https://scholar.dgist.ac.kr/handle/20.500.11750/902 2026-04-04T09:50:44Z https://scholar.dgist.ac.kr/handle/20.500.11750/59952 Title: Supercritical Sliding-Mode Control for Position Tracking of PMSM With Disturbance Rejection Author(s): Kim, Jisu; Choi, Sunghyun; Yun, Dongwon Abstract: In highly dynamic environments, such as industrial automation systems with frequent load changes or electric vehicles, ensuring both robustness and high-precision control remains challenging, particularly in the position control of permanent magnet synchronous motors. Sliding-mode control (SMC) is widely used for its robustness, but traditional SMC methods often suffer from chattering and slow convergence, limiting overall system performance. To address these limitations, this study proposes a robust SMC approach incorporating a novel nonlinear sliding surface inspired by the supercritical pitchfork bifurcation concept. Additionally, a new reaching law is introduced to attenuate chattering and ensure fast convergence of the sliding variable to zero within a finite time. The proposed method also integrates a proportional-integral observer (PIO) with the equivalent-input disturbance (EID) framework to enhance disturbance rejection under both matched and mismatched uncertainties. The stability of the proposed controller was verified using Lyapunov stability analysis, and its performance was validated through simulations and real-world experiments. Comparative evaluations demonstrated that the proposed reaching law significantly reduces chattering amplitude by over 50 % and improves convergence speed by approximately 5.6 times faster than conventional methods. Furthermore, the system's disturbance-rejection capability under matched and mismatched uncertainties is enhanced through the PIO+EID structure. These results confirmed the robust performance of the controller under unknown disturbances. This paper is accompanied by a video that demonstrates the proposed control strategy and provides a comparison with traditional controllers. © 2025 Elsevier B.V., All rights reserved. 2025-12-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59950 Title: 형상 적응 파지를 위한 소형 부족 구동 기반 그리퍼 개발 Author(s): 금재영; 김동현; 정영준; 송진혁; 윤동원 Abstract: This paper proposes a wire-driven gripper that actuates three fingers using a single motor, aiming to enable stable object manipulation in confined and unstructured environments such as battlefields and disaster sites. Unmanned robots operating in such scenarios are increasingly required to perform missions including reconnaissance, search, rescue, and hazardous material removal. To fulfill these tasks, compact and reliable gripper systems are essential. Conventional grippers are categorized into soft grippers, which offer excellent shape adaptability through flexible materials, and rigid grippers, which provide structural strength. However, soft grippers are unsuitable for field environments due to limited stiffness, while rigid grippers lack adaptability for irregular objects. The proposed gripper enhances adaptability by leveraging wire-driven mechanism and reduces size and complexity through single-motor actuation. The design was validated through workspace analysis and motor torque estimation, and grasping experiments confirmed its performance. This paper demonstrates that the proposed gripper is well-suited for unmanned robots tasked with hazardous material handling and rescue operations in constrained environments. 2025-09-30T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/59058 Title: A twisted string actuator using a shape memory alloy for dual actuation Author(s): Nam, Yoonsoo; Choi, Sunghyun; Kim, Bongju; Yun, Dongwon Abstract: A Twisted String Actuator (TSA) is a type of linear actuator that converts rotational motion into linear motion. Due to its lightweight structure and high energy efficiency, TSA has been extensively studied in various fields. In particular, the speed-mode TSA offers the advantage of increasing both actuation range and speed through a simple mechanism. However, a critical drawback of the speed-mode TSA is its relatively low force transmission efficiency. To overcome this limitation, this study proposes a novel actuator concept: the SMA-TSA, which replaces the traditional TSA string with Shape Memory Alloy (SMA). By incorporating SMA, which can generate actuation independently, the SMA-TSA enables dual actuation. This provides an additional driving force alongside the conventional twisted-string mechanism. We designed the SMA-TSA to facilitate dual actuation and experimentally validated its performance. The results demonstrated that the SMA-TSA achieved an additional 14.42 mm of contraction and force output of 95.96 N. Furthermore, when applied to a robotic finger, the SMA-TSA increased the finger tip force by approximately 6.38 N, suggesting its potential for future applications in robotics. © 2025 2025-10-31T15:00:00Z https://scholar.dgist.ac.kr/handle/20.500.11750/58288 Title: Optimizing Snake Robot Locomotion with Decomposed Gait Pattern Representation Author(s): Song, Bongsub; Ju, Insung; Yun, Dongwon Abstract: This paper presents novel Gait Decomposition (GD) and Gait Parameter Gradient (GPG) methods for enhancing snake robot control and optimization. Snake robots face challenges in parameter tuning due to their complex dynamics and the need to preserve gait characteristics during control. GD fine-tunes gait parameters while maintaining their characteristics to prevent unintended changes during the application of serpenoid curves, typical in snake robots. A key feature of GD is the use of a motion matrix to represent joint movements, ensuring the preservation of gait characteristics. This methodology classifies the robot’s gait as a motion matrix, aiding in addressing the common challenge of parameter tuning in real-world scenarios. Furthermore, we introduce the GPG algorithm, designed to efficiently optimize gait parameters by adjusting both the curve function parameters and the motion matrix. Simulations validate the effectiveness of our methods, showing that the decomposed gait closely retains the original gait’s characteristics and achieves stable optimization under various conditions. Together, GD and GPG offer significant improvements in the control, adaptability, and practical deployment of snake robots, potentially expanding their applications across various domains. 2025-04-30T15:00:00Z