A supervisory process control approach to machining is presented in th
is paper, and demonstrated by application to a drilling operation. The
supervisory process control concept incorporates optimization and con
trol functions in a hierarchical structure. This approach utilizes fee
dback measurements to parameterize the constraints of a process optimi
zation problem whose solution determines both strategies and reference
s for process control. For this particular drilling operation, a three
-phase strategy (utilizing a combination of feed, speed, and torque co
ntrol) evolved due to inherent variation in constraint activity as a f
unction of hole depth. A controller comparison study was conducted whi
ch demonstrates the advantages of this approach compared to (1) uncont
rolled ''conventional'' drilling, (2) feed and speed controlled drilli
ng, and (3) torque and speed controlled drilling. Benefits of reduced
machining time, improved hole quality, and the elimination of tool bre
akage are demonstrated, and the potential economic impact is highlight
ed for an example production application.