Rotatory Stepping Piezoelectric Motor With Micro-angle

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1 Rotatory Stepping Piezoelectric Motor With Micro-angle Changde Hu 1 Yongqiang Li 1 Meirong Zhao 2 Sha Zhu 1 1.Department of Non-commissioned Officer, the Academy of Equipment Command & Technology, Beijing China 2.State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University ,China hansenhu@yahoo.cn Abstract The rotatory piezoelectric motor(pzt) with micro-angle, based on Inchworm motion, is presented. By the flexible machinery, the displacement of the piezoelectric actuators is transformed into angle. The clampers and actuators which are made of piezoelectric ceramic are both disposed in symmetrical relationship. By clamping or releasing of clampers and extending or retracting of actuators, it could achieve a kind of push-pull relay movement. In this way, the movement of platform is smooth and continuous. With the proper four-channels driving signals, the motor is moved linearly with single step or multi-step. The performances of the motor are tested through experiments. The results show that the motion of the motor is linear, The moving speed can reach 430.4"/s at the voltage of 160V and the minimal step is less than 3". Key words: Nano-positioning micro-angle Inchworm motion minimum step flexure hinge piezoelectric ceramic. INTRODUCTION Nano-positioning system [1] is that the displacement is about several micron to several hundred micron, of which the resolution the positioning precision [2] or the repeating precision [3] is with a nano-range. Micro-moving actuator, the important part of the micro-positioning system, is a kind of sensor reaching to micron nanometer. Since then, it has played an important role in national defence micro-electronic spaceflight and brought precision optics controlling pricision machining Microscopic analysis artificial intelligence to a fast development [4,5]. In this paper, the rotatory piezoelectric motor with micro-angle, with the flexible machinery, the displacement of the piezoelectric actuators is transformed into angle. In structure design, the structure of rotary motor model which adopts compliant mechanisms, not only increases thrust and clamp force, but also magnifies the displacement of piezoelectric ceramic. In this way, the micro-angle with single step comes true. With the principle of push-and-pull relay movement which is improved from the principle of inchworm motion and proper four-channel driving signals, PZT platform can move continuously and smoothly [6].. PRINCIPLE OF THE PIEZOELECTRIC MICRO-PLATFORM To achieve a linear angle motion, the clampers and actuators which are made of piezoelectric ceramic are both disposed in symmetrical relationship. Fig.1 is about turnplate (1)OFF which would move when spindle (2) C2 clamping (3) A1 A2 extending (4) C1 clamping (5) A1 A2 retracting clamping releasing Fig. 1. Sketch map of the principle of the piezoelectric micro-platform /09/$ IEEE 4-545

2 A1, a2. In fig.1(1) the clampers and actuators are off; and in fig.1(2) c2 is clamping, c1 is off. Then when a1 and a2 are extending together, c2 brings the spindle in the moving disk to move, that is what is showing in fig.1(3). In fig.1(4), c1 is clamping and c2 is off, then when a1, a2 are extending, c1 would brings the spindle To move(fig.1(5)). In this way, the pzt follows the motion as fig.(2), fig.(3), fig.(4), fig.(5) by turns, the spindle runs clockwise, and the spindle runs anticlockwise if c1 and c2 is transposed. Because the displacement and speed of a1 and a2 is the same, the spindle could move linearly and smoothly.the MECHANICAL STRUCTURE DESIGN OF PIEZOELECTRIC MICRO-PLATFORM A. the mechanical structure design of piezoelectric micro-platform As the following Fig.2 and Fig.3 shows, the figure of the equipment is columned. The diameter of the PZT cover is 106 mm. There are 8 pieces of piezoelectric ceramics distributing evenly around the turnplate. And the turnplate is composed of 4 rotors and 4 stators, of which the each 2 face to face is a pair. They control the turnplate to turn clockwise or anticlockwise. The 4 clampers are fixed to the rotors, and when the piezoelectric ceramic is extending. With the flexible machinery, the displacement of piezoelectric ceramic is magnified and the thrust and clamp force is increased. In this way, turnplate is clamped by the clampers, then when the actuators extending, the turnplate rotate along with the clampers, and the displacement of the actuators is transferred to angle [7].. B. torsion stiffness algorithms of flexure hinge There are several kinds of configuration of the flexible machinery, in this paper the simple uniaxial and bi-arc flexure hinge which is showed in detail in the Fig. 2 Because the deformation of the flexure hinge is mainly taken place in XY plane coordinates, the deformation of the XZ and YZ plane coordinates could be ignored [8].. As the Fig. 2 shows, the hinge is uprightnessly cut by 2 symmetrical cylinder, R, the radius of the cylinder, t, the minimum thickness of the hinge, b, width of the hinge, h, height of the hinge. To this kind of flexure hinge, h=t+2r, of which the torsion stiffness is the most important parameter. For the size of the flexure hinge is very small compared with the motor, the torque of both sides could be considered as the same and the angular distortion except the circular part could be ignored. b: width of the hinge; h: height of the hinge; t: thickness of the thinnest part; R: radius of the thinnest part Fig. 2. the configuration of the uniaxial and bi-arc flexure hinge When the rotation angle is small, the formula of the torsion stiffness of flexure hinge is as follow [9].: 12MR sin dx 0 2 (2R t 2Rsin ) By numerical integration of the Romberg integration of the above equation, then we get the commonly used torsion stiffness M / of flexure hinge shown in Tab.1 [10].. R=1. R=1. R=2. R=2. R=3. Tab.1 torsion stiffness of flexure hinge(n.m/rad) t= t= t= C. design of clampers and acutators t= t= For the maximum displacement piezoelectric ceramic actuator is about 10 m, to meet the clamping needs, the flexure hinge is adopt. In this way, not only the clamp force is increased, also the displacement of piezoelectric ceramic is magnified. Like the Fig.3 shown the clampers is designed in symmetrical relationship. In this way, the motor could be move smoothly. Fig. 3. the configuration of the clampers 4-546

