The propulsion system of a projectile is very important for the aerospace industry. To perform space exploration mission, controlling position and posture of the projectile in the terminal stage is very important. In this study, a new lateral thrust system is proposed to control the position and posture of the projectile at the terminal stage. Based on nozzles in a lateral thruster, a high-speed projectile can instantly change its position and posture. After changing its position and posture, reverse thrust is generated to control unnecessary movements for stabilizing. Based on various tests, the operation and performance of the nozzle opening device (NOD) of the separation mechanism were validated. As a result, excellent reproducibility was confirmed with standard deviation of 0.057 ms for the time from the end of igniter operation to the start of NOD separation. The internal pressure of the chamber and NOD separation time were inversely proportional to each other with a linear relation. The internal pressure of the chamber and flight speed of NOD were also proportional to each other. The flight speed of NOD was 37.53 m/s at the maximum expected operation pressure (β), 30.26 m/s at 0.5 β, and 17.05 m/s at 0 psi.
This study aimed to determine mechanisms involved in the decrease of knee adduction moment (KAM) when waking with a contralateral cane without any constraint. Ten young subjects performed walking under two conditions: unassisted (no cane) or with a cane. After collecting data from the stance phase of the left foot, kinematic and kinetic data at early and late peaks of KAM were extracted for further analyses. When using a cane, early and late peaks of KAM decreased (p < 0.05) by 20.5% and 29.6%, respectively. Stepwise multiple regression analysis showed that the moment arm accounted for 59% and 95% of the variance of early and late KAM peaks, respectively. This reduction in moment arm occurred primarily due to lateral rotation of the GRF. Regarding the mechanism behind this, it could be due to the following: 1) by using a cane, the synthetic center of pressure shifted medially, which caused synthetic GRF to become more vertical than that of an unassisted walking and accordingly, and 2) the decrease of horizontal component of synthetic GRF reduced horizontal component of foot GRF, leading to lateral rotation of foot GRF. Understanding these mechanisms might help us improve effective use of canes.
Drones are increasingly used in various fields such as agriculture, logistics, and disaster response due to their agility and versatility. In indoor plant factories, small drones are used to monitor crop conditions and collect environmental data. However, small drones require frequent recharging due to their limited battery capacity, making autonomous charging systems essential for uninterrupted operation of drones. This study proposes an autonomous charging station designed for small drones in indoor plant factories. The system employs a wired charging mechanism to enhance charging efficiency, and a 3-degree-of-freedom (DOF) pose alignment system, utilizing an XY plotter and turntable, to correct drone landing errors. The alignment system ensures that drones, landing with random positions and orientations, are automatically adjusted to the correct position for charging. Experiments demonstrated that the charging station successfully aligned and charged drones with a 93% success rate on the first attempt. Even in cases of failure, the system automatically retried until a 100% success rate was achieved. This autonomous drone charging system has the potential to significantly enhance operational efficiency in indoor plant factories and can be adapted for various drone models in future applications.
In this paper, a deburring tool with 3-axis compliance is presented for deburring using a robot manipulator. Compliance is provided with beam structures instead of pneumatic pressure, which enables integrated 3-axis force sensing and variable stiffness. Two radial compliances were achieved using 4-PSS (Prismatic-Spherical-Spherical) legs, with P joints composed of cantilever beams. The one axial compliance was configured with two ball bushings and a linear spring. Strain gauges were attached to cantilever beams and a load cell was mounted between the linear spring and the universal joint to perform force sensing. The stability of vibrations and force sensing were verified through deburring experiments using the proposed deburring tool. Additionally, experiments on automatic offset for applying a constant force during deburring were conducted and results were validated by comparing the workpiece before and after the deburring process.
