A PLC, PLC three of a large number of is three a lot: in the switch, analog, pulse volume.
Only in the clear the relations between and among, you can skilled master PLC
is the purpose of the switch quantity control, according to the input current of switch quantity combination and history of the input sequence, make the PLC produces the corresponding switch output, in order to make the system to work in a certain order.
So, sometimes also called the sequential control.
The order is divided into manual, semi-automatic or automatic control.
And use the control principles of dispersion, centralization and three kinds of hybrid control.
after the PLC is introduced by relay control micro processing technology, which can be easily and reliably for on-off control.
Due to the analog quantity can be converted to digital quantity, digital quantity more than just the switch quantity, so after converting the analog quantity, will have reliable PLC for processing control.
Due to continuous production process often analog, so analog control sometimes called process control.
analog is power, and the PLC can only deal with digital quantity, power.
All in order to realize the conversion between them must have the sensor, the analog conversion into electricity.
If the battery is not standard, pass transmitter, non-standard power into a standard electrical signals, such as 4 -
10 v, etc.
at the same time also has analog input unit (
A / D)
To keep these standard electrical signals into digital signals;
Analog output unit (
PLC after processing the digital quantity, in order to convert into analog -
Standard electrical signals.
conversion between standard electric signal, the digital quantity, so it is used all kinds of operation.
This needs to clear up the resolution of the analog unit as well as standard electrical signals.
For example: PLC controller
simulation unit is 1/32767, the resolution of the corresponding standard power is 0 -
10 v, to detect temperature value is 0 -
The 0 -
Corresponding to 0-32767
Temperature of 100 ℃.
Then calculate the corresponding digital quantity will be 1 ℃ is 327.
If you want to put the temperature value to 0.
1 ℃, the 327.
67/10 is ok.
analog control include: feedback control, feedforward control, proportional control, fuzzy control, etc.
These are the PLC internal digital quantity calculation process.
quantity of PLC pulse control purpose is mainly position control, motion control and path control.
For example: pulse number in the application of the Angle control.
Stepper motor drives the segmentation is each lap 10000, required stepper motor rotate for 90 degrees.
So the pulse to be action value = 10000 / (
2, more than analog computing just do a simple introduction, different PLC has different resolution, and the measuring range of physical implementation, don't you like.
Calculated results may have certain difference.
note: analog input wiring requirements 1, use the shielded twisted-pair cable, but do not connect the shield.
2, when an input when not IN use, will V and COM terminal IN short answer.
3, analog signal wire and power cable isolation (
AC power cord, high tension line, etc. )
4, when there is interference on the power cord, the input part and install a filter between power supply
after 5, confirm the correct wiring, first of all to the CPU unit is powered on, and then to load on electricity.
6, when the power is cut off the power of the load first, then cut off the CPU power.
3, calculation of quantity of pulse pulse quantity control for the Angle of the stepper motor, servo motor control, distance control, position control, etc.
The following is a step motor as an example to illustrate the control mode.
formula is: Angle motion pulse number = a circle to the total number of pulse * (
Set the Angle / 360 °)
formula is: setting distance pulse number = set distance / [
* 3 roller diameter.
/ a circle to the total number of pulse]
this is just a simple analysis of the stepper motor control mode, may have discrepancy with actual, only for everybody reference.
the action of the servo motor and stepper motor, but want to consider the internal electronic gear ratio of servo motor and servo motor reduction ratio.
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