Rotor Flux Research Articles

Geometric phase shift sensitivity in an area chirped array of atom interferometers

Measuring geometric phase shifts has various applications in both quantum and classical interferometry such as measuring acceleration, distances, rotation and magnetic flux. Theoretical analysis of coupled ring arrays has been shown to be a promising design for creating small inertial rotation sensors on atom chips. In this paper we build on the theoretical models of transmission of matter waves through an area chirped array of ring interferometers to determine phase regions of the transmission that exhibit high sensitivity to geometric phase shifts,these regions are indicated by sharp transmission resonances. We calculate the slopes of transmission resonances for a range of values for two parameters, the chirp factor γ and the product of the wave number and ring circumference kL, we look at the behavior of the slopes of these transmission resonances for defined ranges of kL and γ to see in search of transmission resonances with extreme slopes. We find transmission resonances with sensitivities to geometric phase shifts that exceed those found in previous models of area chirped arrays by several orders of magnitude. The area chirp is applied such that the geometric phase shifts (θGP) in each ring of the array can be expressed in terms of the geometric phase shift in the reference ring of the array, this enables the transmission function T(θGP) to be calculated in terms of the phase shift of a single ring. We investigate T(θGP) for various ring sizes, wave numbers, and chirp factor and look for values of these parameters that lead to sharp transmission resonances in T(θGP). We calculate the sensitivities of rotation via the Sagnac effect and magnetic flux via Aharonov Bohm effect based on the sensitivity of the transmission resonances found in our transmission functions.

Analysis of the Magneto-Mechanical Anisotropy of Steel Sheets in Electrical Applications

We investigate the effect of magneto-mechanical and magnetocrystalline anisotropies in a test application by coupling a multiscale magneto-mechanical model with a finite element method. This first application is composed of a cylindrical conductor surrounded by a ring composed of a non-oriented FeSi3% steel sheet which contains 396 representative grain orientations. Such an application can reveal the anisotropy due to the texture of the material by inducing a rotational flux density within the ring. Moreover, the effect of the texture and the magneto-mechanical characteristic of the steel sheets is analyzed in an axially laminated synchronous reluctance machine. The effect of stress strongly emphasizes the anisotropic behavior of NO steel sheets.

Reactive-power-based MRAC for rotor resistance and speed estimation in bearingless induction motor drives

The reactive power-based model reference adaptive controller (MRAC) is presented in this paper in detail to estimate rotor resistance online. This controller can maintain rotor flux orientation of bearingless induction motor (BIM) driven by indirect

Design and analysis of an outer rotor flux switching permanent magnet machine for light electric vehicles

With the great concerns on alleviating the environment pollution and traffic congestions, there is a trend for developing light electrical vehicles in urban areas. This paper proposes an outer rotor flux switching permanent magnet machine (FSPMM) for

Discrete Sliding Mode Speed Control of Induction Motor Using Time-Varying Switching Line

Sliding mode control (SMC) of electric drives constitutes a very popular control method for nonlinear multivariable and time-varying systems, e.g., induction motor (IM) drives. Nowadays, IM are the most popular electrical machines (EM) applied in many industrial applications as motion control devices, including electrical and hybrid vehicles. Nowadays, the control systems of EM are mostly realized using digital techniques (microprocessors and microcontrollers). Therefore, all control algorithms should be discretized or the whole control system should be designed in the discrete-time domain. This paper deals with a discrete-time sliding mode control (DSMC) for IM drives. The discrete algorithms for sliding mode control of the motor speed and rotor flux are derived in detail and next tested in simulation research. The simulation tests include the discrete nature of the power converter supplying the IM and present excellent performance of the developed control structure. To obtain the rotor speed regulation invariant to external disturbances, like load torque or inertia, especially during the reaching phase of the switching line, the discrete version of a time-varying switching line was introduced. It is shown that the assumed dynamics of the IM flux and speed is achieved and the proposed control algorithm can be realized using commonly available microcontrollers. The paper is illustrated with comprehensive simulation results for 1.5 kW IM drive, which are verified by experimental tests.

