Hyouk Ryeol Choi

• Sungkyunkwan University

Robotic grasping is an essential capability, playing a critical role in enabling robots to physically interact with their surroundings. Despite extensive research, challenges remain due to the diverse shapes and properties of target objects, inaccuracies in sensing, and potential collisions with the environment. In this work, we propose a method fo...

A capacitive six-axis force/torque (F/T) sensor has favorable characteristics for miniature design. However, when designing small-sized force/torque sensors, anisotropy among the six axes can lead to uneven sensitivity across each axis. This is due to increased crosstalk errors, which degrade sensor performance. To design a miniature six-axis force...

The human knee has an asymmetric biomechanical structure, with the medial condyle being larger than the lateral condyle to support loads and facilitate diverse movements, thus leading to complex joint movements. These complex biomechanical properties often lead to kinematic misalignment between the knee joint and conventional wearable robots, resul...

A manipulator mounted on a mobility platform requires a design that simultaneously meets the demands for lightweight, compactness, and energy efficiency. A gravity compensator is an effective solution that mechanically offsets the gravity torque caused by the weight of the manipulator links, enabling the use of low-capacity motors while maintaining...

In soft robotics, actuators using both positive and negative pressures are notable for their high payload-to-weight ratios and wide operating ranges, but they require separate power sources. A single-pump system generating dual pressures presents a promising solution, though addressing pressure fluctuations due to coupled dynamics remains a challen...

Legged robots, especially quadruped robots, are widely used in various environments due to their advantage in overcoming rough terrains. However, falling is inevitable. Therefore, the ability to overcome a falling state is an essential ability for legged robots. In this paper, we propose a method to fully recover a quadruped robot from a fall using...

The range of motion (ROM) of joints in the human body is essential for movement and functional performance. Real-time monitoring of joint angles is crucial for confirming pathologic biomechanics, providing feedback during rehabilitation, and evaluating the treatment efficacy. This study aims to evaluate the concurrent validity of a wearable nanocom...

Increasing the force generation and scalability of soft pneumatic actuators poses significant challenges in robotics applications, especially where high load capacities and precise control are required. This paper presents UniBPAM, a novel, scalable soft pneumatic actuator optimized through 3D printing to enhance force generation. By analyzing desi...

Soft actuators producing bending motions have gained significant attention for their advantages in mimicking the properties and movements of human muscles. However, the research on soft rotary actuators has yet to keep pace with other soft actuators. This paper makes two key contributions to the design and modeling of these actuators. First, we int...

This paper presents a new switchable variable stiffness mechanism (SVSM) aimed at reducing reaction forces in robotic assembly tasks. The introduced switchable variable stiffness device (SVSD) exceeds existing variable stiffness mechanisms (VSMs) by providing a three-degree of freedom. Additionally, it features adaptable switchable springs suitable...

In this study, we propose a fabric muscle based on the Zigzag Shape Memory Alloy (ZSMA) actuator. Soft wearable robots have been gaining attention due to their flexibility and the ability to provide significant power support to the user without hindering their movement and mobility. There has been an increasing focus on the research and development...

Effective and safe physical Human-Robot Interaction (pHRI) hinges on robot proximity and tactile perception. This paper introduces a triple-mode fusion sensor designed to enhance safe pHRI. The sensor combines electromagnetic field radiation sensors and an infrared Time-of-Flight (ToF) sensor on a single hardware platform. This fusion equips the se...

This paper presents a gripper structure that improves the known potential limitations of curved fingertip movements and the restricted range of objects that can be grasped during power grasp in two-finger adaptive grippers. In the proposed gripper, a Grasshopper mechanism is applied to improve the movement of the fingertips, making it closer to a s...

This study introduces a novel algorithm that combines a custom-developed capacitive proximity sensor with LiDAR. This integration targets the limitations of using single-sensor systems for mobile robot perception. Our approach deals with the non-Gaussian distribution that arises during the nonlinear transformation of capacitive sensor data into dis...

With the growth of logistics automation, there is an increasing demand for advanced grippers. This study presents a gripper that integrates suction cups into the fingertips to overcome the limitations of traditional robotic gripping methods. Designed with a 5-degree-of-freedom structure, the gripper allows for angle adjustment of the suction cups,...

