金屬管件氣密性檢測裝置的控制系統(tǒng)設計

金屬管件氣密性檢測裝置的控制系統(tǒng)設計,金屬管,氣密性,檢測,裝置,控制系統(tǒng),設計 西安文理學院機械電子工程系 本科畢業(yè)設計（論文） 題 目 金屬管件氣密性檢測裝置 的控制系統(tǒng)設計 專業(yè)班級 08級機械（2）班 學 號 08102080212 學生姓名 杜迎賓 指導教師 韋煒 設計所在單位 西安文理學院 2012年 2 月 西安文理學院本科畢業(yè)設計（論文）任務書 題 目 金屬管件氣密性檢測裝置的控制系統(tǒng)設計 學生姓名 杜迎賓 學 號 08102080212 專業(yè)班級 機械設計制造及其自動化0802 指導教師 韋煒 職 稱 講師 教 研 室 機械 畢業(yè)設計（論文）任務與要求 任務：在現代化生產中,產品氣密性檢測是必不可少的，設計合適的檢測裝置的控制系統(tǒng)，以優(yōu)化檢測效率，本課題旨在通過水檢法檢測管件氣密性裝置的控制系統(tǒng)設計，選擇一種合適的方案并進行相關設計和實驗。 要求：1、收集和整理氣密性檢測裝置的控制系統(tǒng)的相關資料； 2、通過對各種方法的分析和探討，確定實驗設計方案； 3、在此基礎上編寫并調試程序，完成相關設計； 4、撰寫畢業(yè)論文。 畢業(yè)設計（論文）工作進程 起止時間 工作內容 寒假~2周 2012.1.10~2012.3.4 第3~5周 2012.3.5~2012.3.25 第6~8周 2012.3.26~2012.4.15 第9~11周 2012.4.16~2012.5.6 第12周 2012.5.7~2012.5.13 第13周 2012.5.14~2012.5.20 明確設計內容要求，查（借）閱資料，了解相關的知識，撰寫開題報告。 分析氣密性檢測裝置的原理，探討氣密性檢測裝置的各種控制系統(tǒng)，擬定方案。 確定總體設計方案，完成模塊化設計，在實驗室進行系統(tǒng)調試。 撰寫畢業(yè)論文。 論文定稿并整理資料準備答辯。 答辯。 開始日期 2012-1-10 完成日期 2012-5-11 教研室主任（簽字） 系主任（簽字） 西安文理學院本科畢業(yè)設計（論文）開題報告 題 目 金屬管件氣密性檢測裝置的控制系統(tǒng)設計 學生姓名 杜迎賓 學 號 08102080212 專業(yè)名稱 機械設計制造及其自動化 指導教師 韋煒 開題時間 2012.3.2 班 級 08機械2班 一、選題目的和意義 在工業(yè)生產中，由于某些原因而使產品出現鑄造砂眼、裂紋、氣孔等現象，致使產品氣密性不合格，將會使產品在工作條件下失效，為了保證產品的質量和生產的安全，需要對這些零件的氣密性進行檢測。對于檢測管件氣密性的裝置的研究可以使我們準確的測出其是否合格。 伴隨著工業(yè)大規(guī)模生產的進一步深化，氣密性檢測從以前的機械制造業(yè)己經拓展到了現在的一般日用品行業(yè)、家用電器、食品包裝、醫(yī)療器械等，這些行業(yè)對自己生產的產品進行氣密性檢測是必不可少的，因此氣密性檢測的方法顯得很重要。然而在檢測中我們如能通過系統(tǒng)自動完成，不僅可以節(jié)省成本，更可以提高檢測效率，所以控制系統(tǒng)的研究尤為重要。 二、本課題在國內外的研究狀況及發(fā)展趨勢 目前，國內現有的氣密性檢測系統(tǒng)研究情況或多或少存在著以下問題: 1)氣密性檢測基本停留在定性檢測的階段，不能定量檢測；2)檢測手段簡單、花費較少的檢測方法，靈敏度一般不高，而檢測靈敏度較高、一致性好的檢測往往經濟性較差；3)以上檢測方法檢測時間往往較長，通常只適合單間或少量零件的檢測。究其原因就是在系統(tǒng)開發(fā)中片面強調了系統(tǒng)的技術先進性，而忽略了應用操作性。國內外有很多專業(yè)廠家生產智能氣密性檢測儀器，大多數產品適用于小型裝置的氣密性檢測，缺少對測量工況的綜合分析補償，難以用來在大型裝置。因為這種大型密封裝置的檢測系統(tǒng)容易受到環(huán)境溫度變化、檢測系統(tǒng)本身溫度變化、檢測容積、檢測壓力等因素的影響。如何開發(fā)一套更方便、高效、實用的泄漏點定位系統(tǒng)，是國內外氣密性檢測相關研究機構關注的熱點問題。 氣密性檢測裝置的控制系統(tǒng)有著廣闊的發(fā)展前景，從控制方法上來看，控制手段越來越多，如單片機控制、PLC控制、計算機控制等等，測漏儀的操作界面也越來越人性化，而且操作越來越方便。應用三維實體造型和仿真分析軟件MDT系統(tǒng)對氣密性檢測及干燥處理裝置進行了設計，并對應用過程中出現的問題作了分析與研究，為CAD／CAE／CAM技術在新產品開發(fā)過程中的應用作了嘗試和探索?，F在，提出采用超聲檢測的方法，并利用虛擬儀器良好的人機交互界面，采用基于Labview的系統(tǒng)設計，實現檢測設備的小型化、智能化要求。采用現代計算機及自動控制等技術，解決了泄漏量測量的建模和系統(tǒng)配置問題。采用電荷耦合、提高放大倍數、降低量程等誤差修正技術，提高了系統(tǒng)抗干擾能力和溫度、壓力測量數據的精度；實現了測量數據計算和結果適時顯示、判定等功能。實際使用結果表明，該系統(tǒng)的檢測結果滿足檢漏氣密性指標及試驗任務要求。還有以工控機、可編程控制器和編程軟件的聯合使用為基礎的檢測系統(tǒng)，利用高精度微差壓傳感器來測量壓差，無論是在設計，還是在軟件編寫以及調試方面都相當復雜，但是該方法檢測精度、可靠性以及效率都很高，而且實用性較好，實現了對氣壓制動調節(jié)器智能化的檢測，有效地提高了高性能、高精度產品的合格率，并且提高了勞動生產率，降低了生產成本。 三、主要研究內容 1.分析用水檢法檢測被測工件氣密性裝置的原理，明確其整個檢測過程。 2.提出水檢法檢測被測工件氣密性裝置的系統(tǒng)設計方案，通過比較，確定合適的設計方案。 3.確定實驗方案的總體設計。 4.完成實驗方案的模塊化設計，在實驗室進行調試，完成實驗方案的設計。 5.撰寫畢業(yè)論文。 指導教師意見及建議： 簽字： 年 月 日 教研室審核意見： 簽字： 年 月 日 注：此表前三項由學生填寫后，交指導教師簽署意見，經教研室審批后，才能開題。 Programmable logic controller A programmable logic controller (PLC) or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or lighting fixtures. PLCs are used in many industries and machines. Unlike general-purpose computers, the PLC is designed for multiple inputs and output arrangements, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact. Programs to control machine operation are typically stored in battery-backed or non-volatile memory. A PLC is an example of a real time system since output results must be produced in response to input conditions within a bounded time, otherwise unintended operation will result. 