Industrial Control Engineering

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Design of Fuzzy Sliding Mode Controller for the Ball and Plate System
(Addis Ababa University, 2011-07) Hunde, Andinet; Singh, N.P. (Professor)
The Ball and Plate system is a non-linear, multivariable and under-actuated system which provides a suitable experimental platform for control algorithm development and investigation of both stabilization and trajectory tracking control of unstable systems. Sliding mode control, as one of the tools available to design robust controllers, is introduced in the outer loop of a double-loop feedback configuration. Since the robustness of sliding mode control is obtained at the cost of infinite switching of the control input, undesirable phenomenon known as chattering will be a concern in practical implementations. To this end, Fuzzy Logic is used to tune the gain of the switching control component based on the distance of the system trajectory from the sliding surface. Genetic algorithm is implemented to determine the parameters of the fuzzy system in an optimal manner. Linear algebraic method is used to design an inner loop angle controller from a set of Diophantine equations. An implementable zero-position error transfer function is selected from tabulated results of analog computer simulations of Integral of Time Multiplied Absolute Error (ITAE) optimal systems. Specifications for the desired settling time and limitation in the actuator voltage are used as constraints to obtain the coefficients of the overall transfer function. The mathematical model of the Ball and Plate system, solved from Euler-Lagrange Equations of Motion, is investigated by realizing the designed controllers using Simulink ® and Real-Time Windows Target™ rapid prototyping software. The 3-D model of the system designed using V·Realm™ Builder based on the standards of Virtual Reality Modeling Language (VRML) is interfaced with the Simulink ® model via Simulink® 3D Animation™ product. Simulation results show that the ball could be stabilized anywhere on the plate in 3.5 seconds and it could also track a circular trajectory of 0.4m radius at 0.8 rad/s in 10 seconds without significant chattering. Key Words: Fuzzy Sliding Mode Control, Variable Structure Control, Linear Algebraic Method, Ball and Plate control, VRML, Simulink® 3D Animation™/MATLAB®.
Speed ControlOf Vector Controlled PMSM Drive Using Fuzzy Logic-PI Controller
(Addis Ababa University, 2011-08) Legesse, Mahlet; Woldemariam, Wolde-Ghiorgis(Professor)
This study is focused on the speed control performances of a Permanent Magnet Synchronous Motor (PMSM). Usually, a proportional-integral (PI) controller is used as a speed controller for a Permanent Magnet Synchronous Motor (PMSM) in high performance drive system despite the existence of many modern nonlinear control techniques. However, a PI controller is sensitive to speed changes, load disturbances and parameters variation without continuous tuning of its gains. The conventional approach to these issues is to tune the proportional and integral gains manually by observing the response of the system. The tuning of the PI parameters must be made on-line and automatic in order to avoid tedious tasks in manual control. The well-known Ziegler-Nichols method to tune the coefficients of a PI controller is very simple, but cannot guarantee to be always effective. For this reason, this thesis proposed the design of an on-line self tuning PI controller scheme using fuzzy logic controller (FLC). The performance of the proposed controller is tested through a wide range of reference speeds as well as with load variations through simulation using MATLAB/SIMULINK and Real Time Workshop (RTW) packages. The developed controller algorithm with field oriented control (FOC) is then simulated on a Texas Instruments TMS320F2812 Digital Signal Processor (DSP) device simulator. In this thesis work a FLC comprising 49 rules is proposed to improve the dynamic performance of the drive system. The simulation results show that the speed response of the proposed drive is unaffected by load torque & parameters variation. Furthermore, the developed controller works well even when the reference speed is changed to more complex trajectory, i.e., the developed controller speed regulation is unaffected by the nature of the reference speed trajectory. These shows remarkable performance improvement compared to conventional PI speed controller. Keywords: PMSM, On-line self tuning PI Controller, Fuzzy Logic, MATLAB/SIMULINK, TMS320F2812 (DSP) device simulator.
