Direct Field-oriented Control Research Articles

Decoupled direct control for PWM inverter-fed induction motor drives

A new direct torque and stator flux control method is presented for pulsewidth modulation (PWM) inverter-fed induction motors. This new strategy, called decoupled direct control (DDC), is based on a decoupling matrix that allows for the separate control of the stator flux and the torque. This method is compared to the well-known direct field-oriented control (FOC) and stator flux vector control (SFVC) methods. Two DDC-based methods are presented. The first determines the stator voltage vector such that the torque and the flux track their respective reference trajectories in one sampling time. The second sets separately the dynamic behavior of the torque and stator flux errors by the use of proportional-plus integral (PI)-type controllers. These methods take into account the full motor dynamics without the need of a coordinate transformation and reduce significantly computation requirements compared to FOC and SFVC. The two proposed strategies have been implemented experimentally and comparisons with FOC and SFVC were carried out. The obtained results show the effectiveness of the proposed PI-DDC strategy.

A new sliding mode flux and current observer for direct field oriented induction motor drives

Abstract A direct field orientation (DFO) control for an induction machine is designed and implemented using a new sliding mode technique. The rotor flux is estimated using the current model flux observer. A close loop flux observer, based on the current estimate error, is then constructed. A unique feature of the proposed observer is that the flux and current observers include a sliding function, which is a derivative of the flux. Therefore, when the estimated current converges to the measured one, the sliding function itself is integrated to calculate the flux magnitude and angle. The observer stability is verified via Lyapunov stability analysis. Simulation and experimental results are presented to show the performance of sliding-mode based DFO control for an induction motor drive system.

Induction motors direct field oriented control with robust on-line tuning of rotor resistance

This paper proposes an alternative rotor resistance identification method used in the frame of a direct field oriented control (DFOC) of induction motors. The authors investigate the use of the induction motor instantaneous reactive power for rotor resistance identification on the basis of the model reference adaptive system (MRAS) method. In fact, from a practical point of view, the instantaneous reactive power can give quite sufficient real time information on the induction motor behavior. The proposed identification method can be achieved with on-line tuning of the inverse rotor time constant with robustness against stator resistance variation. Computer simulations are given to highlight the feasibility, the simplicity, and the robustness of the proposed method.

Vectorial torque control: a novel approach to torque and flux control of induction motor drives

A general approach to torque and flux control of an induction motor fed by a voltage-source inverter is described in this paper. It is independent of whether rotor or stator flux is controlled. Based on this, an algorithm can be set up which allows the generation of the inverter switching patterns as a function of the reference values, both of the electromagnetic torque and of the controlled flux. Experimental comparisons with traditional direct torque control and field-oriented control techniques confirm the possibility of achieving very high dynamic performance with the proposed strategy.

Regulation and tracking of the nonholonomic double integrator: A field-oriented control approach

In this paper we show how a slight modification to the well-known field-oriented control of induction motors allows us to provide simple solutions to the problems of global regulation and tracking for the nonholonomic double integrator. Two controllers are proposed, one motivated by the well-known direct field-oriented motor control, which is a simple continuous static-state feedback that guarantees exponential convergence for all initial conditions in R 3 — {x 2 = x 2 = 0}. To overcome the latter restriction we add a dynamic extension to transfer this (initial conditions) singularity to the controller state, hence making the stability global. This controller is a direct outgrowth of indirect field oriented motor control. In view of the well-known Brockett's condition we obviously do not ensure Lyapunov stability.

Voltage control strategy for maximum torque operation of an induction machine in the field-weakening region

In this paper, a novel field-weakening scheme for the induction machine is presented. The proposed algorithm, based on the voltage control strategy, ensures the maximum torque operation over the entire field-weakening region without using the machine parameters. Also, by introducing the direct field-oriented (DFO) control, which is insensitive to the variation of machine parameters in the field-weakening region, the drive system can obtain robustness to parameter variations. Moreover, the speed sensorless control can be achieved in the very-high-speed range, where the utilization of the speed sensor is limited. Experimental results for the laboratory induction motor drive system confirm the validity of the proposed control algorithm.

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. >

Observers for field-oriented control of induction motor drives

One of the major problems associated with direct field-oriented control of induction motors is the sensitivity of the observer to variation of motor parameters. Various types of observer have been proposed but no complete study of sensitivities has been carried out. An analysis of the sensitivity of one class of observer, against the motor parameter variations, is presented. From the results of the analysis, a suitable observer is chosen and implemented as a part of a complete direct field-oriented control system. The results of the implementation are also presented. >

A direct field-oriented controller for induction motor drives using tapped stator windings

The implementation of a direct method of field orientation that requires little knowledge of machine parameters and uses only readily measurable quantities is discussed. The system uses tapped stator windings to measure the air-gap flux. The signals from the tapped windings are also used in a flux-regulation loop. A speed controller is implemented using the ripples created in the tapped windings by the motion of the rotor slots through the flux for speed information.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>