1. History The PLC was invented in response to the needs of the American automotive manufacturing industry. Programmable logic controllers were initially adopted by the automotive industry where software revision replaced the re-wiring of hard-wired control panels when production models changed. Before the PLC, control, sequencing, and safety interlock logic for manufacturing automobiles was accomplished using hundreds or thousands of relays, cam timers, and drum sequencers and dedicated closed-loop controllers. The process for updating such facilities for the yearly model change-over was very time consuming and expensive, as electricians needed to individually rewire each and every relay. In 1968 GM Hydramatic (the automatic transmission division of General Motors) issued a request for proposal for an electronic replacement for hard-wired relay systems. The winning proposal came from Bedford Associates of Bedford, Massachusetts. The first PLC, designated the 084 because it was Bedford Associates' eighty-fourth project, was the result. Bedford Associates started a new company dedicated to developing, manufacturing, selling, and servicing this new product: Modicon, which stood for MOdular DIgital CONtroller. One of the people who worked on that project was Dick Morley, who is considered to be the "father" of the PLC. The Modicon brand was sold in 1977 to Gould Electronics, and later acquired by German Company AEG and then by French Schneider Electric, the current owner. One of the very first 084 models built is now on display at Modicon's headquarters in North Andover, Massachusetts. It was presented to Modicon by GM, when the unit was retired after nearly twenty years of uninterrupted service. Modicon used the 84 moniker at the end of its product range until the 984 made its appearance. The automotive industry is still one of the largest users of PLCs. 2. Development Early PLCs were designed to replace relay logic systems. These PLCs were programmed in "ladder logic", which strongly resembles a schematic diagram of relay logic. This program notation was chosen to reduce training demands for the existing technicians. Other early PLCs used a form of instruction list programming, based on a stack-based logic solver. Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Logic, a very high-level programming language designed to program PLCs based on state transition diagrams. Many early PLCs did not have accompanying programming terminals that were capable of graphical representation of the logic, and so the logic was instead represented as a series of logic expressions in some version of Boolean format, similar to Boolean algebra. As programming terminals evolved, it became more common for ladder logic to be used, for the aforementioned reasons. Newer formats such as State Logic and Function Block (which is similar to the way logic is depicted when using digital integrated logic circuits) exist, but they are still not as popular as ladder logic. A primary reason for this is that PLCs solve the logic in a predictable and repeating sequence, and ladder logic allows the programmer (the person writing the logic) to see any issues with the timing of the logic sequence more easily than would be possible in other formats. 2.1 Programming Early PLCs, up to the mid-1980s, were programmed using proprietary programming panels or special-purpose programming terminals, which often had dedicated function keys representing the various logical elements of PLC programs. Programs were stored on cassette tape cartridges. Facilities for printing and documentation were very minimal due to lack of memory capacity. The very oldest PLCs used non-volatile magnetic core memory. More recently, PLCs are programmed using application software on personal computers. The computer is connected to the PLC through Ethernet, RS-232, RS-485 or RS-422 cabling. The programming software allows entry and editing of the ladder-style logic. Generally the software provides functions for debugging and troubleshooting the PLC software, for example, by highlighting portions of the logic to show current status during operation or via simulation. The software will upload and download the PLC program, for backup and restoration purposes. In some models of programmable controller, the program is transferred from a personal computer to the PLC though a programming board which writes the program into a removable chip such as an EEPROM or EPROM. 