A piezoelectric actuator is widely used in precision positioning applications due to its excellent positioning resolution. However, the piezoelectric actuator lacks in repeatability because of its inherently high hysteresis characteristic between voltage and displacement. In this paper, a controller is proposed to compensate the hysteresis nonlinearity. The controller is composed of a PID and a neural network part in parallel manner. The output of the PID controller is used to teach the neural network controller by the unsupervised learning method. In addition, the PID controller stabilizes the piezoelectric actuator in the beginning of the learning process, when the neural network controller is not learned. However, after the learning process the piezoelectric actuator is mainly controlled by the neural netwok controller. In this paper, the excellent tracking performance of the proposed controller was verified by experiments and was compared with the classical PID controller.

Recently, the rheology on the fluidity of materials has been progressed remarkably. Viscosity measurement for precision-accuracy has needed very important to measure the rheological properties of materials in the field of chemistry-fiber, paint, printing-ink, plastics, rubber, foodstuff-industry, etc. And many methods of measurement have been developed lately. So in this experimental study, small capacity torque transducer with type of strain gage, different method against other existing viscometers, measured viscosity about a liquid that has flowing characteristics of newtonian liquid. Using the assumed computational equation of viscosity, it has same value of viscosity in each different radius of rotating cylinder. In the result, this equipment will be used in the viscosity measurement of a liquid taking flowing characteristics of newtonian liquid.

The block assembly process takes more than half of the total shipbuilding processes. Therefore, it is very important to have a practically useful block assembly process planning system which can build plans of maximum efficiency with minimum man-hours required. However, the process plans are often not readily executable in the assembly shops due to severe imbalance of workloads. This problem arises because the process planning is done on block by block basis in current practice without paying any attention to the load distribution among the assembly shops. this paper presents the development of an automated hull block assembly process planning system which results in the most effective use of production resources and also produces plans that enable efficient time management. If the load balance of assembly shops is to be considered at the time of process planning, the task becomes complicated because of the increased computational complexity. To solve this problem, a new approach is adopted in this research in which the load balancing function and process planning function are iterated alternately providing to each other contexts for subsequent improvement. The result of case study with the data supplied from the shipyard shows that the system developed in this research is very effective and useful.

This paper proposes a redesign procedure for assemblability and automatic assembly of an automobile heater blower motor. According to the procedure, redesign alternatives are generated, then the alternatives are evaluated by a weighted objectives method to select one optimal redesign alternative. First, the redesign objectives are identified and the assemblability of the current motor is evaluated to decide redesign rules. Finally, the redesign variants and alternatives are generated using the redesign criteria. This information is then evaluated to select an optimal alternative, determined by weighted evaluation criteria which is established in advance.

Tool wear is one of major causes occurring defectives in NC machining. In this paper we developed an automatic tool compensation system for the NC lathe machining. The system compensates machining error without any help of operators whenever the specification of a part is out of a tolerance. The configuration of the automatic compensation system consists of a NC lathe, an autoloader, a sensor, and a PLC. The system is operated as follows. A workpiece loaded by the autoloader is machining on the NC lathe. Once the workpiece is machined to be turned to a part, it is moved onto the sensor to be measured. If the sensor detects a part out of tolerance, a tool compensation is made in the NC controller. The system gives a help in increasing the productivity by reducing occurrence of defective parts as well as by eliminating time for the tool compensation. Besides the productivity increase, the system calculates cumulative usage time of the tool and notices the tool replace time to a worker by an alarm signal. A case is introduced to show that the system can be applied effectively in a shop.

The torsional and axial vibrations of shaft system have been calculated independently because of both the limitation of computing time and the complexity of crankshaft model. In actual system, however, the torsional and axial vibrations are coupled. Therefore, in recent, many works in the coupled vibration analysis have been done to find out the more exact dynamic behavior of shaft system. The crankshaft model is very important in the vibration analysis of shaft system because most of excitation forces act on the crankshaft. It is, however, difficult to establish an exact model of crankshaft since its shape is very complex. In this work, an efficient method is proposed to construct the stiffness matrix of crankshaft using a finite element model of half crankthrow. The proposed and existing methods are compared by applying to both a simple thick beam with circular cross section and an actual crankshaft.