The robotic pick-and-place system is applied widely in many fields such as assembly, packaging, bin-picking, and sorting. In this paper, we present a deep learning and analytical-based method for generating antipodal grasping multi-modality in highly cluttered scenes. Our method takes advantage of three types of grasp poses to deal with the complex...

The 3D shape of a solid is the most crucial object property. Object shape and size information can be derived from depth information as it provides rich 3D geometric information. It can be found from the literature a substantial number of strategies to estimate the shape and size of solid objects from depth information. Nevertheless, the quality of...

This paper introduces a “rigidable exosuit” inspired by bow mechanics, which can dynamically alter its frame rigidity based on the tension of the attached string. The exosuit affords posture assistance (rigid phase) or unrestricted movement (flexible phase) as required by tasks. In the flexible phase, relaxed strings enable free shoulder and waist...

This study proposes a new type of series elastic actuator (SEA) utilizing a mixture of air and water. Instead of simply mixing air and water, a control method for its output force based on piston position control is suggested using the stiffness model of the mixture. The actuator is driven by the pressure generated when a stiff linear actuator comp...

To make robots more human-like and safer to use around humans, artificial muscles exhibiting compliance have gained significant attention from researchers. However, despite having excellent performance, pneumatic artificial muscles (PAMs) have failed to gain significant traction in commercial mobile applications due to their requirement to be tethe...

Random bin picking is a crucial task in logistic centers, which is driven by E-Commerce growth. In this paper, we present an end-to-end method for 6-DoF antipodal grasps from cluttered scenes. Our approach includes two main steps: finding Potential Grasp Areas (PGAs) from depth image of the bin and detecting suitable parallel grasps in PGAs from po...

Redundant manipulators are used in several areas because they can work with various postures. They are dexterous and can avoid crashing with obstacles during working in a complex environment. However, suitable redundant joints are difficult to identify. Manipulability is widely used to evaluate the posture of redundant manipulators. This approach a...

There are many studies for desirable tasks in ordinary situations like locomotion quadruped robots because of the advantages of agile and dynamic motion on various terrain compared with wheel-based robots. However, the falling situation by unpredictable causes is inevitable for quadruped robots, considering the actual field situations. We suggest a...

This letter presents a gripper comprising finger and suction with reconfigurable attributes. With the reconfiguration feature, the proposed gripper has a configuration suitable for different working environments of logistic order picking. The finger part of the gripper was configured with the parallelogram remote center of motion (RCM) mechanism to...

Robotic grasping is one of the essential skills in robotics. From industrial to housework, robots are required to handle objects, enabling them to interact with their surroundings. Among the various tasks in robotic grasping, bin-picking is considered one of the most challenging because of the cluttered bin filled with objects. Also, for the next-l...

This paper presents a novel impedance control strategy to improve the performance of a robot manipulator. Impedance control and admittance control have complementary effects on the stability and performance of a control system. Impedance control works well in stiff environments, whereas admittance control works well in soft environments. In this pa...

Pipes, which are the main means of transporting resources, deteriorate over time, thereby leading to defects or accidents. Therefore, periodic inspection of pipes is required, and a pipe robot that moves and inspects the inside of a pipe is one of the solutions. Herein, we propose an inspection robot system capable of autonomous driving inside buri...

This paper proposes a shape-adaptive EA-DEA pad gripper that can actively adapt to the shape of curved objects and quickly handle various objects by combining an electroadhesion (EA) pad and a multi-layered dielectric elastomer actuator (DEA) driven by electrostatic force. This gripper has a rapid release function capable of detaching thin and ligh...

Shape memory alloy actuators (SMA) are widely used in robots owing to their flexibility and light weight. However, there is a drawback in that SMAs need to be used as a bundle owing to their lower force density than the motor. In addition, SMAs require continuous current to maintain a contracted state, which results in the overheating of the actuat...

Existing pneumatic artificial muscles generally rely on the use of either positive or negative pressure for actuation with each having their own advantages and disadvantages. Herein, a hyperbaric vacuum‐based artificial muscle (Hyper‐VAM) making use of both positive and negative pressures almost interchangeably is described. This is done by placing...

