Jaeheung Park

Seoul National University, Transdisciplinary Studies, Faculty Member

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Papers by Jaeheung Park

Optimization of Pelvic Rotation Walking Pattern Considering Future States Using Model Predictive Control to Increase the Step Length

IEEE Access

Pelvic rotation, which is observed in human gait, is used to increase a robot's step length in th... more Pelvic rotation, which is observed in human gait, is used to increase a robot's step length in the humanoid robot walking. Existing methods empirically or experimentally generate the pelvic-rotation angle offline using predetermined pelvis and foot trajectories. Therefore, these methods are difficult to be used with the method to generate the center of mass (CoM) trajectory in real time using techniques such as preview control or model predictive model control. In this study, we propose a method that generates a pelvic-rotation trajectory that can be used with a real-time CoM generation method while reflecting the future state of the robot. The step length increased due to pelvic rotation was kinematically analyzed and compared with the step length increased by the proposed method. Upper body motion to compensate for yaw angular momentum generated by lower body movement during walking using pelvic rotation was optimized using centroial dynamics. The waist yaw joint for pelvic rotation, leg joint for the walking, and upper body joint for arm swing were optimized using separate optimal controllers. Energy efficiency, increase in step length, and decrease in the possibility of singularity occurrence of pelvic rotation walking were analyzed and compared in simulations. The proposed method was experimentally verified using humanoid robot Dyros-Jet.

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최소침습술을 위한 의료용 인스트루먼트의 동작 성능 향상

Journal of Institute of Control, Robotics and Systems, 2013

This paper presents feedforward controllers to improve the control performance of the motion and ... more This paper presents feedforward controllers to improve the control performance of the motion and grasping force of a surgical instrument used in an MIS (Minimally Invasive Surgery) robot. The surgical instrument has a long distance between the drive motors and its active joints. Therefore, the gripper on the instrument is controlled by a cable drive mechanism, which generates a coupled motion between the wrist joint and the grip direction. In order to solve the problem, this paper analyzes the pulley composition of the surgical instrument and proposes feedforward controllers to eliminate the coupled motion. Furthermore, feedforward controllers to regulate the grasping force are proposed to deal with another coupling problem between the grasping force of the instrument and the motion of the instrument joints. The experimental results demonstrate the improved control performance of the motion and grasping force of the instrument.

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From Mechanical Metamorphosis to Empathic Interaction: A Historical Overview of Robotic Creatures

Journal of Human-Robot Interaction, 2014

Humans have had a long history of fascination with building intelligent machines that depict them... more Humans have had a long history of fascination with building intelligent machines that depict themselves or move animatedly. This article explores the history of robotic creatures like Egyptian figurines, Greek mechanical inventions, 18th century ingenious automata, and modern kinetic mise-en-scène and robotic artworks. Several interactive robots showed the potential for emotional interaction between humans and machines. In the context of human-robot interaction, empathy with robots requires further discussions on the interaction design.

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Drum stroke variation using Variable Stiffness Actuators

2014 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2014

One interesting field of robotics technology is related to the entertainment industry. Performing... more One interesting field of robotics technology is related to the entertainment industry. Performing a musical piece using a robot is a difficult task because music presents many features like melody, rhythm, tone, harmony and so on. Addressing these tasks with a robot is not trivial to implement. Most of approaches which related to this specific field lacks of quality to perform in front of human audience. Implementation of human-like motions can not be properly achieved with a conventional robot actuator. Consequently, we exploit a new type of actuator which simplifies the drawbacks of a conventional one. We used Variable Stiffness Actuator(VSA) instead of using conventional actuator. We can control position, force, and stiffness, simultaneously by using VSA. The most important novel feature is its controllable stiffness. When the stiffness of the actuator is changed, the characteristics of the actuator's response also changes. We implemented the specific stroke which is called "double stroke" using one of variable stiffness actuator. Although the double stroke is known as a special stroke which could be performed by human only, double stroke is successfully implemented by stiffness variation.

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Probabilistic Estimation of Whole Body Contacts for Multi-Contact Robot Control

Proceedings 2007 IEEE International Conference on Robotics and Automation, 2007

Today most robots interact with the surroundings only with their end-effectors. However there are... more Today most robots interact with the surroundings only with their end-effectors. However there are many benefits to utilizing contact along the entire length of robot body and links especially for human-like robots. Existing control strategies for link contact require knowledge of the contact point. In an uncertain environment, locating link contact point is difficult for most robots as they do not possess skin capable of sensing. We propose a probabilistic approach to link contact estimation based on geometric considerations and compliant motions. Since for many robots, link geometry is also uncertain, we broaden our approach to simultaneously estimate link shape and environment contact. Our experimental results demonstrate that efficiency of control is significantly improved by link contact estimation.

