Incorporating control trajectories with the direct torque control scheme of interior permanent magnet synchronous motor drive

Interior permanent magnet (IPM) synchronous machines have gained increased attention for applications in electric vehicle, variable speed wind turbine, industrial drives, etc., because of their high torque density, wider speed range and compact construction. The authors present a detailed analysis and modelling of control trajectories and incorporate those trajectories in the direct torque control (DTC) scheme of an IPM synchronous motor drive, for constant-torque and constant-power operating regions. The control trajectories are implemented on a real-time digital signal processor. Because the inputs to the inner torque control loop of DTC are the references for the torque and the amplitude of the stator flux linkage (λ_s), they are transformed in the T-λ_s plane, than in the i_d - i_q plane in the indirect control. The modelling and experimental results are presented. Results show very good dynamic and steady-state performances of direct torque controller, incorporating these control trajectories.     

Direct torque and flux control of an IPM synchronous motor drive using a backstepping approach

A novel direct torque and flux controlled interior permanent magnet synchronous motor (IPMSM) drive using an adaptive backstepping technique is presented. Closed-loop regulation of the speed, torque and stator flux linkage is achieved by a non-linear controller. Using Lyapunov analysis, the stability of the controller is guaranteed. The reference voltage vectors are generated by a space vector modulation (SVM) unit, which replaces the switching table in the conventional direct torque control (DTC) scheme. While retaining its main advantages, the proposed backstepping controller features reduced torque and flux ripples as compared to the classical DTC. On the one hand, a comparison with the proportional-integral (PI) direct torque and flux control (DTFC) scheme shows that the proposed approach is superior. Experimental results confirm the effectiveness of the proposed method.     

高效节能的永磁同步电机混合控制算法

目的 保证永磁同步电机在变速变载时能够快速响应的同时,降低其在稳态时的转矩脉动和开关频率,使永磁同步电机在整个包装过程更加高效节能.方法 分析永磁同步电机的2种控制策略DTC和PIPC的优缺点和共同点,提出在启动、变速和变载过程采用DTC控制策略保证电机的动态响应速度,在稳态时切换到PIPC控制策略,降低电机的转矩脉动和开关损耗.结果 仿真结果表明,2种控制策略能够实现平滑切换,电机动态响应快,抗干扰能力强,稳态时转矩脉动小、开关频率低;相比DTC,在空载、轻载和重载时转矩脉动分别减小了30％,12.5％和2.4％,开关频率降低了约45％;相比PIPC,响应速度提高了约7％.结论 相比单一的控制策略,DTC_PIPC混合控制算法融合了2种控制策略的优点,使电机在整个运行过程既能快速应对各种突变情况,又能降低其在稳态运行时的转矩脉动和开关频率.     

Dithiocarbamates as capping ligands for water-soluble quantum dots

We investigated the suitability of dithiocarbamate (DTC) species as capping ligands for colloidal CdSe-ZnS quantum dots (QDs). DTC ligands are generated by reacting carbon disulfide (CS(2)) with primary or secondary amines on appropriate precursor molecules. A biphasic exchange procedure efficiently replaces the existing hydrophobic capping ligands on the QD surface with the newly formed DTCs. The reaction conversion is conveniently monitored by UV-vis absorption spectroscopy. Due to their inherent water solubility and variety of side chain functional groups, we used several amino acids as precursors in this reaction/exchange procedure. The performance of DTC-ligands, as evaluated by the preservation of luminescence and colloidal stability, varied widely among amino precursors. For the best DTC-ligand and QD combinations, the quantum yield of the water-soluble QDs rivaled that of the original hydrophobic-capped QDs dispersed in organic solvents. The mean density of DTC-ligands per nanocrystal was estimated through a mass balance calculation which suggested nearly complete coverage of the available nanocrystal surface. The accessibility of the QD surface was evaluated by self-assembly of His-tagged dye-labeled proteins and peptides using fluorescence resonance energy transfer. DTC-capped QDs were also exposed to cell cultures to evaluate their stability and potential use for biological applications. In general, DTC-capped CdSe-ZnS QDs have many advantages over other water-soluble QD formulations and provide a flexible chemistry for controlling the QD surface functionalization. Despite previous literature reports of DTC-stabilized nanocrystals, this study is the first formal investigation of a biphasic exchange method for generating biocompatible core-shell QDs.     

