Byungjae Park

An efficient mobile robot path planning using hierarchical roadmap representation in indoor environment

This paper describes a practical approach to solve a path planning problem in a home environment. The proposed approach incrementally constructs the hierarchical roadmap which has a multi-layered structure using a sonar grid map when a mobile robot navigates in unexplored area. The hierarchical roadmap can almost completely cover the traversable areas in the environment. The mobile robot path planner using the hierarchical roadmap can efficiently search for appropriate paths under the limited computing power and time by reducing the search space size. The benefits of the hierarchical roadmap representation were verified by experiments in a home environment.

Odometry calibration using home positioning function for mobile robot

Odometry calibration is a first and essential step to do for a successful navigation because most of control algorithms are based on odomety information. Odometry error can be categorized as systematic and non-systematic error. In this paper, we suggest a novel method to calibrate systematic error using inherent home positioning capability of home cleaning robot. The method is designed for a differential drive type and take advantage of Augmented extended Kalman Fil- ter(AKF) Algorithm to estimates systematic error parameters. Our approach has both characteristics of on-line and off-line. By simulation and experiment, we evaluate the method and the result shows that the proposed method gives odometry error reduction by several times.

Adaptive node sampling method for probabilistic roadmap planners

This paper proposes an adaptive node sampling method for the probabilistic roadmap (PRM) planner. The proposed method substitutes the random sampling in the learning phase of the PRM planner and improves the configuration of the roadmap. This method uses two phase to determine nodes in order to construct the roadmap. First, the proposed method extracts initial nodes using the approximated cell decomposition and the Harris corner detector. Second, the positions of these nodes are optimized using a construction process of the centroidal voronoi tessellation (CVT). The proposed method determines the adequate number and positions of the nodes to represent the entire free space, and the PRM planner based on the proposed method finds out efficient paths even in narrow passages. These properties have been verified though experiments.

Feature map management for mobile robots in dynamic environments

This paper presents a new approach to the management of the environmental map for mobile robots in dynamic environments. The environmental map is built of primitive features, such as lines, points, and even circles, extracted from ambiguous data captured by the robots sonar sensor ring. The feature map must be managed because the indoor surroundings where mobile robots operate are continuously changing due to nonstationary objects, such as wastebaskets, tables, and people. The features are processed by trimming, division, or removal, depending on the dynamic circumstances. All processing refers to the occupancy probabilities of grid squares generated for the map features. The occupancy probabilities of the squares are updated using the Bayesian updating model with the sonar sensor data. Experimental results demonstrate the validity of the proposed method.

Ballistic-Mode Plasma-Based Ion Implantation for Surface-Resistivity Modification of Polyimide Film

Plasma-based ion implantation (PBII) is the well-established technique for material surface modification. In this paper, we described the ballistic-mode PBII process in which repetitive high-voltage pulses are applied to the grid a few centimeters from a polyimide (PI) film target. The high-voltage pulse applied to the grid has the peak values of 30 kV, width of 2.5 μs, rise time of 1.5 μs, and fall time of 0.5 or 40 μs. In this process, ions propagate ballistically from a grid to the PI film and modify the surface resistivity of the PI film. The efficiency of surface-resistivity modification depends on the fall time of the pulse applied to the grid. The ballistic-mode PBII process affects the surface characteristics of PI to a depth of 90 nm.

Path reconstruction method for sampling based planners

A path reconstruction method for sampling based planners is proposed in this paper. The proposed method improves the quality of the initially planned path. The node update and Dijkstras graph search algorithm are used in the iterative process of the proposed method. The proposed method improves the safety and efficiency of the initially planned path simultaneously, and can be applied to any kinds of sampling based planners if the planned path represented by a simple path graph. Quantitative analyses of simulation results were done to verify the proposed method.

A parameter estimation method for the bilateral teleoperation framework for an O 2 lance manipulator

The O2 lance manipulator is used in the electric arc furnace (EAF) process to supply oxygen in order to remove impurities in molten metal. However, since it is controlled by the human operator who can get only visual information about the EAF, the collision between the lance and the EAF can happen which must be avoided in the process. The bilateral teleoperation can be a solution for this problem, but due to the extreme environment of the EAF environment, the feedback force should be generated based on the virtual environment. Since the parameters of the EAF and O2 lance is time-varying, there exist some errors between VE and real environment which lead to the incorrect force feedback. In this paper the estimation method for parameters of the lance and EAF used in this framework is developed. The proposed method can update the parameters of the EAF and O2 lance manipulator in on-line process, so the bilateral teleoperation can generate more accurate feedback force. The functionality of the proposed method is validated by experiment.

Differences in the Electronic Structures of Bulk and Powder FeV 2 O 4 Spinel Oxide Investigated by Using Synchrotron Radiation

The electronic structure of ferrimagnetic spinel oxide of has been investigated by employing soft x-ray absorption spectroscopy (XAS) and soft x-ray magnetic circular dichroism (XMCD). The Fe 2p and V 2p XAS spectra show that the valence states of Fe and V ions are mixed-valent states and states, respectively. In Fe 2p XMCD spectra, finite XMCD signals are observed for divalent states only, but not for states. This finding indicates that the magnetic moments of ions are ordered ferromagnetically but that those of ions are cancelled, implying that ions play an important role in determining magnetic properties of .

Development of Grid Observation Model for Particle Filter-based Mobile Robot Localization using Sonar Grid Map

This paper proposes an observation model for a particle filter-based localization using a sonar grid map. The proposed model estimates a predicted observation by considering the properties of a sonar sensor which has a large angular uncertainty. The proposed model searches a grid which has the highest probability to reflect a sonar beam using the following procedures; (1) the reliable area of a single sonar data is determined using the footprint association model; (2) the detection probability of each grid cell in a sonar beam coverage in estimated. The proposed model was applied to the particle filter based localization, and was verified by experiments in indoor environments.

Surface resistivity modification of polyimide film by plasma source ion implantation

Summary form only given. Plasma source ion implantation (PSII) is a very useful technique in modifying characteristics of the material surfaces. We used a modified PSII process in which repetitive high voltage pulses were applied to grids placed far outside of the sheath region. It was formed at the surface of the polyimide immersed in the plasma. The mechanism of the ion acceleration in the modified PSII system was investigated by the simulation using the XOOPIC program. After the surface treatment using the modified PSII process with the inductive coupled plasma, the surface resistivity of polyimide was decreased from 1016 ohm/square to the range of 106 ~ 109 ohm/square. Polyimide was modified to improve the surface electrical conductivity in the energy range of 5 ~ 30 kV. The TEM analysis showed that the MPSII treatment with -30 kV pulse changed the structure of the polyimide to a depth of 90 nm. We present the modified PSII system and the surface resistivity dependency by the pulse shape and treatment time.