A parasitic-inertia piezoelectric actuator with isosceles trapezoidal flexible mechanism base on parasitic motion exploration and asymmetrical installation

Parasitic-inertia piezoelectric actuators have been widely studied for their ability to achieve both high positioning accuracy and large working strokes. However, backward motion results in parasitic-inertia piezoelectric actuators with the disadvantages of low efficiency and abrasion of driving foot. In this study, a parasitic-inertia piezoelectric actuator with an isosceles trapezoidal flexible mechanism is diegned and optimized to reduce backward motion considering the influence of parasitic motion proportion. It applies the asymmetrical installation of the piezoelectric stack to increase parasitic motion hence the reducing of backward motion. This study discusses the structure and working process of piezoelectric actuators and optimizes the design of flexible mechanism structure parameters with matrix displacement method and finite element method. A prototype of an parasitic-inertia piezoelectric actuator was manufactured, and a series of experiments were conducted. From the experiment, the piezoelectric actuator obtained a minimum backward motion percentage α = 18.36% and forward motion time percentage β = 95.9% at the frequency f = 1 Hz and the voltage U = 80 V. At U = 120 V, f = 500 Hz, the maximum motion speed of the actuator is 916 μm s⁻¹; At U = 20 V and f = 1 Hz, the minimum positioning resolution of the actuator is 0.69 μm. At U = 120 V, f = 1 Hz, the maximum vertical load force is 1600 g, and the maximum parallel load force is 50 g. It has shown that the proposed isosceles trapezoidal flexible mechanism is feasible and can significantly reduce backward motion at the appropriate voltage. The mentioned characteristics of isosceles trapezoidal flexible mechanism can significantly alleviate the abrasion of driving foot, improve working efficiency. Also, it is vital for the miniaturization and practical application of parasitic-inertia piezoelectric actuators.