Shao-Kang Hung

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.

A New Design of a Submicropositioner Utilizing Electromagnetic Actuators and Flexure Mechanism

In this paper, a novel XY-dimensional submicropositioner, including mechanism, control, and analysis, is successfully presented. The design of the submicropositioner utilizes a monolithic parallel flexure mechanism with built-in electromagnetic actuators and optical sensors to achieve the object of 3-DOF precise motion. From the provided experimental results, there are several main goals that have been achieved in this paper: (1) to integrate the electromagnetic actuator and the parallel flexure mechanism for planar positioning system; (2) to establish the mathematical modeling; (3) to develop an advanced adaptive sliding-mode controller; and (4) to perform extensive experiments to test the realistic performance.

Design and Experiment of a Macro–Micro Planar Maglev Positioning System

In this paper, a new planar magnetic levitation (maglev) positioning system is proposed, which is capable of executing dual-axis planar motions purely involving magnetic forces. Functionally, such a mechanism behaves like a planar XY table with micrometer precision. Specifically, in this system, a new structure with an adaptive sliding-mode control (ASMC) algorithm is described, which aims to achieve the following three goals: 1) a large moving range (millimeter level); 2) precise positioning (micrometer level); and 3) fast response. The system consists of a moving carrier platform, six permanent magnets (PMs) attached to the carrier, and six electromagnets mounted on a fixed base. After exploring the characteristics of the magnetic forces between PMs and electromagnets, the general 6-DOF dynamic model of this system is derived and analyzed. Then, because of the naturally unstable behavior inherent in maglev systems, the proposed ASMC guarantees satisfactory performance of the maglev system. Experiments have successfully demonstrated the feasibility and effectiveness of the overall system.

Dual-Stage Piezoelectric Nano-Positioner Utilizing a Range-Extended Optical Fiber Fabry–Perot Interferometer

This paper proposes a new modulation scheme using high-order harmonic information to solve the so-called ambiguity problem of interferometry. To start with, we build a fiber Fabry-Perot interferometer to serve as a displacement sensor, which has two operation modes - coarse and fine modes. Integrating the afore-developed sensor, a piezoelectric actuator, and a scheduled proportional-integral/adaptive-sliding controller, we construct a dual-stage nanopositioning system. The experimental results show that the proposed system has the capability to extend the positioning range beyond the limit of the wavelength while keeping the naturally high resolution, plusmn5 nm, of interferometry.

Postfitting Control Scheme for Periodic Piezoscanner Driving

The hysteresis and other nonlinear properties of piezoelectric scanners cause image distortion in scanning probe microscopy (SPM). Two types of control algorithm, feedback and feedforward, were applied to solve this problem. In general, a feedforward control method has a higher scanning speed, a higher resolution, but a lower accuracy than a feedback control method. In this paper, we propose a postfitting control scheme for driving the x-scanner of SPM periodically. This method possesses the advantages of both the feedback and feedforward methods, and achieves a higher image resolution and a higher accuracy than a pure feedback or feedforward method, without sacrificing scanning speed.

Design and Implementation of a New Six-DOF Maglev Positioner With a Fluid Bearing

This paper proposes a new six degrees-of-freedom (6-DOF) electromagnetic precision positioner, made of a hybrid mechanism utilizing both a magnetic driving force and the uplifting force of the fluid, for which a new structure, the electromagnetic actuator, and an effective controller have been developed. The concept of the mechanism design involves not only the magnetic driving mechanism, but also the fluid buoyancy and damping properties, which help to counterbalance the weight of the platen so as to achieve a very low steady-state power consumption. The four goals of the new system design include the following: 1) to have a large range of motion (at the mm level); 2) to achieve precision positioning; 3) to design a compact but low-cost mechanism; and 4) to achieve low power consumption. In this system, there are a total of eight permanent magnets (PMs) attached to the movable carrier, and eight electromagnetic coils appropriately mounted on a fixed base. After exploring the characteristics of the magnetic forces between PMs and electromagnetic coils, the general 6-DOF dynamic model of this system is derived and analyzed. Then, because of the naturally unstable behavior and uncertainties of the underlying system, a robust adaptive sliding-mode controller is proposed to guarantee system stability for both regulation and tracking tasks. Finally, extensive experiments have been conducted to demonstrate the performance of the proposed system. The experimental results show that the range of motion is 3 mm × 3 mm × 4 mm, and the tracking error in each axis is kept to within 10 μm, which reaches the limit of our optical sensors. These experimental results demonstrate satisfactory performance of the positioner in terms of theoretical analysis and experimental results.

Design and implementation of a new 3-DOF electromagnetic micropositioner utilizing flexure mechanism

In this paper, a compact and three degree-of-freedoms (DOFs) micropositioner with large travel ranges is presented. The design of the micropositioner utilizes the monolithic parallel flexure mechanism with the built-in electromagnetic actuators and uses the optical sensors to achieve the object of 3-DOF precise motion. An adaptive sliding-mode controller is proposed to let the system is more robust and stable in positioning. The developed robust control architecture consists of three components: 1) sliding mode controller, 2) adaptive law, and 3) force allocation. From the provided experimental results, satisfactory performances of the hereby developed system, including stiffness and precision, have been successfully demonstrated

The design and characteristic research of a dual-mode inertia motor

The design of a dual-mode inertia motor involves an actuator that can generate translational and rotational motion without connecting the actuators serially. Traditionally, translational or rotational actuators should be stacked serially to have multi-axis degrees-of-freedom. The experimental results of this study display performance characteristics such as linearity, resolution, velocity and the most excellent operating frequency.

A TEM phase plate loading system with loading monitoring and nano-positioning functions

We present a phase plate loading system developed for a commercial transmission electron microscope (TEM). Our system can be installed without modifying the optical design of the TEM. This system is equipped with a loading monitoring set that allows users to easily and safely locate the phase plate between the pole pieces, and also comes with an airlock that permits quick loading of a phase plate without the need to re-vent the TEM column. The system uses a home-made three-axis nano-positioner to precisely position the phase plate hole at the desired location. Our system has a precision of approximately 10nm, an improvement of one order of magnitude compared with the precision of a phase plate holder modified from an objective aperture. We demonstrate the successful installation and the use of the loading system to place a phase plate at the desired position. Our phase plate loading system can be used to accommodate various types of phase plates and thus provides a good way to greatly speed up the development of TEM phase plates.