无刷直流电动机无位置传感器检测技术

本文介绍了几种目前研究比较热点的无刷直流电动机无位置传感器转子位置信号检测方法,通过论述其基本原理、实现方法,根据它们各自的特点,对不同的方法提出了不同的改进策略,最后对它们进行综合的分析,比较了它们的优缺点及适用场合。     

基于DSP的无位置传感器无刷直流电机控制

围绕无位置传感器无刷直流电机控制中的两个关键技术——位置检测和起动，提出了将瞬时状态检测和预测估计相结合的电机转子位置检测方法和“三段式”起动。     

无位置传感器无刷直流电机调速系统的研究

一引言 无刷直流电机利用电子换向代替机械换向。采用无位置传感器控制技术，从而降低了系统的硬件成本，简化了电机的设计。     

无刷直流电机无位置传感器控制技术研究

在分析研究无刷直流电机无位置传感器控制方法的基础上,设计了反电势过零检测电路,给出了反电势检测信号与功率开关器件之间的对应关系,并进行了试验。结果表明,反电势检测信号可实现对无刷直流电机的准确控制。     

无刷直流电机无位置传感器的矢量控制研究

无位置传感器的无刷直流电机控制技术在变频空调中的应用越来越广泛。在分析了无刷直流电机的无位置传感器矢量控制理论的基础上,提出了一种以XMC1300为控制核心的磁场定向矢量控制方法,并结合一种新的位置观测器检测转子位置,对该方案进行了软件和硬件的设计与实现。实验结果表明,该方法获得了噪音低、效率高、振动小、安全稳定的控制效果,具有重要的实际意义。     

基于DSP的无刷直流电机无位置传感器控制

介绍了数字信号处理芯片TMS320LF2407的结构和性能,研究了PWM控制和A/D转换技术,采用反电势法实现了无刷直流电机的无位置传感器控制,并给出了相关的实验结果.     

永磁无刷直流电机的无位置传感器控制技术

本文对永磁方波无刷直流电机的无位置传感器控制技术——位置检测与起动进行了研究,并给出了所研制的基于ＤＳＰ控制的系统结构及有关实验结果。     

永磁无刷电流电机的无位置传感器控制技术

本文对永磁方波无刷直流电机的无位置传感器控制技术－位置检测与起动进行了研究,并给出了所研制的基于DSP控制的系统结构及有关实验结果。     

无位置传感器无刷直流电机控制系统研究

在分析无刷直流电机控制系统原理的基础上。提出了无刷直流电机控制系统的控制方案,并在此基础上．研究了以TMS320F240 DSP为控制核心的无位置传感器无刷直流电机控制系统的硬件结构和软件结构。最后给出了实验结果。     

无刷直流电机无位置传感器控制系统仿真研究

通过分析无刷直流电动机数学模型,利用Matlab/Simulink对无刷直流电机无位置传感器控制系统进行了建模和仿真。分别用Simulink库中自带的电机模型,反电动势过零点检测法、速度PI控制和电流滞环PWM控制方式对系统仿真,使系统更直观、简化,更加贴近实际控制系统,为无刷直流电机无位置传感控制系统的设计与调试提供了新的方法。仿真结果得到的三相行电流波形和反电动势波形与理论分析得到的波形一致,验证了该无位置传感器控制系统的正确性。     

Effects of prebuckling deformations on the elastic flexural-torsional buckling of laterally fixed arches

The effect of the prebuckling in-plane deformations on the elastic flexural-torsional buckling of laterally fixed circular arches is studied in this paper. The finite strains and the energy equation for the flexural-torsional buckling of arches have been derived based on an accurate orthogonal rotation matrix. A closed form solution for the elastic flexural-torsional buckling resistance of laterally fixed arches in uniform bending, including the effects of the prebuckling deformations, is obtained. It is found that the notion that the prebuckling deformations increase the flexural-torsional buckling moment of an arch or of a beam is not necessarily correct for a laterally fixed arch or beam in uniform bending, in deference to a laterally pinned arch. When a laterally fixed arch is subjected to positive uniform bending, the effects of the prebuckling deformations decrease the buckling moment, and the reduction of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When a laterally fixed arch is subjected to negative uniform bending, the effects of the prebuckling deformations decrease the absolute value of its buckling moment when the included angle is very small, but increase the absolute value of the buckling moment when the included angle exceeds a certain value. The increase in the absolute value of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When the ratio of the out-of-plane to the in-plane second moments of area of the cross-section is not small, both the reduction of the buckling moment of a laterally fixed arch in positive uniform bending and the increase of the buckling moment of a laterally fixed arch in negative uniform bending, are substantial.     

