过载保护在PLC输入和输出控制中的处理方法与原则

介绍过载保护在PLC输入和输出控制中的处理方法与原则.阐述热过载继电器辅助触点置于PLC输入和输出控制线路中的用法.分析热过载继电器辅助触点置于PLC输入和输出控制线路中的优缺点.分析PLC输入控制线路中使用热过载继电器常开和常闭触点的优缺点.通过对热过载继电器在PLC输入和输出控制中的用法和各自优缺点的分析得出:过载...     

基于PLC的铜线装载系统液压设计

针对现有铜线装载工序的复杂性缺陷,设计了一种基于PLC的铜线装载液压系统。根据用途分析了铜线装载的动作循环及工作原理,设计了铜线装载液压系统及PLC控制电路。该装载液压系统结构简单,运行平稳,精度满足工作要求,其液压系统和PLC控制系统简单可靠。     

基子PLC控制的彩灯设计

随着人们生活环境的不断改善和美化,在现代生活中,彩灯越来越多应用于景观.针对现状,介绍了基于PLC控制的彩灯控制设计的过程,给出其PLC控制系统的接线图,设计出了指令程序.该设计具有可编程性、线路简单、可靠性高等特点,提高了系统的灵活性及可扩展性,仿真结果验证了该设计的正确性和实用性.     

基于负逻辑控制的数控机床限位保护装置及方法研究

现有数控机床的限位保护装置普遍采用的控制方式是正逻辑控制,这种控制方式可能因线路开路而产生限位失灵现象。为解决现有数控机床的限位控制电路的缺陷,研制出一种新的限位控制方式,即负逻辑控制。特点是限位行程开关的工作触点采用常闭触点,数控系统的PLC输入端口设置为负逻辑,负逻辑的实现可以通过编写机床的PLC程序和通过设定机床参数实现。这种方法提高了限位电路的可靠性。经过实际使用达到了很好的效果,解决了现有数控机床限位控制电路的缺陷。     

基于PLC的铜线装载液压系统设计

针对现有铜线装载工序的复杂性缺陷,设计了一种基于PLC的铜线液压装载系统。根据用途分析了铜线装载的动作循环及工作原理,设计了铜线装载液压系统及PLC控制电路。该装载液压系统结构简单,运行平稳,精度满足工作要求。     

基于PLC控制的核仪表系统

研究并设计基于PLC的核仪表控制系统。该系统采用西门子的S7-200型PLC对核仪表探测器发出的信号进行运算处理,得到相应的工艺参数。实验证明,利用PLC控制的核仪表系统,大大地降低了核仪表维护成本,结构简单,运行可靠,易于实现。     

基于PLC的同步器性能与寿命试验系统的研制

为了评价汽车变速器同步器的性能与寿命,设计了基于PLC的试验系统。介绍了试验系统的组成、关键技术、测控系统的设计及控制程序的设计。系统由计算机和PLC共同控制,采用气电混合式机械手代替驾驶员进行换挡操作,各路传感器信号高速并行采集。试验结果表明该试验系统能够完成各种长时间、高重复性的变速器同步器试验,运行稳定可靠。     

Robust control of robot manipulator with actuators

A Robust controller is designed for cascaded nonlinear uncertain systems that can be decomposed into two subsystems; that is, a series connection of two nonlinear subsystems, such as a robot manipulator with actuators. For such systems, a recursive design is used to include the second subsystem in the robust control. The recursive design procedure contains two steps. First, a fictitious robust controller for the first subsystem is designed as if the subsystem had an independent control. As the fictitious control, a nonlinearH∞ control using energy dissipation is designed in the sense ofL ₂-gain attenuation from the disturbance caused by system uncertainties to performance vector. Second, the actual robust control is designed recursively by Lyapunov’s second method. The designed robust control is applied to a robotic system with actuators, in which the physical control inputs are not the joint torques, but electrical signals to the actuators.     

Soft-testing of industrial control systems programmed in IEC 1131-3 languages

This paper presents a technique and the means for testing PLC-based control software outside the actual plant environment with the purpose of increasing the confidence level on the compliance of the software to functional and temporal requirements. The need to obtain a high confidence level on the correct software operation arises from the fact that in most of the cases it is quite dangerous and expensive to test unproved PLC operation by linking it with the actual facilities that it is going to control. The proposed technique relies on a combined simulation of the controlled plant and the PLC system and an analysis of the plant responses. The PLC system simulation imitates the way software is executed on a PLC that is programmed in the languages of the IEC1131-3 standard. It is based on the programming model of the IEC standard and analytical formulae for estimating the program runtime. The simulation of the plant is based on a discrete convolution model that is solved at the same rate with the rate determined by the control algorithms. A tool realizing these concepts has been developed and its use in testing the control software of three critical outputs of a distillation column is demonstrated.     

