Commercial exoskeletons currently utilize multiple sensors, including inertial measurement units, electromyography sensors, and torque/force sensors, to detect human motion. While these sensors improve motion recognition by leveraging their unique strengths, they can also lead to discomfort due to direct skin contact, added weight, and complex wiring. In this paper, we propose a simplified motion recognition method that relies solely on encoders embedded in the motors. Our approach aims to accurately classify various movements by learning their distinctive features through a deep learning model. Specifically, we employ a convolutional neural network algorithm optimized for motion classification. Experimental results show that our model can effectively differentiate between movements such as standing, lifting, level walking, and inclined walking, achieving a test accuracy of 98.76%. Additionally, by implementing a sliding window maximum algorithm that tracks three consecutive classifications, we achieved a real-time motion recognition accuracy of 97.48% with a response time of 0.25 seconds. This approach provides a cost-effective and simplified solution for lower limb motion recognition, with potential applications in rehabilitation-focused exoskeletons.
A robotic focal plane system using robotic fiber positioners enables multi-object spectroscopy for hundreds to thousands of galaxies by utilizing a dense array of positioners that are closely packed at the focal plane of a telescope. While this dense arrangement increases the number of observations, it also introduces the potential for collisions between adjacent positioners. A fiber positioner is designed similarly to a SCARA robot. It is driven by two series of BLDC motors. Each positioner is manufactured with an outer diameter of 16 mm. It operates within an annular workspace with an outer diameter of 33.6 mm and an inner diameter of 12.8 mm. As these positioners are arranged with a spacing of 16.8 mm, target assignment and motion planning are critical to avoid collisions caused by overlapping workspaces. To address this, we proposed an optimized step choice algorithm using a motion planning method based on optimization with the sequential quadratic programming algorithm. Simulation results demonstrated that paths for all positioners within a tile were successfully generated with a success rate of up to 93.75% across 80 tiles.
Slot-die coating is a method of coating a wide layer of thin film on a substrate. It has the advantages of large-area coating with high reproducibility and uniform thickness. For this reason, it has been widely applied in various industrial manufacturing fields. To secure higher coating uniformity under various coating conditions, estimating and controlling the flow rate of the coating solution discharged to the substrate is crucial. In this study, a practical gravimetric flow rate measurement method for slot-die coating uniformity evaluation has been introduced. The gravimetric method is a technique for accurately and quickly estimating the flow rate through the mass change over time using a precision weighing balance. We analyzed the measurement principle and errors caused by fluid mechanics such as hydrodynamic force or capillary force. The dynamic properties based on fluid viscosity were also evaluated for flow rates from 5 to 50 μL/s. The repeatability of the fabricated measurement system was ~1.5 μL/s. Finally, it was confirmed that the settling time for high-viscosity fluid could be advanced by 56.4% through multi-step feedforward control.
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Precision Measurement and Control of Flow Rate for Coating Uniformity in Variable Slot Die Coating Yeeun Bae, Kyung-Taek Yoon, Hyun-Ho Lee, Moongu Lee, Hyun-Jung Kim, Young-Man Choi Journal of the Korean Society of Manufacturing Technology Engineers.2023; 32(5): 267. CrossRef
The electromagnetic force compensation (EMFC) measurement principle has been widely adopted in the high-precision mass metrology system due to its sensitive compliant mechanism and nanometer level position sensor. In EMFC, an electromagnetic actuator balances the gravitational weight to maintain zero (or Null) position by feedback control using a position sensor, and the weight is calculated from the current applied to the actuator. Thus, a position sensor in the EMFC system should measure the null position accurately with high sensitivity and resolution. The position sensor commonly used in EMFC balance is an optical sensor that measures the displacement of EMFC balance from the intensity of light coming through a slit using a two-segment photodiode. This paper analyzed the characteristics of an optical position sensor for EMFC balance through parametric analysis using the Fresnel diffraction model. We also evaluated the performance of the sensor and confirmed the feasibility from weighing performance of the balance prototype. Normalized sensitivity of the sensor was 0.04237 μm-1 and measured resolution was 1.09 nm. The weighing repeatability with our optical position sensor was 4.83 mg (1σ) at 10 g measurement, which was 3 times better than the repeatability with an alternative commercial sensor.
