Using PID with the Ramp Soak function is a great way to get accurate and repeatable system process. Join us in this brief video where we connect PID to the Ramp/Soak function and then test it to see how well it works!
Download support materials mentioned in the video here: https://library.automationdirect.com/?p=11129
To see the other videos in this series:
PID Overview Part 1:
PID Overview PArt 2: Hardware
PID AutoTune Part A
PID Autotune Part B
Do-more PID Tuning Simulator Part A
Do-more PID Tuning Simulator Part B
PID Manual Tuning Part A
PID Manual Tuning Part B
PID With Ramp Soak
PID Loose Ends
In all of the previous videos we have been adjusting the setpoint manually by entering the value here. And we standardized on three setpoints so we could do apples to apples comparison of test results from one type of PID tuning to the next. That was for our convenience; you can drive the setpoint with whatever you want. So, for this video, we'll use the same setpoints so we can compare results with the previous videos, but let’s control the ramping using the Ramp/Soak function. We’ll start at our usual 110, but then do a nice controlled ramp over 10 minutes to 115. Hold at 115 degrees for 10 minutes, then a controlled ramp down to 100 degrees over 15 minutes, hold that for 10 minutes, then ramp back to 110 degrees over 10 minutes. I’m using the same ladder code we have been using in previous videos where we take the process variable, filter it, and hand that filtered result to the PID function. All we have to do is add a Ramp/Soak function. We need to create a new structure, tell the Ramp/Soak function to control our OvenPID setpoint, and that we want it to start with the first step in the table below. For that first step, let’s initialize the setpoint at the current process variable value. Then, let’s ramp to 115 degrees over 10 minutes. By the way, we could also have said adjust the setpoint up 5 degrees. So, you have absolute and relative options here. I love that. Let’s hold at 115 degrees for 10 minutes, then do a controlled ramp down to 100 degrees over 15 minutes. We’ll hold there 10 minutes, then ramp back to 110 degrees over 10 minutes. Notice that you can move steps, inert steps and remove steps from the table. Hit OK, and I’ll add a C1 contact we can use to enable the instruction. And let’s make sure the jog and pause are disabled using the always off bit. Accept, save, write it out. Flip over to the PIDView window and we see I have already brought the system up to 110 degrees under PID control. Now we just enable C1 to enable the Ramp/Soak function. This should take almost an hour, so I’ll fast forward. Wow. Look at that! The Do-more PID function did an amazing job of tracking the Ramp/Soak profile. Perfect. The PAUSE control simply tells the instruction to freeze execution at the current step until PAUSE is released. JOG is edge triggered – as indicated by the gray triangle. Each time you toggle JOG, the Ramp/Soak will immediately exit the current step and move to the next step in the table. This Ramp/Soak function is great for any application where you want to specify where and when something needs to be. And when coupled with PID like we did here, you can create some really tight process controls. That ought to be enough to get you started with Ramp/Soak. Click here to see the other videos in this playlist. Click here to learn about our Free tech support options and click here to subscribe to our YouTube channel so you will be notified when we publish new videos.