Kuang-Yuh Huang

Simultaneous detection of translational and angular displacements of micromachined elements

An astigmatic detection system is constructed with a modified digital-versatile-disk optical head. This system, with a detecting spot of ∼1μm, can simultaneously measure the vertical displacements and two-dimensional angular tilts of micromachined elements. It can detect thermal vibrations of microfabricated cantilevers with noise levels of 1.3pmHz−1∕2 for the linear displacement and of 3.2nradHz−1∕2 for angular displacements over a frequency range from 1to800kHz. The detecting frequency can even reach beyond 100MHz if high-speed electronic devices are adopted. Further optimization of the system will broaden its applications in diverse technological fields.

Measurement of Cantilever Displacement Using a Compact Disk /Digital Versatile Disk Pickup Head

We use the optical pickup head of a commercial compact disk (CD)/digital versatile disk (DVD) read only memory (ROM) drive to detect the vertical displacement of micro fabricated cantilever in atomic force microscopy (AFM). Both the contact and AC modes of AFM are demonstrated. The single atomic steps of graphite can be resolved, indicating that atomic resolution in the vertical displacement detection can be achieved with this new setup. The low cost, compact size, and the light weight of CD/DVD optical pickups may offer new advantages in future AFM designs.

Development of an optical pickup system for measuring the displacement of the micro cantilever in scanning probe microscope

This paper presents the development and the verification of a compact optical sensor system for measuring the displacement of the micro cantilever in scanning probe microscope (SPM). An optical pickup head of commercial compact disc (CD)/digital versatile disc (DVD) read only memory (ROM) drive is applied in this displacement sensor system. For fulfilling our tight measuring requirements of sensibility and reliability, the build-in detection device is replaced with a four-quadrant photodiode. The developed system is well functionally verified by measuring calibration sample of 463 nm (pitch) times 30 nm (height).

Magnetic Torque Compensating Methods for Cam Indexing Devices

In automatic production processes, cam indexing devices are frequently utilized to transport workpieces intermittently to the appointed manufacturing positions. However, because of alternating working forces and rotational inertia, indexing devices tend to generate vibration during each positioning process, which retards working speed and degrades positioning accuracy. To minimize positioning vibration, we developed a magnetic compensation concept and diverse devices based on the concept. A magnetic torque compensator basically consists of a magnetic loop with field generator and soft-magnetic elements. The soft-magnetic elements are designed to generate relative motion to each other to realize variable distribution of magnetic field and induce a compensation torque to suppress the positioning vibration. In addition to our experimental research, we investigated analytically the influential parameters of the compensating torque and their relationships by using the equivalent magnetic circuit method and the finite-element method. We found that modifications of magnetic arrangement or geometric parameters of functional elements lead to different characteristics of the magnetic torque curve. On the basis of the verified function and parameters of the magnetic torque compensator, we built some configurations to synthesize the compensating torque needed for countering vibration

Electrostatic linear actuator with a long stroke rolling spring guide

In contrast with diverse design concepts of actuators, we have developed an electrostatic linear actuator integrated with a long stroke rolling spring guide. The rolling spring guide realizes guiding function through rolling movements of two parallel preloaded belt-shaped springs. The electrostatic actuating force is generated by applying electrical fields to the structure of spring guide. Besides the driving voltage, the geometric size and the preloaded span of the spring guide are the main influential parameters of electrostatic actuating force and actuating displacement. With adequate adjustment of the preloaded span, this electrostatic actuator can generate not only a large actuating displacement in /spl mu/m range, but also a fine positioning displacement in /spl mu/m range. The finite element analysis (FEA) and the geometric analysis are applied to analyze spring stress and to derive the shape equation of the spring guide. Furthermore, a theoretical model for our electrostatic actuating principle is deduced on the basis of the shape equation. In addition to the theoretical analyses, the performance of the electrostatic actuator is experimentally tested and studied.

AFM pickup head with holographic optical element (HOE)

This paper proposes a new developed AFM pickup head by using the holographic optical element (HOE) for the atomic force microscope. The holographic optical element is very compact and has been applied in the DVD-pickup head with a stable and precise sensing performance. By comparison with the optical lever method of the ordinary AFM, the holographic optical element makes AFM an easy optical adjustment and a compact configuration. Through this miniaturizing and easy adjusting progress, AFM can also open wider application field. In this paper, we present the development and its performance of the new developed HOE-AFM, which is experimentally verified that it can realize nanometer resolution through measuring the calibration grating and the graphite specimen.

Optical measurement system for error motions of small shafts

The miniaturization trend has enhanced the rapid development of small precision machines. The operational performance of a precision machine is mainly determined by its bearing clearance, the balancing quality of its shafts, and the actuation smoothness of the rotating shafts. In comparison with large shafts, small shafts are more susceptible to external interference and the loading effects of the measurement equipment. Accordingly, the inspection concepts for small shafts should be quite different from those for large shafts. This paper presents our approach to developing an economical optical measurement system with which the error motions of small rotating shafts can be inspected. The shadow method is applied as the measurement concept for the radial error motion. Two perpendicularly installed laser beams are partially shaded by the shaft, and the radial error motion is transformed into the alternations of light and shade on two photodiode arrays. For measuring the tilt error motion, a reflective method is realized to transform a tilt error motion into a 2-D movement of a reflective cross-hair pattern, which is detected by two photodiode arrays. To increase the measurement sensitivity, a novel bilateral configuration using offset pairs of photodiode detectors is developed; the signals of the detectors are processed by the differential principle. The shadow method shows better sensitivity and faster measuring speed than the reflective method because of its distinct projected beam.

SMM actuator for nanoscale positioning

This paper presents a new design of a Shear Motion Mode (SMM) actuator for ultra-high precision positioning in nanotechnological applications. In the SMM Actuator, a V-shape stage is driven by four parallel polarized piezoelectric plates with shear displacement. Based on its simple mechanism, the SMM actuator can be built very compactly. For fast and precision positioning tasks, we develop three different driving modes to control the SMM actuator. For large stroke, the inertial and frictional driving modes are applied for fast and precision positioning, respectively. The scanning mode enables the adjustment of the scanning distance in highest resolution. Positioning function of the developed SMM actuator may also be brought into applications in the low temperature and Ultra High Vacuum (UHV) environment. These three driving modes are experimentally tested to measure their dynamic performance. The stroke of the SMM actuator is 5mm. By applying the frictional driving mode, the SMM actuator can achieve a positioning resolution of 3nm with a pay load of 500g.

DESIGN AND DEVELOPMENT OF MULTI-DOF BALL-TYPE MICROMOTOR

Abstract Based on the inertial driving principle, we developed a novel multi-DOF ball-type micromotor (MDBM) with capabilities of multiaxial rotation and precision angular position control. The actuator is composed of three biaxial shear driving units made of d 15 -type piezoelectric shear plates, which can drive frictionally the ball-type rotor to achieve the multi-DOF rotation. For realizing constant and stable contact force between each shear driving unit and the ball, magnets are adopted to create the magnetic attracting preload. The performance of the ball-type micromotor is verified by analyses and experiments.