外文翻譯--關(guān)于自動化立體倉庫使用雙貨叉問題的探討

1、<p><b>　　附錄一 外文翻譯</b></p><p>　　An Analysis Of Dual Shuttle Automated Storage/Retrieval Systems</p><p>　　Brett A. Peters August 1, 1994</p><p><b>　　Abstract

2、</b></p><p>　　This paper addresses the throughput improvement possible with the use of a dual shuttle automated storage and retrieval system. With the use of such a system, travel between time in a dua

3、l command cycle is virtually eliminated resulting in a large throughput improvement. The dual shuttle system is then extended to perform an equivalent of two dual commands in one cycle in a quadruple command mode (QC). A

4、 heuristic that sequences retrievals to minimize travel time in QC mode is developed. Monte C</p><p><b>　　Keywords:</b></p><p>　　Automated Storage/Retrieval Systems Design; Automated

5、 Storage/Retrieval Systems Operation; Material Handling Systems; Performance Modeling and Analysis </p><p>　　Introduction</p><p>　　Automated storage/retrieval systems (AS/RS) are widely used in

6、warehousing and manufacturing applications. A typical unit load AS/RS consists of storage racks, S/R machines, link conveyors, and input/output (I/O) stations. An important system performance measure is the throughput ca

7、pacity of the system. The throughput capacity for a single aisle is the inverse of the mean transaction time, which is the expected amount of time required for the S/R machine to store and/or retrieve a unit load. The<

8、;/p><p>　　Han et al. [2] improved the throughput capacity of the AS/RS through sequencing retrievals. Intelligently sequencing the retrievals can reduce unproductive travel between time when the S/R machine is

9、traveling empty and thereby increase the throughput. They develop an expression for the maximum possible improvement in throughput if travel between is eliminated for an AS/RS that is throughput bound and operates in dua

10、l command mode. In essence, this means that if the S/R machine travels in a sing</p><p>　　In this paper, we analyze an alternative design of the S/R machine that has two shuttles instead of one as in a regul

11、ar AS/RS. The new design eliminates the travel between the storage and retrieval points and performs both a storage and a retrieval at the point of retrieval, thereby achieving the maximum throughput increase calculated

12、by Han et al. [3]. </p><p>　　The dual shuttle AS/RS is a new design aimed at improving S/R machine performance. most studies on AS/RS systems have been based on a single shuttle design. In our analysis of th

13、e dual shuttle AS/RS performance, we build upon these previous research results. </p><p>　　Alternative S/R Machine Design</p><p>　　A typical unit-load AS/RS has an S/R machine operating in each

14、aisle of the system. The S/R machine has a mast which is supported at the floor and the ceiling and travels horizontally within the aisle. Connected to this mast is a shuttle mechanism that carries the unit load and move

15、s vertically up and down the mast. The shuttle mechanism also transfers loads in and out of storage locations in the rack. Figure 1 provides an illustration of the single shuttle S/R machine. </p><p>　　Figur

16、e 1. Single Shuttle S/R Machine Design </p><p>　　A typical single shuttle AS/RS can perform a single command cycle or a dual command cycle. A single command cycle consists of either a storage or a retrieval.

17、 For a storage, the time consists of the time to pickup the load at the I/O point, travel to the storage point, deposit the load at that point, and return to the I/O point. The time for a retrieval is developed similarly

18、. </p><p>　　A dual command cycle involves both a storage and a retrieval in the same cycle. The cycle time involves the time to pickup the load at the I/O point, travel to the storage location, place the loa

19、d in the rack, travel empty to the retrieval location, retrieve a load, return to the I/O point, and deposit the load at the I/O point. </p><p>　　If we critically analyze the dual command cycle of the S/R ma

20、chine (shown by the solid line in Figure 2), a potential open location for a future storage is created when a retrieval is performed. Furthermore, if both a retrieval and a storage are performed at the same point, the tr

21、avel between time (TB) is eliminated, and the travel time will be equal to the single command travel time. With the existing AS/RS design, this mode of operation is not possible; therefore, an alternative to the S/R mac&

22、lt;/p><p>　　Figure 2. Dual Command Travel Paths of S/R and R/S Machines </p><p>　　R/S Machine Operation</p><p>　　Consider an S/R machine with two shuttle mechanisms instead of one. Thi

23、s new S/R machine could now carry two loads simultaneously. Each shuttle mechanism could operate independently of the other, so that individual loads can still be stored and retrieved. An illustration of the dual shuttle

24、 S/R machine is shown in Figure 3. This new S/R machine would operate as described below. </p><p>　　Figure 3. Dual Shuttle S/R Machine Design </p><p>　　The S/R machine picks up the item to be st