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Stress Analysis of a Robot End-Effector Knife for the Deburring Process Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef
Stress Analysis of a Robot End-Effector Knife for the Deburring Process Jeong-Jin Park, Jeong-Hyun Sohn, Kyung-Chang Lee Journal of the Korean Society of Manufacturing Process Engineers.2025; 24(6): 42. CrossRef
In the field of construction automation, significant research efforts continue to focus on replacing human labor; however, the varied and dynamic nature of construction sites still requires human intervention. The high task intensity in construction sites, particularly in lifting heavy materials, frequently results in musculoskeletal disorders among workers. To address this issue, this paper proposes a lifting device to replace manual material transportation through an opening between floors. The lift is designed with a gear-constrained double parallelogram mechanism to enable straight vertical movement. Moreover, a crank-rocker mechanism is incorporated to improve efficiency in repetitive tasks, reduce the required driving torque, and simplify control complexity. Additionally, this study introduces a passive gravity compensation mechanism that employs springs and cables, tailored to the lifting process, to enhance payload capacity and stabilize actuation. Through the integration of these mechanisms, the necessary motor capacity and control costs are significantly reduced. The effectiveness of the device is validated by actuation experiments with a fabricated prototype.
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Complete gravity balancing of the general four-bar linkage using linear springs Chin-Hsing Kuo Mechanism and Machine Theory.2025; 214: 106140. CrossRef
Manned water-powered aerial vehicles have been implemented into specialized missions around water bodies, such as firefighting and rescue. However, the dual requirement of vehicle motion control and performing tasks challenges operators. Moreover, in the presence of a low visibility, dense smoke, and extreme temperature, they always face potential risks. Motivated by these difficulties, this paper proposed an unmanned water-powered aerial vehicle using a nozzle rotation mechanism. This mechanism allows the vehicle to have a wide range of forces and torques in multiple directions under constant mass flowrate condition. A simple controller was designed to investigate the fundamental flight motions and verify dynamic properties of the vehicle in practical testing. To come up with the control law, the following steps were taken. Firstly, a mathematical model was derived to reflect the vehicle’s dynamic characteristics. Secondly, a well-known proportional-derivative-integral controller incorporating gravity compensation was deployed to regulate the 3-degree-of-freedom motion system. Thirdly, experiments were conducted to confirm the flight ability of the proposed vehicle. Results demonstrated that the control system preserved stability and the vehicle could fly following the desired altitude.
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Intelligent Robust Motion Control of Aerial Robot Cao-Tri Dinh, Thien-Dinh Nguyen, Young-Bok Kim, Thinh Huynh, Jung-Suk Park Actuators.2025; 14(4): 197. CrossRef
A Hybrid Flying Robot Utilizing Water Thrust and Aerial Propellers: Modeling and Motion Control System Design Thien-Dinh Nguyen, Cao-Tri Dinh, Tan-Ngoc Nguyen, Jung-Suk Park, Thinh Huynh, Young-Bok Kim Actuators.2025; 14(7): 350. CrossRef
In recent years, significant progress has been made in functional soft materials, alongside advances in nano/micromanufacturing techniques, driving the evolution of soft grippers to the forefront of robotics innovation. Compared to their traditional rigid counterparts, soft grippers offer unparalleled adaptability, effortlessly conforming to objects of varying sizes and shapes. This comprehensive review explores the latest trends shaping the landscape of soft robotic grippers, providing insights into their diverse functionalities and applications. The exploration begins with an examination of the various actuation mechanisms utilized by soft grippers, including cable or tendon-driven, pneumatic, electroactive, and thermoactive systems. Additionally, the review delves into the intricacies of grasping and manipulating mechanisms, spanning from multi-finger configurations to innovative approaches, such as jamming, suction, and adhesion grasping. Notably, hybrid grippers, which integrate multiple actuation and grasping mechanisms, are of particular interest, thereby enhancing the range of functionalities offered by these grippers. Finally, the review briefly addresses current limitations and future directions in the field.
