Hello

I'm having some trouble with my PID controller to control the speed of a small DC motor.
I'm using an S7-1215 DC/DC/DC and the PID_compact block in Tia Portal.

The setup, we have 2 DC motors which rotate a plastic disc with a bolt in it, we have 2 inductive sensors that registrate the bolt.

The meaning of the setup is, we are testing the given PID controllor in Tia Portal to make sure the 2 motors rotate at the same speed and on the same "position" ( the bolts have to pass the sensors at the same time).

So program. I have a main in which i use a FB to calculate the speed of the motor, i'm reading the sensors and i count them for a certain amount of time to calculate the speed.
Now I'm just testing the PID controller on the speed of the motor, because their speed is variable, so i can keep them on the same speed all the time. But that does not even work.
whichever setpoint I insert, the output is always going to max immediately. As an Input_PER I use the calculated speed (word) and output_PER is the outputword for the speed of the motor.

Can someone help me?
I'm programming in SCL

Thanks in advance
Arnou

Dear Friend 

in this case it does not matter if you are programming in SCL  or not.

I advice you to use the PWM output of the PID compact block to control with DC motor and be careful when you will make a PID tuning , because if you make a wrong tuning the PID will not work will

Then how can I adjust the PWM output to a word because i need an outputword to send to my motor?

Thanks for the advice!

I hope it has already worked for you, if not, you should check if your sensor feedback is measuring accurately, maybe the PID is trying to compensate a measurement that isn't being read.

Another possibility could be the PID tunning, maybe your Kp is way too big, you could also check if the PWM really gets activated when you write on it.

Kind regards