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英文原文
Electrical Winch Controls
by Tom Young
The form of motor control we all know best is the simple manual station with up and down pushbuttons. While these stations may still be the perfect choice for certain applications， a dizzying array of more sophisticated controls is also available. This article addresses the basic electrical requirements of the motors and user interface issues you will need to address before spcifying， building or buying winch controls.
begin with， the manual control stations should be of the hold-to-run type， so that if you take your finger off of the button the winch stops. Additionally， every control station needs an emergency stop (E-stop) that kills all power to the winch， not just the control circuit. Think about it—if the winch isn’t stopping when it should， you really need a failsafe way to kill the line power. It’s also a great idea to have a key operated switch on control stations， especially where access to the stations is not controlled.
Safe operation by authorized personnel must be considered when designing even the simplest manual controls.
Controlling Fixed Speed Motors
The actual controlling device for a fixed speed winch is a three phase reversing starter. The motor is reversed by simply switching the phase sequence from ABC to CBA. This is accomplished by two three-pole contactors， interlocked， so they can’t both be closed at the same time. The NEC requires both overload and short circuit protection. To protect the motor from overheating due to mechanical overloads a thermal overload relay is built into the starter. This has bi-metallic strips that match the heating pattern of the motor and trips contacts when they overheat. Alternatively， a thermistor can be mounted in the motor winding to monitor the motor temperature. Short circuit protection is generally provided by fuses rated for use with motors.
A separate line contactor should be provided ahead of the reversing contactor for redundancy. This contactor is controlled by the safety circuits: E-stop and overtravel limits.
This brings us to limit switches. When you get to the normal end of travel limit the winch stops and you can only move it in the opposite direction (away from the limit). There also needs to be an overtravel limit in case， due to an electrical or mechanical problem， the winch runs past the normal limit. If you hit an overtravel limit the line contactor opens so there is no way to drive off of
the limits. If this occurs， a competent technician needs to fix the problem that resulted in hitting the overtravel limit. Then， you can override the overtravels using the spring return toggle switch inside the starter—as opposed to using jumpers or hand shooting the contactors.
Variable Speed Requirements
Of course， the simple fixed speed starter gets replaced with a variable speed drive. Here’s where things start to get interesting! At the very least you need to add a speed pot to the control station. A joystick is a better operator interface， as it gives you a more intuitive control of the moving piece.
Unfortunately， you can’t just order any old variable speed drive from your local supplier and expect it to raise and lower equipment safely and reliably over kids on stage. Most variable speed drives won’t， as they aren’t designed for lifting. The drive needs to be set up so that torque is developed at the motor before the brake is released， and (when stopping) the brake is set before torque is taken away.
For many years DC motors and drives provided a popular solution as they allowed for good torque at all speeds. The large DC motors required for most winches are expensive， costing many times what a comparable AC motor costs. However， the early AC drives were not very useful， as they had a very limited speed range and produced low torque at low speeds. More recently， as the AC drives improved， the low cost and plentiful availability of AC motors resulted in a transition to AC drives.
There are two families of variable speed AC drives. Variable frequency inverters are well known and readily available. These drives convert AC to DC， then convert it
back to AC with a different frequency. If the drive produces 30 Hz， a normal 60 Hz motor will run at half speed. In theory this is great， but in reality there are a couple of problems. First， a typical 60 Hz motor gets confused at a line frequency below 2 or 3 Hz， and starts to cog (jerk and sputter)， or just stops. This limits you to a speed range of as low as 20:1—hardly suitable for subtle effects on stage! Second， many lower cost inverters are also incapable of providing full torque at low speeds. Employing such drives can result in jerky moves， or a complete failure to lift the piece—exactly what you don’t want to see when you are trying to start smoothly lifting a scenic element. Some of the newer inverters are closed loop (obtain feedback from the motor to provide more accurate speed control) and will work quite well.
