Hello guys,
it's time to talk about modeling and simulation again. I've been doing some research and saw different models. I noticed that in many cases control valves are used but never modeled. I know that when control valve is in good working condition that is not necessary. But nontheless, I'd like to discuss about control valve modeling. Control valves can have different types of flow charactersitcs. Most of them are shown in the attcahed picture:
http://www.plctalk.net/qanda/uploads/C_Valve_Flow_Ch.gif
Now, if valve is motorised, then DC or AC motor model should be taken into modeling phase. For now, we can exclude motorised valves.
I was playing in Matlab trying to make simple but effective model of a control valve and I came to the following structure:
http://www.plctalk.net/qanda/uploads/C_valve_model.jpg
Now, I made little test with ramp input and here's the result:
http://www.plctalk.net/qanda/uploads/Response.jpg
Of course, these time constants and gains are parameters that can be adjusted depending on the real situation in the field.
Saturation block is necessary and because of backlash this can be use to analyze prformanse of control loop in case if controller is used to minimize bad effect of valve with backlash.
Do you have time and will to try to make different models and design controllers to minimize negative effect of backlash?
Do you agree with this model?
it's time to talk about modeling and simulation again. I've been doing some research and saw different models. I noticed that in many cases control valves are used but never modeled. I know that when control valve is in good working condition that is not necessary. But nontheless, I'd like to discuss about control valve modeling. Control valves can have different types of flow charactersitcs. Most of them are shown in the attcahed picture:
http://www.plctalk.net/qanda/uploads/C_Valve_Flow_Ch.gif
Now, if valve is motorised, then DC or AC motor model should be taken into modeling phase. For now, we can exclude motorised valves.
I was playing in Matlab trying to make simple but effective model of a control valve and I came to the following structure:
http://www.plctalk.net/qanda/uploads/C_valve_model.jpg
Now, I made little test with ramp input and here's the result:
http://www.plctalk.net/qanda/uploads/Response.jpg
Of course, these time constants and gains are parameters that can be adjusted depending on the real situation in the field.
Saturation block is necessary and because of backlash this can be use to analyze prformanse of control loop in case if controller is used to minimize bad effect of valve with backlash.
Do you have time and will to try to make different models and design controllers to minimize negative effect of backlash?
Do you agree with this model?