Field-oriented Induction Motor Research Articles

Rotor time constant updating scheme for a rotor flux-oriented induction motor drive

This paper presents a simple online rotor time constant identification scheme of an indirect field-oriented induction motor for the purpose of improving the performance and robustness of the drive. The proposed technique neither requires any special test signal nor any complex computations. This scheme is based on a special switching technique of the current-regulated pulsewidth modulation (CRPWM) voltage-source inverter (VSI), which allows measuring the induced voltage across the stator phase. The rotor time constant is then identified directly from this measured voltage. This proposed technique provides six windows within one electric cycle to update the rotor time constant, which should be sufficient for all practical purposes. Simulated results followed by experiments are presented to validate the effectiveness of the proposed technique.

Performance Improvement of a Field-Oriented Induction Motor Drive via Fuzzy Control

This paper presents a fuzzy slip angular speed estimator for improving the efficiency of an indirect field-oriented (IFO) induction motor drive. The proposed estimator consists of a fuzzy detuning correction controller (FDCC) and a fuzzy excitation controller (FEC). At heavy load, the rated flux excitation of motor is set and the nominal slip angular speed is augmented by a tuning signal generated by the proposed FDCC such that the motor drawn line current is significantly reduced, and thus the field-orientation characteristics can also be much improved. At steady-state of light load, for reducing the line drawn current more effectively, the nominal slip angular speed is set and the flux current command is reduced from its rated value by the FEC. As the transient due to command or load change occurs, the flux current command is restored to its rated value to increase the torque generating capability. Finally, a simple reference model following controller is designed to further yield good rotor speed dynamic response. The design methodology of the proposed controller is detailedly described, and the performance of the resulted motor drive is demonstrated experimentally.

Induction motor drive parameters identification

Two online identifiers of the rotor parameters of the field-oriented (FO) induction motor drive are presented in this paper, The synthesis procedure of the identifiers is based on the model reference adaptive control (MRAC) system theory. An appropriate choice of the reference model allows building a Lyapunov function by means of which the updating law of the rotor time constant can be found. A higher order identifier is also synthesized using hyperstability approach. It allows the simultaneous identification of two rotor parameters. The parameters' convergence is assured thanks to the persistent exciting propriety of the input vector of the identifier, represented by the stator current. Experimental results conducted on an FO-controlled drive, using a digital signal processor (DSP)-based system (TMS320C31), having 40-MHz clock frequency, show the convergent trajectories of the parameters and of the state errors under various significant steady state and transient operating conditions and for different values of the adaption gains. The results show the satisfactory behavior of the proposed identification algorithms.

Robust control of induction motor drive with rotor time-constant adaptation

In this paper, an indirect field-oriented induction motor drive with a rotor time-constant adaptation is presented. Since the deviated rotor time-constant of an induction motor makes the indirect field-orientation inaccurate, an adaptation mechanism is proposed to tune the rotor time-constant to establish a complete indirect field-oriented control for an induction motor drive. With the rotor time-constant adaptation, the indirect field-oriented control has the robustness property for decoupling torque and flux components. In order to further insure the robustness of the servo control, a novel variable-structure speed controller is proposed under the adaptive field-orientation operation. A novel sliding surface with an integral component for the variable structure speed controller is designed, and exponential convergence in speed-tracking control is obtained. Using the proposed variable-structure speed controller, the insensitivity for parameter uncertainty and disturbance load is provided. Finally, a simulation and experimental results are demonstrated.

98/02982 Comparison of power densities and chemical potential variation in solid oxide fuel cells with multilayer and single-layer oxide electrolytes

Sensorless induction motor (IM) drives are widely used in industry for their reliability and flexibility, particularly in hostile environment. However, the performance of many of previously developed observer based speed sensors in very low speeds of IM drives was not satisfactory. In this paper, the model reference adaptive system (MRAS)-based speed and stator resistance estimators of IM drives fed by four switch three phase inverter (FSTPI) in the critical low and zero speed region of operation are presented. The estimated speed is used as feedback in a vector control system. The MRAS approach has the immediate advantage that the model is simple, eliminates the produced error in the speed adaptation, and more stable and robust. Simulation results of the MRAS speed observer based sensorless field-oriented induction motor drives fed by FSTPI are presented at critical low and zero speed region of operations. The performances of the MRAS technique is evaluated in indirect vector control system. Experimental results validate the proposed approach.

Adaptive estimation of rotor time constant for indirect field-oriented induction motor drive

A novel estimation model based adaptive control for indirect field-oriented induction motor drive is presented. A new coordinate reference frame is utilised to describe the dynamical model of an induction motor. Then, the new reference frame based estimator is proposed to adaptively estimate the redefined state variables and the rotor time constant, necessarily used in indirect field-oriented control. Moreover, a modified estimation model also based on the same reference frame is further presented to simplify the estimation and adaptation computation. By utilisation of the estimation approach, robust indirect-field-oriented control with respect to rotor time constant variation due to the effect of thermal changes is obtained. Finally, simulation and experimental results demonstrate the validity of the approach for practical applications.

