Possibility of flexible and automatic drilling such as human work

This paper proposes a new drilling concept from the standpoint of control engineering. One of the most crucial issues in drilling is the detection and prediction of drill breakage in small-diameter holes (less than 2.0 mm). When drilling irregularities are present due to factors such as a worn cutting edge or a hard spot in the material, the drill deflects as a column and induces vibration as it makes contact with the side or bottom of the hole, which results in drill failure. If the position of the drill edge can be observed and controlled in real time such as a work of skilled craftsman, drill breakage will be prevented, and the machining accuracy will improve accordingly. This study proposes a new mathematical drilling model in the form of transfer functions that are modified into a state space expression. The controllability and observability are investigated based on the rank of their matrices, which are obtained from state and output equations. It was found from this analysis that the drill edge position is both controllable and observable.