Design and experimental evaluation of an ultrasonic impact-assisted drilling mechanism for hard rocks

Current research on ultrasonic impact breaking of rocks primarily focuses on the rock breaking mechanism, ultrasonic vibration parameters, and engineering parameters, with less emphasis on ultrasonic drilling devices. A novel, compact, and efficient ultrasonic impact-assisted drilling mechanism is proposed in this paper. The ultrasonic transducer is the source of impact vibrations in the drilling mechanism, and its output performance directly influences drilling efficiency. Therefore, it is modeled theoretically to enhance its output performance, and the effectiveness of the structural design is verified through simulation analysis. In order to prevent the drift of the resonance frequency of the transducer during operation, which can lead to a decrease in drilling efficiency, this paper proposes a PI control strategy based on a static capacitance compensation method. The experimental results indicate that the maximum output amplitude of 43 μm can be stably maintained by controlling the driving transducer using the proposed method. Compared to rotary drilling, the drilling speed of the proposed drilling mechanism increases by 15.5% when drilling sandstone and by 9.9% when drilling limestone. The proposed drilling mechanism features a compact structure and high drilling efficiency, making it highly applicable in narrow environments such as underground coal mines.