An implementation of rotor speed observer for sensorless induction motor drive in case of machine parameter uncertainty

The paper describes observers using model reference adaptive system for sensorless induction motor drive with the pulse width modulator and the direct torque control under the circumstances of incorrect information of induction motor parameters. An approximation based on the definition of the Laplace transformation is used to obtain initial values of the parameters. These values are utilized to simulate sensorless control structures of the induction motor drive in Matlab-Simulink environment. Performance comparison of two typical observers is carried out at different speed areas and in presence of parameter uncertainty. A laboratory stand with the induction motor drive and load unit is set up to verify the properties of observers. Experimental results confirm the expected dynamic properties of selected observer

Verification of a full-order observer design for sensorless induction motor drives

The main topic of this thesis is the full-order flux observer as a part of the induction machine sensorless drives. First the induction machine inverse-Gamma model is presented with a brief overview of space vectors and different coordinate systems. Sensorless vector control principles and theory are presented next. Two very promising full-order observer designs were chosen, presented and tested through computer simulations. The simulations were implemented with the MATLAB/Simulink environment. The full-order observer designs are tried in different situations, like speed reversal, basic load tasks while running at a given speed, or a speed higher than the nominal to see how the design behaves. There is also a trial for stator resistance error, which can signify changes in the resistance due to temperature fluctuations or estimation errors from the mathematical model. From the test results it has been concluded that the original design is hard to tune, and it does not have tolerance to stator resistance changes. The improved design has brought more flexibility in terms of tuning, and there is a better tolerance for stator resistance changes

Gain Scheduling of a Full-Order Observer for Sensorless Induction Motor Drives

This paper deals with the design of a speed-adaptive full-order observer for sensorless induction motor (IM) drives. A general stabilizing observer gain matrix, having three free design parameters, is used as a design framework. A gain-scheduled selection of the free design parameters is proposed. Furthermore, the full-order observer is augmented with the stator-resistance adaptation, and the local stability of the augmented observer is analyzed. The performance of the proposed full-order observer design is experimentally compared with a reduced-order observer using a 2.2-kW IM drive.Peer reviewe

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

International audienc

Performance Comparison of Different Speed Estimation Techniques in Sensorless Vector Controlled Induction Motor Drives

Field-oriented control and direct torque control are fast becoming necessities of modern industrial setups for induction motor drive control. Induction motors are considered as the beginning part to create any electrical drive system to be subsequently utilized for several industrial requirements. So now a day due to its high application the need to control the performance of the induction motor is gaining importance. In modern control system, IM is analyzed by different mathematical models mainly depending on its applications. Vector control method is suitably applied to induction machine in 3-phase symmetrical or in 2-phase unsymmetrical version. For vector control IM is realized as DC motor having its characteristics. This dissertation work is aimed to give a detailed idea about the speed control and variations in an induction motor through vector control technique thereby showing its advantage over the conventional scalar method of speed control. It also focusses on the speed estimation techniques for sensorless closed loop speed control of an IM relying on the direct field-oriented control technique. The study is completed through simulations with use of MATLAB/Simulink block sets allowing overall representation of the whole control system arrangement of the Induction motor. The performance of different sensorless schemes and comparison between them on several parameters like at low speed, high speed etc. is also provided emphasizing its advantages and disadvantages. The analysis has been carried out on the results obtained by simulations, where secondary effects introduced by the hardware implementations have not been considered. The simulations and the evaluations of different control techniques are executed using parameters of a 50 HP, 60 Hz induction motor which is fed by an inverter

Model predictive MRAS estimator for sensorless induction motor drives

Ph. D. ThesisThe project presents a novel model predictive reference adaptive system (MRAS) speed observer for sensorless induction motor drives applications. The proposed observer is based on the finite control set-model predictive control principle. The rotor position is calculated using a search-based optimization algorithm which ensures a minimum speed tuning error signal at each sampling period. This eliminates the need for a proportional integral (PI) controller which is conventionally employed in the adaption mechanism of MRAS observers. Extensive simulation and experimental tests have been carried out to evaluate the performance of the proposed observer. Both the simulation and the experimental results show improved performance of the MRAS scheme in both open and closed-loop sensorless modes of operation at low speeds and with different loading conditions including regeneration. The proposed scheme also improves the system robustness against motor parameter variations and increases the maximum bandwidth of the speed loop controller. However, some of the experimental results show oscillations in the estimated rotor speed, especially at light loading conditions. Furthermore, due to the use of the voltage equation in the reference model, the scheme remains sensitive, to a certain extent, to the variations in the machine parameters. Therefore, to reduce rotor speed oscillations at light loading conditions, an adaptive filter is employed in the speed extraction mechanism, where an adaptation mechanism is proposed to adapt the filter time constant depending on the dynamic state of the system. Furthermore, a voltage compensating method is employed in the reference model of the MP-MRAS observer to address the problems associated with sensitivity to motor parameter variation. The performance of the proposed scheme is evaluated both experimentally and by simulation. Results confirm the effectiveness of the proposed scheme for sensorless speed control of IM drives

Analysis and Design of Full-Order Flux Observers for Sensorless Induction Motors

This paper deals with the flux estimation for sensorless induction motor drives. The linearized model of the speedadaptive full-order flux observer is applied to help choosing the observer gain and the speed-adaptation gains. It is shown that the linearized model reveals potential instability problems that are difficult to find by other means. An observer gain and a method to vary the speed-adaptation gains in the field-weakening region are proposed. Experimental results show stable operation in a very wide speed range.Peer reviewe

Machine Model Based Speed Estimation Schemes for Speed Encoderless Induction Motor Drives: a Survey

Speed Estimation without speed sensors is a complex phenomenon and is overly dependent on the machine parameters. It is all the more significant during low speed or near zero speed operation. There are several approaches to speed estimation of an induction motor. Eventually, they can be classified into two types, namely, estimation based on the machine model and estimation based on magnetic saliency and air gap space harmonics. This paper, through a brief literature survey, attempts to give an overview of the fundamentals and the current trends in various machine model based speed estimation techniques which have occupied and continue to occupy a great amount of research space

Speed Sensorless Induction Motor Drives for Electrical Actuators: Schemes, Trends and Tradeoffs

For a decade, induction motor drive-based electrical actuators have been under investigation as potential replacement for the conventional hydraulic and pneumatic actuators in aircraft. Advantages of electric actuator include lower weight and size, reduced maintenance and operating costs, improved safety due to the elimination of hazardous fluids and high pressure hydraulic and pneumatic actuators, and increased efficiency. Recently, the emphasis of research on induction motor drives has been on sensorless vector control which eliminates flux and speed sensors mounted on the motor. Also, the development of effective speed and flux estimators has allowed good rotor flux-oriented (RFO) performance at all speeds except those close to zero. Sensorless control has improved the motor performance, compared to the Volts/Hertz (or constant flux) controls. This report evaluates documented schemes for speed sensorless drives, and discusses the trends and tradeoffs involved in selecting a particular scheme. These schemes combine the attributes of the direct and indirect field-oriented control (FOC) or use model adaptive reference systems (MRAS) with a speed-dependent current model for flux estimation which tracks the voltage model-based flux estimator. Many factors are important in comparing the effectiveness of a speed sensorless scheme. Among them are the wide speed range capability, motor parameter insensitivity and noise reduction. Although a number of schemes have been proposed for solving the speed estimation, zero-speed FOC with robustness against parameter variations still remains an area of research for speed sensorless control