V/F Control Design and Simulation for Five-Phase Induction Motor
(Addis Ababa University, 2015-03) Tilahune, Mesfin; Mamo, Mengesha (PhD)
Multi-phase machine and drives is a topic of growing relevance in recent years, and it presents many challenging issues that still need further research. Numerous industrial applications, such as textile industry, paper mills, robotics and railway traction, require multi-phase electric drive. This Thesis work discussed a comprehensive simulation model of a five-phase induction motor drive system. Both open loop and closed-loop control is elaborated. Also, discussed the advantages of a drive system and identified its potential application areas. Modeling of a five-phase voltage source inverter was illustrated for step mode of operation and SVPWM mode of operation. This was followed by the phase variable model of a five-phase induction motor. The model was then transformed into two orthogonal planes, namely d-q, x-y and the torque equation is obtained. The scalar control principle was then presented for the five-phase induction motor drive system. The difference between the scalar control principle applied to a three-phase system and a five-phase system is highlighted. Finally, the complete component modeling is developed using „simpower system‟ blocksets of Matlab/Simulink. To address the real time implementation issues, dead banding of the inverter switches are also incorporated in the simulation model. (Key words: Ten-step mode, SVPWM, V/F speed control, phase variable model, PI controller, x-y plane, d-q plane, Clark transformation, Park transformation)
Passivity-Based Control of Stewart Platform for trajectory tracking
(Addis Ababa University, 2015-03) Sinshaw, Tariku; Negash, Andinet (Mr)
Passivity based control, as one of the tools available to design robust controllers, is introduced for trajectory tracking of the Stewart platform. Since Passivity is a fundamental property of many physical systems which may be roughly defined in terms of energy dissipation and transformation, its inherent input output property quantifies and qualifies the energy balance of a system when simulated by external inputs to generate some outputs. PD+ controller is designed based on passivation principle so that the closed loop system becomes globally uniform and asymptotically stable. The mathematical model of the Stewart platform, derived from Euler Lagrange equations of motion, is simulated on MALAB/Simulink with the designed controller. So as to get the desired leg-length trajectory, the inverse kinematics formulation is investigated. The mathematical model is verified using “automatic dynamic analysis of mechanical systems” (ADAMS) software. In the absence of disturbances, the maximum trajectory tracking error is recorded as ( 0.006m) in the time interval between 0sec and 0.8sec . Applying unit step disturbance makes the error 0.006m after 0.8sec , which never be seen in undisturbed system.. The maximum speed of all the six legs trajectory have been found to be 0.43m/ s , 0.49m/ s , 0.48m/ s , 0.5m/ s , 0.5m/ s and 0.49m/ s respectively. More realistic results are observed from ADAMS simulation results. Key words: passivity based control, PD+, global uniform asymptotically stable, Euler Lagrange equation, ADAMS software, inverse kinematics, MATLAB/Simulink.
Rotor Position Extraction by Carrier Frequency Component Method (Cfcm) in Space Vector Modulation (Svm) for Ipm Drives
(Addis Ababa University, 2015-09) Tenaye, Nebiyu; Mamo, Mengesha (PhD)
Sensorless drive of interior permanent magnet (IPM) synchronous motors is possible because the motors’ rotor position information is attached to stator inductance (due to magnetic saliency) and back electromotive force (EMF). The vector controlled sensorless drive, which uses the inductance variation of this motor, comprises a cascaded feedback and single loop SISO control systems. A cascade PI controller is introduced. The inner feedback loop performs the control of q-axis voltage according to the required q-axis current obtained from speed controlling outer loop. The position of the motor is obtained by using high frequency injected signal component of the stator’s currents. High frequency signals increase the bandwidth and reliability of the band pass filter. But further increase in injection frequency results higher THD. In order to find the exact position of the rotor from this saliency, two stationary reference frames are used. PI controller is also introduced for the single loop d-axis feedback system. This loop operates the regulation of the d-axis current for MTPA operation. An SVPWM is used to generate an efficient VSI switching sequence from the reference voltages obtained from the vector controller. The performance of this PWM technique is compared with the sinusoidal PWM in terms of total harmonic distortion (THD) and DC bus voltage conversion ratio. The d-q frame mathematical model of IPMSM, transformed using Park’s and Clarke’s transformation, is investigated on SIMULINK® SimPowerSystems™. The models are based on a per-unit (pu) analysis. Simulation results show that, SVPWM has a 22% low THD value than SPWM, and it improves the DC bus voltage conversion by 7%. The rotor’s position is successfully extracted from the high frequency component of rotor current for different motor operations, and the speed response of the control of the drive system is smooth. Key Words: Interior Permanent Magnet (IPM) Motor, Vector Controlled Motor Drives, Space Vector Pulse width Modulated (SVPWM) voltage source inverter, SIMULINK®
Trajectory Tracking Control of Delta-Robot Using 3rd Order Sliding Mode Control
