This paper presents a novel piezoelectric actuator containing double pushers. By using finite element analysis software, this study simulated the vibration mode and amplitude of piezoelectric actuators. The Taguchi method was used to design the parameters of piezoelectric actuators including length, width, height, and electrodes setting. This paper also presents a discussion regarding the influence that the design parameters had on the actuator amplitudes. Based on optimal design parameters, a novel piezoelectric actuator containing double pushers is produced and some thrust tests are also carried out. From the experiment results, the piezoelectric actuator containing double pushers can provide a greater thrust force than that of traditional actuators containing a single pusher as the preload is greater. Comparing with the traditional actuators, the thrust force of new actuator can be increased by 48% with the double preload.
In 1982, the first piezoelectric actuator was produced by Shinsei. In 1987, piezoelectric actuators were installed in dot matrix printers and mass-produced; this was the first time piezoelectric actuators were used in commercial applications. Canon and Minolta successively applied piezoelectric actuators in the autofocus and shutter units of cameras. In the late 1990s, Toyota used piezoelectric actuators in the automobile industry, specifically in the suspension system and seat adjustment controls of vehicles. In 1995, Epson used piezoelectric actuators to develop print heads in ink-jet printers, thereby beginning the industrial trend of applying piezoelectric actuators in various microsystems [
Piezoelectric actuators are categorized into standing-wave and traveling-wave actuators according to the drive modes. The vibration mode of traveling-wave actuators is a ripple, which travels in an oval trajectory. The motion trajectories of standing-wave actuators are oval, linear, or of other shapes. The biggest difference between the two types is the wave node, which can be used as a reference when designing fixed points. Traveling-wave actuators do not contain wave nodes, thereby limiting the mechanical design; standing-wave actuators possess wave nodes, which ensure relatively simple designs that are easily miniaturized.
According to the drive signals, piezoelectric actuators are categorized into single-phase [
When periodic electrical energy is excited in piezoelectric actuators, periodic deformation occurs. This periodic motion then causes linear or rotational motion in objects because of the friction that pushes or drives objects. Figure
(a) Vibration mode of actuator using a single pusher. (b) Driving principles of the actuator.
Vibration mode of actuator using double pushers.
Taguchi method is a kind of design of experiment (DOE) developed by Genichi Taguchi. It has been widely used to improve the quality of a product or a manufacturing process by means of statistical method. It usually obtains the optimal design factors by tools such as
In this study, “the average vibration amplitude of two different driving points on the piezoelectric plate” is chosen to be the quality characteristics. The quality characteristic is larger-the-better since the larger vibration amplitude is expected. All possible design factors that affect “the average vibration amplitude of two different driving points on the piezoelectric plate” were considered by a brainstorming in an early design stage. The width of the piezoelectric actuator, the length of the piezoelectric actuator, the thickness of the piezoelectric actuator, and the electrode setting are chosen to be the design factors. The four chosen control factors and their levels for the experiment are shown in Table
The control factors and levels table.
Factor |
Level 1 | Level 2 | Level 3 |
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Width ( |
6 mm | 8 mm | |
Length ( |
14 mm | 16 mm | 18 mm |
Thickness ( |
1 mm | 1.5 mm | 2 mm |
Electrode setting ( |
4 : 6 | 5 : 5 | 6 : 4 |
Table
The quality characteristic response table in
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Rank | 3 | 1 | 2 | 4 |
The factor effects response plot in
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The response table in
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Rank | 4 | 1 | 2 | 3 |
The factor effects response plot in
Comparing the above results, it is found that the effects of factors
The pushers should be set at the positions with maximum amplitude on the piezoelectric actuator to produce the larger thrust force. The fixtures should be set at the positions with minimum amplitude on the piezoelectric actuator so as not to affect the operation of the actuator. Figure
The vibrating amplitudes in the
The detailed dimensions of the large thrust piezoelectric actuator.
In order to measure the output thrust force of the piezoelectric actuator containing double pushers, this actuator is used in the linear stage. Figure
The linear stage using the large thrust piezoelectric actuator.
In this study, the thrusts force of novel piezoelectric actuator containing double pushers and the conventional piezoelectric actuator containing a single pusher are measured. The setup of thrust force measurement experiment is shown in Figure
Setup of thrust measurement experiment.
Thrust measurement experiment.
The resonance frequency of piezoelectric actuator containing one single pusher obtained by simulation is about 222 kHz. The actual operating frequency is about 218 kHz after the actuator is assembled in the linear stage. After initial testing, the appropriate preload of 215 g is chosen. Too large or small preload will influence the normal operating of the actuator. The thrusts forces of the linear stage with the preload of 215 g and the drive voltage 30 Vpp are shown in Table
Thrusts of piezoelectric actuator containing single pusher (preload of 215 g, drive voltage 30 Vpp).
Freq. (kHz) | Test 1 (g) | Test 2 (g) | Test 3 (g) | Test 4 (g) | Test 5 (g) | Ave. thrust (g) |
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217 | 60 | 62 | 69 | 63 | 57 | 62.2 |
218 | 64 | 68 | 72 | 73 | 70 | 69.4 |
219 | 54 | 57 | 60 | 52 | 55 | 55.6 |
The resonance frequency of piezoelectric actuator containing double pushers obtained by simulation is about 261 kHz. The actual operating frequency is about 256 kHz after the actuator is assembled in the linear stage. The thrusts forces of the linear stage with the preload of 215 g and the drive voltage 30 Vpp are shown in Table
Thrusts of piezoelectric actuator containing double pushers (preload of 215 g, drive voltage 30 Vpp).
Freq. (kHz) | Test 1 (g) | Test 2 (g) | Test 3 (g) | Test 4 (g) | Test 5 (g) | Ave. thrust (g) |
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255 | 51 | 52 | 54 | 49 | 50 | 51.2 |
256 | 61 | 62 | 57 | 58 | 59 | 59.4 |
257 | 55 | 54 | 58 | 57 | 56 | 56.0 |
The thrust force will be affected because the preload varies since the linear stage is driven via a friction between the pushers and the carriage. Therefore, the measurement experiment was carried out again with the preload of 430 g. The thrusts of the linear stage are shown in Table
Thrusts of piezoelectric actuator containing double pushers (preload of 430 g, drive voltage 30 Vpp).
Freq. (kHz) | Test 1 (g) | Test 2 (g) | Test 3 (g) | Test 4 (g) | Test 5 (g) | Ave. thrust (g) |
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255 | 100 | 105 | 95 | 94 | 98 | 98.4 |
256 | 98 | 99 | 109 | 103 | 106 | 103.0 |
257 | 90 | 95 | 98 | 97 | 95 | 95.0 |
This study presents a novel piezoelectric actuator. The double pushers on the piezoelectric actuator are designed to enhance the thrust output. In the design process, Taguchi method is used to find the optimal combination of parameters including length, width, height, and electrodes setting. The contribution of each design factor of piezoelectric actuator is also discussed in this paper. Furthermore, a novel piezoelectric actuator containing double pushers according to the optimal design factors is produced and used in a linear stage. Some thrust tests are also carried out in this study. From the experiment results, the piezoelectric actuator containing double pushers can provide a greater thrust force than that of traditional actuators containing a single pusher as the preload is greater. Compared with the traditional actuators, the thrust force of new actuator can be increased by 48% with the double preload.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors would like to thank National Science Council (NSC) for their financial supports to the project (Grant no. NSC 101-2221-E-224-009).