This page is borked.  I tried cleaning it up down to 'Theory', standardizing, etc etc.  

 I couldn't come up with a good example of cascading PID.  I was thinking of a waste wood fed steam boiler, with one PID loop internal to the feed auger VFD + steam pressure and a second PID loop of an external loop controller with a sensor on the stack temperature, but then couldn't figure out how you would feed the output of the second controller into the first if it was already a loop with its own input.  What is cascading PID?   

 Input > Controller > Output=Input > Controller > Output???  Why would you want to do that?  Someone clarify?