(Addis Ababa University, 2016-04) Shefaw, Amdail; Mamo, Mengesha
Robots are multi-input multi-output (MIMO) nonlinear systems with uncertainties and high coupling effects ; this makes the control of Robot more difficult and needs a robust control system. This thesis describes, the concept of higher order sliding mode control as applied to trajectory tracking of a 3-DOF Delta Robot using tracking error as the sliding surface. Third order sliding mode control technique is specifically applied for this purpose. With the Robot's complicated electromechanical parts, mutual interactions of Robot mechanics and drives, building the nonlinear dynamic model of the Robot using 3D-CAD (like SolidWorks) program was the best solution to model the Robot. Real parameters were introduced via 3DCAD Modeling. The SimMechanics link utility bridges the gap between geometric modeling and block diagram modeling and simulation. Dynamical model with all the kinematic constraints for a Robot will simply be found by exporting a 3D-CAD model of the Robot to SimMechanics. In this thesis a 3-DOF Delta Robot is designed in SolidWorks, the kinematic and dynamic models of the Robot have been developed, a 3-SMC sliding mode controller is designed and a circular trajectory tracking is achieved, with X & Z axis rms error of 3mm. The simulation result shows that the steady state tracking is reached before 3 seconds. Finite time convergence of sliding function and its first and second derivatives is also achieved. the plant has been subjected to the effects of joint internal mechanics, mass uncertainty and external disturbances of torques. The designed third order sliding mode control have fond to be smooth, model independent, robust and is insensitive to applied model parameter variations, external & internal effects beside eliminating the chattering effect of the standard SMC..
Control of lower limb exoskeleton with simulated EMG signal
(Addis Ababa University, 2016-04) Aberra, Bethlehem; Mamo, Mengesha
An exoskeleton robot is a kind of a man-machine system which mostly uses combination of human intelligence and machine power. The structure of an exoskeleton robot consists of joints and links which correspond to the human body. This thesis presents a control system for exoskeletons that utilizes the simulated electrical signals from the muscles, EMG signals, as the main means of information transportation between the human and the exoskeleton. A support action is computed in accordance to the patient’s intention and is executed by the exoskeleton. The mathematical model of the exoskeleton system was based on the mathematical model of a permanent magnet DC servo motor whose parameters can be selected by either Using system identification techniques on a prototype built or by selecting an actuator based on the requirement of the load torque. A linear quadratic Gaussian (LQG) controller for the lower-limb exoskeleton is designed and implemented. Furthermore the robustness of the system to sensor noise and unmodelled system dynamics were analyzed. The effectiveness of the proposed system is tested through simulation studies using Simulink® software. The 3-D model of the system designed using solidworks® is interfaced with the Simulink® model via Simulink® simmechanics product. The proposed control strategy has shown satisfactory performances in terms robustness and gentleness. The knee joint is to track the ideal range of motion with an error of less than 5 % with the use of LQG controller. The control law is also found to be robust with respect to external disturbances. Key words: Lower limb exoskeleton, Electromyography (EMG), Modeling, linear quadratic Gaussian (LQG) controller.
Design of Super twisting Sliding Mode Controller for Hovering Stabilization of Tricopter UAV
(Addis Ababa University, 2016-05) Belachew, Asalifew; Mamo, Mengesha (Professor)
Unmanned Aerial Vehicles (UAVs) have attracted growing attention in research due to their wide applications. UAVs include many devices such as qua-copter, hexa-rotor, heli-copter, Tricopter. Among them, Tricopter is proposed in this thesis. It has three rotor axes that are equidistant from its center of gravity. Tricopter UAV is multivariable, nonlinear, unstable and under-actuated system. This thesis concentrates on the control and simulation of a Tricopter unmanned aerial vehicle. First coordinate systems with transformation matrix and mathe-matical models are derived based on Newton-Euler formulation technique. By using these equations, we are able to derive the mathematical model to simulate in MATLAB/Simulink environment for the purposes of altitude and attitude control for hovering stabilization of the Tricopter. The Control strategy used is Proportional Integral Derivative (PID) and the Super Twisting Sliding Mode Control (STSMC). STSMC is a viable alternative to the conventional first order sliding mode control for the systems of relative degree-1 in order to avoid chat-tering without affecting the tracking Performance. The PID and STSMC are mathematically derived, and their performance is verified by simulation. Simula-tion results show that the PID controller can maintain the stability of the Euler angles (roll angle, pitch angle, yaw angle). STSMC has been implemented for altitude control. The altitude settles at approximately 2 seconds with no over-shoot and steady state error of 2mm. The proposed STSMC is robust against parameter variation of 10% and able to overcome disturbances and maintain a given height position for hovering Stabilization of Tricopter. Key Words: Attitude Stabilization, PID controller, Super twisting Sliding Mode Control (STSMC), UAV Tricopter, Hovering.