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Soft autonomous mobile manipulators in agricultural automation – a review Tahsin Khan, Mervin Joe Thomas Industrial Robot: the international journal of robotics research and application.2025;[Epub] CrossRef
As advanced driver-assistance systems become more common in commercial vehicles, there is a growing need for evaluating safety of vehicles. Low platform target robot systems play a crucial role in this evaluation process as they can assess safety performances of autonomous vehicles. Driving stability of a target robot during real vehicle tests depends significantly on its suspension system. Therefore, developing an appropriate suspension device for the target robot is of utmost importance. This study aimed to improve driving stability by comparing two different suspension configurations: a single rocker and a double rocker, both incorporating a crank rocker mechanism. Initially, a two-dimensional model that met constraints of the suspension device was developed, followed by an analysis of reaction forces. Subsequently, an optimal design was determined using design of experiments principles based on parameters of a 2D model. The manufactured suspension system model based on the optimal design underwent multi-body dynamics simulation to evaluate driving stability. Comparative analysis of driving stability for both configurations was performed using MBD simulation, offering insights into the superior suspension design for the target robot.
This paper proposes a new rotary welding torch with a ball-jointed mechanical seal structure that simultaneously realizes the enclosure of CO₂ gas, the energization of welding current, and the insulation for system protection. In order to effectively compare the operation mechanism of the proposed device with the conventional rotary welding torch, a schematic technique is introduced to clearly visualize the operation and connection structure of the model. The kinematic state and constraint degrees of freedom of the tool are clearly shown, and it is easy to distinguish between the two designs that use different component parts and connection structures but result in the same final motion. In addition, the four dynamic characteristics of a rotary torch operating at 20 Hz (driving torque, vibration reaction force, natural frequency, and inertial mismatch) were analyzed to demonstrate superior performance to conventional products. The welding test showed that the tool normally operated even in a harsh welding environment, verifying its applicability in the field.
It is difficult for a human operator to find roll, pitch, yaw (RPY) that indicates the desired direction of unmanned aerial vehicle (UAV) in a three-dimensional space. Herein, a controller for UAV was developed allowing the human operator controlling the direction of UAV without finding RPY information. The algorithm implemented in the controller automatically calculated RPY information of UAV from the normal vector of the end effector. The developed controller was designed using a parallel mechanism. The joint angles of the controller were measured using potentiometers to estimate the normal vector of the end effector. Five subjects participated in an experiment to control a vector in three-dimensional space to follow a randomly generated target vector using the developed controller and the thumb sticks. The performance of the two controllers was evaluated by two methods: measuring the required time to reduce the error between the controlled vector and the target vector to be less than 0.1 cm and calculating a normalized error between the controlled vector and the target vector after manipulating the controlled vector for 10 seconds. When using the developed controller, the difference in control ability between subjects was reduced, and both required time and normalized error were generally reduced.
This paper deals with the development of a passive modular hip exoskeleton system aimed at preventing musculoskeletal low back pain, which commonly occurs in heavy weight transport workers, by improving back muscle strength. The passive exoskeleton system has the advantage of being lightweight, making it suitable for modular exoskeleton systems. The cam and spring actuator designed in this study was applied to the passive modular exoskeleton system to build human hip and lumbar muscle strength. In order to evaluate the effectiveness of the passive modular exoskeleton system, a test was performed in which a subject lifted a 15 kg weight three times in a stoop posture, using heart rate measurement and Borg scale recording. According to the results, all subjects showed 26.83% lower maximum heart rate and 34.73% lower average heart rate than those who did not wear the system, and Borg scale evaluation result was lower. All subjects wore this system and did not experience back pain during the experiment. Through this study, we validated the effectiveness of the passive modular exoskeleton system and proved that this system can build the strength of industrial workers and be a solution to prevent musculoskeletal lumbar disease.
Precision positioning stages are devices for precisely positioning objects according to required degrees of freedom and performance. Precision positioning stages are classified into serial and parallel mechanisms. Except for specific applications, the parallel mechanism is preferred. In serial mechanism, dynamic characteristics such as resonant frequency are clearly different from axis to axis and the first resonance frequency is distinctly low compared to the second. These make the control performance different for each axis and incurs limitation in control. In this study, the first and second resonant frequencies in a serial 2-DOF precision positioning stage were increased while maintaining their approximal value. Compliance analysis for the stage was performed by applying the matrix based method. A new concept of resonant frequency isotropy (RFI) was introduced and design optimization was performed in which first and second resonant frequencies almost coincided. This optimization allowed for the design of a serial 2-DOF precision positioning stage with enhanced first resonance frequency by 50.8% and RFI by 80.2% compared to the initial design. This paper is expected to increase the use of precision positioning stages based on serial mechanism and apply the concept of RFI to the positioning stages with more than 2-DOF.
