Feedback-linearizing control of IPM motors considering magnetic saturation effect

This paper describes feedback-linearizing control of interior permanent magnet (IPM) motors which operate in magnetic saturation. First, we propose a current tracking controller for direct control of stator currents. Then, we explicitly characterize all torque controllers that can make the motor torque of an IPM motor exactly linear with respect to torque command even if magnetic saturation occurs. In particular, our torque controller contains a free function that can be used to achieve other control objectives as well as linear dynamic characteristics. Finally, the free function is chosen so optimal as to maximize power efficiency. The practical use of our control method is demonstrated through various simulation and experimental results.     

A torque controller suitable for electric vehicles

A torque controller suitable for electric vehicles is studied. The controller ensures that an induction motor generates motor torque efficiently, stably and accurately. The torque control system feeds back an assumed motor torque calculated using the secondary magnetic flux and the torque current detected from current sensors of the primary currents. The motor torque is controlled by using the torque current reference determined from the generated secondary magnetic flux and the magnetizing current reference. The magnetizing current reference is determined on the basis of the torque current reference so that motor torque generation efficiency is always optimal. The magnetizing current regulator is operated according to the magnetizing current reference. This ensures the motor generates the motor torque stably even in transient states. Fundamental performance characteristics, such as response, accuracy and efficiency of the motor torque are verified by simulation and experiments. The torque controller is judged suitable for the drive system of electric vehicles     

Torque ripple minimization for variable reluctance motors

The design of current waveforms that minimize torque ripples in variable reluctance (VR) motors is addressed. The general problem of torque ripple reduction has been investigated by several researchers using various nonlinear models. The results have been design methods that require exhaustive measurements of motor characteristics. The approach presented here assumes magnetic linearity to derive an efficient ripple-reducing excitation that is much easier to calculate. A nonlinear optimal design problem is developed and then converted to a linear representation by a simple transformation. The transformed linear optimization problem is straightforwardly solved by standard numerical methods, and yields the optimal current waveform characteristics in the new variable. Finally, the optimal current waveform is found by applying an inverse transformation. The analytical result presented in this paper is supplemented by a design example that also addresses the performance tradeoff resulting from ignoring magnetic saturation to achieve simplifications in design.     

Efficiency-optimized direct torque control of synchronousreluctance motor using feedback linearization

In this paper, a nonlinear controller capable of high dynamic torque regulation and efficiency optimization of the synchronous reluctance motor (SynRM) using input-output feedback linearization is proposed. The cross-coupling effects in the SynRM model and the torque nonlinearity due to the iron losses in torque-speed characteristics of the SynRM are discussed. The criterion for the efficiency optimization is also introduced and investigated. Since the proposed nonlinear controller directly regulates the torque by selecting the product of d- and q-axes torque currents as one of the output variables, the nonlinear and cross-coupling aspects between the d-and q-axes torque currents and the terminal currents can he eliminated. Hence, the linear torque-speed characteristic can be achieved. In addition, by controlling the power loss-minimizing criterion directly, the proposed controller can optimize the efficiency of the SynRM without deteriorating the dynamics performance     

Evaluation of alternative evolutionary programming techniques for optimization of an automotive alternator

One of the primary design requirements of automotive generation systems is maximizing power density subject to the constraint of minimizing the overall system cost. However, with the progress made in the reduction of automotive drive train noise, the torque ripple of the generator has been found to be a dominant noise source under idle conditions at high electrical loads. Thus, an added design constraint is the minimization of the torque ripple produced by the machine. In order to evaluate alternative machine designs (and select an optimal), numerical tools are typically applied. In this research, a focus is placed on the creation of numerical tools that can be used to effectively search for an optimal design. A primary tool is an evolutionary algorithm (EA) that has been integrated within a customized magnetic equivalent circuit (MEC) model of the machine. The selection of an EA that is most likely to converge to an optimal solution in the least amount of time is described along with its use in selecting an optimal rotor-pole geometry.     