Speed Control of Permanent Magnet Synchronous Motor Using Higher Order Sliding Mode Controller
(Addis Ababa University, 2016-05) Eskezia, Derege; Mamo, Mengesha (PhD)
Permanent magnet synchronous motor (PMSM) is the most used drive in machine tool servos and other modern high performance applications. In this thesis, a quasi-continuous higher order sliding mode controller is designed for PMSM in order to regulate the desired reference speed with robustness and minimized chattering. Proportional, Integral and derivative (PID) controllers are also designed for direct and quadrature components of the current in order to control the flux and torque. For the investigation of the problem, the controller is tested through a reference speeds as well as with load variations through simulation using MATLAB/SIMULINK. In the simulation, the SVPWM algorithm was written in M-file and embedded on simulation block. To make system control simple, field oriented control (FOC) is used for the operation of the motor to control the torque and flux of the motor directly as DC motor. Simulation results demonstrate that the speed response of the proposed drive is unaffected by load torque and parameters variation. Furthermore, the developed controller has good performance when the reference speed is changed, i.e., the developed controller speed regulation is unaffected by the nature of the reference speed. From the simulation result, the speed error in steady state response is zero, the speed response has a maximum over shoot of 1.08% and the chattering effect on the system is reduced. Keywords: PMSM, HOSM controller, FOC, quasi-continuous HOSM controller, chattering effect
Study of Doubly Fed Induction Generator Control Under Grid Fault Conditions
(Addis Ababa University, 2016-06) Tadesse, Teshale; Mamo, Mengesha (PhD)
Wind power is growing rapidly around the world as a means of dealing with the world energy shortage and associated environmental problems. A wind electrical generation system is the most cost effective of all the environmentally clean and safe renewable energy sources in world. In this thesis, double fed induction generator and grid system are modeled under normal conditions of the grid system and under grid faulty conditions. Any abnormalities associates with grid are going to affect the system performance. Taking this into account, the performance of double fed induction generator (DFIG) variable speed wind turbine under network faults is studied using simulation developed in MATLAB/SIMULINK results show the fault behavior of the double fed induction generator when a sudden short circuit and voltage dip on the grid side. After the clearance the short circuit fault and voltage dip the proportional integral controller manages to restore the wind turbine‘s normal operation. The three-phase fault model is done by giving a fault equivalent resistance value of 0.01Ω and voltage dip at grid side with the value of 0.45p.u. At this time, the current, voltage, active power and reactive power value of DFIG is fluctuating between 0.2p.u and 1.36p.u, 0.7p.u and 1.12p.u, 0 and 6MW, 0.75 and 0.42MVAr, respectively. But in order to operate at normal operation the DFIG current and voltage value is at 1p.u. The maximum active power that generated from DFIG is 9MW. To stabilize the system the proportional integral controller compare the reference voltage and current with generated and minimize the error between voltage and current. The proportional integral controller minimizes the error by decreasing the rising time and makes the value of current and voltage to 1p.u. The detailed results of steady state and faulty or three-phase short circuit on grid system has been noted and analyzed with proper justification. In order to increase the fault ride through capabilities of the system, crowbar protection and series dynamic resistor could be added to the system. This thesis done by modeling and simulating of the controller using Matlab/Simulink in wind turbine system integrated with grid system. Finally, we observed and interpreted the result with Matlab/Simulink simulation software. Keywords:- , doubly fed induction generator; wind turbine; proportional integral controller; MATLAB/SIMULINK;
Control of Quad Rotor Unmanned Aerial Vehicle (UAV) Using LQG Track controller
(Addis Ababa University, 2016-06) Negese, Bekele; Prasad Singh, Nagendra (Professor0
This thesis is focused towards the studies on Vertical Take-Off and landing (VTOL) Unmanned Aerial Vehicle (UAV) quad rotor control. The quad rotor is controlled by four BLDC motors which act in different directions to control the yaw angle, roll angle and pitch angle and z-axis position. The control action basically depends on the controlled voltages fed to the four motors. The dynamic modelling of quad rotor is discussed and the design of Linear Quadratic Gaussian (LQG) is presented. A simulator based on MATLAB/SIMULINK model of UAV quad rotor is developed to carry out simulation studies. The effectiveness of the proposed LQG control algorithm to control the hovering position and cruising position in the presence of disturbances such as plant noise and sensor noise is investigated through simulation studies on the simulator. The effectiveness of the proposed controller is tested with and