外文翻譯--改善電磁閥和液力偶合器的控制

1、<p><b>　　中文2467字</b></p><p><b>　　附錄A 譯文</b></p><p>　　改善電磁閥和液力偶合器的控制</p><p><b>　　摘要</b></p><p>　　本文針對一個電磁閥連接的液力偶合器的操作法，是一種新、改善的控

2、制方法。通過輸送機動力學(xué)模擬對該方法進(jìn)行了驗證，在本文將介紹驗證結(jié)果。</p><p><b>　　1 介紹</b></p><p>　　液力偶合器是自1987 年在南非被用在處理大塊固體生產(chǎn)上。但是, 最初的高期望未被履行, 主要由于缺乏對控制系統(tǒng)聯(lián)結(jié)的限制的理解的一些應(yīng)用。液力偶合器能通過各種各樣的方式完成它的性能[1]，并且對工程師來說是扣人心弦工作，因為唯一的

3、限制也許是某人的假想。扭矩控制最常見的方法依靠電磁閥，電磁閥啟動并在被預(yù)先確定的極限內(nèi)由PLC 系統(tǒng)監(jiān)督整體性能。扭矩特征曲線呈鋸牙樣式。上部和下部的扭矩極限依照具體要求確定。</p><p>　　在多數(shù)場合這個技術(shù)是滿足的, 然而, 有不希望的副作用的源頭譬如那些與所謂的“抨擊”控制技術(shù)相關(guān)的。盡管這些困難, 但電磁閥是一種有效耐用的設(shè)備, 也適合原材料處理產(chǎn)業(yè)的環(huán)境。</p><p>

4、　　隨后人們企圖運用這個具體設(shè)備挖掘它的全部潛能，并在期間用一臺輸送機的改善的控制技術(shù)研制一個適當(dāng)?shù)目刂葡到y(tǒng)。</p><p><b>　　2 背景知識</b></p><p>　　經(jīng)過一段時間研究，我們采用控制參量調(diào)整分離開關(guān)實現(xiàn)連續(xù)控制，在電子學(xué)和農(nóng)業(yè)領(lǐng)域執(zhí)行試驗并且在區(qū)域內(nèi)通過遞象開關(guān)方式實施系統(tǒng)。PUTTER 和Gouws[2]方法，保持相互依賴的參量是可能的

5、，譬如在溫室里使用通過風(fēng)扇、加熱器和噴水隆頭的分離行動使溫度和濕氣保持平衡。當(dāng)接受溫室里高變化動力學(xué)差異時, 對電磁閥和液力偶合器的應(yīng)用開發(fā)和研究一個相似的概念是有意思的。</p><p>　　2.1 控制系統(tǒng)算法</p><p>　　近年來，控制系統(tǒng)在現(xiàn)代控制技術(shù)上應(yīng)用有許多種, 譬如模糊邏輯控制[4] 、神經(jīng)網(wǎng)絡(luò)[5]，它是作為對非線性和多變量控制問題的解決辦法。盡管所有成功例子, 許

6、多典型的技術(shù), 譬如比例-積分-導(dǎo)數(shù)(PID)控制。PID控制比智能控制技術(shù)的優(yōu)勢是少處理器容量和所需時間。但是, 雖然已解決一些問題[6], 但PID 控制器仍然保留一個難題, 尤其是在系統(tǒng)中有不可接受的實驗錯誤方法。PID控制的缺點是調(diào)節(jié)系統(tǒng)非線形性能力受限制。</p><p>　　電磁閥和液體偶合器組合應(yīng)用PID控制技術(shù)。通過控制閥門的開關(guān), 電動機/連軸器扭矩能保持不變。系統(tǒng)失效時間是足夠短的，但對系統(tǒng)非

7、線形性調(diào)節(jié)不明顯, 在這些情況下，可應(yīng)用PID控制技術(shù)，描述控制等式得如下[7]：</p><p><b>　　（1-1）</b></p><p>　　E —誤差，區(qū)別在凝固點和被觀察的價值之間；</p><p>　　T —所需扭矩變動量[Nm]；</p><p><b>　　Kc —比例增量；</b&g

