Patent ID: 8353368

Claim:
A drill-bit control method for use with drilling apparatus comprising a drill-bit capable of oscillatory and rotary loading and a control means for controlling applied rotational and/or oscillatory loading of the drill-bit, the control means having adjustment means for varying the applied rotational and/or oscillatory loading, said adjustment means being responsive to conditions of the material through which the drill is passing; the adjustment means further controlling the applied rotational and oscillatory loading of the drill-bit so as to achieve and maintain resonance at the drill-bit and the drilled material in contact therewith, the method further comprising determining appropriate loading parameters for the drill-bit according to the following steps in order to achieve and maintain resonance between the drill-bit and the drilled material in contact therewith: A) determine a limit of amplitude of the drill-bit when resonating and interacting with the material being drilled; B) estimate a suitable frequency sweeping range for loading the drill-bit; C) estimate the shape of the resonance curve; D) choose an optimum resonant frequency on the resonance curve at a point less than the maximum on the resonance curve; and E) drive the drill-bit based on this optimum resonant frequency.