Sliding Mode Flux Observer Research Articles

FPGA implementation of a robust DTC-SVM based Sliding Mode Flux Observer for a double star induction motor: Hardware in the loop validation

This paper presents an implementation of a robust Direct Torque Control (DTC)-Space Vector Modulation (SVM) strategy for a Double Star Induction Machine (DSIM) using a Field Programmable Gate Array (FPGA). The proposed control technique combines SVM and DTC strategies, incorporating the Sliding Mode Flux Observer (SMFO) to improve robustness and overcome the drawbacks of stator resistance variations. First, SVM is used to improve DTC performance by reducing torque and flux ripples generated with classical DTC strategies. Then, the SMFO is employed to estimate the mechanical speed and stator flux module, ensuring robustness in the face of stator resistance variations. A comparative study between conventional DTC, DTC-SVM, and DTC-SVM-SMFO is presented. Simulation tests of the three DTC strategies were conducted using Matlab/Simulink tools, demonstrating the robustness and high performance of the DSIM under DTC-SVM-SMFO. To further validate these results, the technique was implemented using Xilinx System Generator (XSG) on a parallel processing software environment, the FPGA Virtex 5. Hardware in the loop results confirms the effectiveness of the DSIM under the improved DTC-SVM-SMFO control strategy.

High-Order Sliding Mode Magnetometer for Excitation Fault Detection of Elevator Traction Synchronous Motor under the Background of Industrial Engineering

In order to solve the excitation problem of elevator traction permanent magnet synchronous motors (PMSMs), a new high-order sliding mode flux observer based on a hybrid reaching rate is proposed under the background of industrial engineering to detect loss of excitation faults in real time. Firstly, a new high-order sliding mode flux observer is designed to solve the problem of the traditional sliding mode observer not being able to accurately detect the loss of excitation fault when the load resistance changes. Then, based on the sliding mode variable structure equivalent control principle, a PMSM flux estimation formula is established. The sinusoidal input function replaces the traditional symbolic process, and a mixed approach law is designed to replace the constant speed approach rate. The adaptive adjustment of the boundary layer of the sinusoidal input function is realized through a fuzzy control system, which effectively suppresses the chattering problem caused by the sliding mode variable structure and improves the observation accuracy of rotor position. The stability of the system is verified by Lyapunov’s second method. MATLAB/Simulink is used to build the simulation model of the PMSM control system with the new sliding mode observer, and the simulation results are compared with those of a traditional sliding mode observer. The results show that compared with the conventional observer, the new sliding mode observer can track the rotor position quickly, and the system has better anti-interference abilities and stability. Finally, the feasibility and effectiveness of this method are verified via simulations and experiments.

A new speed adaptive estimation method based on an improved flux sliding-mode observer for the sensorless control of PMSM drives

In this paper, an improved speed adaptive flux sliding-mode observer (FSMO) is presented for the sensorless control of surface-mounted permanent magnet synchronous motor (PMSM) drives. First, to suppress the chattering of the traditional FSMO, an algorithm for online adjusting the observer gain is designed. In this algorithm, a transition mode is introduced between the existing reaching and sliding modes, and an error criterion function with speed and current is constructed for the three motion modes. Second, to reduce the rotor speed estimation error, a new speed adaptive estimation method is presented instead of the traditional phase-locked loop (PLL). In this method, the adaptive law for estimating the speed is derived using Lyapunov stability and model reference adaptive theories. Meanwhile, the physical meaning of the speed adaptive law is illustrated. Finally, the proposed FSMO scheme is implemented on a TMS320F28335 digital signal processing (DSP) microcontroller-based surface-mounted PMSM sensorless control experimental bench. Test results demonstrate the excellent dynamic performance, robustness and stability of the proposed FSMO under various operating conditions.