25、ored from the I/O point, loads it into the first shuttle, and moves to the retrieval location. After reaching the retrieval location, the second shuttle is positioned to pickup the item to be retrieved. After retrieval,

26、the S/R machine positions the first shuttle and deposits the load. The S/R machine then returns to the I/O point. The operation can easily be seen as a single command operation plus a small travel time for repositioning

27、the S/R machine be</p><p>　　Since the R/S machine has two shuttles, the position of the shuttles has a role in the operation of the system. With two shuttles, the R/S machine is able to perform a dual comman

28、d cycle at one location in the rack. This operation is accomplished by first retrieving the load onto the empty shuttle, transferring the second shuttle into position, and storing the load into the empty location in the

29、rack. However, the choice of shuttle configuration does not impact the analysis in this paper. </p><p>　　To perform these operations, the R/S machine must move the second shuttle into position after the firs

30、t shuttle has completed the retrieval. Due to the small distance involved, the R/S machine will use a slower creep speed for positioning, but this travel time is generally small. Furthermore, an amount of creep time is u

31、sually included in the pickup and deposit time to account for this required positioning. A second design characteristic is that additional clearance beyond the first and last row</p><p>　　Throughput Improvem

32、ent</p><p>　　To estimate the throughput improvement by the dual shuttle system over existing designs, we use the expressions for single command and dual command cycle times developed by Bozer and White [1] a

33、nd the tabulated values for the nearest neighbor heuristic from Han et al. [4]. In developing the expressions, the authors in [1] and [4] made several assumptions. The same assumptions hold for the new design and include

34、 the following. </p><p>　　1. The rack is considered to be a continuous rectangular pick face where the I/O point is located at the lower left-hand corner of the rack. </p><p>　　2. The rack lengt

35、h and height, as well as the S/R machine velocity in the horizontal and vertical directions, are known. </p><p>　　3. The S/R machine travels simultaneously in the horizontal and vertical directions. In calcu

36、lating the travel time, constant velocities are used for horizontal and vertical travel. Acceleration and deceleration effects are implicitly accounted for in either a reduced top speed or an increased pickup and deposit

37、 time. A creep speed is used for repositioning the dual shuttle. </p><p>　　4. Pickup and deposit times associated with load handling are assumed constant and, therefore, these could be easily added into the

38、cycle time expressions. </p><p>　　5.The S/R machine operates either on a single or dual command basis, i.e., multiple stops in the aisle are not allowed. (This assumption is later relaxed for the new R/S mac

39、hine to perform a quadruple command cycle.) </p><p>　　6. For the nearest neighbor heuristic, a block of n retrievals is available for sequencing and there are m initial open locations in the rack face. <

40、/p><p>　　Dual Shuttle S/R Systems</p><p>　　The new design of the S/R machine has two shuttles and therefore could be operated as a dual shuttle system: carrying two loads and depositing them, retri

41、eving two loads, and returning to the I/O point to deliver them as shown in Figure 4. The above operation can be performed by storing and retrieving the loads at four different locations. Therefore, the travel time would

42、 consist of the time for a single command travel plus three travel between times. To more efficiently perform the 4 operations</p><p>　　Figure 4. S/R Machine Path Performing Four Operations At Four Locations

43、. </p><p>　　Figure 5. S/R Machine Path Performing Four Operations At Three Locations. </p><p>　　Conclusions</p><p>　　This paper performs an analysis of dual shuttle automated storag

44、e and retrieval systems. Several contributions have been made including the following. </p><p>　　1.Throughput improvements in the range of 40-45% can be obtained using the quadruple command cycle relative to

45、 dual command cycles with a single shuttle system. </p><p>　　2.With the dual shuttle design, travel between is virtually eliminated for a dual command cycle. </p><p>　　The dual shuttle system s

46、hows promise for situations requiring high throughput. The main disadvantage with the new design is the extra cost of the S/R machine. An economic evaluation is needed to determine if it is appropriate for a particular s

47、ituation. However, based on throughput performance, the dual shuttle design appears promising. </p><p>　　The concept of dual shuttle systems can also be extended to other material handling systems. Furthermo

48、re, research is needed to consider other storage strategies, such as class based storage policies, to examine their impact on throughput in conjunction with the dual shuttle design. This paper provides a framework for an

49、alyzing dual shuttle AS/RS, and it provides a foundation for other material handling research related to this concept. </p><p>　　關(guān)于自動化立體倉庫使用雙貨叉問題的探討</p><p>　　布雷特·彼得斯 August 1, 1994</