Fuzzy adaptive vector control of induction motor drives

This paper deals with the design and experimental realization of a model reference adaptive control (MRAC) system for the speed control of indirect field-oriented (IFO) induction motor drives based on using fuzzy laws for the adaptive process and a neuro-fuzzy procedure to optimize the fuzzy rules. Variation of the rotor time constant is also accounted for by performing a fuzzy fusion of three simple compensation strategies. A performance comparison between the new controller and a conventional MRAC control scheme is carried out by extensive simulations confirming the superiority of the proposed fuzzy adaptive regulator. A prototype based on an induction motor drive has been assembled and used to practically verify the features of the proposed control strategy.

Control of induction motor drive for improving operating characteristics and dynamic response

The control strategies of an indirect field-oriented induction motor drive for both good operating characteristics and dynamic rotor speed response are presented. The small-signal model representing detuning behavior around the steady-state of an ideal field-oriented induction motor is first developed and, according to it, the rotor resistance set in the indirect field-oriented mechanism (IFOM) is adjusted by a proposed adaptive inverse model controller (IMC) to improve the decoupling characteristic. Furthermore, a stator current minimization controller is designed for fine tuning of the field-orientation characteristic. In addition, a model following speed controller is proposed. In the proposed speed controller, the model following gain is tuned according to the control effort and the model following error. The effect of control force saturation is much reduced, and good model following and load regulation speed responses are obtained. The good operating characteristics and dynamic speed responses of the motor drive obtained using the developed controllers are demonstrated by simulated and experimental results.

Microprocessor implementation of field-oriented control of induction motors using ANN observers

This paper presents a microprocessor based intelligent controller implemented, in a single processor, for field-oriented induction motor control taking the non-linear parameter variation into account. Previous investigations [2,10] on this subject have neglected the effect of saturation in the air gap flux and hence the corresponding non-linear parameter variation of the induction motor. As the phase angle of rotor magnetizing current (or m.m.f. vector) in a standard induction motor cannot be measured by direct means an observer is generally needed in field-oriented control of induction motors. Two types of observers (based on the linear and non-linear model of the machine) have been used in field-oriented induction motor control schemes [1,2,10]. The reduced-order linear model of observer [10] is easy to implement in real time, but it does not give an accurate estimation of the rotor m.m.f. vector angle, β, since the induction motor can operate in the region of saturation. The non-linear observer model which incorporates this effect of magnetic saturation of the induction motor cannot be practically implemented by using normal methods as it takes too long a time to estimate the angle β. The implementation of the real-time intelligent controller in this project is based on Artificial Neural Networks (ANN) which take into account the effect of saturation and estimate the angle β in a few microseconds which is well within the real time deadline.

Indirect field-oriented induction motor drive with fuzzy detuning correction and efficiency optimisation controls

The detuning correction and efficiency optimisation of an indirect field-oriented induction motor drive for achieving higher efficiency and better field-orientation characteristic are presented. First, the operating characteristics of an indirect field-oriented motor drive under detuned condition are studied. A fuzzy controller is used to tune the slip gain online in the field-orientation mechanism to obtain a better decoupling control characteristic. At heavy loads the rated flux of the motor is set to increase its torque generating capability. The determination of the stator flux current component for obtaining rated flux is suggested. At light loads, with the motor running at steady state, in addition to fuzzy slip gain adaptation another fuzzy controller is used to reduce the stator flux current component from its rated value to minimise the stator input current and thus improve the efficiency of the motor drive. As the transient due to command or load torque change occurs the current adjustment action is temporary inhibited and the rated flux component current is set instead to obtain higher torque generating capability. Measured results show that both the efficiency and rotor speed dynamic responses are improved by the proposed fuzzy detuning correction control and efficiency optimisation control approaches.

Effects of flux level on a CSI-fed field-oriented induction motor

A definite relation exists between the flux level, torque and slip speed of a vector controlled induction motor. An untuned vector controller generates an inappropriate slip frequency that changes the operating flux of the machine. This affects the electromagnetic torque linearity and dynamic performance of the drive system. For an induction motor with magnetic saturation, the ratio of flux and torque-producing components of stator current differs from unity for the maximum electromagnetic torque. With a linear model this ratio is unity. The dependence of this ratio for maximum torque output is explained for linear and nonlinear models of the machine. The torque characteristic is analysed with three aspects of magnetic state: true saturation curve, hard-limit saturation curve, and constant inductance model. Degradation in dynamic performance due to saturation for a CSI-fed system is presented.

A digital signal processor based robust integral-proportional controller for an induction motor servo drive

A digital signal processor (DSP) based computer controlled indirect field oriented induction motor servo drive with robust control characteristics is proposed in this paper. First, the DSP based induction motor servo drive is implemented and the dynamic model of the system at the nominal condition is identified by a curve fitting technique. Based on this model, an integral-proportional controller is quantitatively designed to match the prescribed position tracking specifications. Then a simple robust controller is designed and augmented to reduce the performance degradation due to uncertainties.