车门静态强度的有限元分析模拟

轿车门系统结构设计与优化是整车开发过程中的重要环节。车门的强度直接关系到整车在冲击、碰撞等载荷下的安全问题,车门结构静态强度的计算分析,在车门结构设计进程中非常重要。文中首先简要介绍了静态强度所涉及到的非线性有限元的基本理论,然后以某中高级轿车前车门为例,利用计算机辅助分析车门的静态强度,考虑变形的非线性因素,通过对车门的非线性有限元求解来分析车门强度,由计算所得到的车门强度性能指标来指导车门的结构设计。     

DESIGN AND ANALYSIS OF NOVEL ACTIVE ACTUATOR TO CONTROL LOW FREQUENCY VIBRATIONS OF SHAFT SYSTEM

Aiming at providing with high-load capability in active vibration control of large-scale rotor system, a new type of active actuator to simultaneously reduce the dangers of low frequency flexural and torsional vibrations is designed. The actuator employs electro-hydraulic system and can provide a high and circumferential load. To initialize new research, the characteristics of various kinds of active actuators to control rotor shaft vibration are briefly introduced. The purpose of this paper is to introduce the preliminary results via presenting the structure, functions and operating principles, in particular, the working process of the electro-hydraulic system of the new actuator which includes a set of high speed electromagnetic valves and a series of sloping cone-shaped openings, and presenting the transmission relationships among the control parameters from control signals into the valves to active load onto shaft. The course of the work is dynamic, and a series of spatial forces and moments are put on the shaft to get an external resultant force to reduce excitations that induce vibration of shafts. By checking states of vibration, the actuator can control the impulse width and the interval of injection time for applying different control force to a vibration shaft in two circumference directions through the regulating action of a set of combination directional control valves. The results from simulating analysis and experiment show evidence of that this design can satisfy the case of active process of decreasing of flexural and torsional vibrations.     

INFLUENCE OF ROLL DIAMETERS ON DEFORMATION BEHAVIOUR OF HIGH TEMPERATURE SUPERCONDUCTING TAPE

During plastic process,the material flow is strongly influenced by the contact area between deformed workpiece and die.In rolling process,difference of roll diameter makes the contact area between roll and deformed tape different,which leads to different material flow and the distribution of powder density.A numerical modelling of the first rolling process for 61-filament high temperature superconducting tape is constructed and the influences of roll diameters on deformation behavior of the tape are discussed.It can be found that the BiSrCaCuO(BSCCO)powder in the center of the tape has higher relative density than those in the periphery of the tape during rolling process.With the increase of roll diameter,the length of the contact arc in the roll gap expands which lead to the in- creasing of transversal strain and the decreasing of the related longitudinal strain.It makes the value of longitudinal strain ratio decrease gradually,which decreases the possibility of occurrence of the transversal shear band,simultaneously it increases the risk of occurrence of longitudinal crack.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.     

The effect of basic nitrogen compounds on the tribological performance of sulphurised olefin

The effect of the molecular structure of basic nitrogen compounds on the lubricating properties of sulphurised olefin has been investigated using a Timken tester. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Analysis (EDAX) were used to study the chemical states of sulphur and nitrogen on the rubbed surfaces and the reaction rates of sulphur and iron separately. It was found that the antiwear and friction reduction properties of sulphurised olefin are greatly influenced by the different molecular structures of the basic nitrogen compounds. A composite additive package containing basic nitrogen compounds with sulphurised olefin can produce either synergistic or antagonistic effects, due to the influence of the different molecular structures of the basic nitrogen compounds. XPS analysis revealed that a tribochemical protective film containing nitrogen and sulphur was formed on the rubbed surface. EDAX analysis indicated that the reaction rates between elemental sulphur and iron were influenced by the different molecular structures of the basic nitrogen compounds. It was found that the apparent reaction rates of elemental sulphur and iron are related to the tribological characteristics of the additive package.     

