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电动式转向机综合性能试验台设计,电动,转向,综合,性能,试验台,设计
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n Appication of hydraulic AGC and width control to a hot strip millD.Alan Davies,Project Sale Manager,Engineering and Construction Div. Davy Mckee (Sheffie id)Lid, Sheffieid, U. K. THE Pohang Iron & Steel Co.(POSCO) No.2 hot strip mill at Pohang, South Korea,is a modern, three-quarter continuous mill built by Mitsubishi in 1980.The mill is 2050mm wide,has four roughing stands and seven finishing srands.The seven finishing srands have a combined power of 56,000kw with a maximum strip speed of 21 metres/s.Coil weight is up to 35.3 tonnes. Annual mil capacity is 3.56 million tonnes. To improve width and gage tolerances,POSCO decided to install hydraulic automatic width contol (HAWC) on the last edger (E4) and hydraulic automatic gage control (HAGC) on finishing stands F4 to F7. Davy McKees contract was for the total ackage associat-ed with modernization of the mechanical and hydraulic systems,the computer-bassd AWC/AGC controls, new widthmeter, mechanical installation, commissioning and training. The new equipment was put into service during a 14-day shutdown in 1987.n Outline of new facilities A priority requirement was that the new equipment should be integrated with the existing facility in such a way as to permit reversion to conventional operation in a few seconds. Accordingly, hydraulic AGC and AWC cylinders were designed to withstand normal rolling conditions when in a collapsed state. All of the control systems had to be in parallel with the existing systems (which were retained ) and existing operators desk contromechanical system, depending on which system was selected. The AWC system comprises short-stroke, single-acting cylinders (four in total )engineered between the ends of the horizontal screwa and the vertical roll chocks . These cylinders are servo-controlled, with a stroke speed of 100 mm/s (4 ips) to provide in -bar width control. (With the bar being typically 50 mm thick at this stage, only a limited amount of correction was expected.) A new widthmeter after roughing stand R3 is used to give feed forward control signals to the edger E4 AWC with the existing widthmeter after rougher R4 providing bar to bar updating . The AGC system on the last four finishing stands has short-stroke, single-acting cylinders located between the top chocks and the acrewdown thrust bearing/load cell units.These cylinders have excetionally high dynamic performance (28 Hz ,10 mm/s velocity ). Becayse of the physlcal distance between the edger E4 and the finishing stands F4 to F7 ,separate pump sets serve each atra ,The hydraulic pressure is 275 bars, mineral oil,with a filtration level of 3 microns . The new computer configuration compries a network of seven PDP 11/73 microprocessors linked by an Ethernet highway . An unusual feature of the system was the need to tap into the existing 64-way parallel communications link between the existing supervisory control computer (SCC) and the melplac plcs which perform the screwdown AGC, The tap had to be transparent to existing communication and of a high integrity . (Hence a warm spare stand by computer was included in the system .) The required data for the AGC/AWC was extracted , serialized and communicated to the new system along the Ethernet , highway , This had the advantage of opening up the computer system to easier communications in the future , as new systems could be attached easily to the Ethernet .(A few months later , a further contract for ENCO heat retention panels and interstand water curtains was retention panels and interstand water curtains was received which required a further 11/73 miceoprocessor .)n Mechanical/hydraulic design features AGC cylinders -Various components of the AGC cylinders and their assembly are illustrated in Fig . 