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76 results on '"Choi, Junho"'

13. Development of a Planar Haptic Robot With Minimized Impedance.

Author

Oh, Keonyoung, Rymer, William Z., Plenzio, Ilaria, Mussa-Ivaldi, Ferdinando A., Park, Seunghan, and Choi, Junho

Subjects
HAPTIC devices, MANIPULATORS (Machinery), MECHANICAL impedance, ROBOTS, ROBOT motion, ROBOT kinematics
Abstract

Several studies have reported that stroke survivors displayed improved voluntary planar movements when forces supporting the upper limb increased, and when impeding forces decreased. Earlier haptic devices interacting with the human upper limb were potentially impacted by undesired residual friction force and device inertia. To explore natural, undisturbed voluntary motor control in stroke survivors, we describe the development of a Decoupled-Operational space Robot for wide Impedance Switching (DORIS) with minimized mechanical impedances. This design is based on a novel decoupling mechanism separating the end effector from a manipulator. While the user manipulates the end effector freely inside the workspace of the decoupling mechanism, to which a manipulator of the robot is attached, the robot detects such change in position using a lightweight linkage system. The manipulator of the robot then follows such movements of the end effector swiftly. Consequently, the user can explore the extended workspace, which can be as large as the manipulator's workspace. Since the end effector is mechanically decoupled from the manipulators and actuators, the user can remain unaffected by the mechanical impedances of the manipulator. Mechanical impedances perceived by the user and bandwidth of the control system were estimated. The developed robot was capable of detecting larger maximum acceleration and larger jerk of the reaching movement in chronic stroke survivors with hemiparesis. We propose that this device can be utilized for evaluating voluntary motor control of the upper limb while minimizing the impact of robot inertia and friction forces on limb behavior. [ABSTRACT FROM AUTHOR]

Published
2021
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20. Intelligent Power Equipment Management Based on Distributed Context-Aware Inference in Smart Cities.

Author

Choi, Chang, Esposito, Christian, Wang, Haoxiang, Liu, Zhe, and Choi, Junho

Subjects
SMART cities, INTERNET of things, INFORMATION & communication technologies, SMART power grids, INFORMATION technology
Abstract

Smart cities are systematically promoting the transition to sustainable and effective energy systems by promoting policies for energy efficiency, regionalized/distributed renewable energy generation, and intelligent energy management. In particular, this transition toward a more integrated and intelligent energy supply has created a plethora of energy meta-information made available through the IoT smart grid, thereby allowing big data analytical services to forecast energy consumption and to manage usage patterns. In this article, we propose a context-aware framework for intelligent power equipment management. Our contribution is to present a design of the proposed framework based on context awareness, the definition of a context ontology for power equipment management, a specification of the inference rules for the context ontology, and a context-aware inference service for power equipment management. The proposed system has broad applications to handle system monitoring and express system controls, so as to be easily and effectively applied to various application domains. [ABSTRACT FROM AUTHOR]

Published
2018
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46. A safe joint with a joint torque sensor.

Author

Dong-Eun Choi, Gi-Hun Yang, Choi, Junho, Lee, Woosub, Cho, Changhyun, and Kang, Sungchul

Abstract

In this study, a safe joint with a joint torque sensor is presented. The safe joint, named “Spring-Clutch”, is a simple passive mechanism that consists of a spring, a cam, and a joint torque sensor. When the torque applied is less than a pre-set threshold, the Spring-Clutch acts as a rigid joint between the input and output. However, if the applied torque exceeds the threshold, the Spring-Clutch is released and acts as a revolute joint, which results in reduction of the collision force to prevent damage of human and robot. After the applied torque is removed, the Spring-Clutch is immediately re-engaged. In addition, a compact joint torque sensor is installed in the Spring-Clutch to measure the torque at the joint. This paper describes the design principles and performance evaluation of Spring-Clutch, and discusses practical applications to a joint mechanism for safe manipulator. [ABSTRACT FROM PUBLISHER]

Published
2011
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47. A Robot Joint With Variable Stiffness Using Leaf Springs.

Author

Choi, Junho, Hong, Seonghun, Lee, Woosub, Kang, Sungchul, and Kim, Munsang

Subjects
*JOINTS (Engineering), *STIFFNESS (Engineering), *LEAF springs, *HUMAN-machine systems, *MANIPULATORS (Machinery), *TORQUE, *ACTUATORS, *QUANTUM perturbations
Abstract

Interaction with humans is inevitable for service robots, which results in safety being one of the most important factors in designing the robots. Compliant component is an answer to the safety issue at the cost of performance degradation. In order to reduce the performance degradation, manipulators equipped with variable stiffness have been studied by many researchers. This paper presents a variable stiffness joint (VSJ) designed for a robot manipulator, as well as a control scheme to control the stiffness and position of the VSJ. Compliance is generated by leaf springs and two actuators are used to control the position and stiffness of the joint using four-bar linkages. Two actuators in parallel configuration are connected to the spring. Changing the effective length of the spring results in a change in stiffness. The position of the joint is controlled via two actuators rotating at the same speed in the same direction. A nonlinear controller is used to control the VSJ, and a singular perturbation model is adopted to prove the stability of the closed-loop system. Experiments are conducted to show that the position and stiffness are controlled independent of each other, and having less stiffness at the joint helps in making an unexpected collision with an object safer. [ABSTRACT FROM PUBLISHER]

Published
2011
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