Search

The angle between the piezoelectric stack (PES) and the mover would significantly affect the output performances of stick-slip piezoelectric actuators in theory; however, this issue has not been explored. Accordingly, in this paper, to investigate the effects of the angle, a stick-slip piezoelectric actuator with a changeable angle between the PES and the mover was proposed, and its structure was briefly introduced first. Then, the relationship between the angle and the parasitic motion was theoretically calculated. After that, the output performances of the actuator were characterized under different angles between the PES and the mover. The results indicated that the angle between the PES and the mover significantly affected the one-step maximum displacement and the backward motion. After comprehensive analysis, the best output performances of the actuator were obtained under the angle of 0°.

To investigate the effects of initial gap on the one-stepping characteristics of stick-slip piezoelectric actuators, a stick-slip piezoelectric rotary actuator with changeable initial gap was designed and fabricated. Its output characteristics were tested under various initial gaps. Experimental results indicated that the initial gap indeed significantly affected the output characteristics in one driving cycle, especially at the final stage when the driving voltage was decreased quickly. Gradually increasing the initial gap, an interesting phenomenon was observed that the one-stepping characteristics in the final stage transformed from the sudden return (the so-called backward motion) to a critical status (nearly smooth motion), and finally to sudden jump. By analyzing the practical driving waveform as well as the additional deformation of the actuator, the evolution of one-stepping characteristics was rationalized. These findings and discussion are expected to enhance our fundamental understanding of the stick-slip principle and actuators. In addition, this study suggests a method to suppress the backward motion by simply changing the initial gap.

By imitating skateboarding movement, a novel stick–slip piezoelectric linear actuator was proposed in this study. A specific flexure driving foot mechanism (FDFM) was designed to realize the bionic driving function, and theoretical analysis was conducted to calculate the displacement amplification ratio of the FDFM which was further confirmed by finite element simulation. Being different from most of previous design that the slider moved and the driving mechanism was fixed, here the FDFM was integrated with the slider and they moved together along the guide rail. Being similar to that the train moved along the tracks, this kind of layout would facilitate the realization of larger working stroke of the actuator. By experiments, output characteristics of the designed actuator under various driving frequencies and voltages were tested. The results showed that by changing the waveform of driving voltage, both forward and reverse motions with good linearity and stability could be easily achieved. The speed of reverse motion was higher than that of forward motion because of the relatively larger backward motion during forward motion, which was due to the promotion of deformation recovery of the FDFM. Furthermore, the resolution and loading capacity were characterized. The resolutions of forward and reverse motions were 47 nm and 45 nm, respectively, and the actuator could achieve a relatively stable speed when the vertical load was in the range of 0–2 N. This study is expected to provide a new idea for designing piezoelectric actuators with features of high speed, high stability and large working stroke.

This paper presents a compact two-degrees of freedom (2-DOF) piezo-driven positioning stage. To achieve large working stroke, the stick-slip principle was employed, and to make the stage compact, a lever-type flexure hinge mechanism (LFHM) with the L-shape structure was designed. The LFHM could tune the single-direction output displacement of the stacked piezoelectric (SPE) to be two directional motions, the main motion for stick-slip driving and the parasitic motion for the contact. The L-shape structure makes the SPE being parallel to the slider rather than vertical to it, and therefore, the stage could be compact. The positioning stage had a two-layer structure for realizing motions along x and y axes, and these two layers shared the same structure. The structure design and working principle of the stage were discussed in detail. A prototype was fabricated, and the effects of driving frequency and voltage on the output characteristics were evaluated, followed by measuring its loading capacity and frequency characteristic. Experimental results showed that the output displacement had very good linearity in both x and y axes and as well for both positive and negative motions. Especially, even for a relatively large displacement output being over 1600 μm achieved by stepping accumulation, the output displacement still maintained very good linearity, demonstrating good motion stability. Furthermore, the backward motion was quite small compared with some previous studies. In addition, the vertical load in the range of 0 to 2 N had quite weak effects on the output characteristics, and the first resonant frequency of the driving unit was over 1900 Hz. These results indicated that the designed x-y positioning stage not only had a compact structure but also possessed good performances, which were beneficial to its practical applications.