Aging pipes are a deadly hazard that necessitate continuous and periodic pipe maintenance. However, it is impossible for humans to work directly inside small pipes or pipes with toxic internal environments. Pipeline robots were developed for this purpose. They have already been used in the field and there is ongoing research to increase their effic...

Artificial muscles have been developed for various input power sources. Among them, thermally driven actuators can be easily actuated at a low voltage without an additional device using the Joule heating. Therefore, these actuators can be considered suitable for developing lightweight robots. Shape memory alloy or twisted and coiled actuators are t...

This letter introduces a simultaneous positive and negative pressure controller for a pneumatic pump. For precise position or force control of the pneumatic soft actuator, the pressure from the source has to be regulated. When the positive and negative pressures are regulated, coupled dynamics caused by the pressure change affect the controller per...

Twisted and coiled actuators (TCAs), which are light but capable of producing significant power, were developed in recent times. After their introduction, there have been numerous improvements in performance, including development of techniques such as actuation strain and heating methods. However, the development of robots using TCA is still in it...

Wearable conductive nanocomposite strain sensors have received considerable attention for rehabilitation and human motion detection. However, their practical application has been hindered by the irreversible resistance change upon stretching cycles. Here we report a resistive-type conductive nanocomposite strain sensor with a nearly perfect reversi...

Twisted-coiled polymer actuators (TCAs) are a new promising type of artificial muscles that is light-weight, low-cost and provides high stroke. This paper presents a dynamic model based on long short term memory (LSTM) networks to predict the nonlinear behavior of an antagonistic joint driven by the hybrid TCA bundle made from Spandex and nylon fib...

Robotic hands perform several amazing functions similar to the human hands, thereby offering high flexibility in terms of the tasks performed. However, developing integrated hands without additional actuation parts while maintaining important functions such as human-level dexterity and grasping force is challenging. The actuation parts make it diff...

There are many flexible joint designs that are delivering torque and absorbing shocks simultaneously. One of the most active areas of the research is the Series Elastic Actuator (SEA), which connects the motor and load by lowering the stiffness. The problem, however, is that the non-rigid stiffness causes the system to have a lower bandwidth, there...

For soft grippers to be applied in atypical industrial environments, they must conform to an object’s exterior shape and momentarily change their stiffness. However, many of the existing grippers have limitations with respect to these functions: they grasp an object with only a single curvature and a fixed stiffness. Consequently, those constraints...

Recently, owing to the significant advancement in the field of soft robots, various studies have been conducted on soft actuators. Among the several soft actuators, the double helix twisted and coiled actuator (DTCA), which is fabricated by coiling spandex and nylon under twisted conditions, exhibits considerable performance in terms of large contr...

This paper presents a modularized autonomous pipeline inspection robot called MRINSPECT VII+, which we recently developed. MRINSPECT VII+ is aimed at inspect in-service urban gas pipelines with a diameter of 200 mm. The robot consists of five basic modules: driving, sensing, joint, and battery modules. For nondestructive testing (NDT), an NDT modul...

This paper introduces a dual-type proximity sensor and a control strategy for a robot manipulator to realize safe humanrobot interactions(HRI) by using the sensor. Safety is an essential condition for HRI in practical scenarios. To achieve this condition, information about the relationship between an external objects and the robot is required. To o...

This paper presents an approach to optimize the control torque of heavy-duty redundant manipulators used for dismantling nuclear power plants. Such manipulators must endure intensive and repetitive tasks over long periods. In this regard, the torque minimization is essential for decreasing power consumption and the fatigue load acting on the joint...

Ground reaction force (GRF) plays an integral role in legged robots to control interaction with the ground. However, most techniques in whole-body controller for quadrupedal robots do not explicitly take into account actual torque or force in their control loops and instead use feed-forward force to generate joint torque at every time step. In this...

Humans come into physical contacts with various machines such as robots in daily life. This leads to the underlying issue of guaranteeing safety during such human-robot interactions. Thus, many devices and methods have been studied for impact damage reduction. A safety joint mechanism (SJM) using four-bar linkages has been highlighted as an impact...

In legged locomotion, the contact force between a robot and the ground plays a crucial role in balancing the robot. However, in quadrupedal robots, general whole-body controllers generate feed-forward force commands without considering the actual torque or force feedback. This paper presents a whole-body controller by using the actual joint torque...