8、t;</p><p>　　Td —派生導(dǎo)數(shù)時間常數(shù)[s]；</p><p>　　Tj —累積時間常數(shù)[s]；</p><p>　　Ts —樣品時間常數(shù)[s]；</p><p><b>　　n —樣品數(shù)字；</b></p><p>　　公式1-1與常規(guī)PID方法相反，它相對于當(dāng)前的扭矩(△T)確定所

9、需變化量。這是一種快而方便的確定輸出量的方式, 因為沒有數(shù)字微分或積分。</p><p>　　數(shù)字n 是當(dāng)前的測量誤差, n - 1是早先測量，n - 2是n-1的前一個。測量間的時間是重要的。太短的采樣時間能引起設(shè)備過分循環(huán), 而太長采樣的時間能引起超載和不穩(wěn)定[8]。常數(shù)Kc、Tj、Td最初根據(jù)知名的ZIEGLER-NICHOLS方法在理論上確定[6]。在控制器的性能上這些常數(shù)的每個作用用史密斯描述了[3],

10、 被總結(jié)如下[7]：</p><p>　　Kc值小產(chǎn)生超載現(xiàn)象但穩(wěn)定性好, 但當(dāng)Kc值大時減少超載現(xiàn)象但增加設(shè)備循環(huán)。</p><p>　　Tj值小消除恒定值誤差, 但導(dǎo)致控制設(shè)備迅速循環(huán)。反過來, Tj 值大導(dǎo)致產(chǎn)生恒定誤差。</p><p>　　Td值小導(dǎo)致超載大, 當(dāng)Td值大提高反應(yīng)時間時, 導(dǎo)致穩(wěn)定性提高。</p><p>　　雖然閥

11、門只能關(guān)起, 但如果通過控制開關(guān)開啟、停滯時間的線性地變化的閥來控制開關(guān)是可能的。公式1-2，△T被轉(zhuǎn)換成使用率, 被定義如下：</p><p><b>　　使用率：</b></p><p>　　△T = （1-2）</p><p>　　—交換閥門的時間() [s]；</p><

12、;p>　　—各樣品間在一時間間隔期間閥門交換的最大時間的時間(tmax = )[s]；</p><p>　　實際上，轉(zhuǎn)換能以不同方式完成，涉及△T與閥門操作的時間之間從一個簡單的比例關(guān)系到一相當(dāng)復(fù)雜關(guān)系，其中要考慮扭矩/油流量變化率。假想的發(fā)展或者選擇通過幾個因素治理，其中由軟件控制和硬件限制的簡單化是二個最明顯部分的。</p><p>　　對于這種具體應(yīng)用，閥門交換每秒不可以超過5

13、次或5赫茲。最大工作循環(huán)(tmax)的最佳值要根據(jù)指定的標(biāo)準(zhǔn)或動態(tài)模仿實驗經(jīng)反復(fù)試驗確定。</p><p>　　機模擬實驗校核改善概念的性能：測試概念并通過輸送機模擬校核。第一套由計算機編程建造的輸送機模型是以兩年之前用這種材料的詳細(xì)設(shè)計而研制的。輸送機是通過液力偶合器驅(qū)動，它連接著三項換向閥。有關(guān)系統(tǒng)和輸送機的詳細(xì)的信息可能都來自[9]。偶合器的應(yīng)用指標(biāo)與在[11]中描述的差不多，比如在南非很有代表性的那種液力

14、偶合器。</p><p>　　在重要的零件圖中，需要分析啟動階段的轉(zhuǎn)矩。合格的運行結(jié)果是通過調(diào)節(jié)運行周期和控制設(shè)置來實現(xiàn)的。這樣可以進(jìn)一步探索啟動階段速度。為了完成進(jìn)一步的研究工作，制作的模型將拓展到輸送機的高配置的動力裝置。在這張圖表上涉及到了8.5m長帶有頂部和尾部驅(qū)動裝置的輸送機。盡管是帶有鏟斗的系統(tǒng)操作，但是在這些模擬裝置中輸送機的模型是與液力偶合器連接在單向閥口處。</p><p&g

15、t;　　2.2 輸送機動態(tài)模型的結(jié)果</p><p>　　3.3km長鋼絲輸送機扭矩率116.0Nm/s，在開始階段描繪的圖的坡度大，尤其在泵剛工作的前6秒之間。從而，大約延遲12秒后，控制系統(tǒng)開始啟動，存在兩個問題：</p><p>　　1）最初，低扭矩傳輸不允許輸送機機立即加速度，但通過軟件的調(diào)整這種情況就可以，正如模擬實驗的那樣，注意速度變化和控制開始的時間不少于在電機啟動后的8秒，