Adaptive control of variable reluctance motors: a spline functionapproach

This paper considers nonlinear adaptive control of a variable reluctance motor (VRM) in a low-velocity high-torque mode of operation. A simple dynamic model for the relationship among electric torque, rotor angular position, and phase currents is proposed. The model incorporates spline functions and a set of “Fourier” sinusoids and captures several experimentally verified VRM characteristics, including flux saturation effects. Based on this model, an adaptive controller is derived using the certainty equivalence principle. The controller provides asymptotic tracking of a desired rotor position trajectory. So-called “torque-sharing functions” are employed to smooth the commutation among phases and to increase the peak torque available from the motor, when compared to “hard” commutation that energizes only one phase at a time. Experimental results from a laboratory VRM provide motivation for the model and illustrate the controller's design and trajectory tracking performance     

Dynamic response of a hydraulic servo-valve torque motor with magnetic fluids

As magnetic fluids (MF) show higher saturation magnetization and larger viscosity when exposed to a magnetic field, large damping forces or resistance will be exerted on the armature of a hydraulic servo-valve torque motor by magnetic fluids if they are filled into the working gaps of the motor. This paper focuses on the application of magnetic fluids in a hydraulic servo-valve torque motor, especially the influence of magnetic fluids on the dynamic response of the motor. After introducing the working principle of the torque motor with magnetic fluids, the dynamic mathematical models of the torque motor and magnetic fluids are presented. The torque working on the armature introduced by magnetic fluids is analyzed. In order to study the influence of magnetic fluids, dynamic response of the torque motor is simulated and tested when magnetic fluids are applied or not in the motor. Simulation and experimental results show an obvious influence of magnetic fluids on the dynamic response of the hydraulic servo-valve torque motor.     

Characteristic Analysis of Interior Permanent-Magnet Synchronous Motor in Electrohydraulic Power Steering Systems

This paper presents design and analysis results of a 2.6-kW interior permanent-magnet synchronous motor developed for an electrohydraulic power steering system. The motor was designed by using the proposed equivalent magnetic circuit model in consideration with a core loss. To analyze motor characteristics by using the equivalent magnetic circuit model, inductance and iron-loss resistance, which are affected critically by magnetic saturation, are obtained by using finite-element analysis. Finally, motor characteristics such as armature current, torque, and efficiency are calculated by the equivalent magnetic circuit model and verified by experimental results.     

Vapor Sensing Theoretical Study on Optical Microcavities

When the organic vapors absorbed to the surface of porous silicon（PS）, capillary condensation takes place due to the porous structure of the PS layer, accordingly resulting in the effective refractive index changing. For PS multi-layer microcavities, the different resonant peaks shift in the reflectivity spectrum of porous silicon microcavities（PSMs）. The optical sensing model is set up by applying Bruggeman effective medium approximation theory, capillary condensation process and transfer matrix theoretically analytical method of one-dimensional photonic crystals. At the same time, comprehensively researched on are the sensing characteristics of PSMs which are exposed to give concentration organic vapors. At last, made is the theoretical simulation for sensing model of the PSMs in case of saturation by using computer numerical calculation, and found is the linearity relation between the refractive index of organic solvent and the peak- shift. At the same time deduced is the peak-shift as a function of the concentration of ethanol vapors.     

Design and control of a disk-type integrated motor-bearing system

A disk-type integrated motor-bearing system having axial magnetic flux is newly invented and its design, analysis, and control methods are presented. Sinusoidal motoring currents to four symmetrically placed winding groups produce a torque, whereas control currents of the same magnitude but opposite signs added to the opposite winding groups create radial forces. The control currents are intended to break force symmetry, resulting in unbalanced radial forces. The system employs two stators not only to effectively remove the rotational frequency modulation effect in the radial control forces, but also to reduce the torque ripple. It is shown that the prototype integrated motor-bearing system built in the laboratory succeeds in stable radial direction control and operation of the rotor     

基于MEC的高速铁路无线通信网络优化方案

为实现对高速铁路无线通信网络的优化处理,满足高速铁路安全、可靠、高效运行的多维铁路运输需求,在分析现有高速铁路车地无线通信网络的基础上,结合目前在其他行业广泛应用和推广的MEC技术,提出了基于MEC的高速铁路无线通信网络优化方案。通过实验室搭建仿真环境,对比两种高速铁路无线通信网络的优化方案模型,并对基站和车站MEC服务器功能及MEC平台架构进行阐述,通过高速铁路应用实例,系统地描述基于MEC的无线通信网络优化方案,为后续高速铁路无线通信网络优化提供理论依据,对网络时延、无线传输优化、虚拟化技术等方面的研究和攻关提供模型支持。     

