A dual-mode stick-slip piezoelectric actuator imitating mantis forefoot

Most existing stick-slip piezoelectric actuators fail to achieve smooth motion and linear speed, and the backward motion cannot be actively inhibited during motion. This paper develops a novel piezoelectric actuator with stiffness-variable flexible mechanism imitating mantis forefoot, which utilizes the elastic potential energy to suppress backward motion. Furthermore, the contact condition between the driving foot and the rotor can be adjusted through a joint-like flexible structure. On this basis, contact precisely adjusted driving (CPAD) mode and triangular wave cooperative driving (TWCD) mode are proposed to achieve complete suppression of backward motion, as well as high-speed and high-resolution output. The transfer matrix method (TMM) in the cross-section of multiple state nodes has been improved and applied to accurately establish the theoretical model for the complex flexible hinge structure, with the combination of FEM for structural optimization design and mechanical properties analysis. The error between the calculated results and the experimental results is within 4%. Finally, a prototype with dimensions of Ø36 × 10 mm is manufactured and tested. The results show that both driving modes are able to achieve smooth motion output by actively suppressing backward motion, and a linear speed curve can be achieved under 800 Hz. The prototype achieves a maximum speed of 4491.38 mrad/s and a rotational resolution of 0.332 μrad, which is significantly better than existing actuators with similar size. This study shows great value for applications in the field of fast and precise positioning with size constraints.