Optimal speed–torque control of doubly-fed induction motors: Analytical and graphical analysis

This paper proposes an optimized control approach of a Doubly-Fed Induction Motor (DFIM) based on a field weakening algorithm. This technique ensures a nearly doubled torque–speed operation region in the motor’s acceleration and deceleration operation modes. The novelty of the proposed control lies in the fact of using a DFIM for Electric Vehicle (EV) applications where both stator and rotor circuits are connected to voltage source inverters controlled by Space Vector with Pulse Width Modulation (SVPWM) algorithms. Accordingly, the active power distribution law between the stator and rotor sides is thoroughly investigated. This law imposes a relationship between the rotor and stator pulsations leading to a new variation scenario in the DFIM speed. Besides, a Stator Flux Oriented Control (SFOC) is used to provide a decoupled control between the torque and the flux. Considering the voltage and current constraints in the structure, the reference flux is chosen such that the optimal torque for any operation mode, and at any given speed range, is achieved. Nevertheless, the speed measurement as well as the sensitivity to motor parameter variations remains a major limitation in the over-speed region. Therefore, a Sliding Mode Flux Observer (SMFO) is integrated into the control scheme to ensure a sensorless command. The performance of the proposed optimized control algorithm are assessed by computer numerical simulations and its effectiveness in terms of achieving maximum torque in a wide speed range is verified.

A Modified Flux Sliding-Mode Observer for the Sensorless Control of PMSMs With Online Stator Resistance and Inductance Estimation

In this article, the conventional flux sliding-mode observer (FSMO) is modified by taking the motor parameter variations into consideration, and an embedded flux observer is constructed to replace the conventional phase-locked loop for estimating the speed and position in the permanent-magnet synchronous motor (PMSM) sensorless control system. Compared with conventional FSMO, the improved method has certain robustness to parameter variations and improves the dynamic performance of the system under speed reversal. Furthermore, in the real experimental environment, after the long-term operation, the increasing of the motor temperature changes the values of the stator resistance and inductance. This phenomenon mismatches the actual and the setting motor specifications, which may induce ripples in the estimation results and affect the system stability. To address this issue, an online parameter estimation method is proposed in this article and incorporated into the modified FSMO to improve system performance and eliminate parameter mismatching. The control scheme of a PMSM prototype based on the proposed method is designed, and the corresponding experimental platform is built; the performance of the proposed method is validated and compared with that of the conventional FSMO via simulations and experiments.

Design and performance analysis of an iterative flux sliding-mode observer for the sensorless control of PMSM drives

To improve the performance of permanent magnet synchronous motor (PMSM) drives, a sensorless control scheme based on a novel iterative flux sliding-mode observer (IFSMO) is proposed in this paper. Two major drawbacks of the conventional sliding-mode observer (SMO), namely, chattering phenomena and high-order harmonics, are discussed. These drawbacks affect the estimation accuracy of the SMO and reduce the control reliability of the system. To eliminate high-order harmonics, a flux SMO is designed by expanding the PMSM state equations with the PM flux. The flux SMO estimates the rotor speed and position using the flux linkage instead of back-EMF information. Moreover, to reduce the chattering in the estimation results, the proposed flux SMO is iteratively used in one current sampling period to adaptively adjust the observer gain. An overall PMSM sensorless control system based on the proposed IFSMO is designed, and an experimental platform using the TMS320F28335 digital signal processor (DSP) controller is built. The superior chattering reduction and harmonic suppression characteristics of the proposed IFSMO are experimentally validated, and the experimental results verify the feasibility of using the proposed IFSMO-based PMSM sensorless scheme in practical applications.