The RP&M(Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, in which the production cycle is getting shorter owing to various needs from consumers. Recently RP products which are made of plastics, wax, and paper are used to verify the design of samples. But these products cannot be applied to the real mold because the strength enough to be a mold cannot be given by soft materials such as plastics. So RP products are copied to AFR(Al powder Filled Resin) molds or metal molds, which is called the RP&M. In this paper, RP&M is applied to a casting process. A porous casting mold, which is made from ceramic powder and binder, is used for rapid tooling of aluminum shoes molds.

In this paper, the residual stresses for the wide-band laser heat treatment using a polygon mirror have been analyzed. The results of FE analysis are compared with the experimental results. ANSYS Version 5.3, a commercial FE-code, is used for the FE stress analysis. The structural analysis was performed on after thermal analysis. The residual stress distribution across the hardened area was measured by the X-ray diffraction technique. The laser hardening conditions, 2kW laser power and 2mm/s travel speed, were used for the experiment and the FE analysis. Analysis results, which is maximum tensile residual stress is about 143MPa and maximum compressive residual stress is about -380MPa. Under same parameters with the analysis, experimental results indicate that MTRS is about 152MPa and MCRS is about -312MPa. The experimental results is about 6% higher than the FE analysis. As a result, residual stress data from the experiment close well with that of the FE analysis.

In this study, a stereolithography apparatus (SLA) prototype is used as a master model to be transformed into the silicone pattern by vacuum tool forming. The tool for the first prototype is fabricated by using this silicone pattern. Following this procedure, a temporary tool with metal powder and epoxy for wax injection is prepared for the die set of quick change type which consists of upper and lower base die나 and an insert die. The die set of quick change type appears to be very effective in casting operation by changing tools rapidly. The original wax pattern is formed through the die set, and is made of lost-was. Finally the lost-wax pattern is applied to investment casting. The final casting product is checked regarding its dimensional accuracy.

A conventional quarter-car suspension system is a single input system with one actuator. Thus, the performance enhancement for ride quality could be limited. In this paper, we propose a novel automotive suspension system for a quarter-car with two independent actuators to improve the control performance. The left eigenstructure assignment method for multi-variable systems has been applied to the proposed novel quarter-car model.

A new parallel gripper mechanism is proposed in this work. This device has a parallelogrammic platform which can be flexibly folded. Therefore, this mechanism not only can be used to grasp an object having irregular shape or large volume, but also can be used as a micro-positioning device after grasping. Based on the position and kinematic analysis for this mechanism, this mechanism has been developed and the motion performance has been tested to corroborate the effectiveness of this mechanism.

As the IC(Integrated Circuit) has been densified and complicated, it is required to thorough process control to improve yield. Experts, for this purpose, focused on the process analysis automation, which is came from the strict data management in semiconductor manufacturing. In this paper, we presents the process analysis system that can analyze causes, for a output after processes. Also, the plasma etching process that highly affects yield among semiconductor process is modeled to predict a output before the process. To approach this problem, we use adaptively trained neural networks that exhibit superior accuracy over statistical techniques. And in comparison with methods in other paper, a method that history of trend for input data is considered is shown to offer advantage in both learning and prediction capability. This research regards CD(Critical Dimension) that is considerable in high integrated circuit as output variable of the prediction model.

Design parameters and goals play important roles in design. Design goals are the required functions of the design elements and explicitly expressed by design parameters. Design parameters also indicate the relations among design elements, by which constraint networks can be constructed and some useful information can be induced. In this study, the mechanical design process is assumed to be the assignment of design goals and their realization through the evolutionary refinement of the design parameters. Thus an integrated design system is proposed to support the process of assigning the design goals and refining the values of the design parameters. In the design system, a genetic engine that utilizes a genetic algorithm is installed to simulate an iterative design process, which leads to an evolutionary design. The genetic engine treats design parameters as genes and design goals as evaluation function. Re-design and design modification are facilitated by the design parameters. The re-design can be activated in the design system by using the information stored in the design parameters when design parameters or goals are changed.

Since the material flow near the die part in CONFORM (Continuous Extrusion Forming) process is similar to that of side-extrusion, the side-extrusion model of tube shaped aluminum profiles was studied for the die design in CONFORM process. In this paper, the effects of process parameters in the side -extrusion through a two-hole die face, such as material flow, height and thickness of the tube, velocities of punch and lengths of bearing land were investigated using UBET program and DEFORM commercial FEM code. The optimum lengths of the bearing lands and punch velocities for obtaining the straight shape products required were determined.