50、p><p><b>　　摘要</b></p><p>　　本文通過在自動化立體倉庫中運用雙貨叉設計，來提高立體倉庫的吞吐量。由于這種系統(tǒng)運用，雙指令系統(tǒng)的運行間的時間實際上被消除了，并且吞吐量得到了很大的提高。雙貨叉系統(tǒng)后來被延伸到執(zhí)行一個相等的一個周期內(nèi)執(zhí)行雙指令在四倍指令模式中。一個啟發(fā)式的檢索排序減少了運行時間，使得QC模式得到了發(fā)展。蒙特卡羅仿真的結(jié)果被用來評價啟

51、發(fā)式算法的性能，并且顯示它表現(xiàn)出色，吞吐量得到了很大的提高相比于雙指令周期下最近鄰的檢索序列啟發(fā)。</p><p>　　關(guān)鍵字：自動化立體倉庫，物料運輸系統(tǒng)</p><p><b>　　1.引言</b></p><p>　　自動化立體倉庫被廣泛地應用于倉儲及生產(chǎn)應用中，自動化立體倉庫中一個典型的貨物裝載系統(tǒng)是由堆垛機、連接輸送帶，輸入/輸出部分

52、組成。系統(tǒng)一個重要的指標是系統(tǒng)的吞吐能力。對于單通道系統(tǒng)的貨物吞吐能力值得是堆垛機往返的平均時間，在這個所預期的時間里要求堆垛機儲存一個或取出一個貨物。整個服務的時間包括堆垛機行進的時間和貨物存放的時間。這個時間通常決定于貨架的結(jié)構(gòu)和堆垛機的規(guī)格。</p><p>　　一些人通過對檢索進行排序來提高立體倉庫的吞吐能力，對檢索進行明智的而排序可以減少因堆垛機執(zhí)行空運行而消耗的時間，從而提高吞吐能力。他們制定了一個表

53、達式，為了最大限度的提高系統(tǒng)的吞吐量，通過減少系統(tǒng)的運行時間，如果吞吐量和操作都執(zhí)行雙命令模式。本質(zhì)上，這意味著堆垛機在一個命令的指揮下可以同時完成一個存儲和一個取貨任務，這樣吞吐量的提高就可以實現(xiàn)了。</p><p>　　在這篇論文里，我們設計了一個有兩個貨叉的堆垛機，而不是通常立體倉庫中的一個。這種新的設計可以減少存儲和取貨的運行時間，在一個運行過程中可以執(zhí)行一個存儲和一個取貨任務，從而最大限度的提高了吞吐量

54、。</p><p>　　在立體倉庫中使用的雙貨叉技術(shù)是為了提高堆垛機的性能而設計的一個新技術(shù)。大多數(shù)對自動化立體倉庫的研究還是基于單貨叉技術(shù)。我們也是基于以前的研究成果來設計雙貨叉的性能。</p><p><b>　　2.替代堆垛機設計</b></p><p>　　典型的立體倉庫貨物裝載系統(tǒng)是由每一個通道上的堆垛機進行操作，這種堆垛機有一個大的

55、柱子支撐在地面和天花板之間，在水平過道上行進。連接在這個柱子上的是一副貨叉可以沿著柱子上下的搬運貨物，貨叉也可以搬運貨物進出貨架上的儲存位置。</p><p>　　一個典型的單貨叉系統(tǒng)可以執(zhí)行一個或兩個指令周期，一個指令周期包括一個存儲過程或者一個取貨過程。對于一個存儲過程的時間包括從出入貨臺拾取貨物，再將貨物運到存儲位置，將貨物存放到存儲位置，再返回到出入貨臺。取貨過程的時間與上面類似。</p>

56、<p>　　一個雙指令周期包括存儲和取貨兩個任務在一個周期內(nèi)，這個周期的時間包括堆垛機在出入貨臺拾起貨物，運行至貨位，將貨物存入貨位，再運行至一個取貨的貨位，將貨物取出，返回出入貨臺，將貨物放在出入貨臺上。</p><p>　　如果我們準確的分析雙指令周期的堆垛機，當一個取貨的任務被執(zhí)行后，一個潛在的空位置可以用于將來的存儲，如果一個存貨和一個取貨任務同時都被執(zhí)行，堆垛機的運行時間就被減少了，運行時間相

57、當于單指令運行時間?；谀壳暗牧Ⅲw倉庫設計，這種操作模式是不可能的。因此，一個可共選擇的方案，雙貨叉堆垛機方案被提出來了。</p><p>　　3.取存堆垛機的操作</p><p>　　由于這種堆垛機采用雙貨叉而不是單貨叉，這種新的堆垛機可以同時攜帶兩個貨物。每一個貨叉可以獨立與另一個來進行操作，所以單一的貨物可以被存放也可以被取出。新的堆垛機系統(tǒng)將在下面進行描述。</p>

