The areas of signal processing and feedback control systems go hand in hand.
Are control system questions within the intended scope of this site?
If not, I'm surprised... and where should they go?
Just my opinion: With one exception, I think they belong here. The exception is when it gets into hardware implementation of PID loops: if it involves a discussion of op-amps, RC values, A/D or D/A converters, I'd send the question over to electronics.stackexchange.com
Yes, both analog and digital controls questions are welcome here.
I would add to the point on @Jason's point :
Just ask what the question is about - if you are asking for theoretical perspective in other words - why certain things works the way they are, it is best fit here. If you find that your primary goal is to make the circuit work - and what are the practical titbits to be able to get there fast - essentially how to make it work - it better be at electronics.SE
Are control system questions within the intended scope of this site?
Yes!