PID application through inverter

[Chowdhury_Milon]

hello everyone,

Greetings. I want to control pump flow rate using PID controller through an inverter. I bought an inverter (LS SV015iG5A-2) and when I connected it to the computer through USB, a COM & LPT entry showed on my computer. I have already made a LabVIEW PID code (attached). But I can't understand how can I make an interface between LabVIEW and that inverter.

 Any kind of suggestion is appreciatable. TIA.

[GerdW]

Hi Milon,

I bought an inverter (LS SV015iG5A-2) and when I connected it to the computer through USB, a COM & LPT entry showed on my computer. … But I can't understand how can I make an interface between LabVIEW and that inverter.

Well, there is a COM port to communicate with your inverter.

I guess all the details of this communication is explained in the manual of your inverter: did you read it?

(Just a pure guess because of lack of information: your inverter is using some kind of Modbus protocol!?)

On your VI: There is a huge problem in the VI because you missed to THINK DATAFLOW! (The queue will not work as intended.)

[Chowdhury_Milon]

hello GerdW,

Thanks for your reply. I have connected the inverter to the computer through an RS232 converter and install RS 232 LabVIEW interface. I tried to check the connection by a basic  VISA code (picture attached).You know, I want to control pump flow using PID controller and You helped me to make a LabVIEW code for PID (code attached to the 1st post).  Now the problem is, how can I insert the inverter in that code to control PID action?

Any suggestion or similar examples are welcome. TIA.

[GerdW]

Hi Milon,

how can I insert the inverter in that code to control PID action?

Notes:

- Usually you use the PID to control the inverter/pump, not the other way around…

- You need to send the PID output (which should be pump speed or similar) to your inverter! Right now you only send this "1" constant…

[Chowdhury_Milon]

Hi GerdW,

1. In my PID code, input DAQ will be connected with water level sensor and output will be connected to the inverter which will control the pump. How can I connect the inverter with output DAQ? As it needs separate VISA code to connect to the computer through RS232. Maybe you have understood...

2. in 2nd post you said, there are some problems in queue lines. Would you make that correction, please? 

Thanks in advance. 

[GerdW]

Hi Milon,

1. You need to replace the DAQAssistant2 by some VISA code to send the PID output values to your inverter(s). Are you using more than one inverter when you have set your PID to "array" mode? Are you using more than one level sensor - or why do you convert the DAQAssistant reading to an array?

2. As you only attach an image I cannot to any changes using LabVIEW. Hint: learn to THINK DATAFLOW!

[Chowdhury_Milon]

Hi Mr. GerdW,

Thanks for your quick response. I will use 2 level sensors, that way I used the array option. and I will also control two inverters for two separate pumps. I have attached the PID code here. I have a humble request to you. Would you please modify the code according to your suggestion? Actually, I am not very expert and have to finish my research very soon. Please, don't reject my request....

[GerdW]

Hi Milon,

as I said before: you need to replace that DAQmxWrite by VISAWrite function(s) when your inverters are connected by COM ports!

(Don't forget error handling for those VISA connections!)