Initial rotor position estimation and sensorless direct torque control of surface-mounted permanent magnet synchronous motors considering saturation saliency

For a practical direct torque-controlled (DTC) permanent magnet synchronous motor (PMSM) drive system, the information of the initial rotor position, which is usually obtained by a mechanical position sensor, is essential for starting under the full load. To avoid the disadvantages of using mechanical position sensors, great efforts have been made on the development of sensorless control schemes. An initial rotor position estimation strategy is presented for a DTC PMSM drive based on a nonlinear model of PMSM incorporating both structural and saturation saliencies. In the new scheme, specially designed high-voltage pulses are applied to amplify the saturation saliencies. The peak currents corresponding to the voltage pulses are used, in combination with the inductance patterns, to determine the d-axis position and the polarity of the rotor. The presented initial rotor position identification strategy has been implemented in a sensorless DTC drive for a surface-mounted PMSM. Experiments are conducted to confirm the effectiveness of the method and the performance of the drive system.     

Motion Control at the Nanoscale

Synthetic nanoscale motors represent a major step in the development of practical nanomachines. This Review summarizes recent progress towards controlling the movement of fuel‐driven nanomotors and discusses the challenges and opportunities associated with the achievement of such nanoscale motion control. Regulating the movement of artificial nanomotors often follows nature's elegant and remarkable approach for motion control. Such on‐demand control of the movement of artificial nanomotors is essential for performing various tasks and diverse applications. These applications require precise control of the nanomotor direction as well as temporal and spatial regulation of the motor speed. Different approaches for controlling the motion of catalytic nanomotors have been developed recently, including magnetic guidance, thermally driven acceleration, an electrochemical switch, and chemical stimuli (including control of the fuel concentration). Such ability to control the directionality of artificial nanomotors and to regulate their speed offers considerable promise for designing powerful nanomachines capable of operating independently and meeting a wide variety of future technological needs.     

DTC study of very thin polystyrene films at temperatures of about Tg and above

The depolarization thermocurrent (DTC) method gives the dependence of the dielectric relaxation time on temperature. It has been applied to the study of secondary relaxations within polymers in the glass-like state. The analysis of this method shows that it is also of interest for investigations of the relaxation region associated with the glass transition. The results obtained for polystyrene films prepared by a glow discharge in monomer vapour are presented as an example. As a result of the resolving power of the DTC technique it is possible to separate two relaxations: a process obeying an Arrhenius-like law observed around the glass transition temperature and a mechanism described by a Williams-Landel-Ferry (WLF) equation observed above T_g. The data obtained are consistent with those from other methods.     

Speed limit and ramp meter control for traffic flow networks

The control of traffic flow can be related to different applications. In this work, a method to manage variable speed limits combined with coordinated ramp metering within the framework of the Lighthill–Whitham–Richards (LWR) network model is introduced. Following a ‘first-discretize-then-optimize’ approach, the first order optimality system is derived and the switch of speeds at certain fixed points in time is explained, together with the boundary control for the ramp metering. Sequential quadratic programming methods are used to solve the control problem numerically. For application purposes, experimental setups are presented wherein variable speed limits are used as a traffic guidance system to avoid traffic jams on highway interchanges and on-ramps.     

基于单一DSP的X-Y平台控制器设计

在研究永磁同步电机数学模型和直接转矩控制理论的基础上,介绍了一种基于单一DSP芯片的X-Y平台全数字交流伺服控制系统.该系统以TI公司先进的电机控制专用芯片TMS320F2812为核心,充分利用其丰富的端口资源、快速的运算处理能力,并融合直接转矩控制算法结构简单、对系统参数依赖小、动态响应优良等特性,大大减小了整个系统的体积,降低了成本,提高了系统的鲁棒性.实验设计结果表明该系统控制性能优良.     

Design and application of magneto-rheological fluid

Magneto-rheological fluid (MRF) technology is an old “newcomers” coming to the market at high speed. Various industries including the automotive industry are full of potential MRF applications. Magneto-rheological fluid technology has been successfully employed already in various low and high volume applications. A structure based on MRF might be the next generation in design for products where power density, accuracy and dynamic performance are the key features.

Additionally, for products where is a need to control fluid motion by varying the viscosity, a structure based on MRF might be an improvement in functionality and costs. Two aspects of this technology, direct shear mode (used in brakes and clutches) and valve mode (used in dampers) have been studied thoroughly and several applications are already present on the market. Excellent features like fast response, simple interface between electrical power input and mechanical power output, and precise controllability make MRF technology attractive for many applications.

