A novel two-dimensional linear piezoelectric stepping platform using two parallel longitudinal-bending hybrid piezoelectric actuators was proposed. The proposed platform was moved in X direction by combing the vertical and horizontal bending motions of the parallel actuators, whereas the movement in Y direction was realized by the vertical bending and longitudinal hybrid motions. The platform was designed and its operating principles in two orthogonal directions were described. The finite element method (FEM) simulations were performed to verify the operating principles of the two-dimensional platform. Two piezoelectric actuators were fabricated and a prototype of the platform was assembled. The measured results of mechanical output performance indicated that the velocities of the platform were 101.7 μm/s and 124.2 μm/s in X and Y directions when the voltage and frequency were 400 V$_{p-p}$ and 5 Hz, respectively, which verified the feasibility of the proposed mechanism for two-dimensional stepping platform.

An inchworm type piezoelectric actuator with four driving feet is proposed and tested. The proposed actuator has merits of easy fabrication and miniaturization structure by using a boned-type structure. Horizontal vibration mode and vertical vibration mode are produced synchronously with a certain temporal phase, and their superimposition makes the driving feet produce elliptical movements. The actuators can achieve bidirectional motion easily by exchanging the two driving signals. The resonance frequencies of the two modes are tuned to be close at 41.35 kHz by adjusting the structural dimensions. The mode shapes and trajectories of driving feet are investigated to verify the driving principle. The vibration amplitudes of driving feet in driving direction are trimmed to be nearly the same via changing the phase difference. The design and analysis are accomplished by finite element method. The vibration characteristics of the prototype are verified by a scanning laser Doppler vibrometer. The fabricated piezoelectric actuator achieves a maximum speed of 1641 mm/s and a maximum thrust of 120 gf.

Inspired by a way of rowing, a new piezoelectric driving quadruped micro-robot operating in bending-bending hybrid vibration modes was proposed and tested in this work. The robot consisted of a steel base, four steel connecting pins and four similar driving legs, and all legs were bonded by four piezoelectric ceramic plates. The driving principle is discussed, which is based on the hybrid of first order vertical bending and first order horizontal bending vibrations. The bending-bending hybrid vibration modes motivated the driving foot to form an elliptical trajectory in space. The vibrations of four legs were used to provide the driving forces for robot motion. The proposed robot was fabricated and tested according to driving principle. The vibration characteristics and elliptical movements of the driving feet were simulated by FEM method. Experimental tests of vibration characteristics and mechanical output abilities were carried out. The tested resonance frequencies and vibration amplitudes agreed well with the FEM calculated results. The size of robot is 36 mm × 98 mm × 14 mm, its weight is only 49.8 g, but its maximum load capacity achieves 200 g. Furthermore, the robot can achieve a maximum speed of 33.45 mm/s.

A novel U-shaped piezoelectric ultrasonic motor that mainly focused on miniaturization and high power density was proposed, fabricated, and tested in this work. The longitudinal vibrations of the transducers were excited to form the elliptical movements on the driving feet. Finite element method (FEM) was used for design and analysis. The resonance frequencies of the selected vibration modes were tuned to be very close to each other with modal analysis and the movement trajectories of the driving feet were gained with transient simulation. The vibration modes and the mechanical output abilities were tested to evaluate the proposed motor further by a prototype. The maximum output speed was tested to be 416 mm/s, the maximum thrust force was 21 N, and the maximum output power was 5.453 W under frequency of 29.52 kHz and voltage of 100 V_rms. The maximum output power density of the prototype reached 7.59 W/kg, which was even greater than a previous similar motor under the exciting voltage of 200 V_rms. The proposed motor showed great potential for linear driving of large thrust force and high power density.

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.