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. >

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DSP-based speed adaptive flux observer of induction motor

This paper presents a viable transducerless rotor position and velocity estimation scheme for PWM inverter driven induction, synchronous, and reluctance machines with the capability of providing robust and accurate dynamic estimation independent of operating point, including zero and very high speeds, light and heavy loading. The injection of a balanced three-phase high frequency signal (500 to 2 kHz) generated by the inverter, followed by appropriate signal demodulation and processing combined with a closed-loop observer, enable the tracking of rotor magnetic saliencies from the machine terminals. Although rotor magnetic saliency is inherent within reluctance machines, and most synchronous machines, saliency in the induction machine is introduced via a modulation of the rotor slot leakage with minimal detrimental effects on the machine performance. Experimental verification for the induction machine is included. >

/pdf/transducerless-position-and-velocity-estimation-in-induction-592yxc3fev.pdf

Transducerless position and velocity estimation in induction and salient AC machines

Controlled induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor the information on the rotor speed is extracted from measured stator voltages and currents at the motor terminals. Vector-controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. Dynamic performance and steady-state speed accuracy in the low-speed range can be achieved by exploiting parasitic effects of the machine. The overview in this paper uses signal flow graphs of complex space vector quantities to provide an insightful description of the systems used in sensorless control of induction motors.

/pdf/sensorless-control-of-induction-motor-drives-3ej5lgdrxu.pdf

Sensorless control of induction motor drives

Controlled induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information on the rotor speed is extracted from measured stator currents and from voltages at motor terminals. Vector-controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. Dynamic performance and steady-state speed accuracy around zero speed range are achieved by signal injection, exploiting the anisotropic properties of the machine. The overview in this paper uses signal flow graphs of complex space vector quantities to provide an insightful description of the systems used in sensorless control of induction motors.

Sensorless Control of Induction Machines&#8212;With or Without Signal Injection?

Direct torque control (DTC) is known to produce quick and robust response in AC drives. However, during steady state, notable torque, flux and current pulsations occur. They are reflected in speed estimation, speed response, and also in increased acoustical noise. This paper introduces a new direct torque and flux control based on space-vector modulation (DTC-SVM) for induction motor sensorless drives. It is able to reduce the acoustical noise, the torque, flux, current, and speed pulsations during steady state. The DTC transient merits are preserved, while better quality steady-state performance is produced in sensorless implementation for a wide speed range. The flux and torque estimator is presented and an improved voltage-current model speed observer is introduced. The proposed control topologies, simulations, implementation data, and test results with DTC and DTC-SVM are given and discussed. It is concluded that the proposed control topology produces better results for steady-state operation than the classical DTC.

A modified direct torque control (DTC) for induction motor sensorless drive

A flux observer of an induction motor with a parameter adaptive scheme is proposed. The parameters identified adaptively are stator and rotor resistance, which vary with motor temperature. The stability of the proposed adaptive flux observer is proved using Lyapunov's theorem. The robustness of the induction motor drive system with the proposed flux observer is shown. The adaptive scheme can also be applied to estimate motor speed without speed sensors. >

New adaptive flux observer of induction motor for wide speed range motor drives

The authors present a novel method for estimating the rotor flux and speed of an induction motor based on adaptive control theory. The proposed method can be 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 has been verified experimentally. Furthermore, a novel disturbance torque estimation method has been proposed. >

T. Nakano

Papers

DSP-based speed adaptive flux observer of induction motor

New adaptive flux observer of induction motor for wide speed range motor drives

Field oriented induction motor drives without speed sensor based on adaptive flux observer and disturbance torque compensation