The other family of AC drives is flux vector drives. These units require an encoder mounted on the motor shaft allowing the drive to precisely monitor the rotation of the armature. A processor determines the exact vector of magnetic flux (thus flux vector drive) required to rotate the armature the next few degrees at a given speed. These drives allow an infinite speed range， as you can actually produce full torque at zero speed. The precise speed and position control offered by these drives make them a favorite in high performance applications.
PLC-based controls provide system status as well as control options. This screen give the operator full access to Carnegie Hall’s nine stage floor lifts.
PLC Based Systems
A PLC is a programmable logic controller. First developed to replace the relay based industrial control systems of the ’50s and ’60s， these controls are at home in rugged， industrial environments. These are modular systems with a great variety of I/O modules allowing semi-custom hardware configurations to be assembled easily at a reasonable price. These include position control modules， counters， A/D and D/A converters and all sorts of solid state or hard contact closure outputs. The great variety of I/O components and the modular nature of the PLC make this an effective way to build custom and semi-custom control systems.
The greatest drawback to PLC systems is the lack of really great displays to tell you what they are doing or to help you program them. Monochrome and medium resolution color displays are the norm， as the primary use for these components in on a factory floor.
One of the first major PLC systems used in a large entertainment venue is the complex lift and wagon system at the original MGM Grand (now Bally’s) in Las Vegas. Several manufacturers offer standard PLC-based systems and a host of semi-custom acoustic banner， shell， and lift control systems is also available. The ability to build custom systems from standard building blocks is the greatest strength of PLC-based controls.
High End Controllers
The most sophisticated rigging controllers go well beyond speed， time， and position control. They include the ability to write complex cues， record profiled moves， and manage multiple cues running at once.
Many of the larger opera houses are moving toward point hoist systems， where there is a separate winch for each lift line (the rigging equivalent of dimmer per cir cuit). When multiple winches are used to carry a single piece， the winches must be perfectly synchronized， or the load can shift so that an individual winch can become dangerously overloaded. The control system must be able to keep selected winches in synch or provide a rapid， coordinated stop if a winch is unable to stay in synch with the others. With a typical top speed of of each other 240 fpm and a requirement to keep the winches within a 1/8″， you have less than three milliseconds to recognize a problem， attempt to correct the errant winch’s speed， determine that you’ve failed and initiate a coordinated stop of all the winches in the group. This takes a lot of computing， fast I/O， and well-written software.
There are two very different approaches to large rigging control systems. Originally， a single console was used， with the usual problem of where it should be located for the operator’s optimum view. Unfortunately this can change not only from show to show， but also from one cue to the next. This dilemma has been partially addressed by using video cameras at different locations in conjunction with 3D screen graphics that allow the operator to view the expected rigging motion three dimensionally from any viewpoint. This allows the operator to view the on screen movement of the rigging from a viewpoint that matches his actual view of the stage， or the actual view of a closed circuit camera. For complex moves with inter-related pieces this makes the control and understanding of what is happening much simpler.
The other approach is a distributed system， with several portable consoles. This allows different operators to control different aspects of the rigging， in the same manner we have done with manual sets. A dramatic example of this approach is used by the Royal Opera at Covent Garden， where there are ten consoles controlling a total of 240 motors. Each console has five playbacks， and is set up so that each motor is assigned to a single console. One operator and console could control everything， but frequently one console may be running stage lifts， another the onstage rigging， and a third is being used backstage to move stored drops.
Cutting-edge portable consoles allow multiple operators to control the action from the best vantage points and provide 3D displays.
Reprinted from PROTOCOL， the Journal of the Entertainment Services and Technology Association (www.esta.org) Fall 2003 issue. ?2003 ESTA.
Conclusion
The tremendous variety of rigging control systems currently available ranges from the pushbutton station to complex multi-user computerized control system. When shopping for rigging control systems you generally get what you pay for. The most important features are safety and reliability. These are features with real value， and you should expect to pay a fair price for this security. Work with an established manufacturer who can show you working installations and who will put you in contact with users who have requirements similar to yours.
