programming a VI to perform static tests

[nessun nome]

Dear NI, I am Maria Grazia and I posted a message some days ago but, as you said to me I didn't give much details. Now I want to explain better my research application so I’m going to give more details about my problem. I have to realize some static tests on a steel frame under cyclic loading. By means of an actuator connected to a motor, a force can be applied on the steel frame. An inverter (SSD 650V Series) drives the motor in the required direction (FWD and REV) and controls the motor speed. The motor goes in forward and reverse direction as a result of a relay within the inverter that supplies voltage. A displacement transducer measures the shift caused by the applied force. When it reaches the required shift, the motor stops. Afterwards, the load will be applied in the other sense. I have to realize a VI that drives the inverter which in turn drives the motor connected to the actuator. I would like to know if someone had already realised some similar application and could send it to me in order to understand how Labview works or to have further information about the construction of the VI. I have already the NI hardware required (cDAQ 9172, NI 9476, NI 9263, NI 9205 and NI 9237). Thanks a lot in advance for your help. Maria Grazia

[lucius]

Dear Maria Grazia,

as Centerbolt told you in your previous message, a good solution would be to use the Modbus library, but as I see on the AC650V series specification page, the Modbus Box is optional for these drives; I suspect you don't have one, so the only solution is to program digital and analog inputs and outputs through your DAQ cards in order to drive the inverter.

From what I understood from your description, I think it would not be so difficult to implement it, but I'm afraid you won't find an already developed ready-to-run solution.

I think you would have to acquire a signal from the displacement transducer through an analog input card and process the signal in a loop in order to generate the right outputs for the inverter: in order to understand how the inverter is driven, you should look at its documentation and specification. From the general page of the AC650V drives, they seem to have analog inputs for speed setting and digital inputs for start/stop, for direction and for preset speeds. So you should generate the right digital outputs and, if you want to continuosly change the speed, an analog output.

I can't be more precise, but I encourage you to look at the Getting Started with NI-DAQmx guide and try to implement what I suggested you.

If you'll have more specific problems in doing it, we're here to help you; but please be specific about the single problems you encounter.

Good job

Giorgio