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Robot Control near Singularity and Joint Limit Using a Continuous Task Transition Algorithm

International Journal of Advanced Robotic Systems, 2013

When robots are controlled in the task space, singularities and joint limits are among the most c... more When robots are controlled in the task space, singularities and joint limits are among the most critical and difficult issues that can arise. In this paper, we propose a new approach for the robots to operate in the regions near singularities and joint limits using the operational space control framework. Specifically, a continuous task transition algorithm called the intermediate desired value approach is applied to the hierarchically structured controller in the operational space control framework. In this approach, new tasks are defined for dealing with singularities and joint limits, and the tasks are activated or deactivated using the continuous task transition algorithm to guarantee the continuous execution of the tasks during the execution of the main task. The proposed approach is implemented on a 6-DOF manipulator called Roman-MD. The experimental results demonstrate its performance near the singular regions and joint limits.

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Towards on-site autonomous robotic floor tiling of mosaics

2014 14th International Conference on Control, Automation and Systems (ICCAS 2014), 2014

Humanoid robots have been a central research topic of robotics for the last 30 years. However, it... more Humanoid robots have been a central research topic of robotics for the last 30 years. However, it has not been until the last decade that humanoids became a viable commercial product. While not full scale, robots such as NAO provide a large range of motion with multiple sensors for the environment. With these new robots, this paper explores their application in the manufacturing industry. Floor tiling, a still manual procedure on-site, requires significant time in both awkward positions and bent over. These two movements are main causes of back injury, the leading cause of early retirement and overall injuries in the construction industry. This paper explores the efficacy of using current commercial robots for on-site autonomous floor tiling through specific experiments and methods in programming integrated systems. A novel system for combining the automation of manufacturing of mosaics and the automation of on-site square floor tiling is presented.

The Operational Space Formulation on Humanoids Considering Joint Stiffness and Bandwidth Limit

IEEE Access, 2021

As the applications of robots increase, mobility and capability of interaction in unstructured en... more As the applications of robots increase, mobility and capability of interaction in unstructured environments have become important. Hence, humanoid robots have been developed to have these capabilities, and recently, compliant motions for safe contact have been studied. The Operational Space Formulation can be an effective method for humanoid robots to realize compliant motion via unified motion and force control. Nevertheless, the implementation of the Operational Space Formulation on humanoid robots has not been successful. One of the challenging issues is low position tracking performance. In this study, a control method for solving this problem is proposed by considering the joint stiffness and joint bandwidth limits. To consider joint stiffness, the Operational Space Formulation was derived using flexible joint robot dynamics. Additionally, an extra torque generation method, which penalizes low performance actuators, is utilized to account for the bandwidth limits. Neither methods requires additional sensors or joint space controllers. Hence, they can be useful for conventional humanoid robots composed of electric motors and gears. By integrating the two methods, the position tracking performance of the Operational Space Formulation on the humanoid robot was significantly improved. The proposed method was demonstrated via position and orientation control experiments using our humanoid robot, TOCABI.

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Dance motion generation by recombination of body parts from motion source

Intelligent Service Robotics, 2017

In this paper, we propose an approach to synthesize new dance routines by combining body part mot... more In this paper, we propose an approach to synthesize new dance routines by combining body part motions from a human motion database. The proposed approach aims to provide a movement source to allow robots or animation characters to perform improvised dances to music, and also to inspire choreographers with the provided movements. Based on the observation that some body parts perform more appropriately than other body parts during dance performances, a correlation analysis of music and motion is conducted to identify the expressive body parts. We then combine the body part movement sources to create a new motion, which differs from all sources in the database. The generated performances are evaluated by a user questionnaire assessment, and the results are discussed to understand what is important in generating more appealing dance routines.

Team SNU’s Control Strategies to Enhancing Robot’s Capability: Lessons from the DARPA Robotics Challenge Finals 2015

Springer Tracts in Advanced Robotics, 2018

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Design of JET Humanoid Robot with Compliant Modular Actuators for Industrial and Service Applications

Applied Sciences, 2021

This paper presents the development of the JET humanoid robot, which is based on the existing THO... more This paper presents the development of the JET humanoid robot, which is based on the existing THORMANG platform developed in 2015. Application in the industrial and service fields was targeted, and three design concepts were determined for the humanoid robot. First, low stiffness of the actuator modules was utilized for compliance with external environments. Second, to maximize the robot whole-body motion capability, the overall height was increased. However, the weight was reduced to satisfy power requirements. The workspace was also increased to enable various postures, by increasing the range of motion of each joint and extending the links. Compared to the original THORMANG platform, the lower limb length increased by approximately 20%, and the hip range of motion increased by 39.3%. Third, the maintenance process was simplified through modularization of the electronics and frame design for improved accessibility. Several experiments, including stair climbing and egress from a ca...