Taking a=6.5, b=18.5, then the magnification b 18.5 k 3. a 6.5 A reference to the above table, when taking t 1mm, R 1. ESteel 200GPa b 1, the clamper is designed to meet the requirements.

3 Taking a=6.5, b=18.5, then the magnification b 18.5 k 3. a 6.5 A reference to the above table, when taking t 1mm, R 1. ESteel 200GPa b 1, the clamper is designed to meet the requirements. The actuator is composed of 4 static parts and 4 motive parts like Fig. 4 showing, and the clampers are fixed to the motive parts which are drived by two symmetrical piezoelectric ceramic actuators. As the parameters of the actuators and driving power are the same, the displacement and the force of the actuators are same (F1=F2). As the Fig. 4 showing, the interference introduced by the transmission link in the error could be reduced[11]. The design of the motive parts is used flexure hinge, and the design method reference to the clampers. Dimensions of the flexure hinge are as follows: t=1.7mm R=1.7, reference to the Tab.1, the design is appropriate and meeting the requirements. the opposite direction [12] if we exchange C1 C2 and A1 A2. Fig. 5 the configuration of the four-channel driving signals Fig.6 the elements of composition of hardware system B. composition of control system Fig. 4 the configuration of the clampers. THE DESIGN OF THE CONTROL SYSTEM A. Driving control signal With the movement in line with the principle of supply voltage waveform is showing in the Fig.5, four-channel driving signals, 2-channel square wave signals(c1 C2) and 2-channel triangle wave signals(a1 A2). In the top of the Fig.5 the signals C1 C2 are for clampers, and the bottom are for actuators. In Tr(transition zone), both C1 and C2 are clamping at a time to drive the micro-platform. Because the driving signal for A1 A2 is triangle wave, the platform turns smoothly and continuously. The platform would turn in As the following Fig. 6 shows, Control system should meet the requirements of the four-channel signals as the Fig. 6 shows. These are 2-channel square wave signals(c1 C2) and 2-channel triangle wave signals(a1 A2) in accordance with the output timing. After the 4-channel signals are amplified by DC amplifier, then they are imposed to the platform, which could move linearly with single step or multi-step, forward or backward step. The hardware system is 8031 MCU control system, and the square signals are obtained by 2 ports of P1, while the triangle signals are obtained by DAC0832. Amplified by DC power a, the output of the triangular wave and square wave are imposed to the micro-platfom.. EXPERIMENT ANALYSIS The experimental apparatus including TJU2000 CCD photoelectric autocollimator with high-precision, controller of micro-platform, piezoelectric motor, precision driving power of piezoelectric motor, mirror, the specific connections is as shown in Fig.7. controller Driving TJU2000 CCD photoelectric Fig.7 the schematic of specific connections Micro-platform mirror 4-547

4 CCD photoelectric autocollimator is an automatic high-precision angle-measuring instrumen [13] t, which could transfer small changes in angular displacement or angular displacement into small high-precision measurement of micro-angle. The linear array CCD is used for pixels scanning back on the self-collimation and the MCU is used for data processing, which could get the relative angular displacement to the 2 optical axis of the instrument. Tab.2 the angular displacement with different frequencies at 80V A. At a fixed voltage the angular displacement with different frequency Purpose of the experiment: to test the angular displacement of the platform with different frequency at a fixed voltage. Experimental process: different frequencies, from 1Hz 40Hz(every 5Hz), two groups of data measured at 160V 80V such as shown in the Tab.2 and Tab.3 below. Average step (") Tab.3 the angular displacement with different frequencies at 160V Average step (") conclude that with greater voltage, the micro-platform runs much more faster, while the greater frequency, runs less faster. The reason would be that when the frequency increases the piezoelectric ceramic charge-discharge is incomplete. B. At a fixed voltage the angular displacement with different frequency Purpose of the experiment: to test the angular displacement of the platform with different voltage at a fixed frequency 5Hz. Experimental process: different voltage, from 40V 200V(every 40V), at a fixed frequency 5Hz, the data such as shown in the Tab.4 below. conclude that with greater voltage, the micro-platform runs much more faster, while the greater frequency, runs less faster. The reason would be that when the frequency increases the piezoelectric ceramic charge-discharge is incomplete. C. Speed test Tab.4 the angular displacement voltage at a fixed frequency 5Hz Purpose of the experiment: to test the speed of the platform voltage ( V) Average step (") Experimental process: different voltage 160V 80V, different frequency 1 40Hz, every 5Hz, the data such as shown in the Tab.5 and Tab.6 below. Tab.5 the speed of different frequency at a voltage 160V Average step (") speed /s Tab.6 the speed of different frequency at a voltage 80V Average step (") speed /s

