Application of direct torque control to electric screw presses for speeding up torque response and reducing starting current

Fast response and stable torque output are crucial to the performance of electric screw presses. This paper describes the design of a direct torque control （DTC） system for speeding up torque response and reducing the starting current of electric screw presses and its application to the J58K series of numerical control electric screw presses with a dual-motor drive. The DTC drive system encompasses speed control, torque reference control, and switching frequency control. Comparison of the DTC dual-AC induction motor drive with corresponding AC servo motor drive showed that for the J58K-315 electric screw press, the DTC drive system attains a higher maximum speed （786 r/min） within a shorter time （1.13 s） during a 250 nun stroke and undergoes smaller rise in temperature （42.0 ℃） in the motor after running for 2 h at a 12 min-1 strike frequency than the AC servo motor drive does （751 r/min within 1.19 s, and 50.6 ℃ rise）. Moreover, the DTC AC induction motor drive, with no need for a tachometer or position encoder to feed back the speed or position of the motor shaft, enjoys increased reliability in a strong-shock work environment.     

Novel torque ripple minimization algorithm for direct torque control of induction motor drive

To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control (DTC) of induction machines, the factors of influence torque variation are examined. A new torque ripple minimization algorithm is proposed. The novel method eradicated the torque ripple by imposing the required stator voltage vector in each control cycle. The M and T axial components of the stator voltage are accomplished by measuring the stator flux error and the expected incremental value of the torque at every sampling time. The maximum angle rotation allowed is obtained. Experimental results showed that the proposed method combined with the space vector pulse width modulation(SVPWM) could be implemented in most existing digital drive controllers, offering high performance in both steady and transient states of the induction drives at full speed range. The result of the present work imphes that torque fluctuation could be eliminated by imposing proper stator voltage, and the proposed scheme could not only maintain constant switching frequency for the inverter, but also solve the heating problem and current harmonics in traditional induction motor drives.     

基于预测控制的直接转矩控制系统的研究

针对异步电动机直接转矩控制（DTC）系统在低速时由于开关频率不稳定而引起转矩脉动较大的缺点，提出了一种预测控制方法。该方法根据转矩和定子磁链的误差来确定应该施加的参考电压矢量，最后利用空间矢量脉宽调制（SVPWM）方法来合成该矢量，这样即保证了逆变器的开关频率恒定，从而大大降低转矩脉动。仿真结果表明，在低速下定子磁链轨迹近似为圆，转矩脉动不明显。     

一种减小无刷直流电机转矩脉动的广角波控制方法

In order to deal with torque pulsation problem caused by traditional control method for brushless DC （BLDC） motor and to achieve high precision and good stability, a novel control strategy is proposed. Compared with the traditional control scheme, by using phase voltage as a control objective and making waveform of phase current approximately quasi-sinusoidal, torque ripple of BLDC motor is reduced from the original 14% to 3.4%, while toque is increased by 3.8%. Furthermore, by detecting zero-crossings of back electromotive force （BEMF） with non-conducting phases, sensorless control is realized. The new control strategy is simple. It can minimize torque ripple, increase torque, and realize sensorless control for BLDC motor. Simulation and experiments show good performance of BLDC motor by using the new control method.     

异步电机矢量控制系统仿真研究

异步电动机是一个高阶、非线性、强耦合的多变量系统.文中提出一种异步电动机矢量控制系统方案,并在此基础上设计了一个典型的矢量控制系统,然后利用matlab/simulink仿真软件对该控制系统进行建模与仿真研究.     

电动汽车轮毂电机场路耦合特性分析

分析电动汽车轮毂电机特性,给出一种电动汽车轮毂电机场路耦合分析法,将电磁场有限元模型和外部电路直接耦合到一起,场路耦合分析模型充分考虑到外电路中电流谐波的影响,分析结果更符合实际情况。仿真分析了轮毂电机气隙磁密、负载感应电势等特性,轮毂电机空载起动、加载和卸载等工况,并通过样机试验验证,实验测试结果与场路耦合法计算结果能够较好的吻合。     

电气控制与PLC课程教学改革的探索和实践

根据高等职业教育人才培养目标,结合学院数控技术专业能力人才培养方案和当前高职生学情状况,针对电气控制与PLC课程改革,从教学内容、教学方法、教学模式、考核评价方案4个方面做了探索,力求达到提高教学效果、学生技能操作和技能应用能力的目标。     

胶印机离合压机构示教装置的电气控制设计

研制了胶印机示教装置，简单阐述了该示教装置开发的主要特点及基本要求，并且对该示教装置离合压系统电气控制设计作了详细的分析介绍。胶印机示教装置在低速运行时，演示现象明显。     

