RSLogix5000 autotune feature for PIDE – a simple demo ...

this subject has been cropping up quite a bit lately ... since I was already doing some course development work along these lines, I've decided to post a few graphs for anyone who might be interested ...

these were all developed using the heating section of my Hotrod lab equipment ...

the figure below shows an "autotune" test in progress ... basically, the PIDE was placed in the manual mode with an output setting of 15% and allowed to settle down to a steady state – which turned out to be about 141 degrees F with an airflow of 20% through the system ...

once the steady state had been achieved, I clicked the Start button for the PIDE's autotune feature ... the graph shows how the autotune made a step increase to the output from 15% to 35% ... the autotune then watched the temperature increase – and when it figured that it had collected enough data, it automatically stepped the output back down to the original 15% setting ...

continued in next post ...

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the figure below shows the results that the autotune feature produced ...

as a first test, I selected the "fast results" and plugged those settings into the PIDE's tuning values ...

specifically, Proportional = 6.2735186; Integral = 2.1560543; Derivative = 1.219851 ...

continued in next post ...

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next I put the system into the Auto mode with a setpoint of 100 degrees F ... the airflow through the system was kept at 20% during this initial part of the test run ...

as shown in the trend below, I allowed the system to achieve its setpoint and settle down at a temperature of 100 degrees ... notice that this is a 32 minute graph ...

I then made a step change to the setpoint from 100 degrees to 200 degrees ... I allowed the system to achieve its setpoint and settle down at 200 degrees ... at the point marked in light blue, I changed the airflow through the system from 20% to 40% ... after a slight "deadtime" delay, this increased load on the system dropped the temperature slightly below the setpoint ...

the system recovered rather quickly by increasing the drive to the heater ...

continued in next post ...

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as a second test, I selected the "slow results" from the autotune chart and plugged those settings into the PIDE's tuning values ...

specifically, Proportional = 2.091173; Integral = 0.51334625; Derivative = 0.406617 ...

next I put the system into the Auto mode with a setpoint of 100 degrees F ... the airflow through the system was kept at 20% during this initial part of the test run ...

as shown in the trend below, I allowed the system to achieve its setpoint and settle down at a temperature of 100 degrees ... again, notice that this is a 32 minute graph ...

I then made a step change to the setpoint from 100 degrees to 200 degrees ...

I allowed the system to achieve its setpoint and settle down at 200 degrees ... at the point marked in light blue, I changed the airflow through the system from 20% to 40% ... and after the "deadtime" elapsed, this increased load dropped the temperature slightly below the setpoint as expected ... the system took a little longer to recover this time – as should be expected from the less-aggressive "slow response" tuning values ...

obviously the Hotrod is a rather simple system – but frankly I was rather impressed with the PIDE's Autotune results ...

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Good one, you need to save this on your website or save a link to this thread because this thread will get lost among all the other threads.