Robust fault tolerant control of induction motor system

Research into fault tolerant control (FTC, a set of techniques that are developed to increase plant availability and reduce the risk of safety hazards) for induction motors is motivated by practical concerns including the need for enhanced reliability, improved maintenance operations and reduced cost. Its aim is to prevent that simple faults develop into serious failure. Although, the subject of induction motor control is well known, the main topics in the literature are concerned with scalar and vector control and structural stability. However, induction machines experience various fault scenarios and to meet the above requirements FTC strategies based on existing or more advanced control methods become desirable. Some earlier studies on FTC have addressed particular problems of 3-phase sensor current/voltage FTC, torque FTC, etc. However, the development of these methods lacks a more general understanding of the overall problem of FTC for an induction motor based on a true fault classification of possible fault types.In order to develop a more general approach to FTC for induction motors, i.e. not just designing specific control approaches for individual induction motor fault scenarios, this thesis has carried out a systematic research on induction motor systems considering the various faults that can typically be present, having either “additive” fault or “multiplicative” effects on the system dynamics, according to whether the faults are sensor or actuator (additive fault) types or component or motor faults (multiplicative fault) types.To achieve the required objectives, an active approach to FTC is used, making use of fault estimation (FE, an approach that determine the magnitude of a fault signal online) and fault compensation. This approach of FTC/FE considers an integration of the electrical and mechanical dynamics, initially using adaptive and/or sliding mode observers, Linear Parameter Varying (LPV, in which nonlinear systems are locally decomposed into several linear systems scheduled by varying parameters) and then using back-stepping control combined with observer/estimation methods for handling certain forms of nonlinearity.In conclusion, the thesis proposed an integrated research of induction motor FTC/FE with the consideration of different types of faults and different types of uncertainties, and validated the approaches through simulations and experiments

Adaptive Non-Linear High Gain Observer Based Sensorless Speed Estimation of an Induction Motor

International audienc

Hybrid Sensorless Field Oriented and Direct Torque Control for Variable Speed Brushless DC Motors

The objective of this thesis is to design a hybrid sensorless closed-loop motor controller using a combination of Field-Oriented Control (FOC) and Direct Torque Control (DTC) for brushless DC motors used in multi-rotor aerial vehicles. The primary challenge is the wide range of desired working speeds, which can quickly vary from low speed to high speed. For this range, the control approach must be efficient, effective, and low-cost in order to provide fast response times during initial startup, steady-state, and transient operation. Additional design challenges include minimal response time to desired speed changes and small steady-state speed errors. Finally, the control approach must be robust to motor parameter uncertainties or variations and the operation of the final design must be robust to measurement noise

An Enhanced Sliding Mode Speed Control for Induction Motor Drives

In this paper, an enhanced Integral Sliding Mode Control (ISMC) for mechanical speed of an Induction Motor (IM) is presented and experimentally validated. The design of the proposed controller has been done in the d-q synchronous reference frame and indirect Field Oriented Control (FOC). Global asymptotic speed tracking in the presence of model uncertainties and load torque variations has been guaranteed by using an enhanced ISMC surface. Moreover, this controller provides a faster speed convergence rate compared to the conventional ISMC and the Proportional Integral methods, and it eliminates the steady-state error. Furthermore, the chattering phenomenon is reduced by using a switching sigmoid function. The stability of the proposed controller under parameter uncertainties and load disturbances has been provided by using the Lyapunov stability theory. Finally, the performance of this control method is verified through numerical simulations and experimental tests, getting fast dynamics and good robustness for IM drives.The University of the Basque Country (UPV/EHU) [grant number PIF 18/127] has funded the research in this pape

Hybrid Field Oriented and Direct Torque Control for Sensorless BLDC Motors Used in Aerial Drones

In this study, a sensorless hybrid control scheme for brushless direct current (BLDC) motors for use in multirotor aerial vehicles is introduced. In such applications, the control scheme must satisfy high-performance demands for a wide range of rotor speeds and must be robust to motor parameter uncertainties and measurement noise. The proposed controller combines field-oriented control (FOC) and direct torque control (DTC) techniques to take benefit of the advantages offered by each of these techniques individually. Simulation results demonstrate the effectiveness of the proposed control scheme over a wide range of rotor speeds as well as good robustness against parameter uncertainties within -5to + 10% for inductance and -5to + 5% for resistance parameters. The proposed hybrid controller is robust also against noise in voltage and current measurements. In order to verify the results from simulation, the proposed hybrid controller is implemented in hardware using the TI C2000 Piccolo Launchpad and TI BOOSTXL-DRV8305EVM BoosterPack. Testing is done with a Bull Running motor typically used in aerial drones. Testing experiments demonstrate that the hybrid controller reduces the rotor speed ripple when compared to DTC while operating in steady-state mode and decreases the response time to desired speed changes when compared to FOC