中文譯文
電力絞車的控制
對(duì)于電動(dòng)機(jī)的控制，我們所知道的最好的方式就是使用由許多點(diǎn)動(dòng)式按鈕組成的簡(jiǎn)單的手工操作臺(tái)。而這種操作臺(tái)在某些應(yīng)用方面可能仍然是個(gè)不錯(cuò)的選擇，如一些令人頭痛的復(fù)雜的控制也可以用。這篇文章講述了，在你設(shè)計(jì)、組建或是購買絞車控制器之前，你必須對(duì)電動(dòng)機(jī)的基本電氣設(shè)備和你將需要尋址的用戶接口命令進(jìn)行編址。
首先，手動(dòng)控制臺(tái)應(yīng)該是手動(dòng)控制型的，因此，如果你把你的手指移開按鈕，絞車就會(huì)停車。另外，每個(gè)控制工作站都需要配備緊急制動(dòng)閘，緊急制動(dòng)閘可以切斷絞車的所有電源，而不僅僅是控制電路的。仔細(xì)想想看，如果絞車在該停車時(shí)，它卻沒有停下來，你就確實(shí)需要一種故障保障的方法去切斷線路的電源。在控制工作臺(tái)上設(shè)置一個(gè)關(guān)鍵操作開關(guān)，也是一個(gè)非常好的主意，特別是在通向工作站的線路不能控制時(shí)，就可以用那個(gè)開關(guān)來控制。
(在設(shè)計(jì)控制臺(tái)時(shí)，即使是最簡(jiǎn)單的手工控制臺(tái)，也要考慮設(shè)置由專門人員操作的安全操作按鍵。)
控制定速電動(dòng)機(jī)
對(duì)于一臺(tái)定速絞車的實(shí)際控制設(shè)備是一臺(tái)三相起動(dòng)器。電動(dòng)機(jī)的轉(zhuǎn)向被反向，是通過簡(jiǎn)單的開關(guān)控制相序從A-B-C變換到C-B-A。這些動(dòng)作被完成，是通過兩個(gè)三磁極式電流接觸器，而且它們是互鎖的，所以，它們不可能被同時(shí)關(guān)閉。NEC公司要求同時(shí)擁有過載和短路保護(hù)裝置。為了保護(hù)電動(dòng)機(jī)免受由于機(jī)械過載引起的過熱的影響，在起動(dòng)器內(nèi)要安裝熱量過載延遲裝置。當(dāng)熱量過載延遲裝置過熱時(shí)，它所擁有的雙金屬長(zhǎng)條斷開電動(dòng)機(jī)的電源。除此外，還可以選擇一臺(tái)電熱調(diào)節(jié)器可以用纏繞的方式安裝在電動(dòng)機(jī)上，它可以用于監(jiān)控電動(dòng)機(jī)的溫度變化。對(duì)于短路保護(hù)，我們一般是通過電動(dòng)機(jī)常用的熔斷器來實(shí)現(xiàn)的。
一臺(tái)獨(dú)立的線性電流接觸器，被配置的電流接觸器應(yīng)該超過主回路的電流接觸器，從而達(dá)到冗余的目的。這臺(tái)電流接觸器是由安全電路來控制的，如：緊急制動(dòng)和越程極限。
我們可以使用限位開關(guān)來實(shí)現(xiàn)上述的操作。當(dāng)你到達(dá)正常的行程極限位置末端時(shí)，絞車就會(huì)停車，并且你只能夠向相反的方向移動(dòng)絞車(即遠(yuǎn)離極限位置的方向)。這里也需要一個(gè)越程限制以防萬一，由于電氣的或者機(jī)械的問題，而使絞車的運(yùn)行超過正常的極限位。如果你碰到越程限制器，線形電流接觸器就會(huì)打開，因此，絞車將無法被驅(qū)動(dòng)超過這個(gè)極限位置。如果上述情況發(fā)生，就需要請(qǐng)專業(yè)的技術(shù)人員來檢查導(dǎo)致碰到越程限制器的具體原因。然后，你就能夠用起動(dòng)器內(nèi)部的彈力恢復(fù)撥動(dòng)開關(guān)來處理越程的問題，而不是使用跳閘器或是手工切斷電流接觸器。
