In order to decrease the backward motion and improve the motion efficiency, a walking type piezoelectric actuator has been proposed with two ‘legs’ based on the parasitic motion of obliquely assembled PZT stacks. The structure and motion principle of the proposed walking type piezoelectric actuator are described, and its experiment system is set up. Experimental results indicate the proposed piezoelectric actuator could reduce the backward motion effectively. The minimum backward rate α= 2.26% is achieved under the condition of the phase difference θ= 180°, the input voltage U= 120 V and the input frequency f= 1 Hz; the minimum stepping displacement is 0.24 μm under the condition of U= 5 V, f= 1 Hz and θ= 180°; the maximum speed V max is 2472 μm s−1 under the condition of U =120 V and θ= 180°; the maximum vertical load force F Vmax = 6850 g under the condition of U = 120 V, f = 1 Hz and θ = 180°. Furthermore, a dynamic model of the whole walking type piezoelectric actuator is established, and it has been employed to simulate the motion of the proposed walking type piezoelectric actuator. Simulation results present a great agreement of experimental results. This study shows a novel idea for the design of piezoelectric actuators to eliminate the influence of backward motion and improve the output efficiency of the actuator.

A walking type piezoelectric actuator with two umbrella-shaped flexure mechanisms is proposed to reduce the backward motion. By utilizing two umbrella-shaped flexure mechanisms which could be treated as two 'legs', the 'walking' motion is accomplished. The structure and motion principle are described; Finite Element Method (FEM) is exploited to explore the static and modal performances of the umbrella-shaped flexure mechanism. Moreover, experiments have been carried out to investigate the working performance of the proposed walking type piezoelectric actuator. Results show that the walking type piezoelectric actuator with umbrella-shaped flexure mechanisms could achieve the 'walking' motion and reduce the backward motion. Additionally, the phase difference between two input signals U 1 and U 2 greatly influences the working performance. In the case of the phase difference Φ = 95 • , the backward rate of the slider is able to achieve the minimum 0%; the minimum stepping displacement is 0.3 µm when the frequency f = 1 Hz; the maximum motion speed of the slider is up to 1132 µm s −1 when the input frequency f = 400 Hz and the input voltage U = 120 V; the maximum output force is 700 g while the input voltage U = 120 V and frequency f = 1 Hz.

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A parasitic type piezoelectric actuator with an equilateral triangle flexure mechanism is proposed and investigated to achieve large-stroke linear motion. Right-circular flexure hinges with different thicknesses (t 1 and t 2 ) are utilized in the design of the equilateral triangle flexure mechanism which is able to generate parasitic motion. The working principle is analyzed and illustrated by the theoretical simulation and finite element method (FEM) simulation. A prototype is manufactured to study the performance of proposed parasitic type actuator, together with an experimental system. Experiments indicate that the maximum stepping displacement is ΔL=9.00 μm in the case that input voltage U e =150 V; the minimum stepping displacement ΔL=0.24 μm is achieved under U e =60 V; the maximum speed is V s =180 μm s −1 ; the largest output force is F=106.3 g under that input frequency f=1 Hz and U e =100 V. This study demonstrates the feasibility of symmetrical triangle flexure mechanisms in the design of parasitic type piezoelectric actuators with large working stroke.

Piezoelectric actuators are widely utilized in many research and industrial fields, since they could achieve high positioning accuracy based on inverse piezoelectric effect. However, the working stroke of piezoelectric actuators is always limited, which restricts the further application of piezoelectric actuators. In order to solve this problem on short working stroke, this study introduces an umbrella-shaped linear piezoelectric actuator to achieve a large working stroke. Unlike traditional stick-slip actuators, the PZT stack inside the umbrella-shaped flexure mechanism is assembled vertically to the slider. The composition and motion principle are discussed, and FEM (Finite Element Method) and experiments are utilized to explore the performance of the proposed actuator. Experimental results show that the minimum stepping displacement is 0.495µm in the case that the input voltage U = 30V and the frequency f = 1Hz; the maximum speed is 992.4µm/s under the condition of the input frequency f = 400Hz and the input voltage U = 120V; the maximum load is 220g in the case of the input voltage U = 120V and the frequency f = 1Hz. This study indicates that the proposed umbrella-shaped linear piezoelectric actuator is feasible and could achieve a stable large working stroke. INDEX TERMS Nano positioning, piezoelectric actuator, high accuracy, inverse piezoelectric effect, large working stroke.