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Dive into the research topics where Jae Bok Song is active.

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Featured researches published by Jae Bok Song.


Mechatronics | 2002

Control logic for an electric power steering system using assist motor

Ji-Hoon Kim; Jae Bok Song

Electric power steering (EPS) systems have many advantages over traditional hydraulic power steering systems in engine efficiency, space efficiency, and environmental compatibility. This research aims at developing EPS control logic for reduction of steering torque exerted by a driver, realization of various steering feels, and improvement of return-to-center performance. In addition, the torque sensor capable of measuring the steering torque and steering wheel angle is devised, and the hardware-in-the-loop simulation (HILS) system that can implement an actual load torque delivered to the steering column is also developed. With the proposed EPS logic, the driver can turn the steering wheel with the steering torque whose magnitude is determined from a torque map independent of load torques that tend to vary depending on the driving conditions. Experimental studies show that the proposed EPS control logic can improve return-to-center performance of the steering wheel by control of the assist motor.


international conference on robotics and automation | 2010

Hybrid dual actuator unit: A design of a variable stiffness actuator based on an adjustable moment arm mechanism

Byeong-Sang Kim; Jae Bok Song

For tasks requiring robot-environment interaction, stiffness control is important to ensure both stable contact motion and collision safety. The variable stiffness approach has been used to address this problem. We propose a hybrid dual actuator unit (HDAU) which is a novel variable stiffness unit design. The HDAU is composed of a hybrid control module based on an adjustable moment arm mechanism and a drive module with two motors. By controlling the relative motion of gears in the hybrid control module, position and stiffness can be simultaneously controlled for the same joint. The HDAU provides a wide range of joint stiffness due to nonlinearity obtained from the adjustable moment arm. The joint stiffness can be kept constant independent of the passive deflection angle of the output shaft. Furthermore, stable interaction can also be achieved because the joint stiffness is indirectly adjusted by position control of the hybrid control module. The characteristics of the HDAU are analyzed in this study. We show by experiment that the HDAU can provide a wide range of stiffness variation and rapid response for stiffness change.


international conference on robotics and automation | 2009

Safe robot arm with safe joint mechanism using nonlinear spring system for collision safety

Jung Jun Park; Hwi Kim; Jae Bok Song

Collision safety between humans and robots has drawn much attention since service robots are increasingly being used in human environments. A safe robot arm based on passive compliance can usually provide faster and more reliable responses for dynamic collision than an active one involving sensors and actuators. Since both positioning accuracy and collision safety of the robot arm are equally important, a robot arm should have very low stiffness when subjected to a collision force greater than the injury tolerance, but should otherwise maintain very high stiffness. To implement these requirements, a novel safe joint mechanism (SJM-II) which has much smaller size and lighter weight than the previous model, is proposed in this research. The SJM-II has the advantage of nonlinear spring which is achieved using only passive mechanical elements such as linear springs and a double-slider mechanism. Various analyses and experiments on static and dynamic collisions show that stiffness of the SJM-II is kept very high against an external torque less than the predetermined threshold torque, but abruptly drops when the input torque exceeds this threshold, thereby guaranteeing positioning accuracy and collision safety. Furthermore, a robot arm with two SJM-IIs is verified to achieve collision safety in 2D space.


IEEE Transactions on Industrial Electronics | 2011

Monocular Vision-Based SLAM in Indoor Environment Using Corner, Lamp, and Door Features From Upward-Looking Camera

Seo Yeon Hwang; Jae Bok Song

We examine monocular vision-based simultaneous localization and mapping (SLAM) of a mobile robot using an upward-looking camera. Although a monocular camera looking up toward the ceiling can provide a low-cost solution to indoor SLAM, this approach is often unable to achieve dependable navigation due to a lack of reliable visual features on the ceiling. We propose a novel approach to monocular SLAM using corner, lamp, and door features simultaneously to achieve stable navigation in various environments. We use the corner features and the circular-shaped brightest parts of the ceiling image for detection of lamp features. Furthermore, vertical and horizontal lines are combined to robustly detect line-based door features to reduce the problem that line features can be easily misidentified due to nearby edges. The use of these three types of features as landmarks increases our ability to observe the features in various environments and maintains the stability of the SLAM process. A series of experiments in indoor environments showed that the proposed scheme resulted in dependable navigation.


international conference on robotics and automation | 2004

Robust mobile robot localization using optical flow sensors and encoders

Sooyong Lee; Jae Bok Song

Open-loop estimation methods are commonly used in mobile robot applications. Their strength lies in the speed and simplicity of an estimate. However, these methods can sometimes lead to inaccurate or unreliable positional estimates. Using one or more optical flow sensors, a method has been developed which can accurately track position in both ideal kinematic conditions and otherwise. Using optical flow techniques and available sensors, reliable positional estimates are made. The sensor provides accurate measurement of the movement at the sensor location. Even though the sensor does not provide angular displacement, the robot movement is estimated using only one sensor even with wheel slip. However, when the robot moves sideways due to external disturbance, redundant sensors are used in order to estimate the configuration of the robot. Pseudo inverse based estimation and the extended Kalman filter based estimation are presented to show the effectiveness of the proposed approach. Location of the sensors has also been investigated in order to minimize errors caused by inaccurate sensor readings. Finally, the method is implemented and tested using a potential field based navigation scheme.