變速的必要條件
當(dāng)然，簡(jiǎn)單的定速起動(dòng)器被變速驅(qū)動(dòng)器所取代。這就使事情開始變得有趣起來了！至少，你需要在控制操作臺(tái)上增加一個(gè)速度表盤。操縱桿是一個(gè)較好的操作接口，由于它使你對(duì)部件的移動(dòng)有一個(gè)更直觀的控制。
不幸的是，你不能僅僅從你的本地控制臺(tái)去發(fā)命令控制老式的變速驅(qū)動(dòng)器，此外，你不能希望它在初始階段，就能安全而可靠的提升與下放設(shè)備。大多數(shù)的變速驅(qū)動(dòng)器不能實(shí)現(xiàn)上述的要求，因?yàn)樗鼈儾⒉皇窃O(shè)計(jì)用來做提升工作的。驅(qū)動(dòng)器需要設(shè)置成在制動(dòng)器松開之前，就能夠在電動(dòng)機(jī)上產(chǎn)生扭矩，并且，當(dāng)停車時(shí)，即在扭矩撤銷之前，制動(dòng)器將先動(dòng)作。
許多年來，直流電動(dòng)機(jī)和驅(qū)動(dòng)器提供了一些普遍的解決方案，如它們?cè)诟鞣N速度時(shí)都具有良好的力矩特性。對(duì)于大多數(shù)的絞車所需求的大型直流電動(dòng)機(jī)是很貴的，那要比同類型的交流電動(dòng)機(jī)貴得多。雖然，早期的交流驅(qū)動(dòng)器不是非常有用，如它們有一個(gè)非常有限速度適用范圍，而且僅產(chǎn)生低速小扭矩。如今，隨著直流驅(qū)動(dòng)器的發(fā)展，低成本而且大量可用的交流電動(dòng)機(jī)的出現(xiàn)，導(dǎo)致了一場(chǎng)交流驅(qū)動(dòng)的革命。
變速交流驅(qū)動(dòng)器有兩個(gè)系列。變頻轉(zhuǎn)換器已經(jīng)家喻戶曉，而且的確很容易使用。這些驅(qū)動(dòng)器將交流轉(zhuǎn)換成直流，然后，再把它轉(zhuǎn)換回交流，轉(zhuǎn)換后的交流已經(jīng)是不同頻率的。如果驅(qū)動(dòng)器產(chǎn)生30Hz的交流，一臺(tái)正常的60Hz的電動(dòng)機(jī)將以一半的速度運(yùn)行。從理論上說，這非常好，但是，在實(shí)際中，這將會(huì)有很多的問題。首先，一臺(tái)典型的60Hz的電動(dòng)機(jī)在線性頻率低于2Hz或是3Hz的區(qū)域會(huì)出現(xiàn)誤差，并且，開始嵌齒(即急推，猛拉)，或是停車。這將限制你的速度范圍低于20：1，幾乎不適應(yīng)于運(yùn)行階段的細(xì)微調(diào)節(jié)。其次，許多低成本的轉(zhuǎn)換器也不能夠在低速時(shí)提供額定扭矩。使用這些驅(qū)動(dòng)器，將導(dǎo)致急速移動(dòng)，或是對(duì)于提升部件完全的失效，準(zhǔn)確地說，當(dāng)你試圖去平穩(wěn)的提升一臺(tái)科學(xué)儀器時(shí)，你不愿看到這樣的情況。一些新型的變極器是閉環(huán)系統(tǒng)(從電動(dòng)機(jī)獲得反饋，提供更加準(zhǔn)確的速度控制)，并且使電動(dòng)機(jī)將會(huì)工作的相當(dāng)好。
