Go to the Matlab (i.e. Mathworks) website and see what hardware they support for real time control. I'm sure you'll get just what you need. (I've seen demos but can't remember all the details). The DSpace solutions are good but very expensive and probably way overkill for what you want. Look at some of the cheaper solutions.
Yes, I have and am using the matlab support site to find supported hardware. I never considered Dspace as I prefer a US based company for support.
On the other hand, Dspace has what I need and may be what I use as the I/O is modular and in a rack format.
In the past I have used ARCS, and Bitware for my control systems, both found by using the Matlab site. The Bitware system is up and running and was developed with Matlab. The ARCS system is now a portable system used for system ID and as a controller playground.
I used Bittware for one system and the SDL product for Matlab. These a both fine companies with excellent support.
I had to use a DSP programmer to get all working with a LINUX system and am looking for a solution that can be totally done in Matlab including our encoder IO. The Bittware system used an FPGA for the encoder I/O which I will do again if necessary but trying to avoid. This way I can do it all as I am not a real programmer.
last summer in Glasgow me and my friends Toomas Erm (Caltech, formerly ESO) and Bertrand Bauvier (ESO) have presented a paper at SPIE Conference on Astronomical Telescopes and Instrumentation, in which we showed a slight improvement in control of elevation position of a VLT telescope using H_infinity based loopshaping:
@InProceedings{erm_2004, author = {T.~Erm and Z.~Hur'{a}k and B.~Bauvir}, title = {Time to go $\mathcal{H}_{\infty}$?}, booktitle = {Proceedings of SPIE International Symposium Astronomical Telescopes}, year = {2004}, address = {Glasgow, Scotland, UK}, month = {June}, organization = {SPIE}, }
If you are interested, and have no access to the proceedings, I can send you a copy.
In fact, our major motivation for this adventure of using the H_infinity stuff was to make the bandwidth higher, to attenuate the effect of the disturbing torque induced by the wind buffets over larger frequency range. Finally we succeeded in stretching the bandwith a bit (but the physical limits did not let us go too far). I don't remember exactly, but it was something like one or two Hz, with the spectrum of the wind buffets being significant up to 1 Hz or so.
No. With H_infinity-optimization based loopshaping, you have a direct control over the shape of the frequency response and robustness requirements can easily be included. In fact, with the existing cascaded PI control, the magnitude frequency response must start roll off pretty soon (I mean, at low enough frequency), to guarantee, that at about 8Hz, where the slowest structural resonant modes appear, the amplification of the input signal by the system is low enough. As all these new optimization methods like H_inf usually give controller of higher order, the magnitude frequency response can stay high quite long and then start roll off steeply.
Well, in fact, the whole computation was done in Matlab and Simulink, we could only compare the performance by simulation, using a fairly precise model. As Toomas Erm (control engineer, formerly with ESO) said during his presentation in Glasgow: "we have demonstrated that further improvement in disturbance rejection for positioning the VLT is still possible. The question is, whether this slight improvement is sufficient motivation for the bosses to give us go-ahead with this new controller".
No, the two guys from ESO claimed that friction is no considerable problem with these huge and expensive VLT machines.
Depending on who I talk to, the performance gain of higher order controllers as applied to telescope control systems is marginal to significant. The VLTs are very impressive, well engineered systems that might represent the peak of 8 meter class technology. I met Toomas Erm once and he seemed to be very competent and knowledgeable and so I conclude that at least in the case of the VLT, application of H inf results in only a small gain in performance.
At the moment it seems that I can use simulink/matlab to interface and design with a few high performance DSP systems that will allow me to explore any number of control strategies. In addition, using the computing power of these systems, I can program the complete control system including the tracking vector generation and system telemetry all done in simulink. For safety we will have a small PLC as an observer that will monitor limits (position velocity and acceleration). The independent saftey observer was used in a large telescope control system here and has proven it worth.
thanks for letting me know about your work. I am ready to share some "advanced control-computational" skills exactly as I did with Toomas. Keep in touch if you are interested in such a collaboration.
(my apologies - since I work here you can consider this first part a bit of a plug ...)
here is an alternative to a dSpace system at a fraction of the price:
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This thread is interesting due to our discussions with the NRC (and related parties in North America) regarding the VLOT (now TMT) project. Jennifer Dunn had their controller simulations take into effect wind loading on the flexible telescope structure, but they were only assuming PI control I believe.
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