A stick-slip piezoelectric actuator with measurable contact force

Abstract

The output performances of stick-slip piezoelectric actuators strongly depend on the contact force between the driving unit and the slider. However, quantitative measurement of the contact force is still unsolved, which brings difficulty for keeping the performance uniformity of piezoelectric actuators during mass production. To solve this problem, in this study, a cantilever beam was introduced into the driving compliant mechanism for quantitatively evaluating the contact force by means of its elastic deformation. Correspondingly, a stick-slip piezoelectric actuator with measurable contact force was developed. Its structure design and working principle were analyzed in detail, followed by characterizing the output performances under various contact forces, driving voltages, and frequencies. Furthermore, its loading capacity and motion stability were experimentally tested. The results indicated that the change in contact force would lead to the evolution in stepping characteristics between the backward motion and secondary increase in displacement, which further affected the motion speed of the actuator. Furthermore, it was observed that the contact force also significantly affected the resonant frequency of the actuator, and the increase in contact force would increase the resonant frequency. Comparative analysis demonstrated that even introducing the cantilever beam into the driving unit for measuring the contact force, the actuator could still achieve quite good output performances. For example, it could realize high speed (18.37 mm/s under the contact force of 15.54 N), relatively large loading capacity (2.7 N under the contact force of 25.90 N), as well as good motion stability. Therefore, the proposed measuring method of contact force is feasible and the corresponding actuator is applicable, which is meaningful for mass production of stick-slip piezoelectric actuators.