Design and experimental verification of a bolt-clamped piezoelectric actuator based on clamping and driving mechanism

Highlights

• A non-resonant type piezoelectric actuator operated by clamping and driving principle is proposed.

• The slider is clamped by one or two driving feet during the whole working process, which ensures the motion stability.

• The maximum output velocity of this actuator is about 0.72 mm/s.

• This actuator can still output a velocity about 1.42 μm/s when the load mass is 1.47 kg.

• The experiments show that the actuator achieves a positioning accuracy less than 30 nm.

Abstract

A non-resonant stepping type piezoelectric actuator with bolt-clamped configuration was developed and tested in this work. This actuator was operated under clamping and driving mechanism by using two longitudinal-bending transducers. The longitudinal and bending deformations of the transducer were used to clamp and drive the slider, respectively. Such principle is totally different from the existing non-resonant actuators. This actuator was designed and its working principle was illustrated in detail. The motion characteristics of the driving foot were investigated by finite element simulation and experimental methods. A prototype was manufactured to validate the feasibility of the actuator driven by clamping and driving principle. The average step distance was tested as about 10.8 μm under the voltage and frequency of 400 V_p-p and 1 Hz. This actuator achieved the maximum velocity of 0.72 mm/s under the frequency of 60 Hz, and it outputted a velocity about 1.42 μm/s when the load mass was 1.47 kg. The tested results under PID closed-loop control indicated that this actuator acquired a positioning accuracy about 30 nm for 100 μm target displacement.

Introduction

With the rapid advancements of precision instruments, especially for semiconductor fabricating, grating ruling and ultra-precision machining, the driving devices with long stroke and nanometer accuracy have been drawn widespread attentions by the scholars [1], [2], [3], [4]. Various piezoelectric actuators that can transform the input electric energies into the output mechanical motions by using the inverse piezoelectric effect of the piezoelectric element have been emerged; and they are applied in precision devices due to their unique merits, such as compact size, quick response, self-locking when power off and free of electromagnetic interference [5], [6], [7], [8], [9], [10], [11].

The existing piezoelectric actuators are mainly classified into two categories from the viewpoint of vibration state: the resonant type and non-resonant type [12], [13], [14], [15]. In general, the resonant type actuators also can be called as ultrasonic motors and they use resonant vibrations to generate elliptical trajectory movements on their driving feet. They can acquire high-speed motions with long strokes. But their accuracies are usually limited at micron scale [16], [17]. For example, a two-DOF linear ultrasonic motor was presented by Liu et al. and their prototype obtained a high velocity of 572 mm/s under the voltage of 300 V_p-p [18]. But the displacement resolution of this motor was only 2 μm. A compact dome-shaped ultrasonic motor with diameter and curvature radius of 9.86 mm and 4.6 mm was developed by Yoon et al. and this motor gained a controllable accuracy of 3.12 μm [19]. In addition, the wear problem and heat generation of the ultrasonic motors are always difficult to be solved, which affects their lifetimes and further applications [20], [21].

Comparing with the ultrasonic motors, the non-resonant type actuators use their static deformations to realize output motions under static friction effect; they have many merits like flexible configuration, high accuracy and low heat generation [22], [23], [24], [25]. The non-resonant piezoelectric actuators mainly contain direct pushing type, inertial driving type and inchworm driving type; they are divided by means of their different working principles [26], [27], [28]. The direct pushing type actuators can acquire high accuracies. For instance, Yao et al. designed a two-DOF linear positioning stage with a resolution of 20 nm [29] and Kim et al. proposed a compact nano-positioning platform with control accuracy of 5 nm [30]. But the limited motion stroke is a major shortcoming for this type of piezoelectric actuator, which restricts their practical applications in the case of long stroke. The inertial type piezoelectric actuators can realize precise motions and long strokes with simple structures, while their output forces are relatively small. A torsional piezoelectric inertial actuator was provided by Han et al. and this actuator produced a small stall torque of 80 μN·m under the voltage of 1000 V_p-p [31]. Cheng et al. designed a stick-slip actuator with a novel exciting method combining by the ultrasonic friction reduction and the maximum load capacity was tested as 24 g [32]. Moreover, the rollback motion is an inevitable property for the inertial type piezoelectric actuator due to the working principle; and some methods have been reported for suppressing the rollback motion phenomenon [33], [34], [35]. As for the inchworm type piezoelectric actuators, they can acquire long motion ranges and large output forces comparing with the other non-resonant type ones. But the structures and control systems of the inchworm actuators are relatively complex as they need at least three PZT stacks integrated in different flexure hinges [36], [37], [38]. Thus, it is of great importance to develop a non-resonant type piezoelectric actuator combining the superiorities of compact configuration, high accuracy, large output force and long motion stroke.

A bolt-clamped piezoelectric actuator based on clamping and driving mechanism is developed in this work. This actuator aims at realizing long-stroke motion with large output force and nanometer accuracy driven by two longitudinal-bending hybrid transducers alternately. The structure of the developed actuator is introduced and its working principle is described in section II. Series of FEM simulations of this actuator are accomplished by using ANSYS in section III. Then, a prototype is fabricated and its mechanical output characteristics are tested. Finally, a summary of this work is provided.