This paper presents gain optimization for a controller of a 6- DOF underwater robot with tilting thrusters. PID control system with anti-windup technique is designed to stabilize the hovering motion of the robot. The controller comprises thrust vector decomposition to overcome nonlinearity of the thrust vector and also includes an algorithm to compensate for saturation of thrusters. A total of 24 control gains should be tuned in this controller, and gain optimization is performed according to four system errors using genetic algorithm. First, 18 PID control gains were optimized and then 6 gains were optimized to affect anti-windup. As a result, control gains optimized by the integral absolute error showed the best performance, and it is verified that tracking error in position and orientation of the robot were reduced by 29.38% compared with initial gains.
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Hovering control of an underwater robot with tilting thrusters using the decomposition and compensation method based on a redundant actuation model Jeongae Bak, Yecheol Moon, Jongwon Kim, Santhakumar Mohan, TaeWon Seo, Sangrok Jin Robotics and Autonomous Systems.2022; 150: 103995. CrossRef
Gain Optimization of Kinematic Control for Wire-driven Surgical Robot with Layered Joint Structure Considering Actuation Velocity Bound Sangrok Jin, Seokyoung Han Journal of Korea Robotics Society.2020; 15(3): 212. CrossRef
The process of tattooing to mark the position of lesions in the colon is one of important functions of the conventional endoscope. However, commercial capsule endoscope (CE) devices cannot perform the tattooing procedure because they cannot accommodate the size of the tattooing device. In this paper, we propose a compact tattooing mechanism design which can be accommodated inside the CE. Two conical springs, two triggering modules and a needle that can be installed inside a volume of 840 mm3 are employed to perform the needle insertion/withdrawal and inject the ink. A triggering module to deploy the conical springs is designed to be activated by heating a Ni-Cr wire and melting Wood’s metal. In this study, the activation time of the triggering module is investigated based on a Wood’s metal heating simulation. In order to determine the proper conical springs to ensure the activation of the tattooing mechanism, the elastic force correlation between two conical springs is studied. Then, the components of the proposed tattooing mechanism are fabricated and assembled, and an ex-vivo test is performed. Conclusively, the proposed tattooing mechanism implements the correct needle stroke and the proper ink injection into the submucosal layer of a porcine colon.
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Robotic Localization Based on Planar Cable Robot and Hall Sensor Array Applied to Magnetic Capsule Endoscope Min-Cheol Kim, Eui-Sun Kim, Jong-Oh Park, Eunpyo Choi, Chang-Sei Kim Sensors.2020; 20(20): 5728. CrossRef
This study presented a mechanism overview of a novel modular knee exoskeleton, ACE-Knee, and the analysis of the design requirements by observing human knee-motion characteristics. The ACE-Knee exoskeleton consists of 1) base frame at waist, 2) a 3-DOF (degrees of freedom) passive spherical hip, and 3) a knee driving mechanism. The passive hip is designed based on a 3R spherical serial chain such that it has RCM (remote center of motion) capability. For designing a compact and efficient knee driving mechanism, it is realized by two crank-slider linkages where two sliders are coupled with a linear spring. The proposed kinematic structure enables the driving concept of the passive support by the linear spring and the active following by an actuator. In order to setup design requirements, gait experiments were performed for level walking and ascending/descending stairs. From the analysis of experimental results, unique motion and quasi-stiffness characteristics of human knee were identified.
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Static and Dynamic Friction Characteristics Analysis of Actuation Module for Friction Compensation of Exoskeleton Robot Byoung Ju Lee, Gwang Tae Kim, Hong Cheol Kim, Young June Shin Journal of the Korean Society for Precision Engineering.2019; 36(10): 929. CrossRef
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