MyeongHyeon Kim

Design and optimization of voice coil actuator for six degree of freedom active vibration isolation system using Halbach magnet array

This paper describes the design, modeling, optimization, and validation of an active vibration isolation system using a voice coil motor. The active vibration isolating method was constructed with a passive isolator and an active isolator. A spring was used for passive isolating; an actuator was used for active isolating. The proposed active vibration isolation system (AVIS) can isolate disturbances for many kinds of instruments. Until now, developed AVIS were able to isolate a six degree-of-freedom disturbance effectively. This paper proposes the realization of such a six degree-of-freedom active vibration isolation system that can work as a bench top device for precision measuring machines such as atomic force microscope, scanning probe microscope, etc.

A six-degree-of-freedom magnetic levitation fine stage for a high-precision and high-acceleration dual-servo stage

This paper presents a novel six-degree-of-freedom magnetic levitation fine stage for a dual-servo stage. The proposed fine stage is levitated and actuated, using a voice coil motor actuator with a Halbach magnet array. For a dual-servo stage, fine stage performance is deeply intertwined with coarse stage performance. Because the fine stage is installed over the coarse stage, the overall size of the fine stage can be limited by the moving plate of the coarse stage. Therefore, magnetic flux modeling and optimization are performed to manufacture optimal fine stages. To control the fine stage, actuator kinetics and sensor kinematics are proposed. Homing control is implemented by using linear variable differential transformers, whereas fine control is implemented by capacitance sensors and laser interferometers. Finally, experimental results of in-position stability, moving range, and repeatability are presented.

Systems Metabolic Engineering for the Production of Non-innate Chemical Compounds

Biorefinery has become an important area of research due to the limited fossil resources and the increasing environmental concerns, including global warming. In this regard, microorganisms have gained a great interest due to their great potential to be used as a factory for the production of various chemicals, fuels, and other materials, which were hitherto being produced from petroleum resources. Metabolic engineering based on a comprehensive understanding of the complex biological systems supported by systems biology, or systems metabolic engineering, has enabled the engineering of microorganisms into microbial factories by thoroughly redesigning and reconstructing their metabolic and regulatory networks. Recently, advances in synthetic biology have allowed us to perform more advanced systems metabolic engineering by creating novel biological systems, empowering microorganisms to gain new metabolic capabilities, which they otherwise might not have obtained naturally. In this article, we provide some general strategies and the required technologies for systems metabolic engineering, along with successful examples. At the end, the perspectives of systems metabolic engineering based on synthetic biology are discussed, with selected exemplary case studies.