A novel fuzzy flux sliding-mode observer for the sensorless speed and position tracking of PMSMs

This paper proposes a novel fuzzy flux sliding-mode observer (FFSMO) with a phase-locked loop (PLL) for the sensorless speed and position tracking of permanent-magnet synchronous motors (PMSMs). The purpose of the novel FFSMO is to accurately estimate the position and velocity of the rotor. Compared with the conventional sliding-mode observer (SMO), the novel FFSMO can not only eliminate the low-pass filter (LPF) and phase compensation module but also improve the estimation accuracy. To adjust the SMO gain ε and to reduce the chattering of the sliding-mode variable structure, a fuzzy logic controller (FLC) is proposed and integrated into the observer. Moreover, a PLL method is employed to obtain accurate position and velocity estimates and reduce the adverse influence of noise. The stability of the proposed FFSMO is verified using Lyapunov’s second method. An experimental platform is built, and the experimental results show the effectiveness of the FFSMO.

A New Adaptive SMO for Speed Estimation of Sensorless Induction Motor Drives at Zero and Very Low Frequencies

A speed control of sensorless induction motor (IM) drives at zero and very low frequencies is designed in this paper. A new adaptive sliding mode observer (SMO) to estimate the stator current, rotor flux, and rotor speed is proposed. To improve the robustness and accuracy of an adaptive SMO during very low frequency operation, the sliding mode flux observer uses independent gains of the correction terms. The gains of current and rotor flux SMOs are designed using Lyapunov stability theory to guarantee the stability and fast convergence of the estimated variables. A Lyapunov function candidate utilizing the error of rotor fluxes and speed estimation error is synthesized for speed estimation. Detailed simulations and experiments are given showing the operation of the sensorless speed control at very low frequency. The results prove the accuracy and robustness of the proposed adaptive SMO. Also, comparison results with the state-of-the-art methods prove that the proposed method shows excellent transient and steady-state speed estimation, particularly at very low and zero frequency operations.

Design of an Improved MPPT Control of DFIG Wind Turbine under Unbalanced Grid Voltage using a Flux Sliding Mode Observer

This study presents a control scheme of the electronic interface of a grid connected Variable Speed Wind Energy Generation System (VS-WEGS) based on a Doubly Fed Induction Generator (DFIG). The efficiency of the wind energy is represented to according to the control strategy applied. Thus, in the case of unbalanced grid voltage, the negative sequence voltage causes additional strong oscillation at twice the grid frequency in the stator instantaneous active and reactive powers. The objective of this work is to present an enhanced MPPT controller uses backstepping approach implemented in both and reference frames rotating to keep a safe operation of DFIG during unbalanced grid voltage associated with regulating rotor flux, in order to estimate rotor flux, a nonlinear observer based on sliding mode is proposed in this work. Note that the conventional controllers (PI, PI-R …) are not provided satisfactory performance during unbalanced voltage dips. The validation of results has been performed through simulation studies on a 4 kW DFIG using Matlab/Simulink®.

Accurate torque‐sensorless control approach for interior permanent‐magnet synchronous machine based on cascaded sliding mode observer

To improve the accuracy of torque control for vector control of interior permanent-magnet synchronous machine (IPMSM), this study proposes a torque-sensorless control method based on cascaded sliding mode observer (SMO). First, the active flux model is discussed, which converts the model of IPMSM into the equivalent model of surface-mounted permanent-magnet synchronous machine. Second, to reduce chattering caused by system parameters variations and external disturbances, the cascaded observer is designed, which is composed of a variable gain adaptive SMO and an active flux SMO. The variable gain adaptive SMO is designed to estimate the speed, rotor position and stator resistance in the d–q reference frame. The active flux SMO is designed to estimate the active flux and torque in the α–β reference frame. Global asymptotic stability of the observers is guaranteed by the Lyapunov stability analysis. Finally, simulations and experiments are carried out to verify the effectiveness of the proposed control scheme.

MRAS-based sensorless speed backstepping control for induction machine, using a flux sliding mode observer

In this paper, an induction machine rotor speed and rotor flux control using a sensorless backstepping control scheme is discussed. The most interesting point of this technique is that it deals with the nonlinearity of a high-order system by using the virtual control variable to make this system simple, and thus the control outputs can be derived step by step through appropriate Lyapunov functions. To avoid the use of a mechanical sensor, the rotor speed estimation is made by an observer using the model reference adaptive system (MRAS) technique; in order to estimate rotor flux, a sliding mode observer is proposed in this work. Simulation results are presented to validate and prove the effectiveness of the proposed sensorless control.

