Development of a rotary-percussive ultrasonic drill using a bolt-clamped type piezoelectric actuator

Obtaining rock samples by drilling is an important method of asteroid detection. Due to the strict restrictions on the weight, volume, and weight on bit, conventional drilling devices are difficult to meet the requirements of drilling on an asteroid that has a weak gravitational field. This article proposed a rotary-percussive ultrasonic drill using a bonded-type piezoelectric actuator that can output harmonic vibration and elliptical trajectories simultaneously. The configuration and operation principle of the RPUD is presented and analyzed. Mode shape of the actuator and motions of the driving tips are verified by modal analysis and transient analysis, separately. Ultimately, a prototype of the RPUD is fabricated and experimentally investigated for its output characteristic and drilling performance. The test results indicate that the developed actuator can achieve the maximum no-load rotary speed of 119.2 r/min when the excitation frequency is 17.79 kHz. Furthermore, the maximum torque is 35 mNm, and the corresponding driving speed is about 20 r/min. The maximum drilling rate of the prototype to the sandstone is 7 mm per minute under a weight on bit of 5 N. The experimental results confirm that the proposed RPUD is feasible to drill rocks under a low weight on bit, which has the potential to obtain rock samples on an asteroid.