본 글은 1999년 5월 CASA/SME Blue Book에 Jim Jordan 그리고 Fred Michel이 “Next Generation Manufacturing”라는 제목으로 게재한 자료를 편자의 의도에 따라 재편집한 것입니다. CASA(Computer and Automated Systems Association)는 SME(Society of Manufacturing Engineers)에서 활동하고 있는 하나의 분과로서 CIM Enterprise Wheel을 만들어 내 유명한 곳이기도 합니다. 저자는 본 글에서 앞으로 10여년 간 펼쳐질 차세대 제조 시스템에서는 지식경영이 가장 중요한 요소라고 정의하고 있습니다. 그리고 차세대 제조 시스템의 운영전략으로는 기업통합, 인간자원의 지적이용, 지식의 개발 및 유지, NGM 프로세스 장비 및 기술의 채용을 들고 있습니다.

This paper describes a positioning system for ultra-precision that will be utilized in semiconductor manufacturing field and precision machinery. This system is composed with laser scale unit with 10nm resolution, ball screw with LM guide, brushless DC servo motor, vibration isolator and is equipped in chamber for continuous measuring environment. The dynamic of table, the problem of servo control and the traceability for micro step motion are described. These data will be applied for getting more stable system with 50nm resolution.

This paper presents a method for determining machining parameters in 3-dimentional electrical discharge machining(EDM). The parameters are the peak value of currents, the pulse-on time, and the pulse-off time. It is known that they influence the performance of EDM more than the other else. The parameters are determined from the discharge area between a tool electrode and a work piece. The discharge area is directly influenced by the geometry of a tool surface and the tool discharge position. The discharge area on a tool discharge position is calculated from intersection curves between the tool surface and a horizontal plane. The grid search method is applied to determine the intersection curves. An example is introduced to show that the machining parameters are obtained from the surface geometry of a tool electrode.

In this paper, a modified skyhook control for the semi-active Macpherson suspension system is investigated. A new model for the semi-active type suspension, which incorporates the rotational motion of the unsprung mass, is introduced and an output feedback control law using the skyhook control method is derived. The gains in the skyhook controller are adaptively adjusted by estimating the road conditions. Because two vertical acceleration sensors, one for the sprung mass and another for the unsprung mass, are used rather than using the angle sensor for the rotational motion of the control arm, the relative velocity of the rattle space is filtered using the acceleration signals. For testing the control performance, the actual damping force has been incorporated via the hardware-in-the-loop simulations. The performances of a passive damper and a semi-active damper are compared. Simulation results are provided.

In this Paper a basic technique of gantry robot control system has been developed to weld the curved part of a large structure. A welding robot is designed to rotate torch and make the torch angle normal to the welding surface. The Kalman filter is applied to obtain the smooth welding path signal from the noised Sensing data. A welding path finding algorithm has been developed in Turbo-C language.

In order to design a reliable machine component efficiently, it is necessary to set up the process of durability analysis using computer simulation technique. In this paper, two methods for dynamic stress calculation, which are basis of durability analysis, are reviewed. Then, a user-oriented dynamic stress analysis program is developed from these two algorithms together with a general-purpose flexible body dynamic analysis and structural analysis programs. Finally, a slider-crank mechanism which has a flexible connecting-rod is chosen to show the special characteristics of these two dynamic stress calculation methods.

Gears are the most commonly used parts in automotive and industrial applications. One of most common modes of gear failures is tooth breakage, which is usually produced by the bending fatigue failure. It is important to manufacture the gears which can withstand the applied stresses in view of safety and economic requirement. This paper deals with bending fatigue strength for cold forged bevel gear. Especially, to compare fatigue characteristics for manufacturing processes difference, bending fatigue tests of bevel gears made by three different processes respectively. Results indicate that the fatigue strength of bevel gear is improved by cold forging process. Intergranular fracture is found on fatigue fracture surface, and dimples are observed on final fracture surface. The fatigue failure cannot be considered as a deterministic quantity, but must be characterized statistically. This study proposes a method to estimate bending fatigue lift of the bevel gear using the probability-load-life and Weibull analysis.

In this paper, the robust controller design is performed for the speed control of the underwater vehicle diesel engine. Nonlinear model equations are acquired through the mathematical modeling using mean torque production model technique. It is very difficult to design the robust controller because those are high nonlinear and not expressed in terms of the matched uncertainty Therefore those are converted into the separable model into the linear nominal system and the nonlinear uncertainty term.

