Compared with conventional drill, ultrasonic drill can break into rocks under lower weight on bit and lower power, which is more suitable to sample in low gravity environment for deep-space exploration. However, ultrasonic drill cannot remove rock cuttings effectively when drilling into a certain depth. This paper proposed a rotary-percussive ultrasonic drill (RPUD), which depends on a single piezoelectric transducer to produce rotary-percussive moment to drill into rocks and remove cuttings. RPUD consists of four parts: a piezo-ceramics, a percussive unit, a rotary unit, and a drill tool. Percussive unit magnifies the longitudinal vibration of one side of piezo-ceramics, and delivers percussive motion to the drill tool. Rotary unit transfers the longitudinal vibration of the other side of piezo-ceramics into longitudinal-torsional vibration to drive the drill tool to rotate. Percussive motion and rotary motion of drill tools are relatively independent, and thus their parameters can be adjusted separately. Finite element method is adopted to assist the design of the RPUD. Modal analysis is employed to tune the resonance frequencies of the percussive unit and rotary unit to be close. After the fabrication of a RPUD prototype, contrastive test of rotary percussive drilling and percussive drilling was carried out based on the RPUD prototype. Test results show that the RPUD can drill into the rocks and improve the efficiency of cutting removal.

A novel ultrasonic levitating bearing excited by three piezoelectric transducers is presented in this work. The transducers are circumferentially equispaced in a housing, with their center lines going through the rotation center of a spindle. This noncontact bearing has the ability to self-align and carry radical and axial loads simultaneously. A finite element model of the bearing is built in ANSYS, and modal analysis and harmonious response analysis are conducted to investigate its characteristics and driving parameters. Based on nonlinear acoustic theory and a thermodynamic theory of ideal gas, the radical and lateral load-carrying models are built to predict the bearing’s carrying capacity. In order to validate the bearing’s levitation force, a test system is established and levitating experiments are conducted. The experimental data match well with the theoretical results. The experiments reveal that the maximum radical and axial levitating loads of the proposed bearing are about 15 N and 6 N, respectively, when the piezoelectric transducers operate at a working frequency of 16.11 kHz and a voltage of 150 V_p-p.

The rocks on extraterrestrial objects contain plenty of original geological and biological information. Drilling and sampling are an essential task in lunar exploration or future explorations of other planets like mars. Due to the limitation of payloads, energies, and drill pressure, the investigation of a lightweight and low‐powered rock‐drilling device is crucial for explorations of distant celestial bodies. The ultrasonic drill driven by piezoelectric ceramics is a new drilling device that can adapt to the arduous space rock‐drilling tasks in weak gravitational fields. An ultrasonic drill suitable for mounting on a planetary rover’s robotic arm is developed. The ultrasonic transducer’s energy conversion from electric energy to acoustic energy and the energy transmission from the horn’s high‐frequency vibration to the drill stem’s low‐frequency impact motion are analyzed to guide the design of the drill. To deeply understand the percussive drilling mechanism under high‐speed impact, the interaction between the drill stem and the rock is simulated using LS‐DYNA software. Drilling experiments on rocks with different hardness grades are conducted. The experiment results illustrate that the ultrasonic drill can penetrate into the hard rocks only taking a force of 6 N and a power consumption of 15 W. The study of ultrasonic drill will provide a reference method for sample collection of extraterrestrial rocks.

As a potential alternative to conventional non-contact bearings, ultrasonic bearings are specially suitable for high-speed power machines and the torque-testing devices within a small range. The friction characteristics of the proposed ultrasonic bearing are investigated. The friction torques at low speeds and high speeds are measured by pendulum balance method and current feedback method, respectively. By means of time-frequency spectrum analysis to the rotor center’s orbits, the running stability of the bearing is studied when the bearing operates at starting or stopping stage and at high speeds. In addition, the influence on the bearing’s running stability of some key factors including rotary speed, load on the bearing and diameter clearance is revealed. The effective measures improving the bearing’s running stability at a high speed are presented to guide the bearing’s engineering application.