16、雙向泵啟動后的6秒。</p><p>　　2）油從偶合器卸荷的速度是有限的，也許不夠抵制輸送機機的動態(tài)反應(yīng)，因此，在開始的初始階段注意某種的程度超速。</p><p>　　盡管已提出一些問題，但啟動開始速度的變化的情況比希望從控制操作的分散模塊上解決問題更有深遠(yuǎn)意義。</p><p>　　進(jìn)一步測試, 運用不同的速度曲線或者控制常數(shù)能得到更好的結(jié)果。</p&g

17、t;<p>　　整體的結(jié)果是合理的，但是，值得注意是在某種程度上尾部驅(qū)動比頭部的性能好。</p><p>　　對于每個驅(qū)動裝置，在開始的12秒到22秒之間提高扭矩或者張力是可行的，再一次調(diào)整設(shè)備或者工作因數(shù)，能改善結(jié)果。</p><p><b>　　3 結(jié)論</b></p><p>　　基于模擬的結(jié)果能得一下結(jié)果：</p&g

18、t;<p>　　1）電磁閥的控制概念在很大程度上已實現(xiàn)，把閥的分散運動變成精確的、連續(xù)的輸出是可能的。</p><p>　　2）新系統(tǒng)允許電磁閥的應(yīng)用可根據(jù)原策略的速度，然而，對于扭矩來說控制可能不精確，尤其在開始啟動階段。</p><p>　　3）保證控制參數(shù)的優(yōu)化，模擬實驗的結(jié)果表示選擇不當(dāng)?shù)目刂茀?shù)會導(dǎo)致不好的性能結(jié)果。</p><p>　　4）

19、如所示，這個概念能被應(yīng)用于中長型輸送機中，尾部驅(qū)動不易限制，然而，在這種情況上，只有對開始的扭矩進(jìn)行測試。</p><p>　　5）PID控制是傳統(tǒng)的控制技術(shù)，它廣泛應(yīng)用于加工工業(yè)中，并能解決不同的控制問題。</p><p><b>　　附錄B 外文文獻(xiàn)</b></p><p>　　Improved control of a solenoid

20、valve and drain coupling</p><p><b>　　Summary</b></p><p>　　The paper looks at a new, improved control concept for a fluid coupling operating in conjunction with a solenoid valve.<

21、/p><p>　　Verification of the method has been done by means of conveyor dynamic simulations and some of the results are presented in the paper.</p><p>　　1.Introduction</p><p>　　Drain

22、 fluid couplings have been available in South Africa since 1987 and have found acceptance in the bulk solids handling industry. However, initial high expectations have not always been fulfilled, mainly due to some appl

23、ications which showed a lack of understanding of the coupling’s limits of performance and/or deficient control systems. The drain coupling can be assisted in its performance by various means [1] and in this respect is e

24、xciting to work with for an engineer, as the only limit</p><p>　　This technique is sufficient in most instances, but, however, may be the source of undesirable side effects such as those associated with so

25、called “bang-bang” control techniques. Despite these difficulties, the solenoid valve remains a cost effective and robust device, well suited to the environment of materials handling industry.</p><p>　　Subse

26、quently an attempt has been made to utilize this specific device to its full potential and to develop a suitable control system which would allow improved control of a conveyor during start up.</p><p>　　2.

27、 Background Information</p><p>　　For some time research has been performed into continuous control by means of discrete on/off adjustment of control parameters. Trials were performed and systems implemented

28、 in areas as far afield from bulk solid handing as switch mode power electronics and agriculture. As an example of the potential of this approach PUTTER and Gouws [2] stated that it was possible to maintain a pre-determi

29、ned level of interdependent parameters such as temperature and humidity in a greenhouse by means of disc</p><p>　　2.1 Control System Algorithm</p><p>　　The control system arena has, in recent

30、years, been filled with publications on modern control techniques, such as fuzzy logic control [4] and neural networks [5] as solutions to non-linear and multi-variable control problems. Despite all the success stories,

31、 more classical techniques, such as Proportional-Integral-Derivative Control (PID). An advantage of PID-control, is that less processor capacity and time is required, than with the intelligent control techniques. Howev