Optimization of photomask design for reducing aberration-induced placement error

In semiconductor manufacturing, the accurate placement of circuit components ensures the proper functioning of microelectronic circuits. This is often subject to photolithography, an optical technique that transfers circuit patterns from photomasks to silicon wafers. Sources of placement error include aberration and misalignment between different levels, and we focus on the former. Aberration is an optical phenomenon that often degrades imaging system performance. Since aberration differs from one imaging system to another, a photomask design that minimizes the aberration-induced placement error is desired. In this paper, we discuss the optimization process of a general one-dimensional mask pattern under a general illumination condition. The constraint is a known population mean of the root mean square aberrations for the imaging systems under consideration. To apply the theory, we search for the optimal parameters for two common mask designs: alternating phase-shifting masks (PSMs) and attenuated PSMs. The theoretical results are compared with those from a Monte Carlo analysis on a large set of imaging systems. These results are indicative to mask manufacturers and circuit designers of increasing manufacturability of circuits.     

Optimal control of brushless PM motor in parallel hybrid propulsion system

The paper outlines a case study on optimal control of a brushless direct-current (BLDC) motor as a part of an Integrated Starter-Generator and torque Booster (ISGtB) application in a hybrid propulsion system. The main scope of the introduced research work is the optimization of the BLDC motor torque characteristics. The discussed hybrid propulsion system consists of an internal combustion (IC) engine and a BLDC machine and is in its origin intended to drive the motorcycle. Stringent starting torque demands, electrical machine geometry limitations and a wide rotational speed range of the BLDC motor are reasons for control algorithm analysis in the low-speed operation range. Two approaches for the optimization of the torque characteristics are discussed, the flux-weakening method and a modification of transistor conduction angle. A novel control principle which includes both of the above approaches is proposed. A comparison between a commonly used control method and the proposed control method is presented. Simulation and experimental results fully confirm improvements in the starting procedure of the hybrid propulsion system attained by the proposed control algorithm of the BLDC motor.     

A new approach for minimum-torque-ripple maximum-efficiency controlof BLDC motor

Torque-ripple control of the brushless DC motor has been the main issue of the servo drive systems in which the speed fluctuation, vibration, and acoustic noise should be minimized. Most methods for suppressing the torque ripples require Fourier series analysis and either iterative or least-mean-square minimization. In this paper, a novel approach to achieve ripple-free torque control with maximum efficiency based on the d-q-0 reference frame is presented. The proposed method optimizes the reference phase current waveforms which include the case of three-phase unbalanced conditions. As a result, the proposed approach provides a simple way to obtain optimal motor excitation currents. The validity and practical applications of the proposed control scheme are verified through the simulations and experimental results     

An Optimization-Based Algorithm for Shunt Active Filter Under Distorted Supply Voltages

In this paper, an optimization-based control algorithm for the compensation of steady-state load under distorted supply voltages is presented. For balanced and sinusoidal supply voltages, load compensation using shunt active filter produces perfect harmonic cancellation (PHC) and unity power factor (UPF) source currents. However, when the supply voltages are distorted, compensation for PHC will not provide UPF, as the harmonics in the supply voltages are not utilized for delivering the average power. In the same way, to achieve UPF source currents, the compensated source currents should have the same harmonics, unbalance, shape, and be in phase with the respective supply voltages, thereby violating the perfect harmonic cancellation objective. Hence, there should be an optimal operation between these two important compensation characteristics. The optimization-based control algorithm presented in this paper gives the best power factor while satisfying the constraints such as total harmonic distortion limits and average power balance of source currents. It is also flexible to adopt different compensation characteristics based upon the supply voltage conditions. Matlab and its optimization toolbox are used for simulation studies and solving the nonlinear optimization problem, respectively. The algorithm is validated by using a prototype of digital signal processor (TMS320F2812PGFA)-based shunt active power filter. Detailed experimental results are presented.     

