從計算能力來看，計算機早已超越人腦，但這不意味著計算機有智慧——迄今為止，各種類型的計算機都仍只是人腦部分功能（主要是記憶與運算）的延展。在可編程邏輯控制器系統設計時，首先應確定控制方案，下一步工作就是可編程邏輯控制器工程設計選型。工藝流程的特點和應用要求是設計選型的主要依據。可編程邏輯控制器及有關設備應是集成的、標準的，按照易于與工業控制系統形成一個整體，易于擴充其功能的原則選型所選用可編程邏輯控制器應是在相關工業領域有投運業績、成熟可靠的系統，可編程邏輯控制器的系統硬件、軟件配置及功能應與裝置規模和控制要求相適應。熟悉可編程序控制器、功能表圖及有關的編程語言有利于縮短編程時間，因此，工程設計選型和估算時，應詳細分析工藝過程的特點、控制要求，明確控制任務和范圍確定所需的操作和動作，然后根據控制要求，估算輸入輸出點數、所需存儲器容量、確定可編程邏輯控制器的功能、外部設備特性等，后選擇有較高性能價格比的可編程邏輯控制器和設計相應的控制系統。 [5]點數估算I/O點數估算時應考慮適當的余量，通常根據統計的輸入輸出點數，再增加10%～20%的可擴展余量后，作為輸入輸出點數估算數據。實際訂貨時，還需根據制造廠商可編程邏輯控制器的產品特點，對輸入輸出點數進行圓整。 [5]
In terms of computing power, computers have already surpassed human brain, but this does not mean that computers are intelligent - so far, all types of computers are still only an extension of some functions of human brain (mainly memory and operation).
In the design of PLC system, the control scheme should be determined first, and the next step is the engineering design and selection of PLC. The characteristics and application requirements of the process flow are the main basis for design and selection. The programmable logic controller and related equipment shall be integrated and standard. According to the principle of easy integration with the industrial control system and easy expansion of its functions, the selected programmable logic controller shall be a mature and reliable system with operation performance in relevant industrial fields. The system hardware, software configuration and functions of the programmable logic controller shall be compatible with the device scale and control requirements. Being familiar with programmable controllers, function charts and related programming languages is conducive to shortening programming time. Therefore, when selecting and estimating engineering design, it is necessary to analyze the characteristics and control requirements of the process in detail, clarify the control tasks and scope, and determine the required operations and actions. Then, according to the control requirements, estimate the input and output points, the required memory capacity, determine the functions of the programmable logic controller, the characteristics of external equipment, etc, Then choose the programmable logic controller with high performance price ratio and design the corresponding control system. [5]
Point estimation
Appropriate margin should be considered in the estimation of i/o points. Usually, according to the statistical input and output points, an additional 10% - 20% expandable margin is added as the input and output point estimation data. When actually ordering, it is also necessary to round the input and output points according to the product characteristics of the manufacturer's PLC. [5]
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