This paper presents the state of the art of an actuator with a control arrangement based on MRF technology. The study shows that excellent features like fast response, simple interface between electrical power input and the mechanical power output, and controllability make MRF the next technology of choice for many applications.     

三相异步电机直接转矩控制的建模与仿真

用MATLAB／SIMULINK建立了异步电动机直接转矩控制动态仿真模型，用PWM整流代替了传统的相控整流，对圆形磁链轨迹进行了仿真研究。该模型是深入研究直接转矩控制系统的有效工具。     

Predictable capability control scheme for oxygen‐exchange blood flow regulation in an extracorporeal membrane oxygenation system

Extracorporeal membrane oxygenation system is used for rescue treatment strategies for temporary cardiopulmonary function support to facilitate adequately oxygenated blood to return into the systemic and pulmonary circulation systems. Therefore, a servo flow regulator is used to adjust the roller motor speed, while support blood flow can match the sweep gas flow (GF) in a membrane oxygenator. A generalised regression neural network is designed as an estimator to automatically estimate the desired roller pump speed and control parameters. Then, the proportional–integral–derivative controller with tuning control parameters showed good performance to achieve speed regulation and speed tracking in the desired operating point. Given the pressure of carbon dioxide, drainage blood flow, and cannula size, the proposed predictable capability control scheme can be validated to meet the intended uses in clinical applications.Inspec keywords: haemodynamics, three‐term control, medical control systems, patient treatment, neural netsOther keywords: oxygen‐exchange blood flow regulation, extracorporeal membrane oxygenation system, rescue treatment strategies, temporary cardiopulmonary function support, roller motor speed, sweep gas flow, generalised regression neural network, proportional–integral–derivative controller, tuning control parameters, speed regulation, speed tracking     

Advances in vector control ofac motor drives — A review

This paper attempts to present a comprehensive review of the advances made in vector control or field orientation as applied to high performanceac motor drives. Brief application survey, machine models ind-q representation, implementation issues with inverters and cycloconverters, parameter effects etc for both induction and synchronous motor vector control are dealt with and sample results from studies on them are presented. The latest advance on this control like direct torque control (DTC) has been briefly discussed. A substantial updated bibliography, though by no means complete, is included for those who are interested in keeping track of the present state-of-the-art and working further in this area.     

Torque ripple reduction in direct torque controlled five-phase induction motor using modified five-level torque comparator

The five-phase induction motor inherently has the minimal torque ripple. However, when it is controlled by direct torque control (DTC) technique, the torque ripple increases due to the presence of a hysteresis torque comparator. The classical five-level torque comparator is presented in the previous literatures to control the torque ripple. However, this comparator has the drawback of wrong selection of zero voltage vectors inside the inner band on the positive side of the comparator, which enables the torque ripple to increase and dc-link utilization to decrease. In this paper, in order to reduce the torque ripple and to increase the dc-link utilization, a modified five-level torque comparator is proposed, which selects either medium or small voltage vectors instead of zero voltage vectors inside the inner band on the positive side of the comparator. In addition to torque ripple reduction and improvement in dc-link utilization, the proposed comparator significantly improves the quality of phase current. All the available 32 voltage vectors are selected through the proposed five-level torque comparator based on the location of x–y stator flux in order to eliminate the x–y stator flux so as to obtain reduced distortion in the phase current. By employing all the available voltage vectors, the freedom of utilization of all voltage vectors in the five-phase induction motor DTC drive is availed. The proposed five-level torque comparator is compared to its classical five-level counterpart through simulation and experimental results in order to validate the proposed DTC strategy.     

On‐Demand Control of the Photochromic Properties of Naphthopyrans

Photofunctional compounds have emerged as critically important materials for both fundamental studies and industrial applications. Control of the thermal decoloration speed to within several seconds while sustaining satisfactory photochromic colorability is an important challenge for the application of such materials to photochromic lenses and smart windows. Photochromic naphthopyran derivatives are utilized for photochromic lenses because of their high durability and easily controllable colorability. However, the residual color imparted by the long‐lived transient species upon ceasing light irradiation remains a hindrance to practical applications. In this study, a strategy is demonstrated for on‐demand control of the thermal decoloration speed of the transient colored species of naphthopyran derivatives. The increase in the ring‐size of the alkylenedioxy moiety on the naphthopyrans accelerates the thermal back‐reaction independently of the maximum‐absorption wavelength of the colored isomer, leading to the realization of yellow‐, red‐, and blue‐photochromic naphthopyrans with similar thermal fading speeds. This novel molecular design provides a strategy for the future development of advanced photoresponsive materials.     

