Implementation of a TMO‐structured real‐time airplane‐landing simulator on a distributed computing environment

In real‐time simulation, the simulated system should display the same (or very close) timing behavior as the target system. The simulation accuracy is increased as the simulation time unit is decreased. Although there are several models for such systems, the TMO model is particularly appropriate due to its natural support for real‐time distributed object‐oriented programming. This paper discusses the results of the implementation of a real‐time airplane‐landing simulator on a distributed computing environment using the TMO model. Copyright © 2004 John Wiley & Sons, Ltd.     

Mathematical Modeling and Experimental Identification of an Unmanned Helicopter Robot with Flybar Dynamics

This paper presents a mathematical model for a model‐scale unmanned helicopter robot, with emphasis on the dynamics of the flybar. The interaction between the flybar and the main rotor blade is explained in detail; it is shown how the flapping of the flybar increases the stability of the helicopter robot as well as assists in its actuation. The model helicopter has a fast time‐domain response due to its small size, and is inherently unstable. Therefore, most commercially available model helicopters use the flybar to augment stability and make it easier for a pilot to fly. Working from first principles and basic aerodynamics, the equations of motion for full six degree‐of‐freedom with flybar‐degree of freedom are derived. System identification experiments and results are presented to verify the mathematical model structure and to identify model parameters such as inertias and aerodynamic constants. © 2004 Wiley Periodicals, Inc.     

Optimal Representative Blocks for the Efficient Tracking of a Moving Object

Optimal representative blocks are proposed for an efficient tracking of a moving object and it is verified experimentally by using a mobile robot with a pan‐tilt camera. The key idea comes from the fact that when the image size of a moving object is shrunk in an image frame according to the distance between the camera of mobile robot and the moving object, the tracking performance of a moving object can be improved by shrinking the size of representative blocks according to the object image size. Motion estimation using edge detection (ED) and block‐matching algorithm (BMA) are often used in the case of moving object tracking by vision sensors. However, these methods often miss the real‐time vision data since these schemes suffer from the heavy computational load. To overcome this problem and to improve the tracking performance, the optimal representative block that can reduce a lot of data to be computed is defined and optimized by changing the size of the representative block according to the size of object in the image frame. The proposed algorithm is verified experimentally by using a mobile robot with a two degree‐of‐freedom active camera. © 2004 Wiley Periodicals, Inc.     

Design formalism for collaborative assembly design

Joints in product design are common because of the limitations of component geometric configurations and material properties, and the requirements of inspection, accessibility, repair, and portability. Collaborative product design is emerging as a viable alternative to the traditional design process. The collaborative assembly design (AsD) methodologies are needed for distributed product development. Existing AsD methodologies have limitations in capturing the non-geometric aspects of designer's intent on joining and are not efficient for a collaborative design environment. This paper introduces an AsD formalism and associated AsD tools to capture joining relations and spatial relationship implications. This AsD formalism allows the joining relations to be modeled symbolically for computer interpretation, and the model can be used for inferring mathematical and physical implications. An AsD model generated from the AsD formalism is used to exchange AsD information transparently in a collaborative AsD environment. An assembly relation model and a generic assembly relationship diagram are to capture assembly and joining information concisely and persistently. As a demonstration, the developed AsD formalism and AsD tools are applied on a connector assembly with arc weld and rivet joints.     

Text information extraction in images and video: a survey

Text data present in images and video contain useful information for automatic annotation, indexing, and structuring of images. Extraction of this information involves detection, localization, tracking, extraction, enhancement, and recognition of the text from a given image. However, variations of text due to differences in size, style, orientation, and alignment, as well as low image contrast and complex background make the problem of automatic text extraction extremely challenging. While comprehensive surveys of related problems such as face detection, document analysis, and image & video indexing can be found, the problem of text information extraction is not well surveyed. A large number of techniques have been proposed to address this problem, and the purpose of this paper is to classify and review these algorithms, discuss benchmark data and performance evaluation, and to point out promising directions for future research.     