PLC对输入模拟量的一种处理方法

针对小型机或整体机PLC无法处理模拟量的问题，提出应用双斜式A／D转换器的原理，利用常用的器件组建A／D转换器，再利用PLC的内部的计数功能，将模拟量转换成时间量，在原有的不能处理模拟量的可编程控制器上，实现用很少的输入点数完成模拟量的处理。提高了系统的性价比。已将此方法成功地应用于电弧炉控制系统中。     

控制和事故信号共用一个PLC输入接点的实现方法

在重要的工程项目中,需要对每个设备的状态进行监视并提供实时故障信息,采用常规的设计。实现N个设备的控制和事故报警将至少需要2N个PLC输入接点,通过合理地设计PLC硬件电路和软件编程。只用N＋1个输入接点就可实现对N个设备的控制和事故报警,成倍地减少PLC的输入接点,从而降低设备费用,提高设备的性价比。     

A water pumping control system with a programmable logic controller (PLC) and industrial wireless modules for industrial plants--an experimental setup

This paper describes a water pumping control system that is designed for production plants and implemented in an experimental setup in a laboratory. These plants contain harsh environments in which chemicals, vibrations or moving parts exist that could potentially damage the cabling or wires that are part of the control system. Furthermore, the data has to be transferred over paths that are accessible to the public. The control systems that it uses are a programmable logic controller (PLC) and industrial wireless local area network (IWLAN) technologies. It is implemented by a PLC, an communication processor (CP), two IWLAN modules, and a distributed input/output (I/O) module, as well as the water pump and sensors. Our system communication is based on an Industrial Ethernet and uses the standard Transport Control Protocol/Internet Protocol for parameterisation, configuration and diagnostics. The main function of the PLC is to send a digital signal to the water pump to turn it on or off, based on the tank level, using a pressure transmitter and inputs from limit switches that indicate the level of the water in the tank. This paper aims to provide a convenient solution in process plants where cabling is not possible. It also has lower installation and maintenance cost, provides reliable operation, and robust and flexible construction, suitable for industrial applications.     

Optimal filtering and Bayesian detection for friction-based diagnostics in machines

Non-model-based diagnostic methods typically rely on measured signals that must be empirically related to process behavior or incipient faults. The difficulty in interpreting a signal that is indirectly related to the fundamental process behavior is significant. This paper presents an integrated non-model and model-based approach to detecting when process behavior varies from a proposed model. The method, which is based on nonlinear filtering combined with maximum likelihood hypothesis testing, is applicable to dynamic systems whose constitutive model is well known, and whose process inputs are poorly known. Here, the method is applied to friction estimation and diagnosis during motion control in a rotating machine. A nonlinear observer estimates friction torque in a machine from shaft angular position measurements and the known input voltage to the motor. The resulting friction torque estimate can be analyzed directly for statistical abnormalities, or it can be directly compared to friction torque outputs of an applicable friction process model in order to diagnose faults or model variations. Nonlinear estimation of friction torque provides a variable on which to apply diagnostic methods that is directly related to model variations or faults. The method is evaluated experimentally by its ability to detect normal load variations in a closed-loop controlled motor driven inertia with bearing friction and an artificially-induced external line contact. Results show an ability to detect statistically significant changes in friction characteristics induced by normal load variations over a wide range of underlying friction behaviors.     

基于PLC的风光互补独立发电系统研究

在研究风光互补发电系统构成机理和运行的基本模式基础上,提出了一种基于PLC控制的风光互补发电系统,通过对风力发电子系统与光伏发电子系统中功率输出的检测来控制蓄电池充放电.谈系统能合理利用现有资源,长期有效运行.     

A Web-based programmable logic controller laboratory for manufacturing engineering education

This study presents the design and development of a Web-based programmable logic controller (PLC) system architecture that supports hands-on laboratory exercises in automated manufacturing systems control area for distance education. The system architecture allows remote users to access and control a PLC-based table-top manufacturing system via the Internet. A Web site has been designed and developed that facilitates interactivity and supports PLC programming and control. The architecture has been tested and implemented in the course Emgt 334 Computer Integrated Manufacturing Systems at the Integrated Systems Facility (ISF) in the Engineering Management Department at the University of Missouri-Rolla during Fall 2001. This study shows that software tools available in the market can be integrated to develop a fairly complex, yet effective, learning environment for distance education. The architecture presented in this paper is not dependent on specific PLC hardware or software configuration, it represents a generic infrastructure. This revised version was published online in October 2004 with a correction to the issue number.     

A general technique for the PLC-Based implementation of RW supervisors with time delay functions

The Supervisory Control Theory (SCT) introduced by Ramadge–Wonham (RW) is a general theory to design supervisors (controllers) for discrete event systems. Although over the two decades SCT has received wide attention in academia, industrial applications are very few, due to the fact that there is a discrepancy between the abstract RW supervisor and its physical implementation. In this paper, an easy to use, general and practical technique is proposed for the PLC-based implementation of RW supervisors with time delay functions. The applicability of the proposed method is demonstrated by means of a PLC-based real-time control of an experimental manufacturing system.     

进口专用电液吊具国产化及其控制系统改造

以进口专用电液吊具为研究对象,提出了一种基于PLC的控制系统设计框架,设计反馈电压信号的归一化处理接口,实现对2种不同供电方式下吊具的控制。其多对象的适用性及内部电压的处理技术对类似控制工程的实现有很好的参考价值。