Sensorless Low/Zero Speed Estimation for Permanent Magnet Synchronous Machine Using a Search-Based Real-Time Commissioning Method

This article presents the sensorless low/zero speed estimation and control for permanent magnet synchronous machines (PMSMs) using the innovative search-based real-time commissioning method. An overview of continuous pulsating high frequency injection used in this article is given for different injection angles in the stationary frame of reference. The variations of the saliency at different injection angles and loading operating points of the machine are presented and analyzed. The commissioning, search, and offset of the proposed observer are also discussed. Experimental results showing the performance of the sensorless method are presented in both open-loop and sensorless closed-loop current control. In sensorless mode the PMSM drive is controlled through a rotor flux oriented algorithm which uses the estimated electrical rotor position instead of the encoder measurement. Results for both the estimated mechanical and electrical rotor positions are presented under varying load conditions and speed reversal through the zero-speed region.

Discrete-Time Modeling and Control Based on Field Orientation for Induction Motors

In this article, discrete-time direct and indirect field-oriented controllers (FOCs) for induction motors (IMs) are designed. Based on a discrete-time stationary reference frame model for IMs, which was obtained by means of a variational integrator, the stationary model is oriented to the field. Then, discrete-time FOCs, in the direct and indirect versions, are designed for tracking of reference signals for the rotor velocity and the rotor flux modulus. A simulation study was carried out, and for comparison purposes, discretized continuous-time FOCs were also simulated for three sampling periods. It was put in evidence that the proposed discrete-time controllers performed better than the discretized counterparts when the sampling period was increased. Real-time experiments were carried out for discrete-time direct and indirect FOCs, where their performances were similar to those predicted by simulations.

A Comprehensive Comparison of Extended and Unscented Kalman Filters for Speed-Sensorless Control Applications of Induction Motors

In this article, the real-time comparison of extended and unscented Kalman filter algorithms, which estimate the stator stationary axis components of stator currents, the stator stationary axis components of rotor fluxes, the rotor mechanical speed, and the load torque including viscous friction term, are performed under different operating conditions for speed-sensorless control applications of induction motors (IMs). Thus, it is clarified which algorithm is more suitable for state and parameter (load torque) estimation problem of IMs. For this purpose, four different real-time experimental tests have been carried out, which examine the effect of noise covariance matrices, parameter changes, sampling time, and computational burdens on estimation performance of both algorithms. Unlike the current literature, remarkable comparison results have been obtained.

Simple Stability Enhancement Method for Stator Current Error-Based MRAS-Type Speed Estimator for Induction Motor

In this article, the stability problem of the stator current error-based model reference adaptive system (MRAS) speed estimator for induction motor drive is discussed. The MRASCC that is analyzed in this article is created with a rotor flux simulator based on the stator current (first superscript C) and the stator current estimator (second superscript C), both adapted with the estimated rotor speed. As the original estimator is unstable in the regenerating mode, a simple stability extension solution is proposed based on the introduction of an auxiliary variable in the mathematical model of this estimator. The new adaptation rule is derived using the Lyapunov theory and stability range of a modified speed estimator is determined. This modification is compared with the existing solutions and analyzed in the simulation and experimental tests under motoring and regenerating modes of the drive system in open and closed–loop operation. It has been shown that the modified speed estimator with an additional variable adapted on-line is stable in the whole regenerating mode, contrary to the classical solution and does not require any modifications during the change from the regenerating to motoring mode and vice versa, as it is required in existing solutions.

Predictive Current Trajectory Control for PMSM at Voltage Limit

This paper presents a fast predictive current trajectory strategy for permanent magnet synchronous motors (PMSMs) at voltage limit. The current hexagon obtained from the voltage hexagon of the inverter represents the region that the currents can reach in the next switching periond. The nearest avaliable current point to the reference is solved by geometrical method on the current plane. The output of the proposed algorithm is divided into four cases according to the position of the current points. The algorithm combines FCS-MPC and DPCC, has the merits of both method and also the fast dynamic at voltage limits. In order to increase the robustness against the parameter variations, moving horizon estimator is utilized. The rotor flux is eliminated in the algorithm and the voltage errors caused by resistance and inductance mismatches are compensated by the estimator. Several experiments are performed with DPCC, FCS-MPC and the predictive current trajectory control method. These comparisons validate the effectiveness of the proposed method.

