PLC的控制方式屬于存儲(chǔ)程序控制，其控制功能是通過(guò)存放在存儲(chǔ)器內(nèi)的程序來(lái)實(shí)現(xiàn)的，若要對(duì)控制功能作必要修改，只需改變控制程序即可，這就實(shí)現(xiàn)了控制的軟件化。可編程控制器的優(yōu)點(diǎn)在于"可"字，從軟件來(lái)講，其控制程序可編輯、可修改；從硬件上講，其外部設(shè)備配置可變。構(gòu)建一個(gè)PLC控制系統(tǒng)的重心就在于控制程序的編制，但外部設(shè)備的選用也將對(duì)程序的編制產(chǎn)生影響。因此在進(jìn)行程序設(shè)計(jì)時(shí)應(yīng)結(jié)合實(shí)際需要，硬、軟件綜合考慮。本文就硬、軟兩方面，選取梯形圖為編程語(yǔ)言，以松下電工FPO-C32型PLC為例，對(duì)PLC使用過(guò)程中易出現(xiàn)的幾個(gè)問(wèn)題及解決方法進(jìn)行了分析。
一、外部輸入設(shè)備的選用與PLC輸入繼電器的使用
1. 外部輸入信號(hào)的采集
PLC的外部設(shè)備主要是指控制系統(tǒng)中的輸入輸出設(shè)備，其中輸人設(shè)備是對(duì)系統(tǒng)發(fā)出各種控制信號(hào)的主令電器，在編寫控制程序時(shí)必須注意外部輸入設(shè)備使用的是常開還是常閉觸點(diǎn)，并以此為基礎(chǔ)進(jìn)行程序編制。否則易出現(xiàn)控制錯(cuò)誤。
在PLC內(nèi)部存儲(chǔ)器中有專用于輸入狀態(tài)存儲(chǔ)的輸入繼電器區(qū)，各輸入設(shè)備（開關(guān)、按鈕、行程開關(guān)或傳感器信號(hào)）的狀態(tài)經(jīng)由輸入接口電路存儲(chǔ)在該區(qū)域內(nèi)，每個(gè)輸入繼電器可存儲(chǔ)一個(gè)輸入設(shè)備狀態(tài)。PLC中使用的"繼電器"并非實(shí)體繼電器，而是"軟繼電器"，可提供無(wú)數(shù)個(gè)常開、常閉觸點(diǎn)用于編程。每個(gè)"軟繼電器"僅對(duì)應(yīng)PLC存儲(chǔ)單元中的一位（bit），該位狀態(tài)為"1"，表示該"軟繼電器線圈"通電，則程序中所有該繼電器的觸點(diǎn)都動(dòng)作。輸入繼電器作為PLC接收外部主令信號(hào)的器件，通過(guò)接線與外部輸入設(shè)備相聯(lián)系，其"線圈"狀態(tài)只能由外部輸入信號(hào)驅(qū)動(dòng)。
LSE3A Trutzschler Light Bar Transmitter
LSE3A Trutzschler Light Bar Transmitter
Korjo Zippered Plastic Bags in 3 Colors -ZPB23
Korjo Zippered Plastic Bags in 3 Colors -ZPB23
Hidraulikpumpe S12293922 ZPB10,5/10,5/8,3D
Hidraulikpumpe S12293922 ZPB10,5/10,5/8,3D
EMPORIO ARMANI EA7 GIUBBOTTO GIUBBINO UOMO NUOVO ORIGINALE NERO B29
EMPORIO ARMANI EA7 GIUBBOTTO GIUBBINO UOMO NUOVO ORIGINALE NERO B29
Electrical Equipment & Supplies (1)
EA7 EMPORIO ARMANI BOMBER JACKET Blu mis-XL
EA7 EMPORIO ARMANI BOMBER JACKET Blu mis-XL
trutzschler ZPB3 9 495-12.430.000 AD 495-12.230.001 AE 495-12.230.002 AF CPU
trutzschler ZPB3 9 495-12.430.000 AD 495-12.230.001 AE 495-12.230.002 AF CPU
TRUTZSCHLER ZPB 2 ZPB2 CIRCUIT BOARD CARD PLC MODULE 9 408-00.810.000 AG
TRUTZSCHLER ZPB 2 ZPB2 CIRCUIT BOARD CARD PLC MODULE 9 408-00.810.000 AG
TRUTZSCHLER ZPB 2 ZPB2 CIRCUIT BOARD 9 400-20.810.110 AE A-03-21-1 NEW
TRUTZSCHLER ZPB 2 ZPB2 CIRCUIT BOARD 9 400-20.810.110 AE A-03-21-1 NEW
Trutzschler ZPB 2 400-20.810.110AE
Trutzschler ZPB 2 400-20.810.110AE
Trutzschler SIB 3 (A1) Board ——#9
Trutzschler SIB 3 (A1) Board ——#9
TRUTZSCHLER SBG-1 SBG1 CIRCUIT BOARD CARD 9 493-37.230.000 AA 49337230000 AA
TRUTZSCHLER SBG-1 SBG1 CIRCUIT BOARD CARD 9 493-37.230.000 AA 49337230000 AA
Trutzschler RIB 1 490-18.330.000 Lifetime Warranty !!!