An arc sensor system to compensate positional errors was developed on the foundation of sensor interface system to make use of the on-line shift function of industrial welding robot. Investigating the on-line shift function, we examine the quantitative relationship between the deviation from programmed path and the correction data transferred from personal computer to robot controller. The number of input parameters for weld seam tracking can be reduced by making the relationship between the deviation and the correction data during half weaving be the function of only cross time. With the results of weld seam tracking for the butt joint with V-groove and fillet joint of sheet metal, good performance was implemented. By developing the sensor interface system to compensate the positional errors, industrial welding robot can be expected to contribute to the promotion of welding automation.

Sound intensity method is well known as a visualization technique of sound field or sound propagation in noise control. Sound intensity or energy flux is a vector quantity which describes the amount and the direction of net flow of acoustic energy at a given position. Especially two dimensional sound intensity method is very useful in evaluating periodic characteristics and acoustic propagation mode of noise source. In this paper, we have studied the noise source Identification, acoustic sound field analysis, and characteristics of noise source of rotary compressor and scroll compressor for air conditioner using complex sound intensity method. Also we proposed a now method of time domain analysis which is used in evaluating of position of noise source in rotary and scroll compressor in this paper This paper presents the advantage, simplicity and economical efficiency of this method by analysing the characteristics of noise source with two dimensional complex sound intensity simultaneously.

Die-casting burr due to casting process is removed by post-process for assembly and quality control of product. Though robot has been widely used for deburring job before, CNC exclusive machine is currently developed f3r high power, high speed machining and quick tool change. Deburring tool path with complex 3D curve type is defined to make out deburring NC program. But there is no efficient method to define it currently used methods with teaching probe on machine. In this study the efficient method to make out deburring NC program is developed. 5-axis digitizing machine is used to receive data of deburring path. And the post processor for NC program generation is developed in consideration of the machining conditions. The developed system is not dependent on the skill of operator and has the advantage to maintain the flexibility of job to modify NC program due to the wear of tool and aging of the die casting.

Mutual torque ripple in a brushless DC motor is the main source of acoustic noise, especially fur motor operation with high speed and torque. This paper presents a method to obtain mutual torque ripple to identify acoustic noise source. Mutual torque ripple can be determined by analyzing phase current shape and magnetic circuit with different lead angles. Current shape is determined by state space model of voltage equation with the use of inductance calculated by FEM, and confirmed by experimental results. Mutual torque ripple is also determined by FEM analysis for the calculated current shape. Acoustic noise experiment reveals that mutual torque ripple with different lead angle is one of the main sources for noise generation in a brushless DC motor.

This paper presents simple and effective nonlinear friction compensation methods. When the direction of position command reverses, the integrator output of the PID controller does not change the sign of its output instantaneously, due to friction at zero velocity, i.e. stiction resulting tracking errors, that results in continuous push even though the command direction has been changed. To overcome this problem, we attempt to reverse the sign of the integrator output as the sign of velocity changes. The effectiveness of this approach is demonstrated by experiments on a 3-PRPS (Prismatic-Revolute-Prismatic-Shperical joints) in-parallel 6-D.O.F manipulator. The control strategy has been analyzed for stability. Also discussed are disturbance observer and velocity observer approaches for friction compensation.

One of the major limitations of productivity and quality in metal cutting is the machining accuracy of machine tools. The machining accuracy is affected by geometric errors, thermally-induced errors, and the deterioration of the machine tools. Geometric and thermal errors of machine tools should be measured and compensated to manufacture high quality products. In metal cutting, the machining accuracy is more affected by thermal errors than by geometric errors. This paper models of the thermal errors for error analysis and develops on-the-machine measurement system by which the volumetric error are measured and compensated. The thermal error is modeled by means of angularity errors of a column and thermal drift error of the spindle unit which are measured by the touch probe unit with a star type styluses and a designed spherical ball artifact (SBA). Experiments, performed with the developed measurement system, show that the system provides a high measuring accuracy, with repeatability of $\pm$2${\mu}{\textrm}{m}$ in X, Y and Z directions. It is believed that the developed measurement system can be also applied to the machine tools with CNC controller. In addition, machining accuracy and product quality can be improved by using the developed measurement system when the spherical ball artifact is mounted on the modular fixture.