Sensorless control based on the improved VM NN SC MRAS method for high performance SPIM drives using LPF

This paper proposes a novel Stator Current Model Reference Adaptive System based scheme using neural network (NNSM_SC_MRAS) for sensorless controlled of Six-Phase Induction Motor (SPIM) drives. For this scheme, the measured stator current components are used as the reference model and a two layer linear NN stator current observer is used as an adaptive model. The voltage model (VM) rotor flux identifier with value of stator resistor is update online is used to provide the rotor flux for the adaptive model, this helps to overcome the instability problem and enhance the performance of the observer. Especially, In order to eliminate the drift problems, the pure integrator of VM is replaced with a first-order low-pass filter, and the error due to this replacement is also compensated in proposed scheme. Simulation results have demonstrated that the performance of the proposed observer is significantly improved especially at low and near zero speed range.

Real-Time Simulator of DTC–FOC-Based DFIG During Voltage Dip and LVRT

This paper proposes the decoupling control of direct torque control (DTC) and field orient control (FOC) for doubly fed induction generator (DFIG)-based wind energy system (WES). The proposed technique reduces the transient of system during low voltage ride through (LVRT) as well as voltage dip (VD) with out auxiliary circuit. The combined DTC–FOC regulates both rotor and grid side converters (RGSCs). In particular, DTC controls the generator speed, torque and rotor flux; similarly, FOC regulates the capacitor link voltage and power quality of grid during LVRT and VD. The linear controller is unable to control the nonlinearities of system dynamics with respect to time. Further, the proposed technique is analyzed with sliding mode control (SMC) and conventional controllers independently. The proposed DTC–FOC aims to improve the performance of transient and dynamic behavior of DFIG-based WES during LVRT and VD. It is also tested in real-time environment at 7.5 hp as well as MATLAB/SIMULINK of 5.5 kW rating.

Fractional Order Sliding Mode Speed Control of Feedback Linearized Induction Motor

Abstract Induction machines have of late become the most popular workhorses in the industry replacing DC machines because of their advantages, such as reduced cost, reliability and the absence of commutators, which make them adapt to unfavourable conditions with lower maintenance requirement. However, higher-order models of AC machines, nonlinearities in model equations, uncertainties in parameters and load disturbances make induction motors difficult to control than that of DC motors. In this paper, a robust control strategy considering the recent advances in technology is proposed employing input-output feedback linearization for the exact decoupling of electromagnetic torque and rotor flux using fractional-order sliding mode controller (SMC) for the outer speed loop. The sliding mode observer is also designed to extract the rotor flux from the DC input voltage of the inverter and stator current measurements. Finally, a comparison between the commonly used proportional integral and derivative (PID) controller and the proposed fractional-order SMCs is made and the conclusion is reached.

Development of an axial-flux self-bearing motor using two permanent magnet attractive type passive magnetic bearings

This paper introduces an axial-flux self-bearing motor (ASBM) using two permanent magnet attractive type passive magnetic bearings (PMBs). The ASBM provides both functions of a disc motor and thrust magnetic bearing, and controls motor torque and axial force by single rotational magnetic flux. The PMB consists of a cylindrical permanent magnet and an iron shaft with conical edge, and it supports the rotor in radial directions. This motor has a simple structure and control system, and it is possible to reduce the size and cost. In this paper, the structure and control method are introduced, and the results of levitation and rotation tests whose non-contact rotation speed was achieved up to 1,500 rpm are shown.

Control Strategy for an Open-End Winding Induction Motor Drive System for Dual-Power Electric Vehicles

This work presents the control strategies for the configuration involving an open-end winding induction motor (OW-IM) fed by dual two-level inverters, which can realize the controllable power sharing between two isolated power sources without using the DC/DC converter. Based on the mathematical model of the OW-IM and the principles of the voltage vector distribution, two rotor flux calculation algorithms, namely the motor loss minimization (MLM) algorithm and the maximum power sharing capability (MPSC) algorithm are proposed and compared, with their selection strategy to select the suitable algorithm depending on the operating condition. The MLM algorithm has the optimal efficiency performance, while the MPSC algorithm can maximize the power sharing capability of the dual inverter while holding the widest operation range of the motor. Based on the dual space vector pulse-width modulation (SVPWM) control scheme, the golden section (GS) search method is introduced to allocate the stator voltage vector to the dual inverter for the power sharing demand, with a flexible iteration number to obtain a stable and efficient computational performance, which fully utilizes the power sharing capability via the voltage vector distribution. Simulation results prove the validity and the advantages of the proposed strategy. This system also lays a foundation for energy management function of the dual-power electric vehicles.

