cRIO chassis recommendations for 4 axis with PID

[Apothus]

I could use some recomendations to help me select the right size chassis for our application.

We are looking to control 4 motion axes with simultanious PID control, out of a total of 6 possible axes connected to the hardware. We expect to have 6xAI, 6xAO & 48 D I/O.

Our motion is built on setting analogue output based on analogue input  using PID. Feedback is also integrated with I/O for the quadrature encoder, as well as limit switches.

In the past we have used cRio 9076 4 slot chassis for dual axis systems. We can use high density modules to keep the count at 4 modules however an 8 module chasis would be more flexible and helps us reduce the number of different module types to keep as spares.

Naturally this is a bit of a chicken and the egg scenario as the code will dictate the processing requirements of the chasis, however you need to know what chassis you are using before writing the code. 

Any guidance on this solutiuon and tips for solving this in the future would be appreciated.

[muffin.vi]

Apothus,

Are you looking for advice on which cRIO to get, or only how many modules to use? I would tend to reccomend going for the 8 module chassis, just because I've seen issues before where people bought the four slot, then later wished they had the flexibility of eight slots. But, it's really up to you and which modules you want to use. 

[Sam_Sharp]

Unless you're looking to run your PID controllers at super fast rates on RT (you could always run them on the FPGA...), any of the 8 slot RT chassis like the NI-9066 would be the best bet. I'd always recommend getting the 8 slot chassis. Even if you don't use it for much.