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PID level Control not starting

Created by: jimbo1234 at: 3/4/2015 6:54 PM (28 Replies)

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3/11/2015 5:33 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 9/25/2023 Posts: 6822 Rating: (1349)	What was there error?I create an FBD version of program both in OB100 and OB3X.Please just copy the idea and customize that to your application.In OB100, you call PID with COM_RST active with exact DB that is used on OB3X.It is for initialization purpose.At the end of OB100,COM_RST resets but Man_on is active for starting cyclic execution stopping with LMN=Man. Attachment OB100.zip (121 Downloads)
	Last edited by: hdhosseini at: 3/11/2015 5:36:21 PM Demo Channel on Youtube
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3/11/2015 5:41 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 9/25/2023 Posts: 6822 Rating: (1349)	and for normal operation, parameterize SP_INT and PV_IN. For troubleshooting the PID part, we need the VAT I uploaded some days ago.To energize the pump, please fine the R-Prior flip-flop with a spare rest signal while tank is getting empty and PID can not regulate. Attachment OB35.zip (142 Downloads)
	Demo Channel on Youtube
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3/11/2015 6:14 PM	Rate (0)
jimbo1234 Posts: 74 Rating: (0)	Hi, Thank you I think this is going to work now regards
jimbo1234 Posts: 74 Rating: (0)
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This contribution was helpful to 1 thankful Users hdhosseini

3/12/2015 1:46 PM	Rate (0)
jimbo1234 Posts: 74 Rating: (0)	I have a problem with not reaching the setpoint, there seems to be no effect from the integral term on the output, when I increase the proportional term all that does is get me closer to the setpoint quicker, then the pump speed drops off at pretty much the same point everytime.
jimbo1234 Posts: 74 Rating: (0)
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3/12/2015 4:00 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 9/25/2023 Posts: 6822 Rating: (1349)	This is the time to tune your PID, without having a trend consists of DP_INT,PV_IN,LMN it is hard to recommend.But, you can try the basic and always working solution, start with small gain and long Ti and try to optimize by checking the process reaction. Note: for level , structure de-composition structure is recommended that is not implemented in FB41 plus curve-based parameter optimization is not applicaple for level control.So do it by try and error.
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3/12/2015 6:42 PM	Rate (0)
jimbo1234 Posts: 74 Rating: (0)	Hi, I am mananging to get an response which is unstable with an oscillating output. When I set the "Integral Action Initilized " on the PID Control Online monitoring it cuts my motor speed alot, Otherwise the integral term doesnt seem to be having an effect.
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3/12/2015 8:53 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 9/25/2023 Posts: 6822 Rating: (1349)	Integration part of PID is essential for a smooth operation.If your loop in inactive, just put it in manual.Initialization of I-Part will help if loop is, inactive and auto(this happens in practice while output of PID in manipulated by sequences and PID in auto in one of the sequences).For over/under shoots, gain works perfect while accumulated I part will cause reluctance to settlement.So , please increase Ti and monitor P and I elements on output.
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3/13/2015 1:14 PM	Rate (0)
jimbo1234 Posts: 74 Rating: (0)	I have a near perfect response, with little overshoot and only slight damping as the pump settles on the setpoint, but I cant seem to ge the pump to settle back down to 0, do you think this is because there is a disturbance in the rig I am using? mabye water in the pipes constantly pushing down on the pump? Any ways to stop this regards ( you have been very helpful)
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3/13/2015 3:13 PM	Rate (0)
hdhosseini Diamond Expert Joined: 1/28/2009 Last visit: 9/25/2023 Posts: 6822 Rating: (1349)	I am happy the comments help you , but for new issues I need to see your response (setpoint, LMN and PV).As a general point, you can : Filter your PV because of jumps due to pumping Use deadband if you think slight flactuation in error signal exists
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