Design and Analysis of Normal Saliency IPM Spoke Motor

This article deals with the design of a normal saliency interior permanent magnet (PM) motor, also referred as flux-intensifying PM motor. A multibarrier rotor geometry is adopted and studied through an analytical model to obtain an almost sinusoidal airgap flux density waveform, so as to improve the performance and reduce the torque ripple. The developed analytical model is generic and applicable for any number of rotor flux barriers and for any number of poles. The motor performance improvement has been evaluated by finite-element analysis. Experimental validation has been carried out on a motor prototype.

Enhanced Model Predictive Direct Torque Control Applied to IPM Motor With Online Parameter Adaptation

This paper presents an improved model-based predictive direct torque control (MPDTC) to improve torque accuracy and reduce torque ripples which is a major issue in conventional direct torque control (DTC). Hysteresis controllers and traditional DTC switching tables are replaced by a model predictive controller to achieve an online optimization for voltage space vector selection and optimal duty ratio modulation method for torque ripple reduction. In order to provide an accurate motor model for MPDTC, novel offline and online motor parameter estimation methods are proposed to improve performance of the proposed MPDTC. The proposed parameter estimation adopts Popov's hyper stability theorem to estimate accurate motor parameters, such as stator resistance, stator inductance and rotor flux linkage, which are critical for torque and flux estimation. The parameter adaptive MPDTC is verified by a hardware in the loop emulation platform, and experiment result is demonstrated using a dynamometer test bench, which therefore proves the feasibility of the proposed method.

Dynamic Identification of Rotor Magnetic Flux, Torque and Rotor Resistance of Induction Motor

In the modern high-performance drive applications, a high-precision and efficient control of the induction motor depends on the accuracy of parameter values. However, the motor parameters may change due to the winding temperature fluctuations, flux saturation and skin effect. Any discrepancy between the values of the motor’s actual parameters and the ones used for the design of the controllers may result in degradation of the drive performance. In this work, a new identification method of hardly measurable internal quantities of the induction motor, such as components of the magnetic flux vector and electromagnetic torque, is outlined. Commonly, the measurable quantities of the induction motor like stator currents, stator voltage frequency and mechanical angular speed are used to determine a feedback effect of the rotor flux vector on the vector of the stator currents of induction motor. Based on this feedback, it is also possible to identify the actual value of the rotor resistance, which may alter during the induction motor operation. This has a significant impact on the precision of the identified quantities as well as on the master control of the induction motor. Stability of the identification structure is guaranteed by the position of roots of characteristic equation of its linear transfer function. Simulation and experimental results are given to highlight the quality, effectivity, feasibility, and robustness of the proposed identification method, which is working reliably within the whole range of the motor angular speed.

A Semi-global Hybrid Sensorless Observer for Permanent Magnet Synchronous Machines with Unknown Mechanical Model

In this paper, we present a hybrid sensorless observer for Permanent Magnets Synchronous Machines, with no a priori knowledge of the mechanical dynamics and without the typical assumption of constant or slowly-varying speed. Instead, we impose the rotor speed to have a constant (unknown) sign and a non-zero magnitude at all times. For the design of the proposed scheme, meaningful Lie group formalism is adopted to describe the rotor position as an element of the unit circle. This choice, however, leads to a non-contractible state space, and therefore it introduces topological constraints that complicate the achievement of global/semi-global and robust results. In this respect it is shown that the proposed observer, which employs a clock to periodically reset the estimates, is semi-globally practically asymptotically stable, and thus it improves a continuous-time version designed under the same assumptions. As highlighted in the simulation results, the novel hybrid strategy leads to enhanced transient performance, notably without any modification of the gains employed in the continuous-time solution. These features motivate to augment the observer with a discrete-time identifier, leading to significantly faster rotor flux reconstruction.

Complex-valued sliding mode control of an induction motor

Three-phase induction motors admit a complex-valued space state representation. In this paper, this complex description is used to design a torque controller and a rotor flux observer based on sliding modes. The advantage of using the complex representation is an order reduction of the system and a simplification of the analysis. The obtained results are illustrated by means of numerical simulations.