Comments on “Adaptive sliding mode observer for induction motor using two-time-scale approach”

This short communication is a discussion of the paper entitled “Adaptive sliding mode observer for induction motor using two-time-scale approach” by A. Mezouar, M.K. Fellah and S. Hadjeri published in the Electric Power Systems Research 77 (2007) pp. 604–618. In the discussed paper the authors present a current and flux sliding mode observer for the induction motor that also incorporates an adaptive law in order to estimate the inverse of the rotor time constant. However the proposed observer design uses the real value of the rotor time constant which is unknown and therefore cannot be used in the observer design.

Flux Sliding-mode Observer Design for Sensorless Control of Dual Three-phase Interior Permanent Magnet Synchronous Motor

A novel equivalent flux sliding-mode observer (SMO) is proposed for dual three-phase interior permanent magnet synchronous motor (DT-IPMSM) drive system in this paper. The DT- IPMSM has two sets of Y-connected stator three-phase windings spatially shifted by 30 electrical degrees. In this method, the sensorless drive system employs a flux SMO with soft phase-locked loop method for rotor speed and position estimation, not only are low-pass filter and phase compensation module eliminated, but also estimation accuracy is improved. Meanwhile, to get the regulator parameters of current control, the inner current loop is realized using a decoupling and diagonal internal model control algorithm. Experiment results of 2MW-level DT-IPMSM drives system show that the proposed method has good dynamic and static performances.

Backstepping Control of the Induction Machine, Based on Flux Sliding Mode Observer, with Rotor and Stator Resistances Adaptation

In this paper we present a robust control of rotor speed and rotor flux of the induction machine, using a Backstepping control scheme. In this scheme the induction machine is represented by a model described in the fixed stator frame with rotor flux, stator current and rotor speed as stat variables. The backstepping technique is appropriate for such as non linear system. The outputs control can be derived step by step, over virtual-control, through appropriate Lyapunov functions. In order to improve the control robustness especially against parameters variation, we design an adaption mechanism of parameters based on estimation of rotor and stator resistances. The simultaneous estimation of those parameters is made by an observer using a specific MRAS technique. As the controller and the parameters adaptation mechanism depends on the flux, that is unmeasured, we design a robust and fast flux observer based on sliding mode technique. Simulation is realized and its results are presented to validate and to prove the effectiveness and robustness of the proposed control.

Sensorless Exact Input-Output Linearization Control of the Induction Machine, Based on Parallel Stator Resistance and Speed MRAS Observer, with a Flux Sliding Mode Observer

Abstract: This paper presents an exact input-output linearization control scheme for rotor speed and rotor flux control of induction motor drive. In this scheme the motor model, is described in the fixed stator frame, and it is linearized, using exact inputoutput linearization technique, allowing a decoupled control of rotor flux and torque. To avoid the use of mechanical sensor, the rotor speed estimation is made by an observer using a specific MRAS (Model reference adaptive system) technique; this observer is designed to perform simultaneous estimation of stator resistance and rotor speed. In order to estimate rotor flux, a sliding mode observer is proposed in this paper. Simulation results are realized and presented to validate and to prove the effectiveness of the proposed Sensorless control.

Discussion on “Adaptive sliding-mode-observer for sensorless induction motor drive using two-time-scale approach”

This short communication is a discussion of the paper entitled “Adaptive sliding-mode-observer for sensorless induction motor drive using two-time-scale approach” by A. Mezouar, M.K. Fellah and S. Hadjeri published in the Simulation Modelling Practice and Theory 16 (2008) 1323–1336. In the discussed paper the authors present a current and flux sliding mode observer for the induction motor that also incorporates an adaptive laws in order to estimate the rotor speed and the inverse of the rotor time constant. However the proposed design for the observer and for the adaptive laws, employs the real value of the rotor time constant and the real value of the rotor speed, which are unknown, and therefore cannot be used in the observer design nor in the adaptive laws design.