without disturbance through simulation studies. The first test is observed from model verification of open loop response. It is observed from the open loop response that the altitude control is done through three conditions. This was done by controlling the four input controls through rotors frequencies which are compared with the hovering frequencies. Closed loop simulation studies are carried out with the proposed LQG controller. It is observed that the desired tracking is achieved almost within 9 seconds after giving the step input command signals. Similarly, it is observed that the hovering position is achieved almost within 8 seconds after giving the step input command signals. It is further observed that the quad rotor tracks the command signals almost after 10 seconds under the influence of disturbance of covariance value 0.9. It is further observed that the quad rotor attains the desired hovering position after 9 seconds under the influence of disturbance of covariance value 0.9. Key words: VTOL, UAV, LQG, LQR, Kalman Filter, Tracking control, Hovering position Stabilization
Design and Simulation of a Neuro-Fuzzy Based Temperature Controller for Neonatal Incubator
(2016-12) Demerwe, Dagmawi; Shiferaw, Dereje (PhD)
Premature infant’s birth is a worldwide problem. Their organs are not mature enough to allow normal postnatal survival relative to normal babies, consequently they will became hypothermic, which leads them to death. Premature neonates survive in a very narrow core temperature range (36.5-37.5ºC) and suitable relative humidity. As a result, some parameters have to be monitored and their accuracy remains an important matter. Infant incubators are complex medical devices, which are often used immediately after delivery and for the coming few months of their life depending on the infant’s health condition. They use the convection of warm and humidified air to control the temperature of the infant. They have two modes of operation, either the incubator’s air temperature is sensed and used to control the heat flow or infant’s skin temperature is sensed and used in the feedback control system. Infant’s skin temperature control only often leads to large fluctuations in the incubator’s air temperature, similarly incubator’s air temperature control only also leads to infant’s skin temperature fluctuations. This thesis presents the application of adaptive neuro fuzzy inference controller for ATOM V-850 model infant incubator system, in order to control the incubator’s air temperature and the infant’s skin temperature simultaneously. The corresponding fuzzy logic controller is designed for the same system, in order to work with structured knowledge in the form of rules in the FIS. However, there exists no formal framework for the choice of various design parameters and optimization of these parameters generally is done by trial and error technique. The combination of artificial neural networks and fuzzy logic systems offers the possibility of solving tuning problems and design difficulties of fuzzy logic system. The performance comparison between the proposed ANFIS controller and FLC is analyzed through various conditions using MATLAB/Simulink® software. Simulation results show that the performance of the proposed ANFIS Controller, in tracking the desired incubator’s air temperature and desired infant’s skin temperature, improved to 0.39% and 0.2% error from 16.6% and 1.47% error in the FLC respectively. Results also show that, the ANFIS model on the closed loop infant incubator system provides best control performance over a wide range of operating conditions relative to FLC. Key Words: Neonatal incubator, Preterm infant, ANFIS controller, ANN, FLC, MATLAB/Simulink®
Trajectory Tracking Control Simulation of a 4-DOF SCARA Robot Manipulator Using Fuzzy Sliding Mode Controller with PID Sliding Surface
(Addis Ababa University, 2017) Temesgen, Gelchu; Dereje, Shiferaw (PhD)
Research and development of controlling industrial robot is an active research area. The methodologies for controller design development are considered as the key for the robot in the industrial applications. One of the most widely used industrial robots is the SCARA robot due to its high precision, high speed, small dimensions, simple and reliable structure, and ease of installation. The study reported is on design and simulation of fuzzy sliding mode controller with PID sliding surface for a 4 DOF Selective Compliance Assembly Robot Arm (hereafter called SCARA). The main objective of this thesis is to control a SCARA robot arm using two controllers to track the desired position. Sliding mode controller (SMC) is used as a reference benchmark to compare its result with fuzzy sliding mode controller (FSMC) with PID sliding surface result. Euler – Lagrange approach has been used to drive the complete dynamic model of SCARA robot, the stability of the system has been analyzed by using Lyapunov method, the controller has been implemented using MATLAB and performance analysis has been done. The simulation results show that the newly proposed controller has removed chattering phenomena from input torque, minimized the magnitude of controller effort, and has reduced the tracking error (order of for first, second, fourth joint and of for third joint).