In this paper, a new method of noncontact measurement has been developed for a 3 dimensional topography in semiconductor wafer, implementing a new optical probe based on the precision defocus measurement. The developed technique consists of the new optical probe, precision stages, and the measurement/control system. The basic principle of the technique is to use the reflected slit beam from the specimen surface, and to measure the deviation of the specimen surface. The defocusing distance can be measured by the reflected slit beam, where the defocused image is measured by the proposed optical probe, giving very high resolution. The distance measuring formula has been proposed for the developed probe, using the laws of geometric optics. The precision calibration technique has been applied, giving about 10 nanometer resolution and 72 nanometer of four sigma uncertainty. In order to quantitize the micro pattern in the specimen surface, some efficient analysis algorithms have been developed to analyse the 3D topography pattern and some parameters of the surface. The developed system has been successfully applied to measure the wafer surface, demonstrating the line scanning feature and excellent 3 dimensional measurement capability.

Robot manipulators, which are nonlinear structures and have uncertain system parameters, have complex in dynamics when are operated in unknown environment. To compensate for estimate errors of the uncertain system parameters and to accomplish the desired trajectory tracking, nonlinear robust controllers are appropriate. However, when estimation errors or tracking errors are large, they require large input torques, which may not be satisfied due to torque limits of actuators. As a result, their stability can not be guaranteed. In this paper, a new robust control scheme is presented to solve stability problem and to achieve fast trajectory tracking in the presence of torque limits. By using fuzzy logic, new desired trajectories which can be reduced are generated based on the initial desired trajectory, and torques of the robust controller are regulated to not exceed torque limits. Numerical examples are shown to validate the proposed controller using an uncertain two degree-of-freedom underwater robot manipulator.

X-ray diffraction method detects change of crystal lattice distance under material surface using diffraction angle 2$\theta$. This technique can be applied to the behavior on slip band and micro crack due to material degradation. The relation between half-value breadth and number of cycle has three stages which constitute rapid decrease in initial number of cycles, slight decrease in middle number of cycles and rapid decrease in final number of cycles. The ratio of half-value breadth takes a constant value on B/B$_{0}$-N diagram with loading condition except early part of fatigue life. The ratio of half-value breadth B/B$_{0}$ with respect to number of cycle to failure N$_{f}$ has linear behavior on B/B$_{0}$-log N$_{f}$ diagram. Therefore, in this paper the estimation of fatigue life by average gradient method has much less estimated mean error than the estimation of fatigue life by log B/B$_{0}$-log N/N$_{f}$ relation.elation.ation.

The size effect on fracture toughness was investigated by introducing $J-A_2$ theory. For this application,small size specimens were chosen to establish $J-A_2$ assessment curve with FEM analysis. Two-dimensional FEM analysis was conducted with plane strain model using ABAQUS by domain integral method to calculate both crack tip stress and fracture toughness which were used to establish $J-A_2$ curve. The assessment curve predicted the fracture toughness of large specimens very well when compared to the test values. The results showed good prediction for deep crack specimen, though there were acceptable deviations in shallow cracked specimens, presumably caused by constraint effect. When the curve applied to reactor vessel in order to predict end of life fracture toughness with assumption of on-power pressure test condition, it provided the reasonable pressure compared to the existing design value. Better predictions would be possible if more test data were available.

Important factors in a casting mold are strength at the mold surface and gas permeability of the mold. This study investigates the effects of pre-pressure and sand particle hardness on gas permeability, with a constraint that the norm of a stiffness array at the mold surface should be higher than a certain value. The constitutive relation is obtained using a hypoplasticity model. This study is firstly attempted to investigate sand behavior in mold fabrication, and will give a theoretical base for fabricating better molds.

In this study, an indirect method to estimate the setup runout of a ball-end mill from cutting force signal is proposed. This runout makes cutting forces of each tooth of the milling cutter unequal. By transforming the cutting force model from time domain to frequency domain through time-convolution theorem, the magnitude and phase angle of runout can be explicitly expressed with material constants, cutting conditions, and force signal. The static setup runout can be obtained by extrapolating estimated effective runout, which is independent of feedrate but decreases linearly with increase in axial depth of cut. The setup runout estimated by slot cutting experiments, shows good agreement with the measured one.