The soft robot manipulator is attracting attention in the surgical fields with its intrinsic softness, lightness in its weight, and safety toward the human organ. However, it cannot be used widely because of its difficulty of control. To control a soft robot manipulator accurately, shape sensing is essential. This paper presents a method of estimat...

Twisted-coiled polymer actuators (TCA) have many interesting properties that show potentials for making high performance bionic devices. This paper presents a long short term memory (LSTM) model to predict the behavior of an antagonistic joint driven by hybrid TCA bundles made from Spandex and nylon fibers. By using automatic differentiation, which...

This paper proposes a method for improving the resolution of a capacitive-type (C-type) torque sensor. This method amplifies the output signal variation of a capacitance-to-digital (CDC) chip by designing a series resonant circuit. This study considers the data sampling method of the CDC chip and the effects of the resonant circuit on the output si...

Stiffness adjustability is one of the key characteristics that help humans achieve safe and reliable motions. This paper aims to realize the simultaneous position-stiffness control of an antagonistic joint driven by a type of super-coiled polymer (SCP) artificial muscles, made from a combination of Spandex and nylon fibers. A nonlinear model that c...

Haptic display transfers the sense of touch by applying forces, vibrations, or motions to the user. This article presents a novel bidirectional haptic display responsive to touch. The device is composed of a flexible tactile sensor and tactile actuator, and the actuator is actuated according to the touch signals from the tactile sensor. The tactile...

This paper presents a different type of rotary actuator in contrast to conventional rotary actuators that operate by fiber wound in the form of a helix on a cylinder-shaped elastomer. Our actuator has a fiber set placed in the rθ plane of an elastomer in the form of an annulus, this elastomer expands under pneumatic pressure input to deliver rotati...

This paper presents a new biomimetic soft finger joint with elastic ligaments for enhanced restoration capability. A hemisphere-shaped flexible finger joint is designed to secure omnidirectional restoration and guarantee a reliable recovery function. Joint design comparative studies for enhancing restoration are presented with joint mechanisms and...

The presence of a tactile sensor is essential to hold an object and manipulate it without damage. The tactile information helps determine whether an object is stably held. If a tactile sensor is installed at wherever the robot and the object touch, the robot could interact with more objects. In this paper, a skin type slip sensor that can be attach...

Force/Torque (F/T) sensing technology enables a dexterous robot control such as direct teaching, master-slave system, and pick-and-place task. In general, 6-axis F/T sensor is attached to the end-effector of the robot manipulator to assist in utilizing advanced robot systems. However, in actual applications, various tools such as robotic grippers,...

In missile technology, for the high maneuverability of guided missile systems, miniaturization and lightweight technologies are essential. Therefore, novel actuator technologies are required for the miniaturization and reduction in the weight of fin control systems that control the direction of guided missiles. In this study, we introduce Fin Contr...

Short time-of-flight and safety concerns because of low efficiency and fast rotating propellers, respectively, are two major shortcomings in the practical usage of drones. Thus, the usability of drones is limited to only aerial photography or surveillance. Especially above crowd, it's near impossible. In this study, we present a novel soft drone, S...

As advanced robotic technologies such as human-robot interaction and automatic assembly processes have emerged, torque sensors have become an essential component for robots. However, commercial torque sensors are not suitable for robotic applications because of their large sizes, heavy weights, narrow options, and high prices. In this letter, we de...

This article presents an overview of A rt i ficial DI gitigrade for N atural Environments (AiDIN-VI), a force-controllable quadruped robot system with incorporated mandatory abilities of speed, efficiency, and mobility for providing real-world services. This article describes the design methodologies and principles employed to implement thes...

As highly integrated electronic devices and automotive parts are becoming used in high-power and load-bearing systems, thermal conductivity and mechanical damping properties have become critical factors. In this study, we applied two different fillers of aluminium nitride (AlN) and boron nitride (BN), having polygonal and platelet shapes, respectiv...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Electroadhesion device allows one to pick up almost all the objects regardless of their shape or types of materials by means of the electrostatic Maxwell force, which is developed by the dielectric induced polarization on the subject surface. In this study, we propose the modelling methodology and its experimental verification that could maximize t...

