Servo-Hydraulic Controller Buyers Guide

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Please note that this information is intended as a guide only. This section refers to the PID controller only. For information on the products that are layered onto these controllers, refer to the Analysis and Controls Software review. Individual needs vary, for help with a controller to meet your needs, contact us. Presented in alphabetical order of manufacturer, with no bias.

IST 8800/8400		Performance
		Reliability
		Value
Pros Cons Scalable architecture with clean integration Easy to use graphical interface Lots of features for difficult load loops Large installed base through Instron Small installed base through IST Expensive Structural testing apps buggy Limited support
Comments
I think it is a shame that IST products are not more widely used in the automotive-structural-fatigue-vibration-component testing sector. My opinion is that they have suffered from insufficient marketing, and the prices are set too high. This controller is sold extensively for materials testing (through Instron), and has a lot of features that are unique and very useful for those difficult control situations. They have a PID loop that can be reconfigured easily, the most accurate calibration in the market with intelligent sensors, very useful filtering features, and this is the only controller in the group with gain scheduling. No other controller comes close. These features must be balanced against their lack of support, and small installed base in this market. IST invented the scalable architecture now used by MTS, which is based on a small one channel instrument-based controller, that can stand alone, or integrate through a PC with larger multi-channel-multi-station towers. The only thing I am not keen on is their use of an old parallel interface standard for interconnection.

Moog-FCS SmarTEST ONE/xX		Performance
		Reliability
		Value
Pros Cons Up to four channels in small self contained package, expandable to 32 with up to 8 stations (xX) Sophisticated load control loop Many safety limits Lots of customizable functions Efficient function-key operation Inexpensive Hierarchical menu system makes finding functions difficult Architecture is not scalable Screen layout is fixed
Comments
This controller has a lot of promise, and with Moog backing, there are significant development dollars dedicated to improving it. This is evident already. I must admit that I initially found it difficult to use because it didn't speak my language. However, as I have used it more and more, I am getting the hang of it, and can now move through the menus quickly with the function keys. The big news is that they are implementing a touch screen display, which means that now, instead of counting off the function keys, you can just hit the button on the screen. Another change that they made recently is that they have hidden many of those arcane features that never get used behind an "Advanced" button. So now, when you want to set up a simple PID loop, PID is all you see. The controller has scripting capability and pseudo channels that will allow the controller to be used in a lot of applications, and now there is virtually no limit to the number of pseudo channels. I like the packaging, and I think with experience it is possible to navigate through the menus very quickly, and this controller would be faster to setup and operate than any of the others. At one time they had a problem with the box crashing in certain situations. These were with the earlier versions. I ran into it a few times, but it did not cause a problem for me, and I would assume the product is becoming more stable as they work out the kinks. By not scalable I mean that you cannot combine several SmarTEST ONE units to make a single multi-channel test.

MTS FlexTest SE/GT		Performance
		Reliability
		Value
Pros Cons SE is Easy to use Good integration with RPC Worldwide support Scaleable architecture Industry standard Reliable Limited features for pure PID Expensive No automated scripts GT interface is not intuitive
Comments
MTS is the market leader, and they have a lot of experience. The FlexTest products are solid, but not earth shattering. The SE in particular is a very basic PID controller, but there again you can't go wrong with it for run-of-the-mill testing. However, if you have a challenging control situation, the toolbox isn't very deep. Both of the other controllers listed here will provide you with a lot more tools to tame that tough load-control loop. However, for straight displacement control, these boxes have everything you need. With GT there are more "tools" but you have to buy everything you need a la carte, which means trusting the sales folks to understand what you need. One set of useful options is Calculated Variables and Calculated Channels. If you want to use them to build your own modal controller you have to buy them both.

Watch this space... Shore Western is developing a new controller. As soon as they have one for public consumption, I will let you know.