Joonhong 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.

Adaptive Model Reference Control Based on Takagi-Sugeno Fuzzy Models With Applications to Flexible Joint Manipulators

The control scheme using fuzzy modeling and Parallel Distributed Compensation (PDC) concept is proposed to provide asymptotic tracking of a reference signal for the flexible joint manipulators with uncertain parameters. From Lyapunov stability analysis and simulation results, the developed control law and adaptive law guarantee the boundedness of all signals in the closed-loop multi-input/multi-output system. In addition, the plant state tracks the state of the reference model asymptotically with time for any bounded reference input signal.

Design of an airbag system of a mid-sized automobile for pedestrian protection

The rate of fatalities in vehicle-to-pedestrian crashes is high with respect to the frequency of occurrence. In recent years, a pedestrian safety system, which consists of a pop-up hood and a pedestrian airbag, was developed to reduce pedestrian injuries. However, the effects of the system and a reasonable design direction were not clearly established. In this research, the protection performance of the pedestrian safety system was investigated using actual impact tests. The pedestrian safety system was installed in a mid-size vehicle and tested according to the headform test of the New Car Assessment Program. The necessity and usefulness of the safety system using the test results are discussed. These results are incorporated into the simulation modelling process. The airbag system is designed to reduce head injuries by using computational impact analysis. Two categories are considered when designing the system: the design of the airbag housing and the design of the airbag itself. The airbag housing is designed by selecting appropriate materials. The design flow for the pedestrian airbag employs the orthogonal array and the response surface method. The newly designed airbag system reduces the severity of head injuries.

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.

Analysis and Design Consideration of an Energy Absorbing Steering System Using Orthogonal Arrays

Abstract An occupant analysis code SAFE (Safety Analysis For occupant crash Environment) is utilized to simulate and improve the crash performance of an energy absorbing steering system. The safety standard FMVSS 203 is adapted in the simulation and used in design evaluations. Segments and contact ellipsoids are employed in modelling the body blocks and the components of the steering system with SAFE. Spring-damper elements and force-deflection characteristics are utilized to model the energy absorbing components such as the plate and the polyacetal molding. The plate absorbs the impact energy through tensile deformation. Whereas, the polyacetal molding absorbs the impact energy through compression. The body block test is carried out to validate the simulation model, and real component tests are performed to extract the force-deflection curves. After the model is validated, the parameter study is carried out to evaluate the crash performance of the energy absorbing components. A performance measure is defined for the parameter study. Using the results of the parameter study and managing the orthogonal arrays, optimum design values of energy absorbing components are determined to minimize the occupant injury.

A hybrid system approach to motion control of wheeled mobile robots

Addresses the design of hybrid control systems for the motion control of wheeled mobile robot systems with nonholonomic constraints. The hybrid control system has a 3-layered hierarchical structure: digital automata for the higher process, mobile robot system for the lower process, and the interface as the interaction process between the continuous dynamics and the discrete dynamics. In the hybrid control architecture of mobile robot, the continuous dynamics of mobile robots are modeled by switched systems. The abstract model and digital automata for the motion control are developed. The motion control tasks for desired-paths with edges and dynamic path following with various initial conditions are investigated as the applications by simulation studies.

Development of ethernet based tele-operation systems using haptic devices

In this paper, we investigate the issues for the design and implementation of tele-operated force-feedback system via Ethernet. Here, the 2-DOF haptic device and the X-Y stage are employed as a master controller and a slave system, respectively. In this master-slave system, the force feedback algorithm, the modeling of virtual environments and the control method of X-Y stage with linear motors are proposed. In our research, the Ethernet network is used for data communication between the master and slave controllers. We construct virtual environment of the real wall from the force-feedback in controlling the X-Y stage and getting the force applied by the 2-DOF haptic device.

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.

Resolved motion control of redundant robot manipulators by neural optimization networks

An effective resolved motion control method of redundant manipulators is proposed to minimize the energy consumption and to increase the dexterity while satisfying the physical actuator constraints. The method employs the neural optimization networks, where the computation of Jacobian matrix is not required. Specifically, end-effector movement resulting from each joint differential motion is first separated into orthogonal and tangential components with respect to a given desired trajectory. Then the resolved motion is obtained by neural optimization networks in such a way that: (1) the linear combination of the orthogonal components should be null; (2) the linear combination of the tangential components should be the differential length of the desired trajectory; (3) the differential joint motion limit is not violated, and (4) the weighted sum of the square of each differential joint motion is minimized. The weighting factors are controlled by a newly defined joint dexterity measure as the ratio of the tangential and orthogonal components.<<ETX>>

Robust Optimization Using the Probabilistic Robustness Index and the Enhanced Single-Loop Approach

I N RECENT years, the robust design optimization (RDO) methodology has been developed to consider the uncertainties in conventional design optimization. RDO is a method that minimizes the effect of variation without eliminating the causes [1–9]. It has been known as an effective designmethod to improve the quality of a product. It deals with both the robustness of the objective function and the feasibility of the constraints. In RDO, the robustness of the objective function can be achieved by reducing the change of the objective function with respect to the changes of the design variables. Therefore, robustness indices of the objective function pursue an insensitive design when there are variations on design variables and/or parameters. To accomplish the purpose, various robustness indices on the objective function have been proposed [1–9]. A design formulation with the weighted sum method has beenwidely used due to simple and easy application [3,8]. Robustness of the constraints means that all of the constraints are satisfied within the range of the variations for the design variables and/or parameters. Typical approaches of previous studies can be classified into three types: the worst-case method, the penalty method, and the probabilistic method [3,10–16]. In the probabilistic method, the constraints with uncertainties are replaced by the probabilistic constraints. Generally, it is well known as reliabilitybased design optimization (RBDO). In RBDO, the feasibility of design constraints is calculated exactly by a probability theory in RBDO, whereas it is approximately calculated in the worst-case method and the penalty method. The reliability-based robust design optimization (RBRDO) is known as a method that treats the constraints with uncertainties by using RBDO methods in RDO [17,18]. In this study, the formulation and the numerical method for RDO are addressed. An RDO algorithm is made with the newly proposed robustness index and the enhanced single-loop single vector approach. First, a probabilistic robustness index is proposed to deal with the robustness of the objective function. It is derived from the probabilistic theory. By using the robustness index, the mean value and the variance of the objective function are simultaneously controlled. Second, an effective RBDOmethod is used to achieve the feasibility of the constraints. The feasibility robustness is exactly guaranteed by using the RBDOmethod.Among theRBDOmethods, the single-loop single-vector approach using the conjugate gradient method (SLSVCG), whichwas recently proposed by Jeong and Park, is employed to treat the constraints efficiently [15]. By using the new algorithm, the robustness of the objective function is considered in the optimization process while the feasibility of the constraints is guaranteed with the specified target reliability. Two mathematical problems are defined to show the distinct efficiency of the used methods, and a practical engineering problem is employed for assessment of the methods in the application viewpoint. The results of the proposed method are compared with those from combinations of other methods for RDO.