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1、Development of PLC-based Tension Control SystemAbstractFiber winding tension is an important factor in the molding techniques ofcomposite material which influences the quality of winding product directly,and thetension control is a key technique in fiber winding techniques.This paper introduces aclo
2、sedloop tension control system with the programmable logic controller(PLC）with function modules as its control kernel,the alternating current(AC)servo motoras execute element and the radius-following device to accomplish the real-time radiuscompensation.The mechanism of the tension control system is
3、 analyzed and thenumerical model is set up。The compensation technique of the radius of the scroll isanalyzed。Experimental results show that the system is well qualified with highcontrol precision and high reaction speed.The components of composite material fiber winding possess such advantages aslow
4、 weight，high strength,and high corrosion resistance，and they are widelyapplied in aviation and aerospace industry。Many researches have shown thatimproper or unstable tension leads to a strength loss of 2030%of the fiber woundcomponents。An ideal tension control system should provide stable and adjust
5、abletension during the winding process 1-3。With the development of the winding machine，tension controllers have，sofar，undergone three stages of development，i。e。，mechanical tension controller,electrical tension controller and computerized tension controller45.With thedevelopment of electronic technol
6、ogy and the appearance of the microprocessor ofhigher cost performance,computerized tension controller came into use.Microprocessor becomes the kernel of the control system and thus cuts down thenumber of circuits of the electronic control system,which greatly simplifies thesystem，improves its relia
7、bility and makes possible the application of advancedcontrol methods.Therefore,this type of controllers is widely used6-7。The tension control techniques are becoming mature and the specifications arebeing improved in some developed countries。However,the fiber winding industryof China started up late
8、 and still drops behind compared with the western countries。Mechanical tensioners，with low precision and slow response,account for themain part of domestically applied tensioners，and cannot meet the tensionrequirements。Therefore，this paper presents a PLCbased tension control system.1 Set-up of the S
9、ystem Scheme1.1 Construction of the systemA winding tension control system generally consists of three main parts，namely theunwinder，the processer and the winder，and it may also include the measuring andcontrol parts,ancillary transport apparatus，and a load cell。The type of the winderand that of the
10、 unwinder may be one of the two drive types，surface drive or centerdrive。The surface drive means that a scroll or belt is set on the surface of thewinding material and the drive force is generated through friction.The center drive isto set a drive mechanism on the center shaft of the scroll,where th
11、e linear speed andthe tension force of the winding fiber vary with the radius of the scroll,leading to theso-called“scroll thick8.The phenomenon of“scroll thick”makes the tensioncontrol very complex,but the center drive mode is widely applied due to its wideapplicability.1。2 Design of tension contro
12、l schemeThis system adopts a scheme with a center drive and outward-draw fiberconfiguration.Since the output torque of the AC digital servo motor is in directproportion to the fiber tension force and the scroll radius,the output torque shoulddecrease as the scroll radius decreases to acquire a const
