• Journal of the Korean Society of Industry Convergence
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• v.21 no.4
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• pp.167-174
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• 2018

Presently, the exploration of an unknown environment is an important task for the development of mobile robots and mobile robots are navigated by means of a number of methods, using navigating systems such as the sonar-sensing system or the visual-sensing system. To fully utilize the strengths of both the sonar and visual sensing systems, In mobile robotics, multi-sensor data fusion(MSDF) became useful method for navigation and collision avoiding. Moreover, their applicability for map building and navigation has exploited in recent years. In this paper, as the preliminary step for developing a multi-purpose autonomous carrier mobile robot to transport trolleys or heavy goods and serve as robotic nursing assistant in hospital wards. The aim of this paper is to present the use of multi-sensor data fusion such as ultrasonic sensor, IR sensor for mobile robot to navigate, and presents an experimental mobile robot designed to operate autonomously within indoor environments. Simulation results with a mobile robot will demonstrate the effectiveness of the discussed methods.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2348-2350
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• 1998

The hybrid control system for a wheeled mobile robot with nonholonomic constraints to perform a cluttered environment maneuver is proposed. The proposed hybrid control system consists of a continuous state system for the trajectory control, a discrete state system for the motion and orientation control, and an interface control system for the interaction process between the continuous dynamics and the discrete dynamics The continuous control systems are modeled by the switched systems with the control of driving wheels, and the digital automata for motion control are modeled and implemented by the abstracted motion of mobile robot. The motion control tasks such as path generation, motion planning, and trajectory control for a cluttered environment are investigated as the applications by simulation studies.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.400-404
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• 1994

In this paper, we will investigate the position estimation problem for autonomous mobile robots. Formulating this as a state estimation problem for nonlinear SISO system, then we will apply several types of nonlinear observers. Simulation results of observer-based navigation control will be also provided.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.3
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• pp.208-220
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• 2006

Energy of wheeled mobile robot is usually supplied by batteries. In order to extend operation time of mobile robots, it is necessary to minimize the energy consumption. The energy is dissipated mostly in the motors, which strongly depends on the velocity profile. This paper investigates various 3-step (acceleration - cruise - deceleration) speed control methods to minimize a new energy object function which considers the practical energy consumption dissipated in motors related to motor control input, velocity profile, and motor dynamics. We performed an analysis on the energy consumption various velocity profile patterns generated by standard control input such as step input, ramp input, parabolic input, and exponential input. Based on these standard control inputs, we analyzed the six 3-step velocity profile patterns: E-C-E, P-C-P, R-C-R, S-C-S, R-C-S, and S-C-R (S means a step control input, R means a ramp control input, P means a parabolic control input, and E means an exponential control input, C means a constant cruise velocity), and suggested an efficient iterative search algorithm with binary search which can find the numerical solution quickly. We performed various computer simulations to show the performance of the energy-optimal 3-step speed control in comparison with a conventional 3-step speed control with a reasonable constant acceleration as a benchmark. Simulation results show that the E-C-E is the most energy efficient 3-step velocity profile pattern, which enables wheeled mobile robot to extend working time up to 50%.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.9
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• pp.896-902
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• 2007

This paper proposes a vision-based kinematic control method for mobile robots with camera-on-board. In the previous literature on the control of mobile robots using camera vision information, the forward velocity is set to be a constant, and only the rotational velocity of the robot is controlled. More efficient motion, however, is needed by controlling the forward velocity, depending on the position in the corridor. Thus, both forward and rotational velocities are controlled in the proposed method such that the mobile robots can move faster when the comer of the corridor is far away, and it slows down as it approaches the dead end of the corridor. In this way, the smooth turning motion along the corridor is possible. To this end, visual information using the camera is used to obtain the perspective lines and the distance from the current robot position to the dead end. Then, the vanishing point and the pseudo desired position are obtained, and the forward and rotational velocities are controlled by the LOS(Line Of Sight) guidance law. Both numerical and experimental results are included to demonstrate the validity of the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.1
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• pp.26-34
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• 2015