High-Gain Observer–Based Sliding Mode Control of Multimotor Drive Systems

Multimotor drive systems have been widely used in many modern industries. It is a nonlinear, multi-input, multi-output (MIMO) and strong-coupling complicated system, including the effect of friction, elastic, and backlash. The control law for this drive system much depends on the determining of the tension. However, it is hard to obtain this tension in practice by using a load cell or a pressure meter due to the accuracy of sensors or external disturbance. In order to solve this problem, a high-gain observer is proposed to estimate the state variables in this drive system, such as speeds and tension. An emerging proposed technique in the control law is the use of high-gain observers together with adaptive sliding mode control scheme to obtain a separation principle for the stabilization of whole system. The theory analysis and simulation results point out the good effectiveness of the proposed output feedback for the drive system

Vector control for a bearingless induction motor based on nonsingular terminal sliding mode structure

© 2017 IEEE. To improve the performance of the bearingless induction motor (BIM) under disturbances, a nonsingular fast terminal sliding mode control (NFTSMC) strategy is proposed. The sliding mode surface is designed as a combination of linear sliding mode and nonsingular terminal sliding mode. Besides, considering the power function of the state variables, which make the approaching speed correlate with the state variables, so as to improve convergence performance of the linear sliding mode and solve the singularity of terminal sliding mode. Meanwhile, current signal and radial force are extracted by the electromagnetic torque and the equation of levitation force. Therefore, the convergence speed of system can be accelerated during the whole process, which contributes to chattering-free operating. The simulation and experiment results indicate that the proposed method can not only track the given value of the speed and radial displacement quickly, but also improve the operation quality and enhance the system robustness

Recent Advances in Robust Control

Robust control has been a topic of active research in the last three decades culminating in H_2/H_\infty and \mu design methods followed by research on parametric robustness, initially motivated by Kharitonov's theorem, the extension to non-linear time delay systems, and other more recent methods. The two volumes of Recent Advances in Robust Control give a selective overview of recent theoretical developments and present selected application examples. The volumes comprise 39 contributions covering various theoretical aspects as well as different application areas. The first volume covers selected problems in the theory of robust control and its application to robotic and electromechanical systems. The second volume is dedicated to special topics in robust control and problem specific solutions. Recent Advances in Robust Control will be a valuable reference for those interested in the recent theoretical advances and for researchers working in the broad field of robotics and mechatronics

DFIG Based Wind Turbine System For Clemson Micro-grid

As an important part of the smart grid, the micro-grid interfaces with distributed energy sources, loads and control devices. A doubly fed induction generator (DFIG) based wind turbine (WT) is the main power source of the presented project. The DFIG system is connected to the three phase AC grid via back-to-back power converter and an LCL filter. Decoupled q-d control strategies are investigated for the DFIG system. Matlab/Simulink results will show the performance of the proposed system. Hardware validation results are also presented and discussed. As a rapidly increasing research interest area the dc micro-grid has been extensively investigated. A topology is proposed to connect the DFIG based WT system to a dc link using a diode bridge and a three phase power converter. The rotor side of the DFIG is connected to the dc link through a converter while the stator is connecting to a three phase diode bridge with the dc side connected to a dc link. The control method is developed to regulate the stator frequency and the d-q axis voltage of the diode bridge to operate the DFIG at a desired stator frequency and generate the required power. Undesired harmonics in the three phase system will lead to excessive THD, a decrease the power quality and an increase the power loss of the system. An novel methods to compensate the current harmonics by controlling the power converter of the DFIG system is also proposed. With the DFIG connected to the three phase AC gird, the focus has been put into a scenario: a nonlinear load connected to the same node of the DFIG point of common coupling (PCC) to the gird, to draw the harmonics to the system. In the proposed dc link system, the diode bridge will introduce harmonics to the stator current of the DFIG. In both cases, the selected low-order harmonics are detected and calculated by a multiple reference frame estimator. The control methods of how to regulate the harmonics are developed for both the grid-side converter and the rotor-side converter based on multiple reference frame theory. A hybrid state observer for speed-sensorless motor drives of induction machines is also proposed. The hybrid observer comprises of a Luenberger observer and a sliding mode observer. For a conventional induction motor with shorted rotor, the stator currents and rotor flux linkages are estimating following a Luenberger observer. While, for a DFIG the similar approach will apply to the stator currents and rotor currents. The rotor speed is estimated using a sliding mode observer. The combination of two observers takes advantage of both approaches. The Luenberger observer is easy to realize and the computational burden is small. The sliding mode observer is known for its robustness with respect to model parameter errors and it will also provide a fast convergence rate. The chattering of the sliding mode observer is addressed by applying a boundary layer