This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON AUTOMATION SCIENCE AND ENGINEERING 1 A Totally Decoupled Piezo-Driven XYZ Flexure Parallel Micropositioning Stage for Micro/Nanomanipulation Yangmin Li, Senior Member, IEEE, and Qingsong Xu, Member, IEEE Abstract—This paper reports the design and development processes of a totally decoupled flexure-based XYZ parallel-kine- matics micropositioning stage with piezoelectric actuation. The uniqueness of the proposed XYZ stage lies in that it possesses both input and output decoupling properties with integrated displace- ment amplifiers. The input decoupling is realized by actuation isolation using double compound parallelogram flexures with large transverse stiffness, and the output decoupling is implemented by employing two-dimensional (2-D) compound parallelogram flex- ures. By simplifying each flexure hinge as a two-degree-of-freedom (2-DOF) compliant joint, analytical models of kinematics, statics, and dynamics of the XYZ stage are established and then validated with finite-element analysis (FEA). The derived models are further adopted for optimal design of the stage through particle swarm optimization (PSO), and a prototype of XYZ stage is fabricated for performance tests. The nonsymmetric hysteresis behavior of the piezo-stage is identified with the modified Prandtl-Ishlinskii (MPI) model, and a control scheme combining the inverse model-based feedforward with feedback control is constructed to compensate the plant nonlinearity and uncertainty. Experimental results reveal that a submicron accuracy 1-D and 3-D positioning can be achieved by the system, which confirms the effectiveness of the proposed mechanism and controller design as well. Note to Practitioners—Motivated by the requirement of de- veloping a decoupled XYZ micropositioning stage for 3-D micro/nanomanipulation uses, a novel spatial parallel mecha- nism incorporating flexure hinges is presented in this paper, and piezoelectric actuators (PZTs) owning large output force and stiffness are used for actuation. The piezo-stage has the merits of not complicated structure as well as both input and output decoupling properties. By input decoupling, the PZTs are isolated and protected. With output decoupling, the parallel stage behaviors like a serial one, which enables the adoption of single-input-single-output (SISO) controller for each axis. Before the fabrication of the stage, its parameters are optimized to achieve a high resonant frequency under performance constraints in terms of workspace size, input stiffness, and safety of material, etc. Analytical models for the above performances are derived and the optimized stage is fabricated from Al-7075 alloy by the wire electrical discharge machining (EDM) process for experimental demonstrations. The results provide a sound basis in developing Manuscript received February 07, 2010; revised June 20, 2010; accepted Au- gust 14, 2010. This paper was recommended for publication by Associate Ed- itor S. Fatikow and Editor K. Bohringer upon evaluation of the reviewers’ com- ments. This work was supported in part by the Macao Science and Technology Development Fund under Grant 016/2008/A1 and the Research Committee of the University of Macau under Grant UL016/08-Y2/EME/LYM01/FST. The authors are with the Department of Electromechanical Engineering, Fac- ulty of Science and Technology, University of Macau, Taipa, Macao SAR, China (e-mail: ymli@umac.mo; qsxu@umac.mo). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TASE.2010.2077675 an alternative piezo-stage for micro/nanoscale manipulation. The design and control methodology can be extended to other types of stages as well. Index Terms—Finite-element analysis (FEA), flexure mecha- nisms, mechanism design, micro/nanopositioning, motion control, parallel manipulators, piezoelectric hysteresis. I. INTRODUCTION F LEXURE-BASED compliant micropositioning stages are the devices capable of positioning with ultrahigh precision based on elastic deformations of the structures, and they find broad applications in microelectromechanical systems (MEMS) sensors and actuators, optical fiber alignment, biological cell manipulation, and scanning probe microscopy (SPM), etc. In consideration of high-resolution requirement, the stages are usu- ally driven by unconventional motors, such as stack piezoelec- tric actuators (PZTs), voice coil motors, magnetic levitation mo- tors, and so on. A great number of compliant stages with various types of motions can be found in the literature, e.g., [1]–[10]. In particular, XYZ positioning stage is an ideal choice for some situations, where a 3-D translation is sufficient, e.g., the scanning device in an atomic force microscope (AFM). Several compliant XYZ stages are even commercially available on the market. For instance, the XYZ stage 1 produced by the Physik In- strumente GmbH & Co. KG adopts a stacked structure of three one-degree-of-freedom (1-DOF) positioning stages. The serial connection of three stages enables a simple control strategy be- cause the X, Y, and Z translations can be governed indepen- dently, which is at the cost of a low resonant frequency of the mechanism since the stacked stage increases the mass of moving components. In such an application as AFM, a high-speed po- sitioning of the stage is required to implement a rapid scanning task. Thus, high resonant frequency is preferred in mechanism design of the positioning stage. To conquer the above shortcomings of serial stages, XYZ stages with parallel-kinematics architectures [11], [12] have gained extensive attentions. Many XYZ stages with parallel kinematics have been reported in the literature. For example, several flexure hinge-based parallel stages with orthogonal structures (Delta cube) are presented in [13] and [14], a 3-DOF parallel translational stage with three identical (P+3RRR 2 ) limbs is reported in [15], an XYZ micromanipulator based 1 www.physikinstrumente.com/en/products/prdetail.php?sortnr=800900 2 P stands for prismatics joint and R represents revolute joint. 1545-5955/$26.00 © 2010 IEEE