PHENOMENON OF CARVED DRIVING WHEELS

A newly found phenomenon of carved driving wheels of a rear-wheel-drive tractor used in an airport is discussed. The circum of every driving wheel is damaged at three regions,which distribute regularly and uniformly. Everyday,the tractor tows a trailer which are times heavier than the tractor,and moves on the same road in the airport. The phenomenon is explained by the torsional self-excited vibration system of the powertrain. The simplified torsional vibration system is discribed by a 2-order ordinary differential equation,which has a limit circle. Experiments and numerical simulations show the followings: Because of the heavy trailer,the slip ratio of the tractor’s driving wheels is very large. Therefore,there is severe torsional self-excited vibration in the tractor’s drivetrain,and the self-excited vibration results in severe and regular fluctuations of the rear wheel’s velocity. The severe fluctuations in velocity fastens the damage of the driving wheels. At the same time,the time interval in which an arbitrary point in the circum of the driving wheel contacts with the road twice is two times more than the period of the torsional self-excited vibration,and this times explained the existence of three damaged regions. At last,it points out that the phenomenon can be avoided when the torsional damping is large enough.     

ADAPTIVE RIGID-PLASTIC MESHLESS GALERKIN METHOD AND ITS APPLICATION IN ANALYSIS OF EXTRUSION PROCESSES

Under the hypothesis of the rigid-plastic material,specific efforts are placed on the deve-lopments of the key simulation techniques of the meshless Galerkin method because of the complexity of the deformation process as well as the generality and atomization of the simulation procedures for non-steady state large deformation plastic processes,therefore,an adaptive rigid meshless Galerkin method is developed. The influence domain control method is used in the least square approximation by dynamic evaluation of the magnitude of the influence domain and the effective control of the amount and the positions of the points in the least square approximation in order to improve approxi-mation precision. The amount of the Gauss integration points in the discrete domain is maintained in a considerable magnitude in order to ensure the integration precision in the discrete domain. The length of the frictional boundary of the plastic deformation process may be getting longer when its deforma-tion is getting severe. Thus,the densities of the boundary points of some places get lower. The adap-tive boundary points setting method is employed to improve the approximation precision of the boundary points and enhance the constraint of the boundary condition by adaptive control of boun-dary point density. Some typical extrusion processes are analyzed,detail simulation results such as the deformation field,velocity field,effective strain field,effective strain rate field,the volume loss curve and load-stroke curve are obtained. The effectiveness of the method developed is demonstrated and the precision of the meshless simulation is proved by overall comparison with the results obtained by using the commercial software deform.     

Computer simulation of turbine oil oxidation. 2: Consumption of a hindered phenol antioxidant in laboratory oxidation tests and in service

The computer simulation study of consumption of di-tert-butyl p-cresol (DBPC) was extended to the oxidation of hexadecane/tetralin model oils under conditions of laboratory oxidation tests and in service. The oxidation lives of the model oils in the ALCOA oxidation test and the ASTM D2272 rotary bomb and D943 turbine oil oxidation tests were successfully predicted from the simulation study. The oxidation behaviour of the model oils is compared to that of a turbine oil used in actual service units. The model oil having 6 mass % of tetralin showed almost identical oxidation behaviour to the turbine oil when the same amount of DBPC was added (0.6 mass %). The calculation shows that the direct oxidation of antioxidants is the main process of antioxidant consumption in the laboratory oxidation tests as well as in the model oxidation system without metal catalysts. In most of the service units which operated at moderate conditions the calculation shows that the direct oxidation of antioxidants is also the main, process. As a consequence, the rate of antioxidant consumption does not depend much on the tetralin content in the model oils. The oxidation behaviour of the model oils in the service units which operate under severe conditions, such as in the high temperature regions of turbines, is calculated by setting a flow reactor model. The results of this calculation show in this case that the turbine oil degradation occurs mostly in the high temperature regions and that the rate of antioxidant consumption increases with an increased amount of tetralin in the model oils. This strong dependence on base oil composition can be attributed to the increased importance of antioxidant consumption through the inhibition of oxidation.