32、er, even though many</p><p>　　The solenoid valve and drain coupling combination lends itself to the application of PID control. By controlling the switching of the valve, the motor/coupling torque could mai

33、ntain a pre-determined pattern. The system dead time is short enough not to contribute significantly to system non-linearity, in which case PID-control may be applied. The control equation is described as follows [7]:<

34、;/p><p><b>　　[1]</b></p><p><b>　　where:</b></p><p>　　E -error, difference between set point and observed value</p><p>　　T- required torque change

35、[Nm]</p><p>　　Kc -proportional gain </p><p>　　Td- derivative time constant [s]</p><p>　　Tj- integral time constant [s]</p><p>　　Ts- sample time constant [s]</p>

36、<p>　　n- sample number.</p><p>　　Contrary to the conventional PID approach Eq. (1) determines the change required relative to the current torque (△T) and not the amount of torque required as a functio

37、n of the error. This is a quicker and more convenient way to determine the output, since no numeric integration or differentiation is required.</p><p>　　The number n refers to the current error measurement,

38、n –1 to the previous measurement and n- 2 to the one before that. The time between measurements is critical. A too short sampling time can result in excessive equipment cycling, while a too long sampling time can result

39、 in overshoot and instability [8]. The constants Kc,Tj Td are originally determined theoretically according to the well-known ZIEGLER-NICHOLS method [6]. These values serve as a starting point from where further fine t

40、uning </p><p>　　A small value of Kc produces large overshoot but gives good stability, while larger values of Kc reduce the overshoot but increase equipment cycling.</p><p>　　-Small values of T

41、j eliminate constant errors quickly, but result in rapid cycling of control equipment. In turn, large values of Tj cause constant errors to occur.</p><p>　　-A small value of Td causes large overshoot, whi

42、le a large value of Td increases the reaction time, which results in increased stability.</p><p>　　Although the valve can only be switched on or off, it is still possible to control the switching as if it

43、were a linearly varying valve by controlling the time for which it is switched on or off. By applying Eq. (2), △T is converted to a duty cycle, which is defined as follows:</p><p>　　Duty cycle = [2]</p&g

44、t;<p><b>　　where:</b></p><p>　　-time for which the valve is switched on () [s]</p><p>　　-time between each sample which also represents maximum time for which the valve can be

45、 switched on during one interval (tmax = )[s].</p><p>　　In fact the conversion may be done in several ways ranging from a simple proportional relationship between △T and time of valve operation to a rather

46、complex one where rates of torque/oil flow change are taken into account. Development and/or selection of the concept may be governed by several factors of which simplicity of the control software and limitations of th

47、e hardware are the two most obvious ones.</p><p>　　For this specific application, the valve may not be switched more than 5 times per second or 5 Hz. The optimum length of the maximum duty cycle (tmax) may b

48、e determined by trial and error according to specified criteria or by dynamic simulation.</p><p>　　Conveyor Simulations Verifying the Performance of the Developed Concept: The concept has been tested and ver

49、ified by means of conveyor dynamic simulations. The first set of simulations utilised a computer model of a conveyor which was a subject of a detailed design investigation by Dynamika Materials Handing two years ago. T

50、he conveyor was supplied with drain couplings working in conjunction with a three way valve. Detailed information about the system and the conveyor may be found in [9]. T</p><p>　　The torque based starting

51、 strategy was analysed in significant detail. Acceptable performance results were obtained by adjusting the duty cycles and control settings. This led to further exploration of a velocity based starting strategy.</p&

52、gt;<p>　　To complete the investigation, the simulations were extended to conveyors of greater length and higher installed power. Some of the graphs presented in this paper refer to an 8.5 km long overland conveyo

53、r with head and tail drives [10]. Although the actual system operates with scoop couplings, in these simulations the conveyor was modeled with drain couplings operating in conjunction with solenoid valves.</p>&

54、lt;p>　　2.2 Results of the Conveyor Dynamic Simulations</p><p>　　Torque was ramped at a rate of 116.0 Nm/s which is suitable for a 3.3 km long conveyor with steel cord belting (2100 Nm should be reached in

55、 15 sec). The resulting ramp is too steep for the coupling during the initial stages, specifically during the initial 6 seconds of pump operation. Consequently, the control system comes into action with an approximate

