cRIO using 9502 and 9514 for servo motor

[ZBob]

Hello,

The 9514 states it is an interface from the cRIO to a servo driver and the 9502 states that it is a servo driver.  Can you hook the two together to work as a system?  Is there any benefit of using the two together as opposed to just one?  I couldn't find any reference in either manual of the other's use.

Thanks,

Zach

[NathanK]

Hi Zach,

The 9514 is an interface to a third-party servo drive.

There really isn't a way, or a reason, to use the 9514 to control the 9502. The 9502 is already controlled by the cRIO's FPGA so no extra hardware interface or module is necessary.

You can use the 9502 if you are driving a brushless servo that is within its power limits. If you need to drive a larger motor then you would use the 9514 to control a larger third-party drive.

Nathan

[ZBob]

Thanks Nathan.  So it looks like the 9514 series has much more implemented on board meaning less is required on the FPGA.  The 9502 requires the PID loops to be programmed on the FPGA whereas not as the 9514 has them already implemented on board.  Is this the case?  Our team is new to progamming the FPGAs, so the less programming required, the more confident we would be in our design.  

-Zach

[NathanK]

The 9514 has a lot less logic in general because the 3rd party drive that it controls will implement the low level control loops.

The examples that come with the 9502 give you good starting points for the FPGA. If you have SoftMotion then the 9502 examples are basically complete applications. LabVIEW FPGA programming is pretty easy to pick up anyway.

Do you already have hardware or are you deciding what to get? Is your motor a brushless servo?

What version of LabVIEW are you using and are you using SoftMotion to control your motion?

Nathan

[ZBob]

We have a brushless servo and are currently using 2011.  We are probably going to Purchase SoftMotion here shortly, but do not have it yet.  We want to get the hardware selection worked out first.  Looking at page 2-7 of the 951x user manual, I see a picture of the 9514 with a PID loop microprocessor that makes me think the low level PID loop is already implemented on the 9514 whereas this is not the case with the 9502 because that manual explicitely shows all PID loops done on the FPGA.  Can you comment on this?  Why would the interface to an external drive have the PID loop on board, when the end product driver itself does not?

Thanks,

Zach 

[NathanK]

"Why would the interface to an external drive have the PID loop on board, when the end product driver itself does not?"

Essentially the cRIO FPGA is part of the 9502 module. Putting the control logic on the FPGA instead of in the module means that the module is less expensive and that it is more customizable. The performance is the same if not better.

The goal with a lot of cRIO products, and especially new motion products, is to give customers an API that can be opened and customized by customers all the way down to the actual IO pins if necessary.

In motion that means that when you use the 9502 you can run the example as is, or you can open it up and modify the logic that defines that hardware to customize it to your needs.

While the 9502 is less expensive than the 9514+Drive there are some tradeoffs. The 9502 can support up to 4 Amps continuous current. We are doing a lot of work to make the LV FPGA-based 950x modules integrate seamlessly with NI SoftMotion.  In LabVIEW 2011 it takes some custom programming to write the interface code between the NI SoftMotion engine and the FPGA.

The 9514 can potentially control a drive that can drive larger motors. It is also easier to use with the NI SoftMotion engine in LabVIEW 2011.

[Southern_Cross]

Are there any other "sizing" or "matching" requirements when trying to get the 9502 to work with a 3rd-party BLDC motor (i.e. a non-AKM motor)?