Self-Tuning Observer for Sensor Fault-Tolerant Control of Induction Motor Drive

Abstract

This paper introduces a new solution for the speed and current sensor fault-tolerant direct field-oriented control of induction motor drives. Two self-adjusting observers derived from a modified current-based model reference adaptive system (CB-MRAS) are presented. Finally, the recursive least squares method was used to estimate the parameters of the used observers. The method, in the proposed solution, provides a very fast and accurate finding of the observer parameters while maintaining relative simplicity and ease of implementation. The presented algorithm eliminates the CB-MRAS observer dependence on the induction motor parameters and also compensates for the inaccuracies in the evaluation of the stator voltage vector. The proposed fault-tolerant control offers the drive operation while either a speed sensor or one/two current sensors fault occurs. The drive still works with the direct field-oriented control even when no current sensors are healthy. The proposed scheme was simulated in the MATLAB/Simulink software environment. Then the algorithm was implemented in a floating-point digital signal controller (DSC) TMS320F28335 and tested on an induction motor drive prototype of rated power of 2.2 kW to validate the proposed schemes.

Compensation of Torque-Producing Stator Current Error for Vector-Controlled Induction Motor Drives

“…Members in square brackets in (14) and (15), respectively, represent undesirable coupling between the x and y components.…”

“…Sensorless drives, sensor fault tolerant control and applications of artificial intelligence belong to the top topics in the field of sophisticated control methods for electrical controlled drives. In these cases, the vector control algorithm is mostly used as a basic control method [9][10][11][12][13][14][15]. This is the reason why it is important to suppress the aforementioned current control steady-state error, to reach the best possible performance of the drive.…”

Induction Motor PI Observer with Reduced-Order Integrating Unit

“…The mathematical model of the induction motor described by Equations ( 1)-( 2) is characterized by the symmetry outlined by the general rule in Equation (3). From a practical point of view, it is advantageous for the mathematical model of the observer to fulfill this condition since the dynamic properties of the observer become independent of the direction of the motor's rotor rotation.…”

“…In electric drives with induction motors based on dynamic control methods such as field-oriented control (FOC) [1][2][3][4][5], it is necessary to reconstruct motor state variables such as components of magnetic fluxes coupled with the stator and rotor windings. The Luenberger observer can be used for this task [1,[6][7][8].…”

“…Combining these measurements can be used to develop fail-safe (fault-tolerant) drives that switch to a sensorless mode in the event of an angular speed sensor failure [5,13]. There are also online diagnostic strategies for failure detection based on comparisons of the measured angular speed measured with reconstructed values using an observer [3,8]. When a fault is detected, the drive may switch from the closed-loop mode (e.g., FOC) to the open-loop control (e.g., scalar volts per hertz V/f) [14].…”