I am interested to know what might be the applications for high-speed digital closed-loop controllers, by which I mean sample-rates of 2Msps and higher ?
My own pet application for electrical interface emulation does require complex and flexible controller characteristics with very low latency at 2Msps and up, but I'm assuming such demanding applications are rare ?

I'm not a control expert, but I assume the speed requirements are most likely related to physical world activities.  For many of these, the time constants are relatively long. However, I can see where very small devices - that require feedback systems - would have much shorter time constants, and therefore take faster loops.  My kids gave me one of those very small indoor RC helicopters.  It's response is so fast that I have a really hard time flying it. It could certainly use a stabilization system. Still not nearly requiring 2MHz sampling though. Maybe an application like robotic surgery where the "surgeon" is contained in a capsule.
David

Hi David, Thanks for those thoughts. As you suggest, anything with a bit of mechanical inertia is likely to need much lower rates. Like anyone, I can get to work with Google, but it's always good to have input from practitioners who know about the more obscure real-world applications. Perhaps there is some application in the ultrasound industry ?

As I have also written on another forum.

After a bit of research (Googling), and questions on Forums, I have concluded :-
a) High-bandwidth, Low-latency controllers of say < 100ns, are out of the mainstream of feedback controller designs.
b) Applications are rather niche but do appear in the fields of physics experimentation, MEMs systems, Electrical circuit emulation and other fast all- electronic applications such as SMPS.

It looks like this is an interesting area for research, even if current applications are few and far between.

I have done work on high speed PMSM motor control. For motors with high number of poles rotating at high speeds the control loops benefit from very high rates. I ran some motors at 100s of kHz (which is well below 2MHz) but I could imagine smaller motors running at 100K+ RPM might need control loops at 2MHz.

Hi Andrew, thank you for the insight into that application. I am working on all-electronic applications at present, but I am sure I will get around to some proper surveys of Physics, Ultrasonics, MEMs and other fast mechanical application areas later.