交流驅(qū)動(dòng)器的另一個(gè)系列是流量矢量型驅(qū)動(dòng)器。這些元器件要求在電動(dòng)機(jī)的主軸上安裝編碼器，使用這些編碼器會(huì)使驅(qū)動(dòng)器可以準(zhǔn)確地監(jiān)控電機(jī)電樞的旋轉(zhuǎn)。處理器測(cè)定了準(zhǔn)確的磁性流量的矢量值，這些值要求使電樞在給定的速度下旋轉(zhuǎn)。這些驅(qū)動(dòng)器允許有無窮大的速度，因此，你實(shí)際能夠在零速度時(shí)就產(chǎn)生額定扭矩。這些驅(qū)動(dòng)器所提供的準(zhǔn)確的速度和位置的控制，使這些驅(qū)動(dòng)器在高性能應(yīng)用方面受到歡迎。
(基于PLC的控制器提供有系統(tǒng)狀態(tài)和控制選項(xiàng)。這個(gè)屏幕展示給操作者全面的訪問卡內(nèi)基霍爾德的九層電梯提升的控制面板。)
基于PLC的系統(tǒng)
一臺(tái)PLC的全稱是可編程序邏輯控制器。首先，PLC的控制器發(fā)展到取代了基于五六十年代的工業(yè)控制系統(tǒng)的繼電器，它們工作在室內(nèi)的惡劣的工業(yè)環(huán)境中。這些是模塊化的系統(tǒng)，它們具有大量的各種各樣的I/O模塊。這些模塊化的系統(tǒng)可以很容易的實(shí)現(xiàn)把半自定義的硬件配置組裝起來，而這樣得到的配置的價(jià)錢也很合理。這些模塊包括：位置控制模塊，計(jì)數(shù)器，A/D和D/A轉(zhuǎn)換器，以及各種實(shí)體狀態(tài)或是物理接觸閉式輸出模塊。大量不同類型的I/O元器件和PLC的模塊屬性使得它成為一條有效的途徑去組裝自定義和半自定義的控制系統(tǒng)。
對(duì)于PLC系統(tǒng)的最大的不足就是缺少真實(shí)的大量的顯示功能，從而告訴你PLC正在做什么和幫助你對(duì)PLC進(jìn)行編程。
第一臺(tái)被用于大型娛樂場(chǎng)所的專業(yè)的PLC系統(tǒng)之一，是在拉斯維加斯的原米高梅電影制片公司(現(xiàn)在的貝利公司)的搭車和四輪馬車系統(tǒng)上。許多的制造商提供了標(biāo)準(zhǔn)的基于PLC的系統(tǒng)和半自動(dòng)化聲學(xué)的標(biāo)志的主機(jī)，設(shè)定命令行解釋器的位置，以及提升控制系統(tǒng)也是可用的。使用標(biāo)準(zhǔn)的模塊去組構(gòu)用戶自定義系統(tǒng)的能力是基于PLC的控制器的最大的優(yōu)勢(shì)。
高端控制器
對(duì)于復(fù)雜的傳動(dòng)裝置，控制器開始變得復(fù)雜，超過了速度，時(shí)間以及位置控制。它們包括寫出復(fù)雜的指令，記錄輪廓線的移動(dòng)，以及處理可以立即運(yùn)行的多點(diǎn)指令的能力。
許多大型的歌劇院正向著點(diǎn)提升系統(tǒng)的方向發(fā)展，在那里為每一條提升繩索配置有一臺(tái)獨(dú)立的絞車，那些繩索等同于每條電路的調(diào)光器。當(dāng)多臺(tái)絞車被用來提升單個(gè)的部分時(shí)，這些絞車必須完全的同步，或是載荷能夠轉(zhuǎn)移，如此會(huì)導(dǎo)致一臺(tái)單獨(dú)的絞車變得有過載的危險(xiǎn)?？刂葡到y(tǒng)必須能夠使被選的絞車保持同步，或是在一臺(tái)絞車不能夠保持與其他絞車同步時(shí)，能提供高速的同等的停車能力。對(duì)于一臺(tái)典型的高速達(dá)240英尺/分鐘和一臺(tái)要保持絞車的彼此間的速度誤差在1/8分之內(nèi)的設(shè)備，你只有少于三微秒的時(shí)間去確認(rèn)問題，并嘗試糾正錯(cuò)誤的絞車速度，在確定你失敗后，你起動(dòng)組中所有絞車的停車。這將需要大量計(jì)算，快速I/O接口，以及好用的寫入軟件。
