Variable frequency driver control by analog voltage output

I need to drive a variable frequency inverter to drive a compressor and I am too newbie in this kind of works. The inverter can be controlled by analog voltage input and I have NI9188 and NI9263. I have never used analog output modules before and I have some doubts about them.
1. how could I drive the motor continuously?
2. do I have to use device internal clock or software clock?
3. in some examples, a waveform is generated and sent to the write daqmx vi to generate analog output. do I need to do it? (By the way, I prepared a control subVI to send the required input voltage data to the write daqmx.)
4. It is talked about pulse with modulation sth like that. What is it exactly? Do I need to concern about it?
I need to drive the compressor with two temperature feedback so I prepared a huge program by master/slave design pattern. I attached it. Does this program work? I do not want to harm the motor so I could not test it.
Egemen
Attachments:
Control Project.v0.zip ‏2672 KB

Hi newbieeng,
I hope you are doing well today!  I can help answer questions, but I can't debug a program and say whether it will work or not.
A lot of these question depend on your specific application and can't be answered in general.  I would take a look at the specifications document for the NI 9263 and also the specifications for your motor.  I'm including a link below to the specifications document for the NI 9263.  I would highly recommend looking at the current draw of the motor.  The most the NI 9263 can drive is 1 mA per channel.  
OPERATING INSTRUCTIONS AND SPECIFICATIONS
NI 9263
http://www.ni.com/pdf/manuals/373781e.pdf
As far as hardware timing vs. software timing, it really depends on what you want to do.  Hardware timing provides most more precise control over the timing of the output.
From one of the subVIs you provided, there seems to be a mention of a relationship between frequency and RPM.  Is this representative of a control signal the motor expects?  Is this the pulse width modulation (PWM) you were talking about?  If your motor requires PWM, then you will need to send it the appropriate signals.  I'm attaching a link below to an example regarding PWM.
Pulse Width Modulation
https://decibel.ni.com/content/docs/DOC-17537
Hopefully some of this is helpful!
Josh B
Applications Engineer
National Instruments

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