12/7/2012 10:40 PM | |
Posts: 6 Rating: (0) |
Hi huggy_d1, The hydraulic valves are 3 positions center closed 4 way , which means with both solenoids OFF, the cylinder will be clamped by the center closed of the valve. Do you think one PID for each valve will be enough? I will install a 3 axis tilt sensor which will give me 4-20ma for pitch and 4-20ma roll. My idea is first to set the desired position/elevation and then I will program a button on HMI that when pressed, the program will consider the values (pitch and roll) as set-point. Then, the trick is how i am going to use 2 set-points for the differents PID functions. I was thinking in use only one of the tilt-sensing either pitch or roll. Thanks Fabiano. |
Last edited by: Souza at: 12/7/2012 10:41 PM |
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12/7/2012 10:57 PM | |
Joined: 7/7/2010 Last visit: 10/18/2024 Posts: 15327 Rating: (2432)
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I was thinking you might want several PIDs that you can enable and test as needed. Get one working to prove it works. Then get the roll PID working by itself. Then maybe try both at the same time. If they are not coupled via some 3rd PID mechanism, it might get a little crazy withone valve PID control affecting the other PID control even when not needed. Perhaps if you set your pitch and roll sensors at a 45 degree angle to up/down/left/right, you can counteract those off effects. Just some random thoughts. If you have already modeled the control system and setup the feedback axis to match the control axis precisely, that's easy. Usually thought the physical motion is not in the same direction as the feedback so some allowance may need to be made. Please post your results. And, a video would be really awesome |
science guy |
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12/8/2012 7:36 PM | |
Posts: 6 Rating: (0) |
Hi Huggy...thanks for helping me out with some great ideas. I will definetly share the results when it is ready. I am building a simulator with a S7-1215C with a 4xAI and 16xDO modules. i will simualte both tilt-sensors with POTs and the valves with LEDs. That is just the first taste. Paralelly, I am building a small plataform with 4 hydraulic cylinders and electro-hydraulic valves which will be controlled from the PLC. You are right, I will have to try differents options like both sensors an only one each time...something like that......that will help me to get on the right track. That is an interesting thought....can you explain me better about setting the sensor to 45º? My inclinometer is a 3 axis sensor, and it will give me 2 x 4-20mA output, see attachment. How I am going to use both signal without fight each other...I don't know yet. I may try to use only one either pitch or roll and see how fast and accurate the system will respond. Another doubt I have, if I go with 3 step PID what i should use for both [input/input_per] and [feedback/feedback_per]? If I choose input_per (pitch or roll) what I should use on [feedback_per]? If I go with [input} I will have to convert my input word into real value. If I put my sensor input as my feedback, what should I use as my input? I am not sure if PID 3 step will apply for this application. WDYT? Thank you :-) |
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