3. Functionality The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems and networking. The data handling, storage, processing power and communication capabilities of some modern PLCs are approximately equivalent to desktop computers. PLC-like programming combined with remote I/O hardware, allow a general-purpose desktop computer to overlap some PLCs in certain applications. Regarding the practicality of these desktop computer based logic controllers, it is important to note that they have not been generally accepted in heavy industry because the desktop computers run on less stable operating systems than do PLCs, and because the desktop computer hardware is typically not designed to the same levels of tolerance to temperature, humidity, vibration, and longevity as the processors used in PLCs. In addition to the hardware limitations of desktop based logic, operating systems such as Windows do not lend themselves to deterministic logic execution, with the result that the logic may not always respond to changes in logic state or input status with the extreme consistency in timing as is expected from PLCs. Still, such desktop logic applications find use in less critical situations, such as laboratory automation and use in small facilities where the application is less demanding and critical, because they are generally much less expensive than PLCs. In more recent years, small products called PLRs (programmable logic relays), and also by similar names, have become more common and accepted. These are very much like PLCs, and are used in light industry where only a few points of I/O (i.e. a few signals coming in from the real world and a few going out) are involved, and low cost is desired. These small devices are typically made in a common physical size and shape by several manufacturers, and branded by the makers of larger PLCs to fill out their low end product range. Popular names include PICO Controller, NANO PLC, and other names implying very small controllers. Most of these have between 8 and 12 digital inputs, 4 and 8 digital outputs, and up to 2 analog inputs. Size is usually about 4" wide, 3" high, and 3" deep. Most such devices include a tiny postage stamp sized LCD screen for viewing simplified ladder logic (only a very small portion of the program being visible at a given time) and status of I/O points, and typically these screens are accompanied by a 4-way rocker push-button plus four more separate push-buttons, similar to the key buttons on a VCR remote control, and used to navigate and edit the logic. Most have a small plug for connecting via RS-232 or RS-485 to a personal computer so that programmers can use simple Windows applications for programming instead of being forced to use the tiny LCD and push-button set for this purpose. Unlike regular PLCs that are usually modular and greatly expandable, the PLRs are usually not modular or expandable, but their price can be two orders of magnitude less than a PLC and they still offer robust design and deterministic execution of the logic. 