我做过类似的东西，当时是控制加热器的，用ＯＢ３５做加法，加到一定数值清０，再和每个PWM的设定值比较，控制输出，但也有缺点，就是所有的PWM都同时接通。
Network1
L "MW28"
L 1
+I
T "MW28"

Network2
A(
L "MW28"
L 49
>=I
)
JNB _001
L 1
T "MW28"
_001: NOP 0


Network3
m2: L "MD24"
SLD 3
T LD 0
L "MD34"
T LD 4

OPN "DB_PLC"

L "MW28"
L DBW [LD 0]
= Q [LD 4]

//下一组设定值

L "MD24"
L L#2
+D
T "MD24"
//下一个输出点
L "MD34"
L L#1
+D
T "MD34"

//输出点从Q4.0循环到Q19.7

L "MD34"
L L#152
<=I
JC m2

L L#0
T "MD24"
L L#32
T "MD34"