Mee-Seub Lim

Visual measurement of pile movements for the foundation work using a high-speed line-scan camera

When a construction company builds a high structure, many piles should be driven into the ground by a hammer whose weight is typically 7000kg in order to make the ground under the structure safe and strong. It is essential to determine whether a pile is penetrated into the ground enough to support the weight of the structure since ground characteristics at different locations are different from each other. In order to measure the pile movements, a specially designed mark is designed and a high-speed line-scan camera is used in this paper. A mark, in which black and white right-angled triangles are stacked, is used for the measurements of movement information for vertical distances, horizontal distances and rotational angles simultaneously. The measurement performance of dynamic characteristics of the pile at impact instant is improved dramatically compared with the equipment using speckle laser sensors. The developed visual measurement system is successfully applied for a real penetration measurement system for building construction.

A human-like real-time grasp synthesis method for humanoid robot hands

Abstract This paper addresses a real-time grasp synthesis of multi-fingered robot hands to find grasp configurations which satisfy the force closure condition of arbitrary shaped objects. We propose a fast and efficient grasp synthesis algorithm for planar polygonal objects, which yields the contact locations on a given polygonal object to obtain a force closure grasp by a multi-fingered robot hand. For an optimum grasp and real-time computation, we develop the preference and the hibernation process and assign the physical constraints of a humanoid hand to the motion of each finger. The preferences consist of each sublayer reflecting the primitive preference similar to the conditional behaviors of humans for given objectives and their arrangements are adjusted by the heuristics of human grasping. The proposed method reduces the computational time significantly at the sacrifice of global optimality, and enables grasp posture to be changeable within 2-finger and 3-finger grasp. The performance of the presented algorithm is evaluated via simulation studies to obtain the force-closure grasps of polygonal objects with fingertip grasps. The architecture suggested is verified through experimental implementation to our developed robot hand system by solving 2- or 3-finger grasp synthesis.

Omni Camera Vision-Based Localization for Mobile Robots Navigation Using Omni-Directional Images

Vision-based robot localization is challenging due to the vast amount of visual information available, requiring extensive storage and processing time. To deal with these challenges, we propose the use of features extracted from omni-directional panoramic images and present a method for localization of a mobile robot equipped with an omni-directional camera. The core of the proposed scheme may be summarized as follows : First, we utilize an omni-directional camera which can capture instantaneous 360˚ panoramic images around a robot. Second, Nodes around the robot are extracted by the correlation doefficients of Circular Horizontal Line between the landmark and the current captured image. Third, the robot position is determined from the locations by the proposed correlation-based landmark image matching. To accelerate computations, we have assigned the node candidates using color information and the correlation values are calculated based on Fast Fourier Transforms. Experiments show that the proposed method is effecitve in global localization of mobile robots and robust to lighting variations.

High-speed wall following and obstacle avoidance of wheeled mobile robots using hybrid behavior specifications

In this paper, we propose a new approach to the high-speed wall following of wheeled mobile robots using hybrid control system. The proposed hybrid system consists of the discrete state system as the high-level process and the continuous state system as the low-level process. In discrete state system, the discrete states are defined by the user-defined constraints and the reference motion commands are specified in the abstracted motions. The reference motion commands are translated into the control inputs for each wheel in the continuous state system. The hybrid control system applied for wheeled mobile robots can combine the motion planning and autonomous navigation with obstacle avoidance in indoor navigation problem. Simulation results show that hybrid system approach is an effective method for the autonomous navigation. In the experiments of the indoor environments, we proved that the performance of the high-speed navigation is excellent.

High Speed Indoor Navigation of Mobile Robots Using Hybrid Dynamic Control Approach

Abstract In this paper, we propose a new approach to the high-speed navigation of the indoor environments for wheeled mobile robots using hybrid dynamic control approach. The proposed hybrid system consists of the discrete state system as the high-level process and the continuous state system as the low-level process. In discrete state system, the di crete states are defined by the user-defined constraints and the abstracted motions specify the reference motion commands of mobile robots. The experimental results show that hybrid system approach is an effective method for the autonomous navigation and highspeed maneuvering.

Design and implementation of robust adaptive controller for direct drive manipulators

In this paper, we consider a dynamics of actuator driving system as well as actuator itself to design a robust adaptive controller for robot manipulators. We propose an adaptation law to guarantee the boundedness of parameter estimates irrespective of the boundedness of other closed-loop signals without data normalization. We also propose a control law to ensure the uniform stability of the closed-loop system without a priori knowledge of the unmodeled dynamics. We show that the tracking error belongs to the normalized error bound, and also show the robustness of the proposed adaptive controller by using an experiment referred to a two-link direct drive manipulator.<<ETX>>