This study describes a dynamic model of the hydroforming process which is used for precision forming of sheet metals. To help the controller design for the control of the forming pressure needed for this process as well as to investigate the effect of system parameters on the dynamic behavior, dynamic modeling is performed with emphasis on hydraulic servo system which actuates the forming machine. Since the model contains several unknown parameters, these were estimated via a least square parameter identification method. Based upon the identified model, a series of simulations were performed for various operating conditions. The results were compared with those of the experiments to verify the validity of the proposed model. The comparison study shows that the proposed dynamic model can describe dynamic behavior of the forming pressure of the hydroforming process to desirable accuracy.

3차원 트러스 구조물을 설계대상으로, 구조계와 제어계의 동시최적설계문제에 대하여 고찰하였다. 구조 설계에대한 최소중량설계와 제어 설계에대한 외란 억제문제를 설계목적으로 고려하였다. 그리고, 본연구의 유용성을 입증하기위한 수치 시뮬레이션의 결과를 기술하였다.

Rapid Prototyping has made a drastic change in all industries which needs to reduce the time for the development of new products. Orientation and packing in rapid prototyping is considered as the most important factors to maximize the utilization of space in the build chamber and reduce build time. However, the decision of these parameter is mainly dependant on the operators's experience. This paper presents the methodology to find the optimal build layout considering an orientation and packing of multiple parts in SLS processing. Each part is represented as a voxel structure to deal with the inefficiency in a bounding box approach. Test results show that the adapted BL algorithm with a genetic algorithm(GA) can be applicable to a real industry.

The objective of this study is to investigate the effect of three main chemical compositions(Mg, Zn, Si) on extrudability of 7xxx Al alloy with high tensile strength. A few Al alloys based on 7xxx alloys were metal mold cast with various weight*%) of Mg 0.3-1.2%, Zn 5.0-8.0% and Si 0.4-0.7%, to envestigate the effects of extrudability, as well as mechanical properties. To measure the extrudability of cast billets, maximum extrusion pressure and surface temperature at die exit before tearing occurs were obtained by experiment and simulation of thermo-viscoplastic F.E.M. Also the yield and tensile strength of extruded products were tested.

It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure, a method is presented in this paper which uses hybrid neuro-genetic technique. Feed-forward multilayer neural networks trained by back-propagation are used to learn the input)the location and dept of a crack)-output(the structural eigenfrequencies) relation of the structural system. With this neural network and genetic algorithm, it is possible to formulate the inverse problem. Neural network training algorithm is the back propagation algorithm with the momentum method to attain stable convergence in the training process and with the adaptive learning rate method to speed up convergence. Finally, genetic algorithm is used to fine the minimum square error.

Al forged parts are many cases with rib-web section which is difficult to manufacture precisely. Therefore, process conditions must be optimized for precision forging of Al alloys. In this study, various process parameters such as die design, lubricant, ram speed, forging temperature have been investigated using the experiment, upper bound theory and F.E.M. simulation to develop the precision forging technology for rib-web shape component. When lubricant is applied to both material and die, shear friction factor is 0.1 which shows best effect of lubricant. It is specific corner radius of die that minimized forging load regarding process conditions, especially according to the ratio of the width of rib and web. In conclusion, optimum corner radius is 2~3mm when the width of rib and web is 3mm and 20mm respectively.

This paper describes a research work of developing a computer-aided design of product with bending constraints and piercing for progressive working. an approach to the CAD system is based on the knowledge-based rules. Knowledge for the CAD system is formulated from plasticity theories, experimental results and the empirical knowledge of field experts. The system has been written AutoLISP on the AutoCAD with a personal computer and is composed of four main modules, which are input and shape treatment, flat pattern layout, production feasibility check, and strip-layout module. Based on knowledge-based rules, the system is designed by considering several factors, such as radius and angle of bend, material and thickness of product, complexities of blank geometry and punch profile, bending sequence, availability of press. Strip layout drawing generated by piercing with punch profiles divide into automatically for external area is shown into graphic forms, including bending sequences for the product with piercing and bending constraints. Results obtained using the modules enable the designer and manufacturer of piercing and bending dies to be more efficient in this field.