56、 delay of 12 seconds.</p><p>　　Two problems are apparent :</p><p>　　Initial low torque delivery does not allow instant acceleration of the conveyor. This is possible to rectify by adjustments

57、in the software as is the case for the simulations, it can be noted that the velocity ramp and controlling action starts some 8 seconds after the motors and 6 seconds after the coupling’s pumps were energized.</p>

58、<p>　　The rate at which oil is discharged from the coupling is limited and may be insufficient to counteract the dynamic reaction of the conveyor and as a result, a certain degree of overspeed can be noted in the

59、 initial stages of the start up.</p><p>　　Despite the mentioned problems, it may be stated that the results of the velocity ramp start up are significantly better than can be expected from a discrete type of

60、 control operation.</p><p>　　Further tests, utilizing different velocity curves and/or refined tuning of the control constants may produce better results.</p><p>　　The overall results are acce

61、ptable. However, it can be noted that the performance of tail end drive is somewhat better than that at the head end.</p><p>　　For each drive it is possible to notice a period of increased oscillations of

62、 torque/tensions between the period of 12 and 22 seconds in the start-up. Once again by adjusting settings and/or the length of the duty cycle, the results can improve. </p><p>　　3. Conclusions</p>&l

63、t;p>　　Based on the results of simulations the following conclusions can be made:</p><p>　　—The objectives which were set for the control concept of the solenoid valve have been achieved to a large extent

64、. It was possible to convert the discrete action of the valve into a precise, continuous output.</p><p>　　—The new system allows the application of the solenoid valve for velocity based starting strategy. H

65、owever, control may not be as precise as for a torque based strategy, specifically during initial stages of the start-up.</p><p>　　—Care must be taken in fine tuning of the control parameters. Simulation re

66、sults have shown that badly selected control parameters may lead to poor performance results.</p><p>　　—As was shown, the concept may be applied both to very long and medium length conveyors. Existence of

67、the tail drive is not a restriction for the application. However, only torque based starting strategy has been tested in this case.</p><p>　　PID-control is a classic control technique which is widely appli

68、ed in the process industry and which has provided good solutions to diverse control problems, provided that it is well-tuned</p><p>　　References</p><p>　　[1] CTREBSKI, M.: Torque control using

69、 drain fluid coupling; bulk solids handling Vol.16 (1996) No. 1, pp. 39-41.</p><p>　　[2] PUTTER, E. and GOUWS, J.: An automatic environmental controller for greenhouses; Elektron (Journal for South African

70、Institute for Electronic Engineers) August 1996, pp.66-67.</p><p>　　[3] SMITH, C.L.: Digital Computer Process Control; lntext Educational Publishers, New York, 1972.</p><p>　　[4] ZADEH, L.A.: S

71、imilarity relations and fuzzy orderings; Information and Science, Vol.3,1971, pp. 177-200.</p><p>　　[5] KOSKO, B.: Neural Networks and FLZZY Systems - A Dynamical Systems Approach to Machine Intelligence P

72、rentice-Hall International Editions, New Jersey1992.</p><p>　　[6] FRANKLIN, G.F., POWELL, D.J., and EMAMINAEINI, A.: Feedback Control of Dynamic Systems: Addison-Wesley Publishing, Company, 1986.</p>

73、<p>　　[7] PUTTER, E.: Multi-variable Control Techniques for Greenhouses; Master’s Thesis (Electrical and Electronic Engineering), Rand Afrikaans University 1996, South Africa.</p><p>　　[8] MACDONALD,

74、 R.D., HAWTON ,J., and HAYWARD G.L.: A proportional integral derivative control system for heating and ventilating livestock buildings; J. of CSAE Vol.31,1989, No. 1, pp. 45-49.</p><p>　　[9] PRETORIUS, J

75、.L.: Design of a long conveyor system with combined ascending and descending sections; bulk solids handing Vol.16(1996) No. 2, pp. 195-201.</p><p>　　[10]FAUSREACH, R. and OTREESKI, M.: The Syferfontein ove

76、rland conveyor system at the Sasol Secunda Plant in South Africa; bulk solids handling Vol.13 (1993) No. 2, pp. 289 - 295.</p><p>　　[11]PAGE, J.L. et al.: Design of long overland conveyor with tight horizon