Multi-Phase Induction Motor For Electric Vehicle
(2017) Chenenus, Gelana; Mengesha, Mamo (PhD)
This thesis is presents a multiphase induction motor for electric vehicle, designing of m-phase machine at which constant current and power condition by varying number of phase that increases from single phase to m-phase unto the minimum value of slot size ends. So these paper presents have two major section to fit full operational characteristic m-phase induction for electric vehicle those section are includes designing of induction motor that evaluate the minimum value of slot size and m-phase induction motor modelling for proper control ; then model is based on generalized d-q model of n phase induction motor drive. Multi -phase induction motor (more than three phases) drives possess several advantages over conventional three-phase drives, such as reduced the number of battery needed for supply, reducing the accident due to the sudden condition crashing of car, minimizing of the load on car in cases of minimizing the number battery supply, lower torque pulsation, higher torque density, fault tolerance, stability, high efficiency and lower current ripple. In this paper, a generalize d–q axis model is developed in Matlab/Simulink for an m-phase induction motor. The simulation results are presented for 3,5,9 and 12 phase induction motor under constant current and power conditions by varying phase and analyzing the phase voltage .
Prevention of Blackout Using an Automated SCADA System in Case of EEP
(Addis Ababa University, 2017-01) Mengistu, Addis; Dereje, Shiferaw (PhD)
Nowadays the stability, reliability, sustainability and security of power system are the main concerning issues in Ethiopia because of frequently happening disturbances which will lead to total or partial power system blackout. When disturbances occur in power grid, monitoring and controlling of a power system are required to stop the grid degradation, restore it to a normal state, and hence minimize the effects of disturbances. However, in wide area power grid resulting from large and complex interconnection of power system network, classical systems based on manual operation and decisions are not able to rapidly respond for disturbances, which may cause a local or complete system collapse. Therefore the introduction of automated SCADA system with advanced measurement and very fast communication technologies provide better ways to detect rapidly the disturbances and protect the overall grid from the propagation of the fast cascading outages. Automation system improve the performance by taking advantage of faster computer control instead of human reaction times and also used to increase the efficiency of control by trading off high personnel costs for low computer system costs. This thesis presents the design of an automated SCADA system that can prevent the grid system from blackout in real time through active and reactive power balancing. Active power and reactive power of the system are the most essential parameters in the monitoring, control, and protection of power systems and electric equipments because when a fault or a signiﬁcant disturbance occurs in a power system, the frequency and voltage varies in time and space. A modeling of electrical system elements was developed to have a complete one line diagram of the existing network using DIgSILENT power factory software version 15.1. The study has employed conventional power flow and dynamic analysis for assessing the stability and reliability of the system. Different type of faults has been used for the analysis, which leads the system to cascade outage. Finally, to mitigate these problems, necessary control measures have been presented. The result shows that whatever any disturbance experienced to grid has been controlled automatically without operator intervention and lead to normal operation condition. From the test results, the proposed technique presents better controlling method in comparison with that of the existing manual based control system in black out mitigation along with improvement in stability of the system. The method is implemented on the whole EEP grid and tested on specifically for northern and north western region.
