Robotica (2006) volume 24, pp. 527–528. © 2006 Cambridge University Press doi:10.1017/S0263574705002559 Printed in the United Kingdom

A novel design of a 3-PRC translational compliant parallel micromanipulator for nanomanipulation Qingsong Xu and Yangmin Li∗ Dept. of Electromechanical Engineering, Faculty of Science and Technology, University of Macau, Av. Padre Tom´as Pereira S. J., Taipa, Macao SAR (P. R. China) (Received in Final Form: October 27, 2005. First published online: January 23, 2006)

SUMMARY A novel 3-DOF prismatic-revolute-cylindrical (PRC) translational compliant parallel micromanipulator (CPM) has been designed for 3-D nanomanipulation in this paper. The system is configured by a proper selection of hardware and analyzed via the established pseudo-rigid-body (PRB) model. The CPM workspace is determined taking into account the physical constraints imposed by piezoelectric actuators and flexure hinges.

Mobile Platform C joint P joint R joint

KEYWORDS: Parallel manipulators; Compliant mechanism; Nanomanipulation; Workspace.

I. INTRODUCTION Nanomanipulation can be defined as the manipulation of nanometer size objects using an end-effector with (sub)nanometer precision.1 Several parallel manipulators employing compliant mechanisms have been designed to perform the manipulation in micro/nano meter scales with high accuracy, speed, and load capacity.2−4 However, most of the existing micromanipulators can provide only planar 3DOF motion, or spatial 3-DOF mixed motion of translation and rotation. Since the nanometer-scale manipulation is usually performed via a microscope, that provides a quite limited field of vision and even a slight rotation of the end-effector will result in the manipulation easily sweeping out of the visual field, the most important motion used in such applications is translational rather than rotary motion. Consequently, a micromanipulator which can provide 3-DOF translational motion with high precision is urgently required for 3-D nano scale manipulation. The motivation of this work is to develop a new 3DOF spatial positioning nano-manipulator with a workspace covering the range of about 40 × 40 × 40 µm3 and the resolution of several nanometers.

II. DEVELOPMENT AND ANALYSIS OF THE CPM As shown in Fig. 1, the designed 3-DOF CPM employing flexure hinges at all joints, consists of a mobile platform, a fixed base, and three limbs with identical PRRP kinematic structure. Since the effect of the last R and P joints is equivalent to a cylindrical (C) joint, it possesses a 3-PRC * Corresponding author. E-mail: [email protected]

P joint

Flexure Hinge

PZT

Fig. 1. Schematic of the 3-PRC CPM. 1 C1 K 45 5 0 ( C ) 1 4

1 K 23

3

B1 K 1 24 K121 z 1 1 0 K 01 x O ( P) y 2

1 K 03

A2 0 2

A1

B3

(C ) C2 B2

(C30 )

C3

A3 Fig. 2. PRB model of the 3-PRC CPM.

architecture indeed. With the mechanism topology identified and each flexure hinge replaced by a revolute joint and a torsional spring, the PRB model of the CPM is developed in Fig. 2. For a 3-PRC parallel robot with conventional mechanical joints, it has been shown that such a mechanism can act as a translational parallel manipulator with some certain geometric conditions satisfied.5 Moreover, in order to generate a

528

Nanomanipulation

r = 2.0 mm t = 0.5 mm w = 8.0 mm h = 8.0 mm

h t

w r

so as to obtain a larger workspace. We select a titanium alloy Ti-6Al-4V (E = 113.8 GPa, σy = 880 MPa) to build the CPM. The desired workspace for a 3-PRC CPM is described as a maximum cuboid inscribed within the reachable workspace and defined as the usable workspace. As shown in Fig. 4, the range of V denotes the workspace due to rotary limits of flexure hinges, S represents the workspace range subjected to motion limits of PZT actuators, and the intersection of these two ranges forms the manipulator’s reachable workspace, i.e. the cuboid like range of S. Additionally, the usable workspace is denoted by U.

Fig. 3. Schematic of flexure revolute hinge.

V

S

U

III. CONCLUSIONS A novel 3-PRC CPM utilizing flexure hinges for 3-D nano scale manipulation has been designed in this paper. Since the proposed CPM is composed solely of flexible elements with competent in high precision applications, it is reasonable to expect that with a suitable end-effector mounted on the mobile platform or placing the platform under a specified microscope as a precision XYZ-stage, the CPM can be employed in 3-D positioning and assembly of nano scale objects through nanomanipulation. Acknowledgments The authors appreciate the fund support from the research committee of University of Macau under grant RG083/0405S/LYM/FST. References

Fig. 4. Workspace of the 3-PRC CPM.

regular cuboid like workspace of the manipulator, the three actuated P joints are arranged in orthogonal directions. To achieve the goal of this work, one type of PZT (P178.30) with the stoke of 40 µm and resolution of 0.4 nm is selected from the Polytec PI, Inc. The linear actuator of the CPM is implemented with each PZT embedded in a flexure P hinge as shown in Fig. 1. The flexure R hinge can be designed to have various profile shapes. Here we adopt the right circular one (see Fig. 3) thanks to its nice displacement accuracy. Since the ratio of yield strength (σy ) to the Young’s Modulus (E) of the material heavily affects the rotary limits of flexure hinges, that partially determines the manipulator workspace, it is necessary to choose materials with higher ratio of σy /E

1. M. Sitti, “Survey of Nanomanipulation Systems,” Proceedings of 1st IEEE Conference on Nanotechnology (2001) pp. 75–80. 2. T. Tanikawa, T. Arai and N. Koyachi, “Development of Small-Sized 3 DOF Finger Module in Micro Hand for Micro Manipulation,” Proceedings of IEEE/RSJ International Conference on Intelligent Robots and Systems (1999) pp. 876– 881. 3. Y. Li and Q. Xu, “Design and Analysis of a New 3-DOF Compliant Parallel Positioning Platform for Nanomanipulation,” Proceedings of 5th IEEE Conference on Nanotechnology (2005) pp. 126–129. 4. B.-J. Yi, G. B. Chung, H. Y. Na, W. K. Kim and I. H. Suh, “Design and Experiment of a 3-DOF Parallel Micromechanism Utilizing Flexure Hinges,” IEEE Transactions on Robotics and Automation 19(4), 604–612 (2003). 5. Y. Li and Q. Xu, “Kinematics and Dexterity Analysis for a Novel 3-DOF Translational Parallel Manipulator,” Proceedings of IEEE International Conference on Robotics and Automation (2005) pp. 2955–2960.