4,5 and 6. The cylinder design incorporates a single , low -friction seal that constests of a Teflon band mounted on the piston below a bronze , side trust ring . The base of the piston is chamfered to give a rocking surface when the cylinder is used in a collapsed state .It gives the necessary degree of freedom to absorb the normal deflections in the mill . A hydraulic manifold is mounted to the front of each cylinder that includes the servo-valves.One of the position transducers is slightly discernible behind the small accumulator .Another position transducer is fitted diametrically opposite . The two signals from the transducers are averaged to provide a mean stroke signal . The transducer package is shown in .The Sonymagnescale transducers with 1 micron resolution are hermetically sealed insode the brass bodies . Three-stage servo-valves are employed (Moog 79 series ) .The third stage has its own built-in closed-loop position control . Each valve is nominally rated at 230 litres /min . Two valves are fitted to each cylinder and operate electrically in cascade , ie , as the drive signal to the first valve reaches saturation , it spills over to the second valve . They have a frequency response of 200 Hz . Cylinder parameters and performance data are summarized in Table I . Dynamic performance was checked on a similar cylinder (890 mm dia compared to 960 mm on the POSCO mill ) with identical transducers , servo-valves , etc , installed on a mill housing equipped as a test rig . Steel blocks accurately represent the masses of the chocks and rolls , giving a truerepresentation of the mass-spring conditions in a real mill . The frequency resonse as a function of the rolling load is illustrated in , Loop gain is automatically adjusted by the software to optimize the dynamics . One of the inberent features of a single-acting cylinder design is that the flow rate through the servo-valves and , thus , the cylinder speeds , is a function of the actual pressure in the cylinder . To prevent unnecessarily high speeds at the higher and lower sections of the range , simple software rules limit the electrical drive signals to the servo-valves ,effectively creating a stable and symmetrical velocity performance in both the extending and retacting directions , over the working range of the cylinder .AWC cylinders -The AWC cylinders have a thrust bearing with spherical seating , embedded into the piston . Each cylinder is served by its own 3-stage servo-valve located nearby . The servo-valves and position transducers are interchangeable with the AGC counterparts . Performance details are also summarized in Table 1 . Collapse force is provided by pull-back cylinders acting on the roll chocks . These cylinders are controlled to maintain a constant , low , pull-back force during the body of the bar , but increasing to a higher value to assist in achieving the tail end antinecking feature .n Hydraulic systems -Hydraulic pumpsets are located in the oil cellars . The system serving the HAGC on stands F4 to F7 comprises a stainless steel reservoir tank with gravity feed to four axoal piston pumps ( three duty , one standby ) that deliver at 275 bars ( 4000 psi ) . Filtration throughout is 1 micron nominal ( 3 micron absolute ) with a separate oil cooler/filter unit supplied by a separate recirculation pump , drawing oil from the tank , through the filter /cooler and back to the tank . Accumulator manifolds with 38-litre , high -pressure nitrogen-filled accumulators ( that supply the transient demands mill stand . These accumulators are mounted as close to their respective cylinders as practically possible , to maximize dynamic performance .n Contol system hardware features One of POSCOs major concerns was the integration of the new computer systems without jeopardizing the existing system . (The existing system was to remain service and be available as a standby facility at all times .) The 64-bit parallel interface between the existing supervisory setup computer (SCC) and the PLC ( MELPLAC) responsible for screw AGC could not be expanded or duplicated . The solution was to interpose a PDP 11/73 with its standard digital I/O equipment betweent the SCC and the MELPAC to act as a communications link (Fig .9 ) . Its function was simple . It read-in the data from the a SCC as 64-bit data , stored it in memory and passed it immediately out again as identical digital output to