Trutzschler RIB 1 490-18.330.000 Lifetime Warranty !!!
TRUTZSCHLER PR-1 CIRCUIT BOARD CARD PLC 491-89.230.000 49189230000
TRUTZSCHLER PR-1 CIRCUIT BOARD CARD PLC 491-89.230.000 49189230000
Trutzschler power supply VNB 1 9 494-66.430.000 AB VNB1 949466430000 NEW 8 A 24V
Trutzschler power supply VNB 1 9 494-66.430.000 AB VNB1 949466430000 NEW 8 A 24V
Trutzschler Power Supply NTE 1 9 492-47.430.000 AF New
Trutzschler Power Supply NTE 1 9 492-47.430.000 AF New
Trutzschler PLC Control Station BRE 1C 493-55.332.000 Used
Trutzschler PLC Control Station BRE 1C 493-55.332.000 Used
TRUTZSCHLER KOM 1.2 1 CIRCUIT BOARD 492-40.230.002 492-40.431.000 492-40.230.001
TRUTZSCHLER KOM 1.2 1 CIRCUIT BOARD 492-40.230.002 492-40.431.000 492-40.230.001
TRUTZSCHLER KOM 1 CIRCUIT BOARD 492-40.230.001 492-40.431.000 492-40.230.002. 3A
TRUTZSCHLER KOM 1 CIRCUIT BOARD 492-40.230.001 492-40.431.000 492-40.230.002. 3A
Trutzschler KIB 1A 9 494-61.230.000 Lifetime Warranty !!!
Trutzschler KIB 1A 9 494-61.230.000 Lifetime Warranty !!!
TRUTZSCHLER GMB-1C GMB1C CIRCUIT BOARD CARD 9 494-58.332.000 AC 49458332000
TRUTZSCHLER GMB-1C GMB1C CIRCUIT BOARD CARD 9 494-58.332.000 AC 49458332000
TRUTZSCHLER GMB-1A-9-494-58.230.000 / GMB1A949458230000 (USED TESTED CLEANED)
TRUTZSCHLER GMB-1A-9-494-58.230.000 / GMB1A949458230000 (USED TESTED CLEANED)
TRUTZSCHLER GMB 1B CIRCUIT BREAKER Q067173 WITH HEAT BLOCK $149
TRUTZSCHLER GMB 1B CIRCUIT BREAKER Q067173 WITH HEAT BLOCK $149
Trutzschler Drive Motor - 1LA7166-4AA99-ZN15
Trutzschler Drive Motor - 1LA7166-4AA99-ZN15
Trutzschler Drive FU1 9 495-20.330.00 AA 9 494-70.019.501 Used
Trutzschler Drive FU1 9 495-20.330.00 AA 9 494-70.019.501 Used
TRUTZSCHLER DEG 1 9 494-00.330.000AA, I/O BLOCK CIRCUIT BOARD
TRUTZSCHLER DEG 1 9 494-00.330.000AA, I/O BLOCK CIRCUIT BOARD
Trutzschler DEG 1 9 494-00.330.000AA One Year Warranty !
Trutzschler DEG 1 9 494-00.330.000AA One Year Warranty !
TRUTZSCHLER DEG 1 9 494-00.330.000AA I/O BLOCK CIRCUIT BOARD NEW NOS $899
TRUTZSCHLER DEG 1 9 494-00.330.000AA I/O BLOCK CIRCUIT BOARD NEW NOS $899
Trutzschler DCB1 DCB 1 9 494-80.230.000 ABR28 494-16.210.001 AA
Trutzschler DCB1 DCB 1 9 494-80.230.000 ABR28 494-16.210.001 AA
TRUTZSCHLER CONTROL STATION BRE 1C, 9 493-55.332.000 AD
TRUTZSCHLER CONTROL STATION BRE 1C, 9 493-55.332.000 AD
TRUTZSCHLER CIRCUIT BOARD CARD RAK 1 9 492-58.430.000
TRUTZSCHLER CIRCUIT BOARD CARD RAK 1 9 492-58.430.000
TRUTZSCHLER CIRCUIT BOARD CARD PLC MODULE CCM-UE1 CCMUE1 9 491-91.230.000
TRUTZSCHLER CIRCUIT BOARD CARD PLC MODULE CCM-UE1 CCMUE1 9 491-91.230.000
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