13、ant fiber tension。Thechange of the scroll radius can be measured by a radius following device and thesampled radius change then passes through an analog digital converter and is sent tothe PLC.By reading the desired value of the tension force,the radius and tensionforce are calculated with the prese
14、t calculating algorithm.The speed instruction andtorque limit instruction are issued and digital-to-analog converted to output theanalog voltage signal to control the servo driver。The servo driver controls therotating speed and output torque to control the fiber tension.The servo motors speedand tor
15、que are measured by the pulse encoder and the Hall element and fed back tothe PLC system to compose a closed loop system.The mechanism of the system isshown in Fig。1.The main components in the system include(1）A Panasonic programmable controller（FP0C10RS)，a 12bit FP0A80and an FP0-A04Vancilliary conv
16、ersion module。(2）A Panasonic AC digital servo driver and servo motor.(3)A radius-following device including a radiusfollowing arm and a rotarypotentiometer.2 Mathematical ModeEffective control of the fiber tension is required in fiber winding.Due to theversatility of the core mold shape and winding
17、shape,the linear speed of the fiber isdifficult to be kept constant and the variation principle is extremely complex。Therefore，the influence of the speed on the tension force should be taken intoconsideration in the mechanical analysis of the controlled object。The PLC withfunction modules as the con
18、trol systems control kernel,and the needed tension canbe enacted from man-machine interface through the serial communication betweenPLC and upper computer.The input of the radius value,the torque feedback and thevelocity feedback,the running of the preset calculating algorithm and the output ofthe s
19、ystem are done by the PLC with function modules。When the unwinder is considered，the dynamic torque equilibrium equation canbe expressed as followsM（t)=J（t)(t）+J(t)(t)+TR（t)+Mf+M0（1）where T is the yarn tension，R(t）is the real-time scroll radius，M（t）is theresistant moment of the AC servo motor,Mf is t
20、he viscous frictional moment，（t）is the angular velocity of the scroll，J（t)is the rotating inertia of the scroll and theyarn roll,and M0 is the dry frictional moment.As shown in Eq。(1），the scroll radius,the resistant moment，the angularvelocity of the unwinder and the rotating inertia of the scroll ar
21、e all functions of time，and the system is thus a complex multivariable timevarying system。Proper simplification of the torque equilibrium equation is carried out withclassical control theory based on the following rules：（1)The dry frictional moment and the viscous frictional moment are very littlean
22、d may be ignored.（2)The influence of J（t）(t）on the tension force may be ignored sincethe instantaneous inertia changes very slightly.(3）The scroll radius is real-time measured and fed back by the radius followingdevice.Eq.(1)is then simplified asTR(t)=M（t)+J（t）(t）(2）Therefore,the variations of scrol
23、l diameter and scroll angular velocity are themain influencing factors of the yarn tension。3 Compensation of the Radius of the ScrollThe radius change of the scroll causes the change of the scroll moment,i.e。,thechange of the TR（t)in Eq。(2)。One end of the radius following arm touches thescroll，and t
24、he other end is connected to the rotary potentiometer via gear magnifyingstructure,thus transforming a change in the spindle radius to a change of voltage，asshown in Fig。2where L is the length of radius following arm，Rmax is the maximum radius ofscroll,and R(t)is the instantaneous scroll radius。Supp