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A rehabilitation exercise robot for treating low back pain

2017 IEEE International Conference on Robotics and Automation (ICRA), 2017

Low back pain is one of the world's most serious health problems. Conservative methods are re... more Low back pain is one of the world's most serious health problems. Conservative methods are recommended for back pain, and stabilization exercise as one of these methods has been proven to be effective. The “big 3” exercises are proven stabilization exercises, and it is able to train most of the muscles associated with low back stability. However, they are hard to be performed by some patients because the big 3 require sufficient strength in the upper and lower limbs as well as in the low back to maintain their postures. In this paper, we propose a rehabilitation robot SERA (Stabilization Exercise Robot Assistance system) to compensate for this shortcoming, and we describe the robot's developments and experiments. The proposed robot is designed to achieve effects similar to the big 3. The robot also ensures active exercises by voluntary control of the exerciser and provides anti-gravity force generated by series elastic actuators (SEAs) in order to adjust the exercise load. Experiments using surface electromyograph (sEMG) sensors with three subjects show the results for these features.

The Hierarchical Operational Space Formulation: Stability Analysis for the Regulation Case

IEEE Robotics and Automation Letters, 2018

The Operational Space Formulation (OSF) from the 1980s is probably the most frequently applied ta... more The Operational Space Formulation (OSF) from the 1980s is probably the most frequently applied task-space controller in robotics. In multi-priority control of redundant robots via the OSF, a feedback linearization is performed on the first hierarchy level while lower-priority tasks are executed in the dynamically consistent null space of the Jacobian matrices of all higher-priority tasks without disturbing them. However, it has been observed in the past that a formal stability analysis for the overall closed loop is rather difficult, especially for the null space dynamics. Except for exponential stability on the main task level, a complete proof is still missing when the tasks conflict with each other. Here we provide this formal proof of asymptotic stability for the regulation case of a passivity-based OSF controller by means of conditional stability theory and semidefinite Lyapunov functions. Simulations support the intuitive, energy-based interpretation of the proof. This stability analysis lifts the widely used OSF onto a more solid foundation.

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Grasping Force Estimation by sEMG Signals and Arm Posture: Tensor Decomposition Approach

Journal of Bionic Engineering, 2019

Grasping force estimation using surface Electromyography (sEMG) has been actively investigated as... more Grasping force estimation using surface Electromyography (sEMG) has been actively investigated as it can increase the manipulability and dexterity of prosthetic hands and robotic hands. Most of the current studies in this area only focus on finding the relationship between sEMG signals and the grasping force without considering the arm posture. Therefore, regression models are not suitable to predict grasping force in various arm postures. In this paper, a method to predict the grasping force from sEMG signals and various grasping postures is developed. The proposed algorithm uses a tensor algebra to train a multi-factor model relevant to sEMG signals corresponding to various grasping forces and postures of the wrist and forearm in multiple dimensions. The multi-factor model is then decomposed into four independent factor spaces of the grasping force, sEMG signals, wrist posture, and forearm posture. Moreover, when a participant executes a new posture, new factors for the wrist and forearm are interpolated in the factor spaces. Thus, the grasping force with various postures can be predicted by combining these factors. The effectiveness of the proposed method is verified through experiments with ten healthy subjects, demonstrating the higher performance of proposed grasping force prediction method than the previous algorithm.

Balancing of humanoid robot using contact force/moment control by task-oriented whole body control framework

Autonomous Robots, 2015

Balancing control of humanoid robots is of great importance since it is a necessary functionality... more Balancing control of humanoid robots is of great importance since it is a necessary functionality not only for maintaining a certain position without falling, but also for walking and running. For position controlled robots, the for-ce/torque sensors at each foot are utilized to measure the contact forces and moments, and these values are used to compute the joint angles to be commanded for balancing. The proposed approach in this paper is to maintain balance of torque-controlled robots by controlling contact force and moment using whole-body control framework with hierarchical structure. The control of contact force and moment is achieved by exploiting the full dynamics of the robot and the null-space motion in this control framework. This control approach enables compliant balancing behavior. In addition, in the case of double support phase, required contact force and moment are controlled using the redundancy in the contact force and moment space. These algorithms are implemented on a humanoid legged robot and the experimental results demonstrate the effectiveness of them.