IEEE-ASME Transactions on Mechatronics | 2010

A Serial-Type Dual Actuator Unit With Planetary Gear Train: Basic Design and Applications

Byeong Sang Kim; Jae Bok Song; Jung Jun Park

Control of a robot manipulator in contact with the environment is usually conducted by a direct feedback control system using a force-torque sensor or an indirect impedance control scheme. Although these methods have been successfully applied to many applications, simultaneous control of force and position cannot be achieved. To cope with such problems, this paper proposes a novel design of a dual actuator unit (DAU) composed of two actuators and a planetary gear train to provide the capability of simultaneous control of position and stiffness. Since one actuator controls position and the other actuator modulates stiffness, the DAU can control the position and stiffness simultaneously at the same joint. Both the torque exerted on the joint and the stiffness of the environment can be estimated without an expensive force sensor. Various experiments demonstrate that the DAU can provide good performance for position tracking, force estimation, and environment estimation.


IEEE-ASME Transactions on Mechatronics | 2001

Acceleration estimator for low-velocity and low-acceleration regions based on encoder position data

Se-Han Lee; Jae Bok Song

Acceleration computation based on simple numerical differentiation from an optical encoder signal may be very erroneous, especially in the low-velocity and low-acceleration regions. To overcome this problem, a novel approach to estimating acceleration in these regions is proposed in this paper. This low-acceleration estimator, which is a computer algorithm, is based on the fact that the displacement signal from the encoder is accurate. Since the bandwidth of this estimator is rather limited, it can be used in combination with the traditional numerical differentiation approach in order to cover a wide velocity range. It was shown in various simulations and experiments that this combined acceleration estimator can yield accurate acceleration estimates over a wide range of velocities. Furthermore, when this estimator is applied to a friction compensation system, the effect of low-velocity friction can be reduced significantly by its capability to detect small changes in acceleration caused by friction.


IEEE Transactions on Industrial Electronics | 2009

Safe Navigation of a Mobile Robot Considering Visibility of Environment

Woojin Chung; Seokgyu Kim; Minki Choi; Jaesik Choi; Hoyeon Kim; Chang Bae Moon; Jae Bok Song

We present one approach to achieve safe navigation in an indoor dynamic environment. So far, there have been various useful collision avoidance algorithms and path planning schemes. However, those algorithms possess fundamental limitations in that the robot can avoid only ldquovisiblerdquo ones among surrounded obstacles. In a real environment, it is not possible to detect all the dynamic obstacles around the robot. There are many occluded regions due to the limited field of view. In order to avoid collisions, it is desirable to exploit visibility information. This paper proposes a safe navigation scheme to reduce collision risk considering occluded dynamic obstacles. The robots motion is controlled by the hybrid control scheme. The possibility of collision is dually reflected to path planning and speed control. The proposed scheme clearly indicates the structural procedure on how to model and to exploit the risk of navigation. The proposed scheme is experimentally tested in a real office building. The experimental results show that the robot moves along the safe path to obtain sufficient field of view. In addition, safe speed constraints are applied in motion control. It is experimentally verified that a robot safely navigates in dynamic indoor environment by adopting the proposed scheme.


international conference on robotics and automation | 2007

Double Actuator Unit with Planetary Gear Train for a Safe Manipulator

Byeong Sang Kim; Jung Jun Park; Jae Bok Song

Control of a robot manipulator in contact with the environment is usually conducted by the direct feedback control system using a force-torque sensor or the indirect impedance control scheme. Although these methods have been successfully applied to many applications, simultaneous control of force and position cannot be achieved. Furthermore, collision safety has been of primary concern in recent years with emergence of service robots in direct contact with humans. To cope with such problems, redundant actuation has been used to enhance the performance of a position/force controller. In this paper, the novel design of a double actuator unit (DAU) composed of double actuators and a planetary gear train is proposed to provide the capability of simultaneous control of position and force as well as the improved collision safety. Since one actuator controls position and the other actuator modulates stiffness, DAU can control the position and stiffness simultaneously at the same joint. The torque exerted on the joint can be estimated without an expensive torque/force sensor. DAU is capable of detecting dynamic collision by monitoring the speed of the stiffness modulator. Upon detection of dynamic collision, DAU immediately reduces its joint stiffness according to the collision magnitude, thus providing the optimum collision safety. It is shown from various experiments that DAU can provide good performance of position tracking, force estimation and collision safety.


international conference on robotics and automation | 2004

Control of a mobile robot with passive multiple trailers

Myoungkuk Park; Woojin Chung; Munsang Kim; Jae Bok Song

A mobile service robot can achieve reconfigurability by exploiting passive trailer systems. Reconfigurability provides significant practical advantages in order to deal with various service tasks. However, a motion control problem of a passive multiple trailer system is difficult, mainly because a kinematic model is highly nonlinear. It is shown how a robot with n passive trailers can be controlled in backward direction. Once a desired trajectory of a last trailer is computed, then the control input of a pushing robot is obtained by the proposed control scheme. A kinematic design of a trailer system is proposed in our prior work. It is shown that the high performance of trajectory tracking is also valid for the backward motion control problem. Experimental verifications were carried out with the PSR-2 (public service robot) with three passive trailers. Experimental result showed that the backward motion control could be successfully carried out using the proposed control scheme.

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Munsang Kim

Korea Institute of Science and Technology

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Woojin Chung

Korea Institute of Science and Technology

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Sungchul Kang

Korea Institute of Science and Technology

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Sooyong Lee

Kyungpook National University

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