25、ose the transmission ratio of the gear is i，then the angle of the small gearis given as =iFor the potentiometer,where U is the output voltage of rotary potentiometer,US is the power supplyvoltage of rotary potentiometer,and s is the total angle of rotary potentiometer.Trimmed as4 Software Developmen
26、t of the SystemThe software development makes full use of the capabilities of FP0-C10RS,thedigital-analogy I/O modules，the hardware and software resources of the PCcomputer。The precision of the analogdigital or digital analog conversion dependson the number of bits of the analogdigital converter and
27、 digital-analog converter.FP0-A80 and FP0-A04V both are 12 bits,and the resolution is 1/4 000 when theoutput and input range 10V-+10V，while the FP0 is 16 bits，so the controlresolution of the system can be assured。The operation speed of each basicinstruction is 0.9 s/step，thus 500 steps program needs
28、 only 0。5 ms,and theconversion speeds of FP0A80 and the FP0A40V both are 1 ms/channel,so thecontrol speed of the system is assured.The PLC ladder diagram is applied to developthe whole control program.However，the input of the parameters is not intuitionistic,neither is the display of the realtime te
29、nsion and the scroll radius.In order to solvethis problem，a control program is developed for the host computer on the interfaceof which the operator can perform the input of the parameter and the display of thereal-time tension，the speed and the scroll radius.The programming port of all the FPPLCs s
30、upport OPEN MEWTOCOL PROTOCOL.Upper computer sends aCOMMAND to PLC as an ASCLL string.Then the PLC automatically returns theRESPONSE based on the COMMAND.The inputs of the system are the voltage feedback by radius following device，the torque feedback of alternating numeric servoelectromotor and the
31、velocityfeedback.The output of the system are alternating numeric servo-electromotor torqueand velocity voltage.The software control flow of the tension control system is shownin Fig.3.5 Simulation and Experimental ResultsExperimental research of the tension control in real winding states was carrie
32、dout through simulating the real working circumstances to test the feasibility andcontrol precision。When the tension was set to 10 N，the constanttension curveunder simulation and experimental conditions can be acquired with a near constanttension，as shown in Fig。4 and Fig.5，respectively。In order to
33、know the work stateof the AC servo motor when the tension changes,the tension force was changed from5 N to 10 N and the variation curves of which are shown in Fig。6 andFig.7 under simulation and experimental conditions，where the overshootingand fluctuation are rather small and the response time is l
34、ess than 0.3 s.5.1 Analysis of static difference rateStatic difference rate is a very important indexfor evaluating the performance ofthe system。It canbe expressed as followswhere T=Tmax Tmin,Tmax is the maximum tension,Tmin is the minimumtension,and Tm is the average tension.The analysis of static
35、difference rate of tensionis shown in Table 1。Table 1 The analysis of static difference rate of tension5。2 Analysis of fluctuation rateWhether the tension fluctuating rate meets the requirements is a key index forevaluating the performance of the designed tension control system.Enacted ainitialized
36、yarn tension，after compensation calculation，output it.Then，test theactual tension and find out the maximum and minimum tensions.6 ConclusionsSimulation and experimental results show that the system is feasible with thePLC as the kernel，the AC digital servo motor as the execute element and a radiusfo
37、llowing device to perform the radius compensation.The characteristics of thesystem include（1）A Panasonic FP-series PLC and functional modules serve as the controlkernels。The small volume,high integrity，high reliability,excellent controlcapability and the low cost all make the system convenient and c