58、<p>　　堆垛機從出入貨臺拾起一個要被存放的貨物，將它放在第一個貨叉上，然后移動到取貨位置，當堆垛機到達取貨位置，堆垛機的第二個貨叉到位開始取貨，當取貨完畢，堆垛機的第一個貨叉到貨位將要存儲的貨物存如貨位。堆垛機然后返回出入貨臺。這種操作可以簡單的看為單指令操作，加上一段轉(zhuǎn)換貨叉的很短的一段時間。因此，這種堆垛機就是原來的堆垛機在兩個指令周期內(nèi)先完成一個取貨任務，再完成一個存貨任務。</p><p>

59、　　這種堆垛機有兩個貨叉，所以在這種操作系統(tǒng)中兩個貨叉的定位就應該有一個規(guī)則。堆垛機可以在一個貨位前完成兩個指令周期。這種操作是由先將貨物存入空貨位，轉(zhuǎn)移第二個貨叉到位置，再將要存的貨物存入貨位。但是貨叉結(jié)構(gòu)的選擇不會影響這篇文章的設計。要完成這個操作，堆垛機必須將第二個貨叉移動到位當?shù)谝粋€貨叉已經(jīng)完成了取貨任務。考慮到這個距離很短，堆垛機必須以一種蠕動的速度移動到位，移動時間總體上講是很小的。此外，貨叉存貨取貨時也應像移動貨叉一樣以蠕

60、動的速度。第二個設計特點是第一行和最后一行以外要留有一定的間隙，貨架的每一列必須滿足堆垛機的超程以適應雙貨叉的機械結(jié)構(gòu)。</p><p><b>　　4.吞吐量的提高</b></p><p>　　為了估計雙貨叉系統(tǒng)比單貨叉系統(tǒng)的吞吐量提高了多少，我們采用了由Bozer和White發(fā)明的單操作指令和雙操作指令周期時間的公式。為了發(fā)展這個公式，作者做了幾個設想，對于新的設

61、計的設想主要有一下幾方面。</p><p>　　1. 被看做一個連續(xù)的矩形接面，出入貨臺位于貨架的左下角。</p><p>　　2. 貨架的長度和高度，還有堆垛機在垂直和水平方向上的速度，是已知的。</p><p>　　3. 堆垛機可以在水平和垂直方向上同時的運行，在計算時間時，水平和垂直行進采用勻速，加速和減速效果運用與高速的降低或者存取貨速度的提高。貨叉的定位采

62、用蠕動的速度。</p><p>　　4. 存取貨物的時間與貨物的處理時間有關(guān)，被認為是一個常數(shù)。因此，這將可以輕易的加進了周期時間表達式。</p><p>　　5. 堆垛機的運行是以單指令或者雙指令為基礎(chǔ)的，這也就是說在通道中多樣的停止方式是不被允許的。</p><p>　　6. 對于最近鄰的啟發(fā)，一大塊n個檢索對排序有效，而貨架上最初有m個空位置。</p&g

63、t;<p>　　5.雙貨叉堆垛機系統(tǒng)</p><p>　　堆垛機新的設計有兩個貨叉，所以可以按照雙貨叉系統(tǒng)進行操作：攜帶兩個貨物并存儲它們，取出兩個貨物返回出入貨臺。上面的操作可以在四個不同的位置存儲和取出貨物。因此，整個運行時間由一個指令運行時間加上三個運行間的時間。為了更有效的執(zhí)行這四個操作，存儲和取貨在一個位置上穿插著雙重命令操作，這種操作模式，被成為四指令周期。消除了一個運行間時間，比以往的

64、方式更有效。四指令周期模式可以在隨機位置進行存貨，而取貨則按照先到先取的模式。但是，通過智能檢索列表排序,，四個操作時間將會大大的減少。這種方式被Han等人用來單一貨載的立體倉庫的吞吐量。在本文中我們是以他們的研究為基礎(chǔ)。</p><p><b>　　5.結(jié)論</b></p><p>　　本文對雙貨叉存儲系統(tǒng)進行了分析，主要有以下幾個貢獻。</p>&l

65、t;p>　?。?） 對于采用單貨叉系統(tǒng)使用兩倍指令周期，采用四指令周期可以提高吞吐量40%-45%.</p><p>　?。?） 用雙貨叉設計，行進間的時間實際上減少到一個雙指令周期。雙貨叉系統(tǒng)可以保證所要求的高吞吐量。主要的缺點是新的設計會使堆垛機的成本上升。一個經(jīng)濟評估是必要的,以決定是否適合某一特定的情況。但是就吞吐量的性能指標而言，雙貨叉設計是滿足要求的。</p><p>