A fuzzy adapted field-oriented mechanism for induction motor drive

The detuning of an indirect field-oriented induction motor drive due to variation of rotor resistance may lead to low efficiency and poor transient response. To improve this, an induction motor drive with a fuzzy adapted field-oriented mechanism is proposed. During steady state conditions, an adapted slip angular speed signal is synthesized by a fuzzy controller and used to adjust the original estimate of slip angular speed signal such that minimum stator current is obtained. When the transient due to command or load torque change occurs, the fuzzy tuning mechanism is temporarily inhibited and the final value of the adapted signal is held. A discrete two-degree-of-freedom controller (2DOF) is designed to yield good speed command tracking and load regulating responses. The effectiveness of the proposed motor drive is demonstrated experimentally.

Parameter identification of vector-controlled induction machines

This paper describes the identification of electromagnetic time constants and stator resistance for field oriented induction motor drives. The model of an induction motor at standstill in terms of state representation is discussed. A direct continuous-time identification from the standstill time-domain test data is based on the parametrized observer state vector. In a laboratory configuration the stator resistance is influenced by the non-linear inverter gain function. Two categories of current responses to voltage steps and to pseudo random binary sequences are examined. The current transients indicate saturation effects. Parameter estimates of a linear machine model are determined using least squares algorithms. Simulation and experimental studies are carried out in a Matlab software environment. Corresponding results obtained for two induction motor drives of different power ratings are included.

Robust two-degrees-of-freedom control for induction motor servodrive

A robust two-degrees-of-freedom (2DOF) position controller for an induction motor servodrive is proposed. First, a DSP-based indirect field-oriented induction motor servodrive is implemented and its dynamic model for the nominal case is estimated. Based on this model a 2DOF controller is quantitatively designed. Then a simple robust controller with dead-time compensation is designed and augmented to reduce the effects of parameter variations and system dead-time on the control performance. The effectiveness of the proposed controller is demonstrated by simulated and measured results.

A robust speed controller for induction motor drives

A speed controller considering the effects of parameter variations and external disturbance for indirect field-oriented induction motor drives is proposed in this paper. First a microprocessor-based indirect field-oriented induction motor drive is implemented and its dynamic model at nominal case is estimated. Based on the estimated model, an integral plus proportional (IP) controller is quantitatively designed to match the prescribed speed tracking specifications. Then a dead-time compensator and a simple robust controller are designed and augmented to reduce the effects of parameter variations and external disturbances. The desired speed tracking control performance of the drive can be preserved under wide operating range, and good speed load regulating performance can also be obtained. Theoretic basis and implementation of the proposed controller are detailedly described. Some simulated and experimental results are provided to demonstrate the effectiveness of the proposed controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An artificial neural network based identification and control approach for the field-oriented induction motor

Abstract In this paper, a high-performance speed control approach using artificial neural networks (ANNs) for the field-oriented induction motor is proposed. By using the proposed approach, the speed of an induction motor can be controlled to follow an arbitrarily selected speed trajectory. In particular, an accurate tracking of the speed can still be obtained when uncertainties in the motor and its load exist. The uncertainties include both the unknown load on the motor and the variation of the motor rotor resistance due to temperature change. Two ANNs have been designed to handle these two types of uncertainties. A series of computer simulations has been performed to evaluate the proposed control system. Simulated results show that the proposed control system can achieve satisfactory performances in the tracking of the speed trajectory and the adaptability to rotor resistance parameter variation.

Speed sensorless field-oriented control of induction motor with rotor resistance adaptation

Several field-oriented induction motor drive methods without rotational transducers have been proposed. These methods have a disadvantage that the rotor resistance variation causes an estimation error of the motor speed. Therefore, simultaneous estimation of the motor speed and the rotor resistance is required. This paper presents a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command. The validity of the proposed method is verified by simulation and experimentation. >

Control of indirect field-oriented induction motor drives considering the effects of dead-time and parameter variations

A speed controller that considers the effects of system dead time and parameter variations is presented. An indirect field-oriented induction motor drive is implemented, and its dynamic model is found, using a stochastic approach. A two-degree-of-freedom speed controller is designed to match the prescribed speed command tracking and load regulating specifications. Since the performance of the closed-loop controlled plant is greatly influenced by the presence of the inherent system dead time and parameter variations during wide-range operations, a dead-time compensator and a model-following controller are proposed to enhance the robustness of the two-degree-of-freedom speed controller. The simulated and experimental results show that good control performance both in speed command tracking and load regulating characteristics is achieved. >

DSP-based speed adaptive flux observer of induction motor

A method for estimating the rotor flux and speed of an induction motor based on adaptive control theory is presented. The method is applied to a direct field-oriented induction motor control without speed sensors. The influence of the parameter variation on the speed estimation can be removed by the proposed parameter adaptive scheme. The validity of the adaptive flux observer is verified experimentally. >