5 conclude that with greater voltage, greater frequency, the micro-platform runs much more faster. D. Minimal step Purpose of the experiment: to test the minimal angular step. Experimental process: with a fixed voltage of 20V, at a fixed frequency of 5Hz, the data such as shown in the Tab.7 below. Tab.7 the angular displacement of 2 steps at a voltage 20V with frequency of 5Hz times of the tests displacement of 2steps Through the tests it finds that the micro-platform runs instablly when the voltage less than 20V, the angular displacement could not be distinguished. In this way, the angular displacement that is relative stability of the 20V, 5Hz voltage is regarded as the minimal angular step. Through the tests it gets the average angular displacement of 2 steps 5.2". So the single step is 2.6"..CONCOLUSION The rotatory piezoelectric motor(pzt) with micro-angle, based on Inchworm motion, is presented. By the flexible machinery, the displacement of the piezoelectric actuators is transformed into angle. The clampers and actuators which are made of piezoelectric ceramic are both disposed in symmetrical relationship. The performances of the motor are tested through experiments. The results show that the motor is moved smoothly and linearly with single step or multi-step. There is no entanglement with the actuators, which has a continuous rotation speed in the range of 360. The moving speed can reach 430.4"/s at the voltage of 160V and the minimal step is less than 3" [8] Yang Guoxing, Zhang Xianmin, Wang Hua. Optimal design hinge micro-gripper actuated by PZT based on FEM[J]. China Mechanical Engineering, 2006,5,17(10): [9] LIU Jianfang, YANG Zhigang, ZHAO Hongwei. Novel piezoelectric precision step rotary actuator[j]. Journal of Jilin University, 2006,9 36(5): [10] LIU Pinkuan,SUN Lining. Dynamic analysis on a novel nanopositioning stage driven by PZT[J]. Optics and Precision Engineering, 2002,10 (2) : [11] WU Yingfei ZHOU Zhaoying. An XY mechanism actuated by one actuator[j]. Mechanism and Machine Theory (10) [12] ZETTL B SZYSZKOWSKI W. Accurate low DOF modeling of a planar compliant mechanism with flexurehinges:the equivalent beam methodology [J]. Precision Engineering (2) [13] ZHANG Deyuan CHANG Chienliu TAKAHITO Ono et al. A piezodriven XY-microstage for multiprobe nanorecording [J].Sensors and Actuators (1-3) REFERENCES [1] Budinger Marc, Rouchon Jean-Francois, Nogarede Bertrand. Analytical modeling for the design of a piezoelectric rotating-mode motor[j]. IEEE/ASME Transactions on Mechatronics, , Vol.9: 1~9. [2] Michele Pozzi Tim King Piezoelectric Actuators in Micro-positioning[J] Engineering Science and Education Journal February [3] CHENG Dongruing DUAN Zhiyong. Design and Fabrication of Hybrid Piezomotor Applied in Precision Positioning Devices[J]. Semiconductor Photonics and Technology [4] Ko Hyun-Phill, Lee Kyong-Jae, Yoo Kyoung-Ho et al. Analysis of tiny piezoelectric ultrasonic linear motor[j]. Japanese Journal of Applied Physics, 2006,5 Part1: Regular Papers and Short Notes and Review Papers: 4782~4786. [5] HU Changde. the study on rotatory stepping piezoelectric motor with micro-angle and its driving power[d]. Master s Degree of Tianjin University [6] ZHANG Jianxiong, SUN Baoyuan. Design and Analysis of 2-DOF Nanopositioning Stage Based on Dual Flexure Hinges[J]. PIEZOEL ECTECTRICS & ACOUSTOOPTICS, 2006,10, 28(5): [7] ZHAO Hongwei, WU Boda, CHENG Guangming. Precise stepping rotary motor based on piezoelectric actuation[j]. Proceeding of the CSEE, 2006,5,26(10):

2044. Dynamics analysis for the clamping mechanisms of a rotary inchworm piezoelectric motor

2044. Dynamics analysis for the clamping mechanisms of a rotary inchworm piezoelectric motor Yongfei Gu 1, Jichun Xing 2 1, 2 School of Mechanical Engineering, Yanshan University, Qinhuangdao, China 1