A classic solution for the control of a high-performance drilling process

The drilling process has often been insufficiently addressed from the control standpoint, in spite of the important role it plays in production and the enormous gains that automatic control could bring. Moreover, high-performance machining (HPM) process identification and control have been barely studied in the available literature. The creation and assessment of a hierarchical control system for the drilling process under HPM conditions in a professional machining centre is introduced in this paper. A classic linear PID controller for cutting-force control is designed using a linear model experimentally validated for an operating region. The controller is then modified to respect the technological restrictions that are specific to high-performance drilling. The control system is thus implemented, taking advantage of up-to-date hardware and software tools and rapid-prototyping techniques. Finally, the system undergoes field tests. The resulting system performance is rigorously investigated by means of input/output analysis and error indices. Under closed-loop control action, the cutting-force deviation was kept within an interval 2.4 times smaller than without control, always remaining below the nominal value. The drilling cycle time is approximately 1.3% shorter than the cycle time without control, a marked improvement on process efficiency.