永磁直线同步电机磁阻力优化的设计

The detent force of a permanent magnet linear synchronous motor （PMLSM） is analyzed and the corresponding optimization methods are presented to reduce it. The detent force, which is divided into two components, i.e. resulting from the end effect and resulting from the slotting effect, can be analyzed respectively by the finite element method （FEM）. To reduce the detent force arising from the end effect, several optimal design techniques are utilized, namely, adopting the suitable length and end shape of the primary armature. The detent force resulting from the slotting effect is reduced by means of skewing and adjusting the width of the magnets mounted on the secondary armature, and adopting the fractional slots of the primary armature. The validity of the analytical detent force predictions and the effectiveness of the detent force reduction techniques are verified by the experimental measurements.     

项目教学法在机床电气与PLC课程教学中的运用

以机械设计制造及其自动化专业中的主要专业基础课程机床电气与PLC为载体,运用以工作过程为导向的项目教学法进行课程教学改革,精心设计了课程的项目教学体系。在项目的实施过程中,采取以学生为主体,＂教学做＂合一的教学模式,对于培养学生的应用技能,增强学生的＂大工程意识＂,提高课程教学的质量具有良好的效果。     

机电领域卓越工程师培养质量监控及管理体系研究

教学质量监控及管理是卓越工程师培养规划的重要研究内容之一,以天津职业技术师范大学机电技术教育专业卓越工程师培养为研究对象,进行了教学质量管理概念及现状的分析。     

Design and implementation of a position sensorless control method for brushless DC motors

Because brushless direct current (BLDC) motors have the advantages of a compact size, high power density, high efficiency, and long operating life time, they are widely used in many industrial products and electric traction systems. It is known that the BLDC motors have no brushes for commutation. They are commutated with electronically commutation. So, the rotor position information of the BLDC motors must be known to understand which winding will be energized according to the energizing sequence. In most of the existing BLDC motor drivers, rotor position information is detected by Hall effect sensors. This kind of mechanical position sensors will bring additional connections and costs, reliability decrease and noise increase. In order to improve the control performance and extend the range of speed regulation for BLDC motors, a position sensorless control method is proposed in this paper. In the proposed control method, rotor position information of the BLDC motors is detected from the back electromagnetic forces (back-EMFs) which are estimated by an unknown-input observer with line to line currents and line to line voltages. For the purpose of verifying the effectiveness of the proposed control method, a model is built and simulated on the Matlab/Simulink platform. The simulation results show that the speed regulation performance of BLDC motors is improved compared with using Hall effect sensors. At the same time, the reliability of the BLDC motors is improved and the costs of them are reduced because the position sensor is eliminated.     

基于Rockwell PLC-5温度控制系统实验设计与实现

基于Rockwell PLC-5设计温度控制系统。为了便于实现比例-微分-积分控制器参数整定,对被控对象——电热箱进行实验建模;为了降低输入输出误差,对温度采集及变送环节进行实验建模;基于被建模型,采用改进欧拉法完成被控对象的数值仿真,提供数值仿真对象,可以方便进行控制参数整定,快速看到控制效果;采用模糊比例-微分-积分控制器,实现温度控制;基于Rsview完成人机交互界面和数据动态显示;完成了Rockwell PLC-5温度控制系统仿真平台和实际系统的开发,实现了温度控制系统演示实验和温度控制系统半开放实验设计,达到了预期的实验设计目标。     

复烤片烟箱芯温度自动检测装置设计及应用

针对打叶复烤箱芯测温工序中人工测量劳动强度大、效率低、易受环境温度波动影响等不足,自主研发了一套温度自动检测装置及隔温降噪测温杆。该装置由动力输送机构、多轴测温机构和PLC控制系统组成。仿真分析和现场实验研究的结果表明:自动测温装置检测效率比人工提高了280%;自主研制的测温杆测得的温度与实际温度偏差不超过0.2℃,比常规测温杆与红外测温仪更准确。该装置实现了打叶复烤烟叶箱芯温度的自动打孔、检测,现场运行动态稳定性好,可为复烤厂提质增效提供有效途径。     

Analysis and optimization of assembly variations for non-rigid parts

Traditional variation analysis methods are not applicable to non-rigid assemblies due to possible part deformation during the assembly process. This paper presents the use of finite element methods to simulate assembly deformation. The relationship between the parts＇ variation and the variation of the key points in final assembly for quality control is set up by calculating the spring back deformation after assembly. Moreover, the optimization method for non-rigid assembly variations based on finite element analysis is presented. The optimal objective is to reduce the manufacturing cost. The approach is implemented by using ANSYS and MATLAB. The test example shows that the proposed method is effective and applicable.