In this paper, a fuzzy compensated PID control system is proposed for formation control of mobile robots. The control system consists of a kinematic controller based on the leader-follower approach and a dynamic controller to handle dynamics effects of mobile robots. To maintain the desired formation of mobile robots, the dynamic controller is equipped with a PID controller; however, the PID controller has poor performance in nonlinear and changing environments. In order to improve these problem, we applied the additional fuzzy compensator. Finally, the proposed control system has been evaluated through computer simulation to demonstrate the improved results.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.6
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• pp.527-534
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• 2016

The non-rail mobile rack, which is used for cargo storage, can improve the storage capacities of logistics centers. Furthermore, it has the advantage that it can be used in traditional logistics centers without making any changes or renovation, such as installing rails. However, when the rack is operated by separated drive actuators mounted on the left and the right wheels, precise position control of the wheels is necessary even if the unbalanced cargo weight on the rack would affect the control. Therefore, internal synchronization control for position tracking between the left and right wheels on the non-rail mobile rack is necessary in this study. In addition, external synchronization control for realizing the same straight movements between mobile racks is necessary. For the internal and the external synchronization control, we propose a synchronization control algorithm based on the repetitive control theory. An internal synchronization control algorithm with repetitive control theory requires the application of the robust servo control method owing to parameter variations. In this case, we can set up the gains for the robust servo control system by considering the cargo variations on the mobile rack. Furthermore, for developing the external synchronization control algorithm, we use a double repetitive control system to perform synchronization control between mobile racks. The efficiency of the proposed control algorithm will be verified by simulation and experimental results. The proposed algorithm can be easily applied in the industry.

• The Transactions of the Korea Information Processing Society
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• v.6 no.11
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• pp.2845-2862
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• 1999

As the technical advances in portable computers and wireless communication technologies, mobile computing environment has been rapidly expanded. The mobile users on mobile host can access information via wireless communication from the distributed heterogeneous multidatabase system in which pre-existing independent local information systems are integrated into one logical system to support mobile applications. Hence, mobile transaction model should include not only the features for heterogeneous multidatabase systems but also the ones for mobile computing environment. In this paper, we proposed a mobile flex transaction model which extends the flexible transaction model that previously proposed for heterogeneous multidatabase systems is extended to support the requirements of mobile heterogeneous multidatabase systems. We also presented the execution control mechanism of the mobile flex transaction model. The proposed mobile flex transaction model allows the definition of location-dependent subtransactions, the effective support of hand-over, and the flexibility of transaction executions. Hence, the proposed mobile flex transaction model can be suit to mobile heterogeneous multidatabase systems that have low power capability, low bandwidth, and high communication failure possibility.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1418-1423
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• 2003

In this paper, a nonlinear controller based on sliding mode control is applied to a two -wheeled Welding Mobile Robot (WMR) to track a smooth-curved welding path at a constant velocity of the welding point. T he mobile robot is considered in terms of dynamics model in Cartesian coordinates and its parameters are exactly known . To obtain the controller, the tracking errors are defined, and the two sliding surfaces are chosen to guarantee that the errors converge to zero asymptotically. Two cases are to be considered: fixed torch and controllable torch. In addition, a simple way of measuring the errors is introduced using two potentiometers. The simulation results are included to illustrate the performance of the control law.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.2
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• pp.308-313
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• 2018

In this paper, we propose a sampled-data model predictive tracking control deign for leader-following control of multi-mobile robot system. The error dynamics of leader-following robots is modeled as a Linear Parameter Varying (LPV) model. Also, the Lyapunov function is presented to guarantee stability of the networked control system. Based on the stabilization condition using a quadratic Lyapunov function approach, model predictive sampled-data controller is designed. Finally, the leader-following control of multi mobile robots is simulated to show effectiveness of the proposed method.