Since fast and accurate motion profiles are directly related to the productivity of manufacturing, many studies have been performed to optimize such motion profiles. However, previous research has not provided an appropriate solution regarding which motion profile is the best for a given situation. Therefore, in this article, we propose an optimization process for polynomial-function-based motion profiles to achieve fast movement with low vibration. The proposed process describes a method of optimizing an nth-order polynomial motion profile to achieve a fast transfer time and minimal residual vibration characteristics with extra robustness to system uncertainty for a given moving distance and given actuator capacities. Then, we describe how to determine the best order of the optimized motion profile for given conditions, such as the allowable computational load, the required residual vibration bound, and the required robustness against system uncertainties. The performance of the optimized motion profile is demonstrated, and the suggested process for obtaining the best order of the optimal motion profile is applied to a practical example of a wafer transfer robot.

The manufacturing process of OLED displays requires a high accuracy and a highly clean transport system because during the evaporation process, organic materials are inherently sensitive to contamination and uniform deposition of an organic layer is important. Roller-based transfer systems are not suitable for OLED evaporation processes because the roller-based system has a poor driving performance due to nonlinear factors such as friction and generates a large amount of dust. On the other hand, the magnetic levitation transport system has the advantage of not generating any dust, and it is possible to achieve high-precision control. In this paper, a magnetic levitation transport system for the OLED evaporation process is introduced. In particular, experimental verification of the developed system under vacuum is addressed. In terms of levitation control performance, the maximum fluctuation of the levitation airgap at a standstill is 15.3 μm$pp$, and in low-speed and high-speed operation modes, it is 95.0 and 282.3 μm$pp$, respectively. In terms of propulsion control performance, the maximum position error based on ISO-230-22006 standard is 1.5 mm, and the maximum speed error at constant speed of 30 mm/s is 0.43%. To achieve such a highly precise control, especially under vacuum, novel control algorithms such as intelligent section control are applied to minimize abrupt changes in the activation of electromagnets as the carrier moves, and command shaping algorithms are applied to prevent excitation of the resonance mode of the system while at a higher control bandwidth. Moreover, to verify long-term reliability, a 12-hour continuous operation test is conducted.

Brake discs play a crucial role in braking railway vehicles, but the frictional heat generated during the braking process can lead to high temperatures on the disc. Changes in the friction block location on the brake pad result in variations in the temperature distribution across the brake disc. This study aims to optimize the positioning of friction blocks on the brake pad using artificial neural networks (ANN) and the Design of Experiments (DOE) approach based on the Taguchi methodology. The primary objective of this study is to mitigate temperature discrepancies in the frictional heating rate among distinct sectors along a radius from the center of the brake disc. To analyze the temperature variations caused by frictional heat, finite element analysis (FEA) is executed to account for the thermomechanical characteristics of the brake disc. The optimized brake pad, obtained through the ANN, is evaluated based on the temperature and thermal stress applied to the brake disc. The optimized model displays a larger hot band on the brake disc compared to the original model, leading to a more even distribution of thermal stress across the brake disc. In conclusion, the use of optimized pads offers significant performance benefits, resulting in a reduced maximum temperature and thermal stress, thus improving the overall braking performance of railway vehicles.

A novel design of a magnetic levitation (maglev) ropeless elevator for semiconductor wafer vertical transport is newly presented. To satisfy high cleanliness during vertical transport of the wafer, linear motor lifting and maglev guiding are desirable instead of the conventional rope lifting and wheel-based guiding method. Owing to the physically noncontact maglev guiding, particle-free and high-speed operation can be achieved with remarkable ride quality. In this paper, practical challenges for wafer transport, such as the eccentricity of the mass center from the actuating axis, severe acceleration/deceleration conditions as well as periodic large disturbances from normal forces of the linear motor, resonance of the elevator, and manufacturing tolerance of the guide rail, are further considered to satisfy the ride performance in wafer transport by designing a robust feedback controller with a loop shaping technique. A full-scale maglev ropeless elevator was constructed to experimentally validate the effectiveness of the proposed method. The experimental results demonstrated excellent magnetic levitation guiding performance in 5 degrees of freedom, with a maximum airgap fluctuation of 227 μm under harsh lifting conditions ( V_max = 2600 mm/s).

Magnetic levitation can reduce particulate contamination that occurs during wafer transportation in the semiconductor manufacturing process. This technology radically eliminates contact between the wafer and the transport system, reducing friction, wear, and particle generation. Therefore, it is suitable for achieving high cleanliness in the ultra-fine line-width semiconductor production process and solving the need for particle removal in a vacuum environment. In this study, the roller and linear motion guide components of the wafer transfer system were replaced with a magnetic levitation module, and a robot arm was installed on top to transport a single wafer. A posture controller and a current controller were designed, and test equipment simulating the wafer transfer system was also manufactured and tested. Regarding mover and system identification, a sine sweep test was performed on the motion axis of the five degrees of freedom. Through the obtained system identification, it was possible to design the posture controller more precisely. Moreover, through levitation in standstill experiments and high-speed operation experiments, the wafer transport system can be used to verify dust-free high-speed transport and accurate positioning performance.