the MELPLAC . The same exchange occurs in reverse order when data is passed back to the SCC . At each transaction , the 64 bits are decoded and converted into serial form for distribution to the remainder of the new systom . Such data would include all PDI and sretup information . Because of the extreme concern for reliability in this exchange , a standby PDP 11/73 was included .When not in use , the standby machine is available as a software development facility for the entire new system . These two machines were installed and commissioned approximately four months before the main shutdown when their function , operation and reliability were established prior to the main commissioning .In the main 14-day shutdown , the remaining conputer systems were brought on -line , although the AWC was given a lower priority than the AGC . The overall system configuration is shown . Functionally , the HAGC for four stands were split between two 11/73 microprocessors to give a reasonable compromise between cost and utilization . Approximately 40% of the processor capability remains unused . The roll eccentricity compensation (REC ) microprocessor can be switched to serve any one of stands F4 and F7 , whichever is seen to have the most significant eccentricity input . Afurther microprocessor could sasily be added in the future ( the REC function is described later in more detail ) . The functions of the coordinating and logging microprocessor are evident ; it organizes the data flow between the various processors on the Ethernet and analyzes , stores and points out engineering and production data . n Control system operational features AWC system -The AWC system has two functions ; l Reduce end crop losses by minimizing under-width ends .l Improve width tolerances in the body of the bar . Since the edger concerned is E4 and the bar is comparatively thin ( approximately 50 mm ) , little can be done to improve necking already created by the previous roughing /edging stands .Nevertheless , a small improvement can be expected by avoiding further worsening through stand E4/R4 . This is accomplished by preopening the edger roll gap a calculated amount and then swiftly closing onto the target width as the head end enters the edger . A similar procedure occurs at the tail end , when the gap is quickly opened a calculated amount . The loci of these fast cylinder movements (eg , linear , expontial , parabolic , etc ) can be chosen by the setup computer , as well as the required gap adjustment velocity and stroke length . Accurate tracking of the approach of the head and tail end is essential . This is achieved by special hot metal detectors coupled with bar speed measurement . In-bar width control has two modes : BISRA gagemeter , and feedforward . Although the potential for the former mode of control ( which relies on the accurate sensing of instantaneous roll force to reduce mill stretch ) was always considered limited , due to the high frictional forces relative to the low rolling loads , it was , nevertheless , investigated . It was found to be unsatisfactory for the reason stated . The feedforward mode , utilizing incoming width error variations detected by a widthmeter after stand E3/R3 , was successful . It resulted in exit width variations , measured after stand E4/R4 , within +2.0 mm for 95% of the bar length , as measured by the new widthmeter in this location . This instrument is used to give bar to bar width updating to maintain system calibration . However , it is not used for in -bar monitor feedback , because the transport distances involved are a significant proportion of the bar length . n Hydraulic AGC-The operational features included in the hydraulic AGC system can be divided into those that can be considered as conventional and those that have a novel element . Conventional AGC features include : absolute and lock-on BISRA gagementer modes for each hydraulic stand ; variable mill modulus ; oil film compensation ; draft comensation and absolute or lock-on feedback monitor . Absolute and lock-on BISRA gagemeter modes for each hydraulic stand are selectable either automatcally by the SCC or