A Novel Hysteresis Direct Torque Control for Matrix Converter Drives

In this paper, the application of classical hysteresis direct torque control (HDTC) to the IPM synchronous machine fed by a matrix converter is investigated and one of the problems associated with this scheme is highlighted. A modified HDTC scheme for matrix converter drives is proposed to solve this problem by applying two switching combinations at each sampling period, which allows significant reduction of input current harmonics without any adverse effect on the drive performance or increasing the complexity of the system. The fast dynamics is preserved in the proposed scheme by applying a single current vector in the rectifier stage and thus the maximum line-to-line input voltage is utilized to generate the voltage vector in the inverter stage. A novel input power factor correction strategy is proposed to compensate the effect of input capacitors on the displacement angle by introducing a power-related displacement angle in the duty cycle calculations. The joint stator flux and rotor speed estimation is implemented with an adaptive sliding mode flux observer in the estimated rotor reference frame to enhance the robustness and reliability of the drive system. The comparisons between the classical and proposed HDTC schemes for matrix converter fed IPMSM machine have been carried out by both simulation and experiments.

Fuzzy speed control and stability analysis of a networked induction motor system with time delays and packet dropouts

Connecting a spatially distributed system with sensors, actuators, and controllers as a networked control system by a shared data network can reduce the wiring and cost remarkably. Networked control strategy has been utilized in remote operation of linear systems. Nonlinearity is the major barrier in implementing a networked control scheme on an induction motor, which is the most widely used motor in industrial applications. In this case, we designed a sliding mode flux observer to linearize the induction motor model, such that the application of the networked control scheme is feasible. Due to the variable QoS, a fuzzy logic speed controller is proposed to adapt various network conditions. As part of the networked controller, a state predictor is designed to compensate the time delay in the feedback channel. In stability analysis, the upper bounds of time delays and packet dropouts are both given in terms of the Lyapunov theorem. Finally, simulations are conducted employing TrueTime toolbox to demonstrate the effectiveness of the control strategy.

Sliding-Mode Flux Observer With Online Rotor Parameter Estimation for Induction Motors

Field orientation techniques without flux measurements depend on the parameters of the motor, particularly on the rotor resistance or rotor time constant (for rotor field orientation). Since these parameters change continuously as a function of temperature, it is important that the value of rotor resistance is continuously estimated online. A fourth-order sliding-mode flux observer is developed in this paper. Two sliding surfaces representing combinations of estimated flux and current errors are used to enforce the flux and current estimates to their real values. Switching functions are used to drive the sliding surfaces to zero. The equivalent values of the switching functions (low-frequency components) are proven to be the rotor resistance and the inverse of the rotor time constant. This property is used to simultaneously estimate the rotor resistance and the inverse of the time constant without prior knowledge of either the rotor resistance or the magnetizing inductance. Simulations and experimental results prove the validity of the proposed approach

Sensorless direct field-oriented control of three-phase induction motors based on "Sliding Mode" for washing-machine drive applications

Sensorless direct field-oriented (SDFO) control of three-phase induction motors based on "sliding mode" has been studied and applied to domestic washing-machine drives. In this paper, three related techniques, sliding-mode flux observer, sliding-mode speed controller, and direct rotor-speed estimator are presented for the application of SDFO "sliding mode" in induction-motor control system. Specifically, the investigations focus on how improving speed regulation, system robustness, and some special technical issues in washing-machine drives. The complete control schemes have been developed and implemented in a low-cost digital signal processor-based electronic controller. Through a variety of system performance validation tests, it has been proved that the developed SDFO control not only achieves satisfied steady as well as a dynamic performance, but also is robust for washing-machine driving applications.