MorphuisOGrady
Member
Hi Guys,
First off I'll put my hand up and admit this is my first time ever having to tune a PID Loop. I wasn't involved in the project and have being drafted in for a couple of weeks. However its a perfect opportunity and I'd love to learn. I know there is a lot of PID experts here so hopefully I'll get some help.
The purpose of the PID control is by using a variable speed drive to maintain a constant level of 0.7 metres in a tank and hence a steady flow from the tank. The Platform is a Controllogix L-61 PLC using the standard PID instruction.
I know you guys appreciate as much detail as possible to assist in problem solving so with my limited knowledge of PID control I'll do my best.
The commissioning Engineer has advised me that there is a lot of lag in the system due to the distance between the pumps and the flowmeter we are using as the Process Variable.
As this is my first time tuning I really don't know what I should be doing. Rather than just trial and error I would really like to understand this.What I am asking is for any advice on how you guys approach this. I have tried adjust the gain and integral slowly up and down and the best I can get is close to 0.7M but with on/off control of the Pump. The Pump starts ramps up to 100% and then turns off again.
I apologise for such a poor description of the problem. I have made some trends of the system response in RSLogix if someone would be willing to view them.
From some posts here it might appear the PIDE instruction could help? Also a couple of new instructions have been introduced in Logix V17, the IMC, MMC and CC could be of use. Any thoughts? There is an Autotune function that could be beneficial?
First off I'll put my hand up and admit this is my first time ever having to tune a PID Loop. I wasn't involved in the project and have being drafted in for a couple of weeks. However its a perfect opportunity and I'd love to learn. I know there is a lot of PID experts here so hopefully I'll get some help.
The purpose of the PID control is by using a variable speed drive to maintain a constant level of 0.7 metres in a tank and hence a steady flow from the tank. The Platform is a Controllogix L-61 PLC using the standard PID instruction.
I know you guys appreciate as much detail as possible to assist in problem solving so with my limited knowledge of PID control I'll do my best.
The commissioning Engineer has advised me that there is a lot of lag in the system due to the distance between the pumps and the flowmeter we are using as the Process Variable.
As this is my first time tuning I really don't know what I should be doing. Rather than just trial and error I would really like to understand this.What I am asking is for any advice on how you guys approach this. I have tried adjust the gain and integral slowly up and down and the best I can get is close to 0.7M but with on/off control of the Pump. The Pump starts ramps up to 100% and then turns off again.
I apologise for such a poor description of the problem. I have made some trends of the system response in RSLogix if someone would be willing to view them.
From some posts here it might appear the PIDE instruction could help? Also a couple of new instructions have been introduced in Logix V17, the IMC, MMC and CC could be of use. Any thoughts? There is an Autotune function that could be beneficial?