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Modeling and Tolerance Analysis of Compliant Mechanism for Axis-Symmetric Mass Comparator Kyung-Taek Yoon, Young-Man Choi IEEE/ASME Transactions on Mechatronics.2024; 29(2): 878. CrossRef
Practical Gravimetric Flow Rate Measurement Method for Slot-Die Coating Uniformity Evaluation Kyung-Taek Yoon, Jeong-Hyun Bae, Young-Man Choi Journal of the Korean Society for Precision Engineering.2023; 40(2): 105. CrossRef
Novel Multi-Electromagnetic-Force-Compensation Weighing Cell With Axis-Symmetric Structure Kyung-Taek Yoon, Hyunho Lim, Jeong-Hyun Bae, Won Kyu Lee, Dongmin Kim, Young-Man Choi IEEE/ASME Transactions on Mechatronics.2022; 27(6): 6018. CrossRef
Micro hot-embossing is a powerful tool in the agile additive manufacturing industry. Its applications include optical components, micro-fluidic devices, MEMS, hydrophobic/hydrophilic surfaces, and energy harvesting devices. To overcome a drawback of low-process speed, the R2R process has been innovated, with novel embossing mechanisms and process optimization. Also, new materials beyond thermoplastic polymers have been applied to develop new devices, or enhance device performance. This review surveys recent progress in micro hot-embossing technology, in terms of new mold fabrication process, process innovation, and various applications.
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Manufacturing Process for Highly Stable Thermal Imprinting Transparent Electrode Using IPL Sintering Yunseok Jang Journal of the Korean Society for Precision Engineering.2025; 42(1): 75. CrossRef
Finding Ways to Deform Fine Patterns Fabricated by UV Curable Resin Woo Young Kim, Su Hyun Choi, Seonjun Kim, Young Tae Cho Journal of the Korean Society for Precision Engineering.2020; 37(4): 291. CrossRef
Hot embossing techniques are used to engrave patterns on plastic substrates. Roll based hot embossing uses a heated roll for a continuous process. A heated roll with relief patterns is impressed on a preheated plastic substrate. Then, the substrate is cooled down quickly to prevent thermal shrinkage. The roll speed is normally very slow to ensure substrate temperature increase up to the glass transition temperature. In this paper, we propose a noncontact preheating technique using focused infrared light. The infrared light is focused as a line beam on a plastic substrate using an elliptical mirror just before entering the hot embossing roll. The mid range infrared light efficiently raises the substrate temperature. For preliminary tests, substrate deformation and temperature changes were monitored according to substrate speed. The experiments show that the proposed technique is a good possibility for high speed hot embossing.
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Manufacturing Process for Highly Stable Thermal Imprinting Transparent Electrode Using IPL Sintering Yunseok Jang Journal of the Korean Society for Precision Engineering.2025; 42(1): 75. CrossRef
Study of a Line‐Patterning Process Using Impact Print‐Type Hot Embossing Technology Myeongjin Kim, Jaewon Ahn, Junseong Bae, Donghyun Kim, Jongbum Kim, Jonghyun Kim, Dongwon Yun Advanced Engineering Materials.2020;[Epub] CrossRef
Variation of a Triangular Pattern Shape due to Shrinkage in the Repeated UV Imprint Process Jiyun Jeong, Su Hyun Choi, Young Tae Cho Journal of the Korean Society of Manufacturing Process Engineers.2020; 19(7): 67. CrossRef
Recent Research Trend of Micro Hot-Embossing Seung-Hyun Lee, Jeongdai Jo, Kwang-Young Kim, Young-Man Choi Journal of the Korean Society for Precision Engineering.2018; 35(11): 1027. CrossRef
Flexible electronics have been to the fore because it is believed that flexibility can add incredible value such as light weight and mobility into the existing electronic devices and create new markets of large-area and low-cost electronics such as wearable eletronics in near future. Offset printing processes are regarded as major candidates for manufacturing the flexible electronics because they can provide the patterning resolution of micron-size effectively in large-area. In view of mechanics, the most important viewpoint in offset printing is how to achieve the synchronized movement of two contact surfaces in order to prevent slip between two contact surfaces and distortion of the blanket surface during ink transfer so that the high-resolution and good-overlay patterns can be printed. In this paper, a novel low-cost measurement method of the synchronization error using the motor control output signals is proposed and the compensation method is presented to minimize the synchronization error.