Chemical Mechanical Polishing (CMP) refers to a material removal process done by rubbing a work piece against a polishing pad under load in the presence of chemically active and abrasive containing slurry. CMP process is a combination of chemical dissolution and mechanical action. The mechanical action of CMP involves hydrodynamic behavior. The liquid slurry is trapped between the work piece and pad forming a hydrodynamic film. For the first step to understand material removal mechanism of the CMP process, the hydrodynamic analysis is done with semiconductor wafer. Three-dimensional Reynolds equation is applied to get pressure distribution of the slurry film. Shear stress distributions on the wafer surface are also analyzed

Direct ＆ adaptive slicing of sculptured surfaces in RP improves, quality ＆ accuracy of the final product, compared to the slicing with uniform layer thickness or the slicing of facets (ie, STL). Present D＆A slicing procedures adaptively compute the next layer thickness based on the surface information of current sliced contour, which assumes constant normal curvature values. In some cases, however. such assumption leads to intolerable slicing result which cannot correctly consider the entire local feature shape. We propose improved adaptive slicing algorithms which can determine near-optimal layer thickness, including illustrated examples.

In CNC machining, a free curve is cut into small linear segments using the linear interpolation(G01) method. Therefore, the interpolation error along the curve is not constant due to the changing curvature. This paper presents a NURBS (Non-Uniform Rational B-Spline) interpolation algorithm for machining free curves with high precision and high speed. The proposed NURBS interpolation defines the tool path with NURBS parameters and limits the interpolation error to any desired level by adjusting the feed rate considering the curvature of the shape and sampling time. Both linear and NURBS interpolations are compared to show the validity of the proposed algorithm.

In this paper, a numerical analysis is carried out to show the effect of friction farce on the dynamic characteristics of a flow divider valve. The continuity equations and the equation of motion fur spool are numerically solved. The viscous friction force acting on the spool is considered analyzing the Reynolds equation which governs the viscous flow in the clearance gap between the spool and sleeve. Dynamic characteristics are highly affected by the viscous friction farce whose magnitude is relatively small compare with other fluid forces. Therefore present theoretical formulation and numerical scheme can be used generally in designing and performance evaluation of all the hydraulic spool valve.

An approximate similarity theory has been applied to predict the forming load of non-axisymmetric forging of aluminum alloys through model material tests. The approximate similarity theory is applicable when strain rate sensitivity, geometrical size, and die velocity of model materials are different from those of real materials. Actually, the forming load of yoke, which is an automobile part made of aluminum alloys(Al-6061), is predicted by using this approximate similarity theory. Firstly, upset forging tests are have been carried out to determine the flow curves of three model materials and aluminum alloy(Al-6061), and a suitable model material is selected for model material test of Al-6061. And then hot forging tests of aluminum yokes have been performed to verify the forming load predicted from the model material, which has been selected from above upset forging tests. The forming loads of aluminum yoke forging predicted by this approximate similarity theory are in good agreement with the experimental results of Al-6061 and the results of finite element analysis using DEFORM-3D.

Precision forging technology that can control flow velocity of workpiece have been developed to minimize the amounts of machining. To get the uniform rib length, flow velocity distribution is needed to be estimated and controlled. Computer-aided design is known for very effective to estimate the deformation behavior and design the die for controlling the flow velocity. In this study, die design to control the deformation velocity are investigated using the DEFORM-2D about rib-web shape parts. Also we can get uniform rib length by enforcing the back pressure at end section of rib. The applied load of back pressure farming is lower than that of conventional forging. These results are analysed and confirmed by the experiment.

A robot arm with free joints has some advantages over conventional ones. A light weight and low power consumed arm can be made by a reduction of the number of joint actuators. And this arm can easily overcomes actuator failure due to unexpected accident. In general such underactuated arm does not have controllability because of the lack of joint actuators. The two-link arm with a free joint introduced in this paper is also uncontrollable in the sense of linear system theory. However, the linearized system sometimes can not represent the inherent dynamic behavior of the nonlinear system. In this paper the dynamic characteristics of the two-link arm with a free joint in view of global motion including damping and friction effect of the joints is investigated. In the case of considering only the damping effect, the controllable goal positions are confined to a specific trajectories. But in the case of considering the friction effect, the system can be controlled to arbitrary positions using the friction of the free joint as a holding brake. Also numerical example of position control is presented.