Purpose The purpose of this study is to propose a novel plane-based mapping method for legged-robot navigation in a stairway environment. Design/methodology/approach The approach implemented in this study estimates a plane for each step of a stairway using a weighted average of sensor measurements and predictions. It segments planes from point clo...

This paper presents a novel bidirectional tactile display by integrating an antagonistic dielectric elastomer actuator (DEA) with a V-shaped electrostatic actuator (EA), called electrostatic dielectric elastomer actuator (EDEA). Within a simple structure, this device can provide large out-of-plane vibration of the silicone-based DEA membrane. It is...

Most legged animals use their flexible body and supporting muscles to produce power for their locomotion, resulting in superior mobility and fast motions. In reality, an animal body consists of multiple bones and joints as well as legs having two or three segments with mass and inertia. In this paper, we study the bounding locomotion of a quadruped...

Skeletal muscles produce contractile motions and a couple of skeletal muscles antagonistically arranged are required to create bidirectional active movements. The musculoskeletal system is mainly composed of two skeletal muscles, joint, bones and tendons, and thus, a joint performs active bidirectional rotations. Likewise, twisted and coiled soft a...

Recently many new actuators have been developed in order to overcome the limitations of conventional actuators. The pneumatic artificial muscle actuator (PMA) is one of the typical examples. Although many studies have been conducted on the single PMA, there are still many limitations of the single PMA operation. The typical problems are low efficie...

Twisted and coiled actuators (TCAs) composed of fishing lines or sewing threads are one of the most promising artificial muscles because of their high specific power, large stroke, and low fabrication cost. Since the TCA can be thermally actuated, the thermal properties of the actuator determine its actuation performance. Here, graphene materials w...

This paper introduces the addition of torsional pre-strain into the manufacturing process of shape memory alloy (SMA) springs to form torsionally pre-strained SMA (TPSMA) springs. These springs have higher performance at the same power input for the same loads and same coil dimensions as regular SMA springs. A modified thermoconstitutive model was...

The Acknowledgements, not given in the original publication, are as follows.

A sampling-based planning algorithm is one of the most powerful tools for collision avoidance in the motion planning of manipulators. However, this algorithm takes a long time to generate motions of the manipulator. This work proposes a goal-oriented (GO) sampling method for the motion planning of a manipulator. The GO sampling method can identify...

Lignin powder was modified via ring-opening polymerization of caprolactone to form a lignin–polycaprolactone (LPCL) particulate. The LPCL particulates were mixed with an acrylonitrile–butadiene–styrene (ABS) matrix at an extremely high rotational speed of up to 3000 rpm, which was achieved by a closed-loop screw mixer and in-line melt extruder. Usi...

This paper presents a variable admittance control method to achieve intuitive human-robot interactions that consider human intentions. Human intention is classified into two categories-direct and indirect. With respect to direct intention, the concept of standard force is introduced to adjust the interacting force. The proposed variable admittance...

Electroadhesive devices can lift materials of different shapes and various types using the electrostatic force developed at the interface between the device and the object. More specifically, the electrical potential generated by the device induces opposite charges on the object to give electrostatic Maxwell force. Although this technology has a gr...

The human hand provides excellent grasp capabilities by using the interaction of the thumb and other fingers, and thus, how to dextrously interact with each other can represent the performance of the robot hand. This paper presents the kinematic design optimization for an anthropomorphic robot hand based on the interactivity of fingers. We propose...

Nowadays, researchers and developers are trying to obliterate the boundaries between robots and humans to create the connection between robots and humans in daily work as well as in industry. Therefore, this topic describes in detail the features, manufacturing methods, and experiments on robots for large scale coverable stretchable inductive proxi...

For more secure and delicate robotic surgery, force sensing ability is essential but it has still not been used in actual robot surgery. This is because the environmental factors that occur during actual operation affect the sensor and the sensor cannot give reliable force information. In this paper, we aim to develop reliable sensorized-forceps th...

This paper presents a new mechanical design of an anthropomorphic robot hand. The hand is designed such that it is adaptive, backdrivable, modularized to provide both dexterity and robustness. The hand has 18 joints, 14 degrees of freedom, and a new joint mechanism called an active DIP–PIP joint for the robot finger. The mechanism includes a pair o...