SUPERVISORY CENTRAL OF DRILLING

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.