對(duì)于大型的繩索控制系統(tǒng)有兩種非常不同的解決方法。首先是，使用單獨(dú)的控制臺(tái)，對(duì)于一般的問題而言，這樣的控制臺(tái)應(yīng)該安裝在適合于操作者視角的位置。然而，這不僅不能夠從一個(gè)角度到另一個(gè)角度觀察，而且還不可以從一條指令到另一條指令的控制。這些困難已經(jīng)被部分解決。通過使用安裝在不同位置的視頻攝像機(jī)，而且這些攝象機(jī)連接于三維屏幕圖形，這些圖形使得操作者可以從任意的視角去觀察在三個(gè)坐標(biāo)方向上的預(yù)期的繩索運(yùn)動(dòng)。這些可以使得操作者，從一個(gè)適合他在實(shí)際的操作臺(tái)處的視角，或是實(shí)際的閉環(huán)電路照相機(jī)的視角，來觀察在屏幕上的繩索的運(yùn)動(dòng)。對(duì)于有內(nèi)部關(guān)聯(lián)的部件的復(fù)雜的移動(dòng)，上述的觀察使得實(shí)現(xiàn)控制和查出故障原因變得更加簡(jiǎn)單。
另一個(gè)解決的方案就是分布式系統(tǒng)，這個(gè)系統(tǒng)使用了多個(gè)輕便的控制臺(tái)。這將允許不同的操作者以同樣的方式控制傳動(dòng)裝置的不同方面，我們已經(jīng)改進(jìn)了手動(dòng)控制裝置。一個(gè)生動(dòng)的例子，就是在倫敦中部一個(gè)蔬菜花卉市場(chǎng)的皇家歌劇院使用了上述的方案，在那里用十個(gè)控制臺(tái)控制著240臺(tái)電動(dòng)機(jī)。每個(gè)控制臺(tái)有五個(gè)錄音重放裝置，并且已經(jīng)被開啟，以便于每臺(tái)電動(dòng)機(jī)被指派給一個(gè)單獨(dú)的控制臺(tái)。一位操作者和一個(gè)控制臺(tái)就能夠控制所有的裝置，但是，常常是一個(gè)控制臺(tái)可能是運(yùn)行臺(tái)幕的提升，另一個(gè)控制臺(tái)是控制臺(tái)上的傳動(dòng)裝置，以及第三個(gè)控制臺(tái)被用來在后臺(tái)將必要的背景畫面放下。
(刃口式輕便的控制臺(tái)允許多位操作者從最優(yōu)點(diǎn)出發(fā)來控制機(jī)器的運(yùn)動(dòng)，并且提供三維圖象的顯示。)
結(jié)論
有巨大變化的繩索控制系統(tǒng)，已經(jīng)從按鈕式的工作站發(fā)展到復(fù)雜的多用戶的計(jì)算機(jī)化的控制系統(tǒng)。當(dāng)要購買繩索控制系統(tǒng)時(shí)，你總是可以找到滿足你需要的?？刂葡到y(tǒng)最重要的性能是安全性和可靠性。這些是有真實(shí)價(jià)值的性能，而且你會(huì)期望能以一個(gè)合適的價(jià)格買到這樣的安全性。與某個(gè)確定的產(chǎn)品制造商共事，他會(huì)使你知道如何進(jìn)行安裝。而且，他將會(huì)讓你和用戶接觸，那些用戶有著與類似的要求。
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