manually . The BISRA gagemeter action artificially stiffens the mill modulus . This occurs because the feedback from the measured roll foece causes the AGC cylinders to extend to compensate for mill stretch . The amount of compensation can be varied from zero ( ie , no gagemeter action ) , which leaves the mill with its natural mechanical stiffness , to 100% which , in effect , increases the mill modulus to infinity . Each hydraulic stand can be given a stiffness value ( 0 to 100% ) either from the SCC or manually . Dynamic oil film compensation is obtained by cylinder movement to correct for dynamic changes in the backup roll bearing oil-film thickness , which varies as a function of speed and roll load . Every gage correcting movement of the AGC cylinders results in a strip mass-flow change that alters the looper angle which , in turn , requests the stand speed to change . This sequence is anticipated and effectively shot circuited by direct speed trim signals sent directly from the AGC . With regard to absolute or lock-on feedback monitor ,stand F7 etit x-ray gage can be selected to back in either mode . In the former mode , the system continues to make corrections until the target gage is achieved . In the latter mode , the head-end gage is accepted and maintained consistently for the remainder of the coil . Novel AGC features include : auto-steering ; distibuted monitor feedback ; and roll eccentricity compensation . Auto-steering , in which the tendency for the strip to steer to one side as a consequence of uneven heating across its width , is opposed by the control system . The roll force difference side to side is measured and fed to a functional representation of the tilt modulus of the mill stand ( the measured mill modulus characteristic when the roll gap is tilted differentially ) . The output of this functional block represents the amount of roll stack tilt that must have taken place to cause the force difference . The correction , similar to BISRA gagemeter , then restores parallelism to the roll gap and , hance , improves strip tracking . Feedback from the exit x -ray gage to stands F4 , F5 , F6 andF7 is , in itself , conventional . However , the novel feature of this approach is that the distribution of correction is calculated to cause incremental force changes at stands F4 to F7 in direct proportion to the original roll force pattern calculated by the SCC . This minimizes the disturbance to profile and shape ( Fig .10 ) .Calculation of factors x , y and z take into account the following pattern ; required force distribution pattern ; percentage gagemeter set at each stand ; and calculated material stiffness at each stand . The eccentricity of the backup rolls and bearings can cause a significant imprint in the material being rolled , particularly with gagemeter AGC , where the mill stands behave as if they were infinitely stiff . Roll eccentricity is a complex function , generally different for top and bottom rolls , and from side to side . The resulting waveform is multivariable , changes with time and exhibits high frequency components ( up to 5th harmonic ) caused by bearing key effects . The requirements for an effective automatic roll eccentricity compensation ( REC ) system are :l Dynamic to follow the changing pattern .l Cappble of isolating and identifying top and bottom backup roll effects , and the drive side and roll change side effects (ie , 4-axis operation ) .l AGC cylinder response is sufficiently fast to respond to the REC system demands and counteract the disturbances . A block diagram of the system is shown in Fig . 