Fiber optic displacement sensor with a large extendable measurement range while maintaining equally high sensitivity, linearity, and accuracy

This paper presents a fiber optic displacement sensor composed of a transmissive grating panel, a reflection mirror, and two optical fibers as a transceiver. The proposed fiber optic displacement sensor guarantees a stable reflected signal acquisition for application in real industrial fields. Through a parametric study of the grating pitch of the transmissive grating panel, the signal-to-noise ratio, linearity, resolution, accuracy error, and sensitivity of the proposed sensor were investigated. The measured bidirectional movement demonstrated a peak to peak accuracy of 10.5 μm, high linearity of 0.9996, resolution of 3.1 μm at the full bandwidth, signal-to-noise ratio of 27.7, and high sensitivity of 31.8 μm/rad during a movement of 16,004.0 μm using the transmissive grating panel, which had a grating pitch of 200 μm. Even for an extended measurement range, the proposed scheme enables the same accuracy, linearity, and sensitivity to be maintained when compared with conventional laser displacement sensors and fiber optic displacement sensors.     

A novel smooth impact drive mechanism actuation method with dual-slider for a compact zoom lens system

In this paper, a novel actuation method for a smooth impact drive mechanism that positions dual-slider by a single piezo-element is introduced and applied to a compact zoom lens system. A mode chart that determines the state of the slider at the expansion or shrinkage periods of the piezo-element is presented, and the design guide of a driving input profile is proposed. The motion of dual-slider holding lenses is analyzed at each mode, and proper modes for zoom functions are selected for the purpose of positioning two lenses. Because the proposed actuation method allows independent movement of two lenses by a single piezo-element, the zoom lens system can be designed to be compact. For a feasibility test, a lens system composed of an afocal zoom system and a focusing lens was developed, and the passive auto-focus method was implemented.     

Design of a Drilling Torque Controller for a Machining Center

In the drilling process, cutting torque control through feedrate manipulation has significant benefits in prevention of tool breakage and reduction of machine tool vibration and tool wear. In this paper, a PID torque controller was designed for real time drilling torque control in a machining centre. The drilling torque was estimated from the spindle motor current and regulated by feedrate control. The plant including the feed drive system, cutting process, and spindle system was modelled for controller design. For a certain cutting condition, the Ziegler-Nichols method was used to determine the proportional gain and derivative and integral control action times of the controller. Also, the root locus plot was used to tune the proportional gain of the controller. A simple method was also suggested to obtain the tuned controller gain instead of the Ziegler-Nichols method and the root locus plot for an arbitrary cutting condition. Experimental works have been performed to verify the performance of the proposed controller. It is shown that the gain tuning is essential for enhancement of the controller performance and the designed controller can regulate the drilling torque well at a given reference level.Nomenclature G_fc(s) transfer function of combined system of feed drive and cutting process - G_s(s) transfer function of spindle system - G_p(s) transfer function of plant - G_CL(s) transfer function of closed loop system - G_con(s) transfer function of controller - _fc1, _fc2 time constants of combined system of feed drive and cutting process - _s time constant of spindle system - K controller gain - K_c cutting process gain - K_s spindle motor current gain - K_plant plant gain - K_cr critical gain - K_p proportional gain of controller - K_{p_tune} tuned proportional gain of controller - I_s spindle motor current - I_u,v,w u, v, and w phase current of spindle motor - I_idle idling current of spindle motor - damping ratio - T oscillation period of system response - T_c cutting torque - T_m motor torque - T_idle idling torque of spindle motor - T_i integral control action time - T_d derivative control action time     

Experiments on thermal stratification in inlet nozzle of steam generator

Nuclear power plant components suffer pipe shedding, cracking, thermal fatigue, bending and supporting bracket breakage during their life span. Notably, the horizontal inlet nozzle of steam generator is prone to thermal stratification frequently due to its operational characteristics. As a result, PWRs in many countries including the U.S.A. suffered a lot of pipe cracks and leakages around the late 1970s, as the thermal stress inflicted by thermal stratification formed in the horizontal inlet nozzle of steam generator during transition (auxiliary feedwater injection) was not reflected on power plant design. Therefore, we classified the nuclear power plants in Korea into KSNP and Westinghouse-type(W) power plants (Kori # 1,2,3,4, Yeonggwang # 1,2 and Uljin # 1,2) and conducted an experiment on thermal stratification and thermal cycling in relation to the volume of auxiliary feedwater injected into the horizontal inlet nozzle of steam generator and hot water flowing back from steam generator. As a result, it was found out that KSNP was hardly prone to thermal stratification while thermal stratification occurred in the horizontal inlet nozzle of steam generator in Westinghouse-tvpe(W) power plants, necessitating a solution to address such a phenomenon.••