Model Reference Adaptive Control Based Sensorless Speed Control of Induction Motor
(Addis Ababa University, 2017-01) Tatek, Workagegn; Mamo, Mengesha (PhD)
In this thesis, stator current based model reference adaptive system (MRAS) speed estimator is used for closed loop speed control of induction motor without mechanical speed sensor. Due to high sensitivity of motor parameters variation at low speed including zero, stability analysis of MRAS design is done to correct any mismatch parameters value in the MRAS is done to estimate the motor speed at these value. As result the induction motor sensorless control can operate over a wide range including zero speed. The performance of stator current based MRAS speed estimator was analyzed in terms of speed tracking capability, torque response quickness, low speed behavior, step response of drive with speed reversal, sensitivity to motor parameter uncertainty, and speed tracking ability in regenerative mode. The system gives good performance at no load and loaded condition. Hence, it can work with different load torque conditions and with parameters variation.Stator current based MRAS estimator sensorless speed control technique can make the hardware simple and improve the reliability of the motor without introducing feedback sensor and it becomes more important in the modern AC induction motor. The sensorless vector control operation has been verified by simulation on Matlab and experimentally using Texas Instruments HVMTRPFCKIT with TMS320 F28035 DSP piccolo control card and 0.18kw AC induction motor. From the experimental work the actual speed of the motor with maximum steady state error of 0.00458pu has been achieved. Keywords: Induction motor, Vector control, Stator current based MRAS, Sensorless, Piccolo™ TMS320F28035 Control Card
Maximum Power Extraction of PMSG Based Variable Speed Wind Turbine Using Self-Tuning Fuzzy Controller
(2017-02) Belay, Addisie; Shiferaw, Dereje (PhD)
The interest in wind energy system is growing worldwide to reduce dependency on fossil fuel and to minimize the adverse impact of climate change. However, because of its unpredictable and random availability, wind power management concepts are essential to extract as much power as possible from the wind when it becomes available. The purpose of this thesis is to develop fuzzy logic controller to tune the parameters of PI controller for a maximum power tracking strategy of variable speed wind turbine. The system consists of 8.5kW direct drive permanent magnet synchronous generator (PMSG), uncontrolled rectifier which is used to convert the ac output voltage from the wind generation unit into dc voltage, a dc/dc switch-mode step up boost converter which is used to catch the maximum power from the wind, and a power control system. The output of the controller was given to the dc-dc converter to adjust the duty cycle and when adjusting the duty cycle the rotor speed of PMSG was controlled to get the maximum power. The proposed control algorithm allows the generator to track the optimal operation points of the wind turbine system under fluctuating wind conditions. This algorithm does not require the knowledge of intangible turbine mechanical characteristics such as its power coefficient curve, power characteristic or torque characteristic instead it uses rotor speed measurement as control variable inputs. MATLAB simulation study results confirm that the proposed controller algorithm is effective in tracking maximum power with good dynamic and steady state performance. From the power extracted plots it is observed that the overshoot given by the self tuning fuzzy PI controller is reduced to 0.09% from 0.2% while the regulation time is reduced to 0.6 s from 1.4s from the PI controller, when the wind speed is 12 m/s (steady state). The overshoot given by the self tuning Fuzzy PI controller is reduced to 0.07% from 0.1% and 0.01% from 0.09% in comparison with the PI controller while the regulation time is reduced to 5.4s from 6.1s and 10.5s from 11.2s from the PI controller, when the wind speed changes suddenly from 12 m/s to 10 m/s and 10m/s to 8m/s respectively. Keywords- Variable Speed Wind Turbine, Permanent Magnet Synchronous Generator, Uncontrolled Rectifier, DC/DC Switch-Mode Boost Converter, PI Controller, and FLC.