11 .n Performance Early equipment reliability problems , generally associated with the high shock forces created as this high-speed mill threads and tails-out , have been resolved for the most part with minimum loss of productivity due to the ability to revert almost instantaneously to the old system The AWC system achieved its target of 95% bar length within +2 mm . AGC performance for the coil body is well within + 0.050 mm (+ 0.002 in . ) . Occasional misses at the head end are attributable to mill setup . A new scheduling and setup computer system is to be installed . Data collected over a 2-week period in March 1998 , covering approximately 3900 coils , showed that close to 96% of light gage coil lengths were within +0.035 mm (+0.00138 in . ) and that , for heavier gages (up to 6 mm ) , close to 95% of coil lengths were within +0.045 mm ( +0.00177 in . ) . ( These lengths refer to the coil lengths after exclusion of the first and last 5 metres of each coil . )n Summary The AWC and AGC systems , incorporating many new hardware and software features , with extremly exacting performance requirements , have met their objectives of improving strip quality .The potentially difficult area of interfacing with existing computer systems , while retaining their integrity , was accomplished through extensive planning and design .n 对电控带式铣床运用液压自动精度控制和宽度控制戴维斯.艾伦博士，英国谢菲尔德股份有限公司工程与建筑部门项目经理及营业主任。戴维.麦凯，英国谢菲尔德股份有限公司 。 在韩国南部浦项钢铁公司第二分公司的电控带式铣床是在1980年建造的现代的，四分之三的连续的铣床。该铣床工作台宽2050mm，能进行4次粗加工和7次精加工，其带的最大速度 21m/s ,此时的总功率为 56,000kw.限卷重量是达 35.3吨以上。 该铣床的年产量为356万吨。 为了改善加工宽度和精度公差， 浦项钢铁公司决定在尾末的修边机安装液压自动控制(HAWC)，并在精加工F4-F7处安装液压自动精度控制 (HAGC) 。 戴维.麦凯的任务是将现代化的机械系统和液压系统连接在总体机器上，利用计算机建立 AWC/AGC的控制，实现新的宽度，机械的安装,进行试车训练。 新的机器在1987年在14 天的截止期间投入使用。n 新设备的概述 一个先决条件是新的设备必须结合现有设备寻求一个方法，在很少次品的基础上运用传统操作实现反转。 因此，液压AGC和AWC气缸设计成产生失稳状态时能够抵挡正常的滚动。 所有的控制系统依靠被挑选的系统与现有系统保持平行，现有的操作员在实验台控制时,必须熟练地操作任何液压系统和机电系统。 AWC 系统包含短行程,单作用气缸设计在水平螺杆的后面与垂直滚动止动器之间，该气缸是伺服控制的,以行程速度为100毫米/s提供在缓冲地址寄存器中的宽度控制，并且实现了顶部量器和尾部刀槽的效果控制。 在粗加工实验台R3后的一些宽度量具过去习惯于给正向反馈电传送控制信号对修边机E4进行自动宽度控制，现在现行的宽度量具在粗加工设备R4后，只需要面对面地调整。 自动精度控制系统在最后4次精加工中被设为短行程，单作用气缸被定位在顶部止动器与螺杆下方的牵引轴承/载荷单元之间。这些气缸具有异常的动态性能（28Hz,速度10mm/s). 由于实际距离在修边机E4与精加工F4至F7之间，分离泵的总成装配能供应到每一个地方。液压设备需要压力为275 bar,具有3微米过滤水平的矿物油。 新的计算机配置包含在以太网总线上连接7个程序数据处理机和11/73微理器处，系统的不同的零件需要被连接在现有的计算机监督管理机构（SCC）和可编程逻辑控制器（PLC)之间的现有的64位通讯端口上。再这之上有被透视的现有通讯和高速结构（因此，现有的计算机系统包含有升温设备站）。 给自动宽度控制/自动精度控制（AGC/AWC）的必须的数据被提取，并沿着以太网总线被连续的传达给新系统。将来，如同新系统能简单地被绑到以太网上那样，这样具有给计算机系统开垦更简单的通信的优点（两三个月以后，更进一步的契约给ENCO加热保留了展示板，并且，更多11/73微处理器必须的中间机座的云状水纹被受到）。n 机械/液压的设计特点自动精度控制（AGC）气缸-自动精度控制（AGC）气缸以及它们的部件的各种零件的视图。 气缸设计为单一的整体，低摩擦的封口的聚四氟乙烯万能插孔带被悬挂在青铜下的活塞上。当气缸处于失稳状态时基准活塞被倾斜用于调节摆动曲面。在进行铣削时，反馈正常的偏差以达到所需要的自由度。 液压管被安装在每个气缸的前面，包括伺服阀。其中一个位置检测器在小型蓄力器之后稍稍可被辨别。其中一个位置检测器在其正对面作配合使用。两个信号从检测器被平均地提供平均行程信号。 检测器组件见。具有1微米分辨率的索尼magnescale 检测器被密封在黄铜体内。 第三类伺服阀被运用（穆格79系列）。第三类伺服阀有它自己的内置组合式闭合环进行位置控制。每个阀的理论额定流量为2230升/分。两个阀被配合每个气缸安装，并且被电线串联运行。在工业工程学上，相当于传动信号从最初的阀到达极限，并且远远超过第二类阀。他们具有200Hz的频响应率响应，提供给所有28Hz的气缸。气缸参数和性能数据见表I。 其动态的性能的检测是：将其安装在相当于试验设备的轧机机架装备上，在一个类似气缸上进行检验（浦项钢铁公司铣床上,直径890mm与960mm比较），伴随完全一样的检测器，伺服阀等等。钢块准确的表现了止动块和滚子的质量，给出质量弹簧在实际铣削条件下的实际表达。频率响应相当于载荷滚压的作用，。环路增益通过动力学最优化软件自动校准。 一个单作用气缸设计的固有特点是流动速率通过伺服阀被测定，因此气缸的速率说明了气缸的实际压力。在气缸的整个工作范围内，在较高和较低区域的范围内，为了防止不必要的高速率，用简单的软件规则把电传动限制在伺服阀范围内，并在延伸和收缩两个方向有效地产生稳定的，对称的速度性能。 自动宽度控制（AWC）气缸-AWC气缸具有一个有球形座的止推轴承和压入活塞。每个气缸均可以通过它附近的自身带的第三类伺服阀确定并使用。伺服阀和位置传感器可与自动精度控制（AGC）相对的部位相互交换。性能细节见表1。条 件气 缸自动精度控制（AGC）自动宽度控制（AWC）内径（mm）980350行程(mm)3050压力(bars)245275负载（吨）1850115速度(mm/s)10100频率响应(HZ)2828位置分辨率(mm)0.0010.001位置精度(mm)0.0040.004表格1失稳强度通过滚子止动器上的牵动背气压缸提供。这些气缸为了在缓冲地址寄存器的主体部分中保持稳定的，低的牵动背压强度而被进行控制，但要增加高压阀来增加推力，以获得尾部结束antinecking切口的特点。n 液压系统-液压泵的总成装配被放在润滑装置里。从F4到F7的液压制动精度控制服务系统包含为四个轴向活塞泵（三个运行设备，一个备用设备）提供275bar（4000磅/平方英寸）压力的具有重力反馈的不锈的钢油箱。 过滤部分是1公称微米（3绝对微米）通过一个网状分离泵单位供给的过滤油的冷却器/过滤器，拉制用油从油箱出来，通过冷却器/过滤器然后回到油箱。 38升的蓄电器集气管，充满氮的高压蓄电器（提供AWC和AGC气缸的暂时需要），被用来关闭每一个轧机机座。这些蓄电器尽可能被固定以达到最佳的动态性能，就象关闭他们各自的气缸一样。n 控制系统的硬件设备 浦项钢铁公司的一项主要业务是在不危害目前系统的前提下，进行新的计算机系统综合。（目前的系统持续运行，并总是象备用设备一样被利用。） 在现有的计算机监督管理机构（SCC）和可编程序逻辑控制器（PLC）之间的64位并行接口使制器丝杠制动精度控制（AGC）不能被扩大或者复制。 解决的办法是在计算机监督管理机构（SCC）和可编程序逻辑控制器（PLC）之间插入一个带有标准数字输入/输出（I/O）设备的程序数据处理机（PDP）11/73，以达到通讯连接的效果（图9）。它的功能很简单。从SCC读入数据作为64位数据，把它存储在存储器，并立即将同样的输出数据再一次传递出去，到达PLC。当数据被转达SCC的时候，发生相同的交换返回命令。每一次程序处理，64位数据为分布给新设备的余项被解码并转换成串行形式。这样的数据将包含所有的输出数据（PDI）和准备资料。 由于在这个转换里对可靠性极端关心，所以包含了一个备用PDP11/73。 当没有机器在使用中时，备用机器象软件开发工具那样可以用于全部新系统。 在主线停机前大约4个月，在它们的功能，操作和可靠性被确定前，这两台机器被安装进行主线试运转。 在主线14天的停机时间里，剩余的计算机系统被拿来联机，尽管AWC得到比AGC低的优先权。全部的系统配置见图9。 功能上，供给4站的HAGC在2台11/73微处理器之间被分开，为了给出在成本和利用之间的合理损害。处理机能力的大致40保持尚未使用。 卷偏心补尝（REC）的微处理器为了服务于任何一个F4和F7站，被看见把最有效偏心输入的任何一个进行转换，在将来，更进一步的微处理器能简单的被加（REC功能上的更多细节晚一会儿会描述）。 配位和记录微处理器的功能是很明显的；它组成以太网上的各种处理机之间的数据流，并分析，储备，指出设计和生产数据。n 控制系统操作特点
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