Suk Gyu Lee

Decentralized dynamic output feedback controller design for guaranteed cost stabilization of large-scale discrete-delay systems

In this paper, we discuss how to solve dynamic output feedback controller design problem for decentralized guaranteed cost stabilization of large-scale discrete-delay system by convex optimization. Based on Lyapunov second method, an linear matrix inequality optimization problem is formulated to design the controller which guarantees the asymptotic stability and minimizes the upper bound of a given quadratic cost function. A numerical example is given to illustrate the proposed method.

Leader-follower-based formation control of nonholonomic mobile robots with mismatched uncertainties via integral sliding mode:

This article focuses on the control of a group of nonholonomic mobile robots. A leader-follower coordinated control scheme is developed to achieve formation maneuvers of such a multi-robot system. The scheme adopts the methodology of integral sliding mode control to form up and maintain the robots in predefined trajectories. The dynamic equations of the scheme are subject to mismatched uncertainties. The mismatched uncertainties challenge formation stabilization because they cannot be suppressed by the invariance of integral sliding mode control. In light of Lyapunov’s direct method, a sufficient condition is drawn to guarantee the reachability condition of integral sliding mode control in the presence of the mismatched uncertainties. To verify the feasibility and effectiveness of the proposed strategy, simulation results are illustrated by an uncertain multi-robot system composed of three nonholonomic mobile robots.

Development of a Combined Energy-Demands Calculator for Urban Building Communities in Korea

A decision-support tool based on relational database technology is developed to aid the planning of energy supply systems for urban communities. The building-load models derived from the data measured or surveyed in Korea over the last two decades are computerized using Microsoft Access® as an application platform. The tool calculates energy demands for arbitrary combinations of buildings in an urban community without requiring detailed technological information. Nonexpert urban planners can use the package by providing simple input parameters such as floor area, building type, and city where the site is located. The program calculates the time series based on the demands for electricity, heating, cooling, and hot water loads for the 8760 hours of a year. It also produces indicative characteristics of each load type such as the annual maximums, trends of the daily maximums and minimums, and the annual sums of energy. Urban planners can use these characteristics of the load profiles in their decision processes at the early stages of planning. The detailed time series can be further exploited for subsequent analysis, such as device operational simulation or cost estimation if more sophisticated analysis is necessary. A case study for an actual project is presented for demonstrational purposes.

Comments on “Sliding-Mode Formation Control for Cooperative Autonomous Mobile Robots”

One of the formation schemes in multirobot systems is named as the leader-follower scheme. Dynamic equations based on the scheme are formulated for multirobot systems with uncertainties by Defoort et al. ( IEEE Trans. Ind. Electron. vol. 55, no. 11, pp. 3944-3953, Nov. 2008). This paper focuses on the equations, clarifies their drawbacks, and revisits the modeling of the leader-follower formation scheme for multirobot systems with uncertainties.

Development of remote control system for boiler based on Internet

We developed the remote boiler control system based on internet to enhance the flexibility with minimum change of the structure of the conventional boiler system. The Hello Device 1300 is applied to the system as a Web server between the Ethernet and the boiler system manufactured by Kiturami Boiler Co., which is accessible from the HD 1300 via the RS0232 serial terminal. The developed control system is operated on a client program based on Java Applet independently from the OS. Some experimental results shows the reliability and flexibility of the proposed system.

Localization using Ego Motion based on Fisheye Warping Image

This paper proposes a novel localization algorithm based on ego-motion which used Lucas-Kanade Optical Flow and warping image obtained through fish-eye lenses mounted on the robots. The omnidirectional image sensor is a desirable sensor for real-time view-based recognition of a robot because the all information around the robot can be obtained simultaneously. The preprocessing (distortion correction, image merge, etc.) of the omnidirectional image which obtained by camera using reflect in mirror or by connection of multiple camera images is essential because it is difficult to obtain information from the original image. The core of the proposed algorithm may be summarized as follows: First, we capture instantaneous 360° panoramic images around a robot through fish-eye lenses which are mounted in the bottom direction. Second, we extract motion vectors using Lucas-Kanade Optical Flow in preprocessed image. Third, we estimate the robot position and angle using ego-motion method which used direction of vector and vanishing point obtained by RANSAC. We confirmed the reliability of localization algorithm using ego-motion based on fisheye warping image through comparison between results (position and angle) of the experiment obtained using the proposed algorithm and results of the experiment measured from Global Vision Localization System.

Adaptive Formation Control and Collision Avoidance Using a Priority Strategy for Nonholonomic Mobile Robots

This paper presents four novel collision avoidance processes for nonholonomic mobile robots to generate effective collision-free trajectories when forming and maintaining a formation. A collision priority strategy integrates the static and dynamic collision priorities to avoid a collision efficiently and effectively. In addition, it minimizes the turning angle of the follower robot and decreases system computation time. When avoiding collisions between robots, a novel collision avoidance algorithm is used to find a safe waypoint for the robot, based on the velocity of each robot. An adaptive tracking control algorithm, using the Lyapunov analysis, guarantees that the robots trajectory and velocity tracking errors converge to zero considering parametric uncertainties of both the kinematic and dynamic models. The simulation and experiment results validate the effectiveness of the proposed method.

Navigation strategy of an intelligent mobile robot using fuzzy logic

When a robot confronts large, non-convex or scattered obstacles, it is apt to be trapped in the local minimum points. This paper suggests a new fuzzy algorithm to solve this problem using some simple data. The proposed algorithm has two-layered hierarchical structure: the lower layer for avoiding and approaching, and the upper layer for combination of these logic. Some computer simulation results for a mobile robot equipped with three ultrasonic range sensors show that the suggested navigation algorithm is very effective to escape from local minimum points under unknown environment.

Development of image stabilization system using extended kalman filter for a mobile robot

This paper proposes a robust image stabilization system for a mobile robot using Extended Kalman Filter (EKF) Though image information is one of the most efficient data for robot navigation, it is subject to noise which results from internal vibration as well as external factors such as uneven terrain, stairs, or marshy surface The vibration of camera deteriorates the definition of image by destroying image sharpness, which seriously prevents mobile robots from recognizing their environment for navigation In this paper, inclinometer was used to measure the vibration angle of the camera system mounted on the robot to obtain a reliable image by compensating for the angle of the camera shake caused by vibration In addition angle prediction by using the EKF enhances responsibility of image analysis for real time performance The Experimental results show effectiveness of the proposed system to compensate for the blurring of the images.

Leader-Follower Formation Control Based on Hybrid Formation Control Framework and Waypoint in Cone Method

This paper proposes a novel leader-follower robot formation based on relative motion states of robots. The follower robot calculates its waypoint by desired distance-angle d-¦Â or desired distance-distance d-d. Since the robots velocities are constrained, the proposed waypoint in cone method guarantees that the follower robot moves to its desired waypoint correctly. In order to form and maintain the formation of multiple robots, we use a stable tracking control method to control each robot. Finally, the simulation results based on the proposed approach show that the follower robot moves to its waypoint effectively to make a formation.