Voltage Control of A Dc-Dc Buck Converter Using Second Order Sliding Mode Control
(Addis Ababa University, 2017-02) Tolossa, Zawde; Shiferaw, Dereje (PhD)
DC-DC converters are non-linear and the most widely used circuits in power electronics. Generally they are used in all situations where there is need of stabilizing a given DC voltage to a desired value. DC-DC buck converter is used in applications for voltage step-down. The output voltage of this converter alone is usually unstable, oscillates, it has large overshoot, and long settling time. Also it is unable to give the desired output voltage under input voltage and load variations. To overcome this problem and obtain constant stable output voltage and fast response various controllers are required. PID controllers have been usually applied to the converters to obtain the desired output voltage because of their simplicity. But application of PID controller is not reliable and satisfactory in the case of non-linear systems. Therefore, non-liner controllers are required to improve system performance. In this thesis second order sliding mode controller based on the prescribed convergence algorithm has been designed to achieve fast and stable performance of buck converter. The proposed controller performance is compared with PID controller based on dynamic response of the system in terms of overshoot, settling time, rise time, and voltage deviation from desired value using MATLAB/Simulink. In order to test the performance of proposed controllers the load resistance increased and decreased by 62.5% from operating point while input voltage decreased by 20.83% and increased up to 41.67% from operating point. Also to test effectiveness of SOSM control the input voltage is varied from operating point (i.e. 24V) up to 200V. Simulation results show that, using SOSM controller the rise and settling time is improved by 5.228% and 46.39% respectively as compared to that obtained using PID controller. The overshoot is reduced from 51.3% to 9.455% using PID controller while SOSM controller totally removes it. Both controllers overcame the effect of load resistance variations. The overshoot is increased from 9.455% to 17.5% for input voltage increased by 41.67% using PID controller is eliminated using SOSM controller. The actual output voltage is not deviated from desired value even for large input voltage variation using SOSM controller. Generally from the result it is possible to conclude that the performance of SOSM controller is better than PID controller. Key words: DC-DC Converter, Buck Converter, PID Control, SOSM Control.
Fuzzy PID Based Temperature Control of Electric Furnace for Glass Tempering Process
(Addis Ababa University, 2017-03) Achenef, Sisay; Shiferaw, Dereje (PhD)
Tempered glass is a safety glass processed by a controlled thermal or chemical treatment to increase its strength compared with the ordinary (or annealed) glass. In thermal tempering process, the glass is heated to a temperature just below the softening point and is then quenched rapidly in air. Thus, in thermal tempering manufacturing process temperature control of tempering furnace is the main task. Our country Ethiopia has some glass manufacturers hence we can use thermal tempering process to manufacture tempered glass. This thesis deals with the temperature control of electric furnace. The temperature of electric furnace is controlled to a desired value. In tempered glass furnace industry, the widely used controller for temperature control is conventional PI and PID controllers. Since electric furnaces are nonlinear and time varying processes, using PID controllers is difficult to meet the control requirement. Because they are not robust, haven’t good dynamic response and have large overshoot. Hence in this thesis, fuzzy logic controller which is fault tolerant and nonlinear controller is used to improve the PID and achieve steady state and transient requirements. Therefore, in this thesis a model of glass tempering furnace is prepared using MATLAB/SIMULINK and then fuzzy PID controller has been designed and simulated and its performance has been compared with conventional PID controllers. The performance of the controllers is compared in terms of disturbance rejection, transient and steady sate performance. It is observed from the simulation results that the average overshoot is 2.129%, rising time is 44 seconds and the settling time is 170s seconds with the proposed fuzzy PID controller while overshoot is 16.129%, rise time is 45 second and settling time is 290 seconds with PID controller. Moreover, the robustness and disturbance rejection of the controllers is checked by parameter variation like time constant, delay time & DC gain and giving disturbance signal after settling time respectively. It is further observed that the proposed controller has better disturbance rejection and more robust. Key words: Glass tempering furnace temperature control, Fuzzy PID controller, PID controller.
Modeling and Analysis of Regenerative Braking of an Induction Motor
(AAU, 2017-04) Lidia, Habtamu; Mengesha, Mamo (PhD)
Due to the increase in demand of energy, new technologies have evolved to improve energy efficiency like regenerative braking. In this thesis, the energy storage device, battery, with converters and IM are used to analyze regenerative braking. Using only battery and IM is easy in control but adding converters result in a better performance. The analysis is performed using vector control method and MATLAB SIMULINK as simulation tool. The results show that the desired energy saving (around 500Watt) can be obtained during regenerative braking. An experimental analysis using Texas instruments Digital Signal Processor C2000 F28035 was performed. The torque producing current component, the dc bus voltage and decelerating speed has been analyzed during regenerative braking mode. From the experiment the torque producing current component becomes negative when regeneration starts. To analyze the time needed for the motor to stop two experiments have done. The result demonstrates that the braking time during regenerative braking is shorter than that of free fall. During regenerative braking the dc bus voltage was supposed to increase however due to the small inertia of the motor the voltage increase was not observed. But by adding additional disk to IM, the inertia of the motor was increased and energy regeneration was observed.

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