Development of an eddy-current-type magnetic floor hinge

A magnetic floor hinge is suggested to use a magnetic damping characteristic obtained by the eddy-current effect. It has a superior advantages compared to the conventional hydraulic floor hinge. First, there exists no wear in the magnetic damper since the disk rotates between the magnets without contact. Second, the deviation of the damping torque is very small in varying seasons due to the low temperature dependence of the conductivity of the disk to which the magnetic damping torque is proportional. The analytical models obtained for the damping torque and the recovering torque are experimentally investigated. The cost optimal design is carried out using the analytical models while satisfying the performance requirements. The analytical results are compared with experimental results. Finally, a prototype of the magnetic floor hinge is built.     

IPM synchronous machine drive response to a single-phase open circuit fault

This paper investigates the steady-state and dynamic response of an interior permanent magnet (IPM) synchronous machine drive to a single-phase open-circuit fault. This fault results in rotational electromagnetic asymmetry on both the stator and rotor, making it difficult to analyze using classical dq-transformation techniques. This paper presents a new dq synchronous-frame machine model that is capable of handling this highly asymmetrical fault condition, including the effects of q axis magnetic saturation. Fault responses with two alternative post-fault control strategies are investigated: (1) opening all of the inverter switches so that the machine behaves as an uncontrolled generator (UCG), with the two unfaulted phases connected to the inverter DC link via the antiparallel diodes; and (2) shorting the two remaining unfaulted phases together using the inverter switches. Results of this investigation show that the fault response is generally more benign using the UCG control strategy, with significantly lower phase currents and pulsating torque than corresponding values delivered using the phase-shorting strategy.     

Analytical and experimental investigation on the magnetic field and torque of a permanent magnet spherical actuator

This paper presents the torque model of a ball-joint-like three-degree-of-freedom (3-DOF) permanent magnet (PM) spherical actuator. This actuator features a ball-shaped rotor with multiple PM poles and a spherical stator with circumferential air-core coils. An analytical expression of the magnetic field of the rotor is obtained based on Laplace's equation. Based on this expression and properties of air-core stator coils, Lorentz force law is employed for the study of the relationship between the rotor torque and coil input currents. By using linear superposition, the expression of the actuator torque in terms of current input to the stator coils can be obtained in a matrix form. The linear expression of the actuator torque will facilitate real-time motion control of the actuator as a servo system. Experimental works are carried out to measure the actual magnetic field distribution of the PM rotor in three-dimensional (3-D) space as well as to measure the actual 3-D motor torque generated by the actuator coils. The measurement results were coincident with analytical study on the rotor magnetic field distribution and actuator torque expressions. The linearity and superposition of the actuator torque were also verified through the experiments.     

High-performance speed servo system considering Voltage saturation of a vector-controlled induction motor

Generally, a speed servo system of a vector-controlled induction motor has limitations of motor voltage and current. When the speed servo system has a large torque reference, the output of its PI controller is often saturated. In this case, the conventional servo system stops the integral calculation of its PI controller. However, this system often has a large overshoot and/or an oscillated response caused by both a windup phenomenon and phase error on the vector control condition. This paper proposes a new speed servo system considering voltage saturation for the vector-controlled induction motor. The proposed control method compensates the phase error on vector control condition quickly, and always keeps the vector control condition. The experimental results show that the proposed system well regulates the motor speed and the secondary magnetic flux for a large torque reference without a windup phenomenon.     

Design and control of a novel spherical permanent magnet actuator with three degrees of freedom

The paper describes the design and control of a new version of a spherical permanent magnet actuator, which is capable of three degrees of freedom and a high specific torque. Based on an analytical magnetic field distribution, the torque vector and back-emf are derived in closed forms. An optimal design procedure is proposed to achieve maximum output torque or maximum acceleration for a given payload. The control of the actuator, whose dynamics are similar to those of robotic manipulators, is facilitated by the establishment of a complete actuation system model and the application of the computed torque control law. The validity of the analysis and design techniques, and the effectiveness of the control strategy, are confirmed by measurements.