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PID Help...

Created by: huseyin_x at: 11/21/2011 3:24 PM (5 Replies)

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11/21/2011 3:24 PM	Rate (0)
huseyin_x Experienced Member Joined: 12/1/2006 Last visit: 11/10/2023 Posts: 26 Rating: (0)	Using the S7-1200 compact PID. I have PID. Where I want to set the time to reach the set point. Examples of SetPoint: 250 degrees to 30 min or 1 Hourssuch as the Reach. I want to use this time as a variable.

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11/21/2011 8:20 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 12/8/2023 Posts: 4284 Rating: (1381)	Hi, I think that you mean about TI parameter. Take a look at: Tips: PID (FB PID_Compact) /tf/WW/en/Posts/33957#top However, the bether way to be sure about of the warming time is to work with a ramped setpoint.
	Denilson Pegaia Siemens Industry Sector Technical Support
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11/21/2011 10:34 PM	Rate (0)
LuenObserver Regular Member Joined: 9/1/2011 Last visit: 1/24/2023 Posts: 13 Rating: (1)	I do not know if I understand you correctly. If you want to parameterize the time of getting respond of process to the setpoint, it's not so easy. Due to fact it's stricly depends of inertia of your whole system. Through setting PID parameters (Kp, Td, Ti) it's wanted to shorten the time.

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11/22/2011 1:11 AM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (149)	LuenObserver I do not know if I understand you correctly. If you want to parameterize the time of getting respond of process to the setpoint, it's not so easy. Due to fact it's stricly depends of inertia of your whole system. Through setting PID parameters (Kp, Td, Ti) it's wanted to shorten the time. Some technology needs furnaces that heat on with defined temperature gradient - ramp setpoint, the same regulation loop is required - pid regulator, except thatuser has to write his owntemperature diagram over time.

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11/22/2011 9:04 AM	Rate (0)
LuenObserver Regular Member Joined: 9/1/2011 Last visit: 1/24/2023 Posts: 13 Rating: (1)	All right. So if you want to have as you called "ramp setpoint". That's leads to "motion planning". It's commonly used in robotics for example. Firstly you tune a regulator to balance the inertia of system then you add the setpoint as a function that's depends of time. (ex. linear function or so on). Best regards

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11/22/2011 4:18 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 12/8/2023 Posts: 4284 Rating: (1381)	Hi, In general, you tunning your PID for responses "as quick as possible". Makes no sense to slowdown the PID response just to create a heating characteristic for a step of setpoint. Normaly, you tunning a PID for quick responses and makes the setpoint go slowley, follow a ramp, from the actual temperature to the target temperature. In this way you use the "power" of the PID to garaty that the heating will follow exactally the desired heating curve.
	Denilson Pegaia Siemens Industry Sector Technical Support
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