4. PLC Topics 4.1 Features The main difference from other computers is that PLCs are armored for severe conditions (such as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O) arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog process variables (such as temperature and pressure), and the positions of complex positioning systems. Some use machine vision. On the actuator side, PLCs operate electric motors, pneumatic or hydraulic cylinders, magnetic relays, solenoids, or analog outputs. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a computer network that plugs into the PLC. 4.2 System scale A small PLC will have a fixed number of connections built in for inputs and outputs. Typically, expansions are available if the base model has insufficient I/O. Modular PLCs have a chassis (also called a rack) into which are placed modules with different functions. The processor and selection of I/O modules is customised for the particular application. Several racks can be administered by a single processor, and may have thousands of inputs and outputs. A special high speed serial I/O link is used so that racks can be distributed away from the processor, reducing the wiring costs for large plants. 4.3 User interface PLCs may need to interact with people for the purpose of configuration, alarm reporting or everyday control. A simple system may use buttons and lights to interact with the user. Text displays are available as well as graphical touch screens. More complex systems use a programming and monitoring software installed on a computer, with the PLC connected via a communication interface. 4.4 Communications PLCs have built in communications ports, usually 9-pin RS-232, but optionally EIA-485 or Ethernet. Modbus, BACnet or DF1 is usually included as one of the communications protocols. Other options include various fieldbuses such as DeviceNet or Profibus. Other communications protocols that may be used are listed in the List of automation protocols. Most modern PLCs can communicate over a network to some other system, such as a computer running a SCADA (Supervisory Control and Data Acquisition) system or web browser. PLCs used in larger I/O systems may have peer-to-peer (P2P) communication between processors. This allows separate parts of a complex process to have individual control while allowing the subsystems to co-ordinate over the communication link. These communication links are also often used for HMI devices such as keypads or PC-type workstations. 4.5 Programming PLC programs are typically written in a special application on a personal computer, then downloaded by a direct-connection cable or over a network to the PLC. The program is stored in the PLC either in battery-backed-up RAM or some other non-volatile flash memory. Often, a single PLC can be programmed to replace thousands of relays. Under the IEC 61131-3 standard, PLCs can be programmed using standards-based programming languages. A graphical programming notation called Sequential Function Charts is available on certain programmable controllers. Initially most PLCs utilized Ladder Logic Diagram Programming, a model which emulated electromechanical control panel devices (such as the contact and coils of relays) which PLCs replaced. This model remains common today. IEC 61131-3 currently defines five programming languages for programmable control systems: FBD (Function block diagram), LD (Ladder diagram), ST (Structured text, similar to the Pascal programming language), IL (Instruction list, similar to assembly language) and SFC (Sequential function chart). These techniques emphasize logical organization of operations. While the fundamental concepts of PLC programming are common to all manufacturers, differences in I/O addressing, memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers. Even within the same product line of a single manufacturer, different models may not be directly compatible. 