38、ompact with highenough reliability and precision。（2）The yarn-retaking device can be left out，because the servo motor canperform the same function。（3）The modularized software design facilitates the construction expansionand the secondary development of the customers.（4)The friendly programming enviro
39、nment of the Panasonic FPWIN_GRsoftware encapsulates the capability of online programming.Parameters can bechanged on line and the control effects can be seen instantaneously。基于基于 plcplc 的张力控制系统的发展的张力控制系统的发展摘要摘要光纤弯曲力是复合材料影响成型工艺质量的一个重要因素弯曲的产品直接张力器是纤维缠绕工艺的关键技术技巧。本文介绍了闭环张力控制系统与可编程逻辑控制器（PLC）和功能模块为控制核心，交
40、流电（AC)伺服电机为执行要件、radiusfollowing 装置,实现实时半径补偿。机理的张力控制系统进行了分析，并对其数值模型。补偿技术的半径滚动进行了分析。实验结果表明,在较高的控制精度和很高的反应速度下，系统是合格的。复合材料纤维缠的成分绕具有重量轻、强度高,抗腐蚀性等优点，广泛应用于航空、航天工业.许多研究表明，不正确或不稳定的张力导致纤维损伤的部件有20-30的强度损失。缠绕过程中一个理想的张力控制系统将提供固定和可调的张力1-3。在绕线机的发展下，到目前为止,张力控制器经历了三个发展阶段，即:机械张力控制器、电气张力控制器和计算机化的张力控制器4-5。随着电子技术的发展，微处理
41、器拥有了更高的性能价格比，计算机化的张力控制器也开始使用了。微处理器成为控制系统的内核,从而降低了电路的数量的电子控制系统,大大简化了系统,有可能应用先进的控制方法改善了其可靠性。因此,这种类型的控制器得到了广泛的应用6-7。张力控制技术正在走向成熟，在一些发达国家其规格也正在提高。然而，中国的弯曲光纤产业起步较晚,仍然落后于西方国家。精度低、反应慢机械张力器件,主要面向国内的运用张力器的市场，不能满足张力要求。因此，本文反映了基于plc的张力控制系统。1 1、该系统的结构方案、该系统的结构方案1。1系统架构一个弯曲张力控制系统大体上由三部分组成，即放卷机、处理器和卷取机，也包括测量与控制部分
42、，辅助运输装置和测力传感器。放卷机和卷取机是两种驱动类型之一,表面驱动模式或者中心驱动模式。表面驱动模式指一个卷轴或者带子开始于弯曲材料的表面，驱动力通过摩擦产生。中间驱动模式是卷轴杆上的中心轴的滚动,缠绕纤维的线速度和张力随着卷轴的半径变化而变化,这导致了所谓的“滚动厚。这种现象使张力控制非常复杂，但是中间驱动模式因其广泛应用性而被广泛应用.1。2设计张力控制方案这个系统采用中心驱动的方案和外拉纤维配置.因为交流数字伺服电动机的输出转矩和纤维张力以及卷轴半径成比例，所以输出转矩应该随着卷轴半径减小到要求的恒定纤维张力。一种测量半径的装置和取样的半径变化可以测量卷轴半径的变化，通过模拟数字整流
43、器，卷轴半径变化被发送给PLC.通过读取张力的期望值,预算法则可以计算出半径和张力。系统发布了速度指令和转矩限制指令,并把它们转换成能控制伺服驱动的输出模拟电压信号。伺服驱动控制系统控制着转速和控制纤维张力的输出转矩。脉冲编码器和霍尔开关可以测量伺服电动机的速度和转矩，并把速度和转矩反馈给构成闭环循环系统的PLC系统。这种系统的原理如图1所示。系统中的主要成分包括(1)一个日本松下可编程控制器（2)一个日本松下空调交流数字伺服驱动和伺服电动机（3)一个测量半径的装置和旋转电位计2 2、数学模型、数学模型在纤维缠绕中对张力的有效控制是必要的。由于模型和弯曲形状的多样性，张力线速度难以保持不变，变
44、分原理也相当复杂。因此，在机械分析被控对象时，我们应该考虑张力速度的影响.通过PLC和计算机的串行通信，在人机接口处，可以制定PLC的功能模块如控制系统的控制核心以及所需的张力。PLC的功能模块可以计算出输出半径、转矩和速率反馈、预算法则的规律和系统的输出。考虑退绕机时，动态扭矩的平衡方程式可以表示如下M(t)=J(t)（t）+J（t）(t)+TR（t）+Mf+M0（1）此处 T 是纱线张力，R（t)是实时滚动半径，M(t)是交流伺服电动机的粘滞摩擦力矩，J(t）是卷轴的旋转惯性,以及 M0 是干摩擦力矩.如公式(1）所示，实时滚动半径、力矩、角速度和卷轴的旋转惯性是正常的，因此系统是一个复杂
45、的多变量的时域变化系统.我们可以用经典控制理论计算出正确的简单的转矩平衡方程式，基于以下法则：（1）干摩擦力矩和粘滞摩擦力矩是十分小的,以至于可以被忽略.（2)关于张力 J（t)（t）的影响可以被忽略，因为瞬间的惯性改变微乎其微。(3）通过利用可测量半径装置，我们可以实时测量卷轴半径的大小.公式（1）可以简化成：TR(t）=M(t）+J(t)(t)（2)因此，卷轴直径的变更和其角速度是决定纱线张力大小的主要影响因素。3 3 卷轴大小的补偿卷轴大小的补偿卷轴半径大小的变化可能引起卷轴瞬间的状态改变，即公式（2)中 TR(t）的变化。半径滚动变化结束后,另一端连接通过对电位计齿轮的放大结构，转变成
46、一个变化主轴半径变化的电压,如图 2。4 4 软件开发系统软件开发系统这个软件的开发充分利用 FP0-C10RS 的能力,由数字化 I/O 模块、硬件和软件，计算机的软件资源组成。具有较高计算精度的数字化或数字模拟转换取决于位的数字转换器和模拟的转换器。FP0-A80 和 FP0A04V 都是 12 位，当输出输入范围-10V-+10 伏特时分辨率是 1/40000 次,而 FP0 是 16 位,所以这样控制系统的分辨率可以放心.每个基本指令的运算速度是 0.9s/步骤,因此 500步骤程序只需要 0.5ms。FP0A80 和 FP0A40V 的转换速度都是 1 ms/通道，因此这个系统的控制
47、速度可以放心。PLC 的梯形图适用于整个控制程序.然而,输入参数是不真实和直观的，展出的实时性张力和滚动半径也是如此。为了解决这个问题，控制程序的开发主机上的操作界面可以输入执行的参数和显示实时张力、速度与滚动半径。这个程序的可编程序控制器接口支持所有开放式的MEWTOCOL 协议。上层计算机发送一个命令给可编程序控制器作为一种 ASCLL 字符串。然后 PLC 自动返回基于这个命令的回应。系统的输入是电压反馈，伺服电机的转矩反馈和速度反馈。系统的输出有伺服电机力矩和交流电压.该软件的控制流张力控制系统如图 3 所示。5 5 仿真和实验结果仿真和实验结果实验对张力控制真正的弯曲状态、真正的工作
48、环境试验的可行性和控制精度进行了模拟。当张力值设置为 10 N，仿真和实验条件下的张力曲线可以获得几乎恒定的张力，如图 4 和图 5 分别显示。当张力改变时,为了知道交流伺服电机的工作状态，如图 6 的变化曲线所示，张力改变的范围是 5N 到 10N，在仿真和实验条件下如图 7 所示，波动响应相当下,响应时间小于 0。3 秒。5.1 静态差异率的分析静态差异率是评估系统的性能非常重要的指标.公式可以如下表示:此处T=TmaxTmin，Tmax是张力最大值，Tmin是张力最小值，Tm是张力均值，张力的静态差异率分析如表1所示。表一 张力静态差异率的分析5。2 波动比的分析张力波动率是否符合是一个
49、评价张力控制系统的设计的绩效的关键指标。制定一个初始化后,计算张力补偿，输出该值.然后,测量实际的张力大小并找出最大值和最小值。6 6 结论结论仿真和实验结果表明这个系统是可行的。本系统以可编程序控制器(PLC）为核心，数字伺服电机为执行元件，一个半径补偿设备进行半径补偿，仿真和实验结果表明该系统是可行的.系统的特点包括：（1）松下FP 系列 PLC 和功能模块作为控制核心。小容积，高诚信，高可靠性，良好的控制能力和低成本使系统方便，可靠性高以及精度高。(2)不需要绕纱装置，因为伺服电机可以提供同样的功能。（3)模块化的设计促进工程扩建和二次开发客户的需求.（4）松下 FPWIN_GR 软件的较好编程环境包括在线编程的能力和参数。程序员可以改变对线的控制，并看到实时效果.