In this paper, a dynamic modeling approach is introduced to identify the dynamic characteristics of the structural/mechanical joints within an one-dimensional structure. A structural joint is represented by the four-pole parameters and the four-pole parameters are determined from the measured frequency response functions by using the spectral element method. As the illustrative examples, a cantilevered beam a clamped-clamped beam, both consist of two beams connected by a bolted joint, are investigated to evaluate the present modeling approach. It is found that the dynamic responses predicted by using the identified for-pole parameters for the bolted joint are well agreed with the measured dynamic responses measured

This stability of a plate structure is very crucial problem which results in wrinkle and bucking. In this study, the effect of the pattern of spot-welding points of the two rectangular plates on the compressive buckling load is studied with respect to the thickness, aspect ratio of plates, number of welding spots. buckling coefficient of the plate not welded was compared with that of two plates with various thickness to extract the effect of thickness. The effect of number of welding spots are studied in tow directions, longitudinal and transverse directions. The conclusions obtained were that the reinforcement effect was maximized when the aspect ratio was close to 1.25 and that the effect of number of welding spots in transverse direction was large than that in longitudinal direction.

Increasing demands on precision machining have necessitated the tool to move not only position error as small as possible, but also with smoothly varying feedrates. Because of the lack of accurate and efficient algorithms for generation of 3-dimensional lines and circles, a full accomlishment for available machine tool resolution is generally unavailable. In this paper, a reference-pulse type 3-axis PC_NC milling system is developed for the precision machining of complex shapes in 3-dimensional space. Three AC servomotors are used as the actuator instead of the hand wheel to operate a 3-axis milling machine under the same mechanical structure. A PC is used to handle the control signal calculation for various types of motion command. To achieve the synchronous 3-axis motion, a real-time reference-pulse 3-dimensional linear and circular interpolator based on the intersection criteria is developed in software. The performance test via computer simulation and actual machining have shown that the PC-NC milling system is useful for the machining of arbitrary lines and circles in 3-dimensional space.

In this paper, the vibrational motion of a flexible beam clamped on a translating base and carrying a moving mass is investigated. The equations of motion which describe the total dynamics of the beam-mass-cart system are derived and the coupled dynamic equations are solved by unconstrained modal analysis. In modal analysis, the exact normal mode solutions corresponding to the eigenfrequencies for the position of the moving mass and the ratios of the mass of the flexible beam, the moving mass and the base cart are used. Proper transformations of the time solutions between the normal modes for a position and those for the next position of the moving mass are also adopted. Numerical simulations are carried out to obtain the open-loop responses of the system in tracking the pre-designed path of the moving mass.

In this paper, input-output transmission characteristics of the Eclipse, which is a parallel machine tool capable of 5 face rapid machining, are investigated. By splitting the weighted Jacobian matrix into two parts, the force and moment transmission characteristics together with the velocity and angular velocity transmission characteristics are analyzed. A new manipulability measure, which combines the volume of the manipulability ellipsoid and the condition number of the splitted Jcobian matrix, is proposed. Two link parameters, the ratio of upper and lower platforms' radii and the length of a supporting link of the Eclipse, are designed by applying the new manipulability measure derived. Computer simulations are provided.

The quality of injection molded parts is affected by the variables such as materials, design variables of part and mold, molding machine, and processing conditions. It is difficult to consider all the variables at the same time to predict the quality. In this paper neural network was applied to analyze the relationship between processing conditions and volumetric shrinkage of part. Engineering plastic gear was used for the study, and the learning data was extracted by the simulation software like Moldflow. Results of neural network was good agreement with simulation results. Nonlinear regression model was formulated using the test data of 3,125 obtained from neural network, Optimal processing conditions were calculated to minimize the volumetric shrinkage of molded part by the application of RQP(Recursive Quadratic Programming) algorithm.

In this paper, a method for assessment of the anisotropic machined surfaces is proposed. Fractal dimension (FD) is calculated using structure function and an index of the anisotropy is obtained as a ratio of its maximum and minimum value. The upper limit of fractal region on the structure function is determined as the length of the lag where the autocorrelation function shows 20% of its maximum value. The model of the structure function is derived from that of the auto correlation function. And, it shows that the new method and the proposed index of anisotropy are useful.

Carbon nitride coatings on the substrates of 0.55wt% C - 1.68wt% Mn induction-hardened rolling elements were prepared by ion beam assisted deposition. It was found through metallographic observation that the carbon nitride coatings appeared lamellar-type repeated layers parallel to the surface of substrate. Surface roughness of the coated specimens was improved in comparison with that of the substrates. Wear resistance of the coatings was evaluated using Polymet RCF-1 machine with a constant supply of lubricant followed by Weibull statistical analysis and scanning electron microscopy. the results indicated failure due to old-age wear-out of the coatings was mainly caused by numerous micropits formed on the wear track during repeated rolling contact.