Step7 with PID SIMO (single input, multiple outputs)

hello..

I use S-315 to run plastic Extruder. There is heating zone with cooling fan to stabilize the temperature

I have not found PID SIMO (single input, multiple outputs) in Step7 v5.4. There are solutions (also paid)??

Thanks.

zivk,
it would be very helpful if you actually explain your application and why you need to have SIMO. What is single input and what are multiple output (what process variables) and similar....

I'm looking PID or other solution to maintain a stable temperature by heating and cooling
Have a flow of hot plastic into the zone
if the temperature above SP so should cool by fan
if the temperature under the SP then need to heat
Of course the temperature is measured continuously
I hope this explains better
Thanks.


Single-Input, Multiple-Output (SIMO) Example

there is a single input coming from a temperature sensor, but then two controller outputs, or actuators, being used to change the temperature. PID can output both positive and negative values, so this example uses a case structure to decide when each actuator will be used. Let’s say that output channel 1 is connected to a heater and output channel 2 connects to a fan for cooling the system. If the PID output value is positive, then we want to raise the temperature by writing the output value to the heater and turning the fan off by writing a zero to channel 2. However, if the PID output value is negative, the false case structure writes the output value to the fan, and a zero to output channel 1. This is a very common way of implementing PID with multiple outputs.

You should look in the Step7 help files about FB42. That is STEP7 PID controller made for controlling motor actuators.
This is actually step controller. It has two outputs. It is aimed to control motors with discrete outputs. One output means move left other means move right. Of course, these outputs can be assign via DO module to relays. One relay would turn on heater, other would turn on cooler. Example is attached. When error is positive, one output is active, when error is negative, other output is active.
You can experiment with this and judge if this can be useful.
I know nothing about your particular application, but this could work.
Cheers,
Pandiani

Thanks, I'll check it out.

Diffrences between FB42 and FB59
https://www.automation.siemens.com/...PS=REDIR&PageIndex=1&PostID=98210&Language=en
What do you think more suitable for my case?

Zivk,

I explained the difference in that thread on Siemens web site. They are basically the same. Either will do. If temperature probe is directly wired to the input module you can use FB59 if you like and don't want to bother with conversion and scaling. You can try both and see for yourself. Under laying algorithm is the same. Since step controller is made for motorized valves, it requires MTR_TM (motor running time) which doesn't make much sense for heaters. Essentially this parameter determines the pulse duration. For example, for the same control deviation (error) the positioning pulse (output) will be active longer if MTR_TM is greater and vice versa. Duration of the control pulses is proportional to controller gain and MTR_TM and, of course, control error.

Please, let us know if you manage to get it to work.