Pathpair: a fast available bandwidth estimation tool with the asymptotic one way delay comparison model

Significant research has been dedicated to active probing methods used to estimate the end-to-end available bandwidth (avail-bw) of a network path. The measurement speed of an avail-bw estimation tool is vital to real-time network services such as transport control protocol (TCP) slow start, path selection for P2P applications and video streaming services and so on. In addition, a fast avail-bw estimation tool sends less probing traffic to a measured network. Pathload, a one way delay (OWD) based tool, has been widely regarded as one of the most accurate tools, but its estimation speed is often 10 or more seconds per measurement. A fast OWD-based avail-bw estimation scheme has been explored. This scheme is based on the proposed asymptotic OWD comparison model, and an estimation tool called Pathpair has been developed. Validated in a real Internet environment, experimental results show that with Pathpair the measurement speed has been significantly improved (1-3 s per measurement), while preserving accuracy compared with other major tools like Pathload and Spruce.     

An experimental analysis of effective high speed turning of superalloy Inconel 718

Superalloy, Inconel 718 is widely used in the sophisticated applications due to its unique properties. However, machining of such superior material is difficult and costly due its peculiar characteristics. The present article is an attempt to suggest Taguchi optimization technique to study the machinability of Inconel 718 with respect to cutting force, cutting temperature, and tool life in high speed turning of Inconel 718 using cemented tungsten carbide (K20) cutting tool. Therefore, the objective of this work is divided into two phases: (i) to demonstrate a correlation between cutting speed, feed, and depth of cut with respect to cutting force, cutting temperature, and tool life in a process control of high speed turning of Inconel 718 in order to identify the optimum combination of cutting parameters; (ii) to show the effect of high speed cutting parameters on the tool wear mechanism and chip analysis. These correlations were obtained by multiple linear regressions. The confirmation tests were carried out to make a comparison between the experimental results and mathematical models proposed. The proposed models agree well with the experimental results.     

用IBM－PC计算机测试SSPA器件参数的数据采集系统

介绍用ＩＢＭ－ＰＣ计算机辅助测试ＳＳＰＡ器件参数的１２位高速数据采集系统。该系统带有缓冲ＲＡＭ，对ＳＳＰＡ的视频信号采集速度可达５００ｋＨｚ，适合于各种需要对ＳＳＰＡ器件进行高速高精度采集的应用。     

Investigation of quadruplex oligonucleotide-drug interactions by electrospray ionization mass spectrometry

Selectivity, binding stoichiometry, and mode of binding of Tel01, distamycin A, and diethylthiocarbocyanine iodide (DTC) to the parallel stranded G4-quadruplex [d(T2G5T)]4 were investigated by ESI-MS. The first drug/quadruplex complexes observed by ESI-MS are described. Tel01, distamycin A, and DTC all form complexes with quadruplex DNA, but only Tel01 is completely selective for quadruplex versus duplex oligonucleotide under the conditions employed. Previous solution determinations of the binding mode of Tel01 and distamycin A to quadruplex oligonucleotides indicate that Tel01 interacts through end-stacking with guanine tetrads of quadruplex DNA, while distamycin A interacts by binding to quadruplex grooves. When these two different drug/quadruplex complexes are subjected to collisionally activated dissociation in a mass spectrometer, the observed fragmentation patterns are distinct. Tel01/quadruplex complexes undergo facile loss of drug and dissociation to single-strand oligonucleotide ions, while distamycin/quadruplex complexes fragment into single-strand oligonucleotide ions in which the drug molecule is retained. Dissociation patterns for DTC/quadruplex complexes are similar to those of distamycin; therefore, it is concluded that DTC interacts with [d(T2G5T)]4 through groove-binding. These ESI-MS results are applicable to both the identification and characterization of G-quadruplex interactive agents and may also be useful in probing unusual DNA structures.     

Estimation of rotor and load angle of direct-torque-controlled permanent magnet synchronous machine drive

A dynamically well performing rotor and load angle estimation method for direct-torque-controlled (DTC) permanent magnet synchronous machines drives is presented. The rotor or load angle is needed as example in the limitation of the load angle. The method uses the same flux linkage estimate that is used in the core of the DTC and calculates the load and rotor angle directly from the motor equations. The effect of the flux linkage estimation method is analysed through simulation. Both the steady-state and dynamical measurement results are also provided, showing the good performance of the suggested method. The performance is adequate to be used as example in the limitation of the load angle in order to prevent the machine falling from synchronism