Development of six-axis parallel nano-positioning system based on flexure joints and piezoelectric stepping positioners

Abstract

In many cases, the quality in areas such as semiconductor manufacture, precision optics alignment, and microbiological cell manipulation depends on the positioning capability of ultraprecision positioning systems. These applications frequently require a positioning system that can deliver nanometer level resolution while maintaining other positioning characteristics such as large motion range, high force capacity, high speed, quick response, high stiffness, compactness, and wide dynamic range, as well as low power consumption. In this thesis, a novel flexure jointed precision parallel manipulator in combination with piezoelectric stepping motor was developed to apply a precision optics alignment. The important performance criteria of the positioning stage for the precision optics alignment are the position accuracy, the motion range of a few millimeters and a few degrees, the stability for measurements and processing, and the compactness. The position stability could be improved by designing the system to have high stiffness, power-off hold, and high thermal noise susceptibility and the position accuracy could be improved by removing friction during motion. According to above requirements, a parallel configuration which guarantees a higher structural stiffness was chosen. Because a fully-parallel hexapod is most preferable to obtain higher stiffness, however, its structure and kinematics are so complex, the hybrid parallel configuration was selected. Considering the stiffness, 3-PPSR parallel configuration was used. Basic analyses of 3-PPSR manipulator such as inverse kinematics, forward kinematics, and workspace were performed. There exist at most the sixteen forward kinematics solutions and eight inverse kinematics solutions. The effect of active joint stroke limitation and passive joint angle limitation on the workspace is simulated. Actuators are important parts of the system because the motion characteristics of system are determined depending on them....