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Kernel-based actor-critic approach with applications
Baeksuk Chu,Keunwoo Jung,Jooyoung Park 한국지능시스템학회 2011 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.11 No.4
Recently, actor-critic methods have drawn significant interests in the area of reinforcement learning, and several algorithms have been studied along the line of the actor-critic strategy. In this paper, we consider a new type of actor-critic algorithms employing the kernel methods, which have recently shown to be very effective tools in the various fields of machine learning, and have performed investigations on combining the actor-critic strategy together with kernel methods. More specifically, this paper studies actor-critic algorithms utilizing the kernel-based least-squares estimation and policy gradient, and in its critic’s part, the study uses a sliding-window-based kernel least-squares method, which leads to a fast and efficient value-function-estimation in a nonparametric setting. The applicability of the considered algorithms is illustrated via a robot locomotion problem and a tunnel ventilation control problem.
Mechanism and Analysis of a Robotic Bolting Device for Steel Beam Assembly
Baeksuk Chu,Kyungmo Jung,Kang Ho Ko,Daehie Hong 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10
Tasks for steel beam assembly in construction field are usually performed by human labors that are exposed to various dangers. This research is about developing a robotic bolting device which assembles TS(Torque-Shear)-type bolt and nut used for steel beam assembly and prevents workers from operating in risky construction environments. The suggested robotic bolting device consists of a bolting end-effector, which actually conducts bolting tasks, and a gantry-type robotic manipulator, which places the bolting end-effector to each bolting position. The bolting process performed by the bolting end-effector, which furnishes two different bolting tools, has two assembly steps to increase the bolting productivity. In the first step, the first-assembly bolting tool assembles the bolt and nut with high speed but low torque, while, in the second step, the second-assembly bolting tool finishes the tightening task with high torque but low speed. Moreover, nut and washer feeder based on robotic manipulation are developed for automatic supply. The two bolting tools equip compliance mechanisms respectively for compensating an angular misalignment between the bolting tool axis and bolt axis which interferes the bolting tool completely grasps the bolt.
Robotic Automation Technologies in Construction: A Review
Baeksuk Chu,Dongnam Kim,Daehie Hong 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.3
Robot technology is a remarkably interdisciplinary research area, one that can be employed in various industrial fields as well as higher value-added fields. The construction industry, on the other hand, has been known as one of the most difficult research fields to apply robotic schemes. Therefore, applying robot technologies in the construction industry is quite a challenging topic. This paper aims to introduce the progress of automated robotic systems in construction fields, namely with respect to construction robots. While construction robots have a very wide range of application depending on the huge market size of the construction industry, there still exist a lot of problems such as highly risky working environment and inefficiency due to the labor intensive characteristic. In order to solve these problems, a variety of construction robots have been developed and, in this paper, the current state of the robotic systems for construction works and the vision of future robot technology in the construction field are introduced.
수동 동역학 보행로봇을 위한 강화학습 기반의 제어기 설계
주백석(Baeksuk Chu),홍대희(Daehie Hong),박주영(Jooyoung Park) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Passive dynamic walker is a kind of bipedal walking robots that are able to walk stably down a small decline without using any actuators. The purpose of this research is to design a controller in order to build actuated robots capable of walking on flat terrain based on passive dynamic walking. To achieve the objective, the control algorithm used in this research is reinforcement learning (RL) method. RL is a goal-directed learning of a mapping from situations to actions. The goal of RL is to maximize a reward which is an evaluative feedback from the environment. Constructing the reward of the actuated passive dynamic walker, the control objective, which is stable walking on level ground, is included. In this research, RL algorithm based on actor-critic architecture and gradient-following algorithm is applied. The control algorithm is verified with computer simulations. It is confirmed that with the suggested controller, the control objective is sufficiently achieved.
Tunnel Ventilation Control Using Reinforcement Learning Methodology
CHU, Baeksuk,KIM, Dongnam,HONG, Daehie,PARK, Jooyoung,CHUNG, Jin Taek,KIM, Tae-Hyung The Japan Society of Mechanical Engineers 2006 JSME international journal. Series C, Mechanical s Vol.49 No.4
<P>The main purpose of tunnel ventilation system is to maintain CO pollutant concentration and VI (visibility index) under an adequate level to provide drivers with comfortable and safe driving environment. Moreover, it is necessary to minimize power consumption used to operate ventilation system. To achieve the objectives, the control algorithm used in this research is reinforcement learning (RL) method. RL is a goal-directed learning of a mapping from situations to actions without relying on exemplary supervision or complete models of the environment. The goal of RL is to maximize a reward which is an evaluative feedback from the environment. In the process of constructing the reward of the tunnel ventilation system, two objectives listed above are included, that is, maintaining an adequate level of pollutants and minimizing power consumption. RL algorithm based on actor-critic architecture and gradient-following algorithm is adopted to the tunnel ventilation system. The simulations results performed with real data collected from existing tunnel ventilation system and real experimental verification are provided in this paper. It is confirmed that with the suggested controller, the pollutant level inside the tunnel was well maintained under allowable limit and the performance of energy consumption was improved compared to conventional control scheme.</P>