We developed a compact high-precision slot-die coating machine for thin-film deposition on a flexible substrate. For smooth and precise coating, air-bearing and linear motor system were employed to minimize velocity ripple. The gap control mechanism is specially designed to have repeatability of gap between nozzle and substrate under 1 μm. Due to extremely precise gap control, the machine can coat thin-films down to 50 nm with 200 mm × 100mm size. A thin film of Ag nano-particle ink is coated for demonstration.
This paper describes a robust control scheme for high-speed and long stroke scanning motion of high precision linear motor system consisting of linear motor, air bearing guide and position measurement sy stem using heterodyne interferometer. Nowadays, semiconductor process and inspection of wafer or LCD need high speed and long travel length for their high throughput and extremely small velocity fluctuations or tracking errors. In order to satisfy these conditions, linear motor system are widely used because they have large thrust force and do not need motion conversion mechanisms such as ball screw, rack & pinion or capstan with which the system are burdened. However linear motors have a problem called force ripple. Force ripple deteriorates the tracking performances and makes periodic position errors. So, force ripple must be compensated. To maximize the tracking performance of linear motor system, we propose the control scheme which is composed of a robust control method, Time Delay Controller (TDC) and a feedforward control method, Zero Phase Error Tracking Control (ZPETC) for accurate tracking a given trajectory and an adaptive force ripple compensation (AFC) algorithm for estimating and compensating force ripple. The adaptive ripple compensation is continuously refined on the basis of tracking error. Computer simulation results based on modeled parameters verify the effectiveness of the proposed control scheme for high-speed, long stroke and high precision scanning motion and show that the proposed control scheme can achieve a superior tracking performance in comparison to conventional TDC control.
This paper presents one-axis high precision scanning system and illustrates the design of modified X-Y-θ stage as a tracker using VCM and commercialized air bearings for it. The scanning system for 100㎚ resolution is composed of the 3-axis stage and one axis long stroke linear motor stage as a follower. In this study a previous proposed and presented structure of VCM for the fine stage is modified. The tracker has 3 DOF(X-Y-θ) motions by four VCM actuators which are located on the same plane. So 4 actuating forces are suggested and designed to create least pitch and roll motions. This article will show about the design especially about optimal design. The design focus of this fine stage is to have high acceleration to accomplish high throughput. The optimal design of maximizing acceleration is performed in restrained size. The most sensitive constraint of this optimal design is heat dissipation of coil. There are 5 design variables. Because the relationship between design variables and system parameters are quite complicated, it is very difficult to set design variables manually. Due to it, computer based optimal design procedure using MATLAB is used. Then, this paper also describes the procedures of selecting design variables for the optimal design and a mathematical formulation of the optimization problem. Based on the solution of the optimization problem, the final design of the stage is also presented. The results can be verified by MAXWELL. The designed stage has the acceleration of about 5 ㎨ with 40㎏ total mass including wafer chuck and interferometer mirror. And the temperature of coil is increased 50°C. In addition, the tracker is controlled by high precision controller system with HP interferometer for it and linear scaler for the follower. At that time, the scanning system has high precision resolution about 5㎚ and scanning resolution about 40㎚ in 25㎜/s constant speed.
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