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Primary controller

Created by: Ugljesa at: 6/5/2015 7:44 AM (9 Replies)

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6/5/2015 7:44 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 10/18/2024 Posts: 102 Rating: (1)	Maybe, this is a stupid question, but can someone explain to me meaning of sentence in TIA Portal help for PID_ES: "The controller can be used individually as a fixed setpoint controller, or in secondary control loops in cascade, blending or ratio controls; however it cannot be used as the primary controller". Thanks in advance.
	Last edited by: Ugljesa at: 6/5/2015 7:45:12 AM
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6/5/2015 8:38 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	Hello, Primary controller is Master controller that produce the setpoint for the secondary (slave) controller in form of a number (real).A PID controller with binary outputs never can produce real outputs so it is disqualified to be the master controller. I hope this helps, hdhosseini
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6/5/2015 8:46 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 10/18/2024 Posts: 102 Rating: (1)	Dear sir, As always your explanations are excellent. If I understud correctly, I can use this controller to control two ON/OFF valves ? I don't have to use another controller in loop ? Once again, thank you for quick answer.

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6/5/2015 8:54 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	Thanks for the feedback, PID_ES is only used to operate integrating actuators like " Motorized Operated Valves" and slide valves in practice.It is not suitable for ON/OFF valves .
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6/5/2015 8:56 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 10/18/2024 Posts: 102 Rating: (1)	Is there any controller that I can use for such application?

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6/5/2015 9:05 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	I have not seen a PID regulator application with ON/OFF valve as actuator of controller
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6/5/2015 9:43 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 10/18/2024 Posts: 102 Rating: (1)	Maybe, I didn't described my system well. I have one hydraulic pump, and two valves (one device, I don't know word for that hydraulic component on English). For example when I switch on pump and one valve, piston opens and I have greater speed, on other side when I switch on pump and other valve pistons start to close and speed lowering.
	Last edited by: Ugljesa at: 6/5/2015 10:30:57 AM
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6/5/2015 11:02 AM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	If you can define 2 binary actuators to speed up and down the hydraulic system , possibly this is close to an integrating actuator.But still a remaining question, what happen if your both binary signals are in OFF status?After we come to a conclusion that they are integrating actuators, you can try CONT_S for simplicity.
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6/5/2015 11:12 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 10/18/2024 Posts: 102 Rating: (1)	I'm going to try with PID_ES, becouse I used before one PID controller without D parametar and system was unstable. For example, when speed is around 1400 rpm/min (target 1500) and I open piston, nothing happens. As my controller open system more and more, speed goes over 1500. So I need "brake" in my controller. When both signals are off, piston is not moving. (It's difficult for me to explain system behavior, language barrier is..)
	Last edited by: Ugljesa at: 6/5/2015 11:15:39 AM
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6/5/2015 2:21 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 10/26/2024 Posts: 6852 Rating: (1365)	If both outputs are off and speed is constant as the old value, I think you are working with a integrating actuator and you option of using PID_ES/CONT_S .The point is , if you can possibly manage the parameter adjustment and safety of your entire hydraulic system and for that I suggest consulting the manufacturer.
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