Robust path planning for autonomous vehicle in position uncertainty

2014 11th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI), 2014

The abrupt and frequent change of a path for autonomous vehicle might occur in the presence of po... more The abrupt and frequent change of a path for autonomous vehicle might occur in the presence of position uncertainty due to sensor noises or errors in localization. While path planning of an autonomous vehicle utilize multiple sensors to generate the path, it is necessary to not only reduce such errors but also to plan a consistent path. Therefore, we propose a framework that can generate a stable path by considering the history of previous paths. The result of experimental simulations indicates the decrease in rate of switching path directions in three different scenarios in position uncertainty. This framework demonstrates the effectiveness of path generation by applying a history parameter to modify cost function of the A* algorithm.

3D registration of multi-view depth data for hand-arm pose estimation

2014 11th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI), 2014

Human motion analysis has been applied in a wide range of applications. Specifically, hand-arm mo... more Human motion analysis has been applied in a wide range of applications. Specifically, hand-arm motion plays an important role in the tele-operation of a robot and in pattern analyses of human motions. However, estimations of the full pose of a human hand with the arm are challenging due to the limited recognition range and the computational cost for real-time processing. In this paper, we propose a fast and efficient solution to articulate hand-arm pose estimations for different modal depth sensors. A marker-less motion capture system is built using multiple depth sensors with different recognition areas. In the 3D registration process, a new and fast outlier rejection method is proposed. It uses the concept of skeletal consistency, which the computation time of the 3D registration process without a loss of robustness. The performance is demonstrated to assess the accuracy, the robustness and the computational cost by of the proposed system in comparison with other methods.

Feedforward global/inertial sensor fusion algorithm for accurate global positioning of a mobile robot

Proceedings, 2005 IEEE/ASME International Conference on Advanced Intelligent Mechatronics.

This paper introduces a coordinate transform method for global/inertial sensor fusion minimizing ... more This paper introduces a coordinate transform method for global/inertial sensor fusion minimizing modification of an existing control program of a mobile robot. Most of GPS/INS sensor fusion algorithms use Kalman filters and modify the INS states by feedback loops. Because the structure of the proposed method has a feedforward filter, the proposed method has an advantage in case the user does not want to change an existing control program of mobile robot. The feedback type Kalman filter is designed so that the error between global position from GPS and odometry from INS converges to zero. Therefore the coordinate matching between the odometry and measured global position is not necessary in those approaches. However, in the feedforward structure described in this paper, the errors gradually increase over time. A coordinate transform method has been developed for dealing with the error. This method provides an easy way to make an add-on function without any changes in the existing functions of the control program of a mobile robot.

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Aesthetic design and development of humanoid legged robot

2014 IEEE-RAS International Conference on Humanoid Robots, 2014

This paper presents a new full sized humanoid leg robot that combines aesthetics and design theor... more This paper presents a new full sized humanoid leg robot that combines aesthetics and design theory with practical research goals in robotics. The research goal of the robot is to create human-like and compliant motion in multiple contact situations through the use of torque controlled joints. Low gear ratio and direct connections are used at each joint for low-friction and back-drivability but without explicit joint torque sensors. On the other hand, in creating human-like motions, not only technical specifications but also aesthetic design is important as the same performance of the robot can be perceived very differently depending on the design. The aesthetic design is, in this paper, achieved by the robot design process using an integrated design and frame through multi-axis CNC machining. The unique integration of the frame and design also drastically reduces parts and complexity of assembly for easy maintenance. In this paper, the design process and features are presented with range of motion, weight, and key aesthetic decisions. Compliant motion capability is demonstrated by experimental results.

Parking Line Based SLAM Approach Using AVM/LiDAR Sensor Fusion for Rapid and Accurate Loop Closing and Parking Space Detection

Sensors, 2019

Parking is a challenging task for autonomous vehicles and requires a centimeter level precision o... more Parking is a challenging task for autonomous vehicles and requires a centimeter level precision of distance measurement for safe parking at a destination to avoid collisions with nearby vehicles. In order to avoid collisions with parked vehicles while parking, real-time localization performance should be maintained even when loop closing occurs. This study proposes a simultaneous localization and mapping (SLAM) method, using around view monitor (AVM)/light detection and ranging (LiDAR) sensor fusion, that provides rapid loop closing performance. We extract the parking line features by utilizing the sensor fusion data for sparse feature-based pose graph optimization that boosts the loop closing speed. Hence, the proposed method can perform the loop closing within a few milliseconds to compensate for the accumulative errors even in a large-scale outdoor environment, which is much faster than other LiDAR-based SLAM algorithms. Therefore, it easily satisfies real-time localization perfo...

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