5. PLC compared with other control systems PLCs are well-adapted to a range of automation tasks. These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation, and where changes to the system would be expected during its operational life. PLCs contain input and output devices compatible with industrial pilot devices and controls; little electrical design is required, and the design problem centers on expressing the desired sequence of operations. PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design. On the other hand, in the case of mass-produced goods, customized control systems are economic due to the lower cost of the components, which can be optimally chosen instead of a "generic" solution, and where the non-recurring engineering charges are spread over thousands or millions of units. For high volume or very simple fixed automation tasks, different techniques are used. For example, a consumer dishwasher would be controlled by an electromechanical cam timer costing only a few dollars in production quantities. A microcontroller-based design would be appropriate where hundreds or thousands of units will be produced and so the development cost (design of power supplies, input/output hardware and necessary testing and certification) can be spread over many sales, and where the end-user would not need to alter the control. Automotive applications are an example; millions of units are built each year, and very few end-users alter the programming of these controllers. However, some specialty vehicles such as transit busses economically use PLCs instead of custom-designed controls, because the volumes are low and the development cost would be uneconomic. Very complex process control, such as used in the chemical industry, may require algorithms and performance beyond the capability of even high-performance PLCs. Very high-speed or precision controls may also require customized solutions; for example, aircraft flight controls. Programmable controllers are widely used in motion control, positioning control and torque control. Some manufacturers produce motion control units to be integrated with PLC so that G-code (involving a CNC machine) can be used to instruct machine movements. PLCs may include logic for single-variable feedback analog control loop, a "proportional, integral, derivative" or "PID controller". A PID loop could be used to control the temperature of a manufacturing process, for example. Historically PLCs were usually configured with only a few analog control loops; where processes required hundreds or thousands of loops, a distributed control system (DCS) would instead be used. As PLCs have become more powerful, the boundary between DCS and PLC applications has become less distinct. PLCs have similar functionality as Remote Terminal Units. An RTU, however, usually does not support control algorithms or control loops. As hardware rapidly becomes more powerful and cheaper, RTUs, PLCs and DCSs are increasingly beginning to overlap in responsibilities, and many vendors sell RTUs with PLC-like features and vice versa. The industry has standardized on the IEC 61131-3 functional block language for creating programs to run on RTUs and PLCs, although nearly all vendors also offer proprietary alternatives and associated development environments. 