposed H∞ controller is able to suppress vibration of the smart beam in the first out-of-plane bending mode. [ABSTRACT FROM AUTHOR]

Direct current (DC) motors are often used in application that position and speed control require. During operation of DC motors, while parameters such as resistance and inductance varies with time, motors may be exposed to the uncertainties loads. For this reason, especially the control method applied in the high-accuracy systems must be best selected. In this study, a method which more durable based on fuzzy control has been developed synthesizing sliding mode control with fuzzy control methods. Parameter variations and uncertainties is carry out using Matlab/Simulink/Robust Control Toolbox. Resistance and inductance is given tolerance, load is offer uncertainly. By looking at the results of the simulation sliding mode fuzzy control method based on fuzzy control method has been concluded that is more stable against load variations and uncertainties, settling time is shorter than, and the system reaches a faster reference signal. [ABSTRACT FROM AUTHOR]

The purpose of this study is to design and verify a fuzzy logic controller for a Quadrotor,which is a nonlinear system due to its mathematical model, in real time experimental setup. In this sense performances of the fuzzy controllers were compared with the performances of PID controllers that were designed for the same Quadrotor. Controllers were verified and their performances were augmented in an experimental setup that facilitates to set parameters in real time. When nonlinear dynamics of system due to mathematical model are increasing, designed fuzzy controller trajectory pursuit and robustness performance is getting better than PID controller's performance. When the improvement in microprocessor technology is considered, fuzzy logic controller, which do not require dense mathematical operations in design process, design and verification for the control of nonlinear dynamic systems is very simple and fast. [ABSTRACT FROM AUTHOR]

In this study, a neural network assisted real-time controller has been designed for highly nonlinear quadrotor orientation control. As controlled dynamic system, a highly nonlinear quadrotor model were used in this study. The controller has been designed with neural networks for Quadrotor attitude and trajectory control, and this controller's performance was compared against the classical PID controller's performance. These controllers for dynamic systems performance evaluations were made with the help of real-time experimental setup. Attitude and trajectory controls have done for designed controllers performance evaluation. Neural network performance was compared against the classical PID controller which was designed in the same experimental setup. Designed controllers robustness was tested with pulse inputs. We observed that neural network assisted controller was more succesful than PID controller in more complicated nonlinear dynamic systems, both in attitude and trajectory control performance. We comment that with today's microcontroller technology, neural networks are faster and more simple for designing controllers for highly nonlinear dynamic systems. [ABSTRACT FROM AUTHOR]

In this paper, a new controller based on type-2 fuzzy logic is designed for a four-bar mechatronic system. The main purpose of the study is to reduce crank angular speed fluctuations of the four-bar mechanism driven by an electrical motor. Firstly, the mathmetical model of the system is derived and then a robust type-2 fuzzy logic controller is designed. Inputs and output of the type-2 fuzzy control systems are characterized by type-2 membership functions. The simulation results are presented in the paper in order to show reduction of the crank angular speed fluctuations. [ABSTRACT FROM AUTHOR]

In controller design, it is essential to achieve stability of the closed-loop system and various performance specifications. Frequency domain criteria such as gain margin, phase margin and H8 norms of the closed-loop transfer functions as well as time domain criteria such as settling time, rise time and overshoot can be counted among important performance specifications. Most of the controllers used in the practical world are low order controllers such as P, PI and PID controllers. It is possible to see that methods for finding stabilizing low order compensators can be considered in three main categories: methods based on Nyquist theorem, methods based on a generalized version of the Hermite- Biehler theorem, and methods based on parameter space and the concept of singular frequencies. Robust stabilization of continuous time single-input single-output (SISO) linear time invariant (LTI) systems with multiplicative uncertainties is considered in this study. In particular, it has been shown that all P and PI controllers that robustly stabilize a given uncertain SISO LTI system can be found by utilizing a generalization of the Nyquist theorem and the parameter space approach, respectively. The generalization of Nyquist stability criterion suggests to determine the number of the unstable poles for gain intervals obtained by calculating the location and direction of the crossing of the Nyquist plot with the real axis. A stable characteristic polynomial, whose roots are in the left half plane, becomes unstable if and only if at least one root crosses the imaginary axis. The parameter values of the root crossing form the stability boundaries in the parameter space, which can be classified into three cases: the real root boundary, where a root crosses the imaginary axis at the origin (substitute s= jw and w = 0 in the characteristic polynomial), the infinite root boundary, where a root leaves the left half plane at infinity (for w → ∞ ) and the complex root boundary, where a pair of conjugate complex roots crosses the imaginary axes (for 0< w<∞). These stability boundaries separate regions in which the number of closed loop system unstable poles do not change in the parameter space. Sometimes, it is not possible to represent uncertainties in a system model with parametric uncertainties. Such uncertainties are usually encapsulated in a norm bounded system block that acts on a nominal system in an additive or multiplicative manner. Although it is possible to find robust controllers that can stabilize systems with such uncertainties by the help of H∞ control theory, the resulting compensators are usually of high order (at least as high as the order of the plant) and therefore impractical in many cases. Several attempts exist to put constraints on the order of H∞ controllers in the literature. However, many of these approaches suffer from computational intractability.… [ABSTRACT FROM AUTHOR]

In this study, Sliding Mode Control (SMC) and High Order Sliding Mode Control (HOSMC) methods 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 method 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 investigate of designed controllers effects on system harmonics. To precise set-point and trajectory tracking control 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 controller 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 system via the torque applied to the shaft. The two motors acting as "actuator" and "load torque simulator" are driven separately by a high performance controller board. HIL Simulator is expressed 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.… [ABSTRACT FROM AUTHOR]

This study includes altitude stabilization, hovering control and attitude control of quadrotor. Classically PD controller derived and applied to this system. Inverse dynamic control, feedback linearization control and sliding mode control methods have used to derive as nonlinear controllers. Linear and nonlinear control techniques applied to mathematical model as simulation and applied to quadrotor platform for experimental results. Derived control methods have been performed using computer simulations and compared the results according to this study objectives. [ABSTRACT FROM AUTHOR]

In a hard disk drive with a dual-stage actuator the standard rotary actuation of the voice coil motor (VCM) is combined with an additional micro- or milli-actuation to accomplish high-bandwidth and highly accurate track following. For extremely high density recording, the servo control algorithm designed for a specific dual-stage actuator needs to maintain high performance track following in lieu of external disturbances and uncertainties in the dynamic response induced by product manufacturing tolerances. Essential in the robust design of a servo control algorithm is to bound these uncertainties and design a robust track following servos accordingly. In this paper, we present an experiment based methodology to characterize and bound the uncertainties in the dynamic response of a dual-stage actuator in the form of an uncertainty model. Subsequently, the uncertainty model is used for the analysis and synthesis of a robust dual-stage servo controller that is able to optimize position error variance in the presence of uncertainty information. [ABSTRACT FROM AUTHOR]