6. Digital and analog signals Digital or discrete signals behave as binary switches, yielding simply an on or off signal (1 or 0, True or False, respectively). Push buttons, limit switches, and photoelectric sensors are examples of devices providing a discrete signal. Discrete signals are sent using either voltage or current, where a specific range is designated as on and another as off. For example, a PLC might use 24 V DC I/O, with values above 22 V DC representing on, values below 2VDC representing off, and intermediate values undefined. Initially, PLCs had only discrete I/O. Analog signals are like volume controls, with a range of values between zero and full-scale. These are typically interpreted as integer values (counts) by the PLC, with various ranges of accuracy depending on the device and the number of bits available to store the data. As PLCs typically use 16-bit signed binary processors, the integer values are limited between -32,768 and +32,767. Pressure, temperature, flow, and weight are often represented by analog signals. Analog signals can use voltage or current with a magnitude proportional to the value of the process signal. For example, an analog 0 - 10 V input or 4-20 mA would be converted into an integer value of 0 - 32767. 可編程邏輯控制器 可編程邏輯控制器（PLC）或可編程序控制器是用于機電過程自動化的數字計算機，例如控制機械廠生產線、游樂設施或照明裝置。可編程控制器在許多工業(yè)和機器中使用。與通用的計算機不同的是，PLC是專為多個輸入和輸出管理，擴展溫度范圍、不受電磁噪音影響、抗震動和沖擊所設計?？刂破鞯牟僮鞒绦蛲ǔ４鎯υ陔姵毓╇娀蚍且资缘膬却嬷?。PLC是實時的系統(tǒng)，因為系統(tǒng)產生的輸出結果必須在有限的時間內回饋到輸入，否則會導致錯誤操作。 1.歷史 PLC發(fā)明是針對于美國汽車制造行業(yè)的需要?？删幊踢壿嬁刂破髯畛跬ㄟ^了在軟件版本更換硬連線的控制板生產模式更改時的汽車工業(yè)。 在PLC之前，控制、程序化和安全聯鎖邏輯制造汽車是使用上百或上千的繼電器、凸輪計時器、鼓定序儀和專用的閉環(huán)控制器來完成的。在每年更新模型等設施轉變過程是非常耗時并且成本高昂的，這是因為電工需要單獨地再接電線給每個中轉。 在1968年 GM Hydramatic（自動輸電分局）發(fā)布通用汽車公司的提議，電子替代布線中繼系統(tǒng)。獲獎的提案來自貝得福得，馬薩諸塞的貝得福得同事。第一個PLC選定084，因為它是貝得福得同事的第八十四個項目。貝得福得同事建立了一家新的公司致力開發(fā)、生產、銷售，和服務這一新產品：Modicon，代表模塊化數字控制器。迪克·莫利，被認為是PLC之父，他是從事該項目的人之一。1977年古爾德電子公司當前所有者收購法國施耐德電氣公司同德國公司AEG并售予該品牌為Modicon。 084模型之一首次被設在北部安多弗的Modicon總部馬薩諸塞州。這是專門為通用汽車服務的，并且經過了近二十多年的不間斷服務。直至984出現，Modicon使用的84名字才在其產品范圍中結束。 汽車工業(yè)仍是PLC的最大用戶之一。 2.發(fā)展 早期的可編程控制器是設計來取代繼電器邏輯系統(tǒng)。這些可編程控制器的“階梯邏輯”是與繼電器邏輯示意圖非常類似的。選擇此程序表示法的目的是為了減少對現有技術人員的培訓需求。其他早期的可編程控制器使用指令列表編程，基于一個堆棧編程邏輯求解器進行求解。 現代可編程控制器在各種各樣的方式可以被編程，從梯形邏輯語言到更加傳統(tǒng)的編程語言例如BASIC和C語言。另一個方法是狀態(tài)邏輯，被設計的一種非常高級編程語言根據狀態(tài)轉換圖的可編程控制器編程。 很多早期可編程控制器沒有可編程終端的邏輯圖形表示法，邏輯反而是被描繪成一系列在一些版本的布爾格式的邏輯表達式，類似于布爾代數。隨著編程碼發(fā)展，由于上述原因它變成更常見的梯形邏輯語言。更新的格式如國家邏輯和功能塊（這是類似的邏輯描述使用數字邏輯集成電路時的方式）的存在，但它們仍沒有梯形邏輯語言流行。一個主要原因是可編程控制器解決問題用一個可預測和重復的序列的邏輯，并且梯形邏輯語言可以用其他格式讓程序員（寫邏輯）的人看到邏輯的時間，所有問題更加容易地程序化。 2.1編程 早期的PLC，到80年代中期，都是用專有的編程版或專用編程終端，往往有專門的功能鍵，代表各種PLC程序邏輯元件。程序存儲在盒式磁帶盒上。由于缺少的內存容量很少用于打印設備。最古老的可編程控制器使用的是非易失性磁核心內存。 最期PLC在個人計算機上使用應用軟件編程。計算機連接到PLC通過以太網RS-232,RS-485或RS-422纜線連接。編程軟件允許輸入梯式邏輯編程。通常，軟件提供了用于調試和故障排除的功能，例如在操作過程中或通過仿真的邏輯部分PLC軟件突出顯示當前狀態(tài)。該軟件將上傳和下載PLC程序以便備份和恢復。在某些型號的PLC中雖然程序寫入一個可移動的芯片，如EEPROM或EPROM，但該方案還是得從個人電腦傳輸到PLC編程版。 3.功能 PLC的功能經過多年的發(fā)展，包括連續(xù)的繼電器控制，運動控制，過程控制，分布式控制系統(tǒng)和網絡。一些現代PLC的數據處理，存儲，處理能力和通信能力相當于臺式電腦。PLC編程結合遠程I/O硬件，一臺通用臺式計算機允許在某些應用中重疊使用某一可編程控制器。在重工業(yè)中PLC被認為沒有這些桌面計算機為主的邏輯控制器的實際性強，因為PLC在臺式計算機系統(tǒng)中運行不是很穩(wěn)定，并且，因為臺式計算機硬件沒有被設計成耐溫度、濕氣、振動和耐用作為可編程控制器的處理器。除桌面基于邏輯的硬件局限之外，例如Windows操作系統(tǒng)不適合自己的確定性邏輯的執(zhí)行，結果是PLC邏輯不可能總是對規(guī)定邏輯變化的輸入狀態(tài)與極端性預計的時間一致。盡管如此，這樣桌面邏輯被應用在較不重要情況，像實驗室自動化和小型設施中使用該應用程序的要求不高，因為他們的價格一般都遠遠低于昂貴的PLC。 在最近數年，小產品稱為PLR（可編程邏輯繼電器），并且因為名字相似，變得更常見并被接受。這些很像PLC已經應用于輕工業(yè)，它只有少部分的輸入/輸出（例如一些真實的輸入輸出信號）參與，低成本，很理想。這些小設備尺寸和形狀比較普通地幾位制造商制作，并且由更大的PLC制作商來填滿他們低端產品規(guī)格。俗名包括PICO控制器、納米PLC和其他的小控制器。多數這些控制器有在8到12數字輸入、4到8數字輸出，多達2個模擬輸入。尺寸通常是4英寸寬、3英寸高、3英寸深。大多數這樣的設備有一個小郵票大小的液晶屏幕來觀看簡化梯子邏輯的輸入/輸出點（只有一小部分程序被可見于給定的時間）和狀況，并且這些屏幕由一個電磁四通搖臂按鈕操縱加上四個不同的用于瀏覽和編輯的邏輯電鈕，類似于錄像機遙控按鈕。控制器大多數有一個小插座為通過連接RS-232