Autonomous cutting parameter regulation using adaptive modeling and genetic algorithms

In this research, a turning process is modeled adaptively by a backpropagation, multilayered neural network with an iterative learning method, and cutting parameters of the process model are optimized through genetic algorithms (GAs). Some constraints were given on the input conditions and the process outputs to provide for the desired surface integrity and to protect the machine tool. Introducing penalty values, which are included in the fitness evaluation of the GAs, we can solve such a constrained problem. Experimental results show that the neural network has the ability to model the turning process on-line, and such cutting conditions as spindle speed and feed rate can be adaptively regulated for maximizing the material removal rate using the GAs.     

Design of a two-phase loop thermosyphon for telecommunications system (I)

A two-phase loop thermosyphon system is developed for the B-ISDN telecommunications system and its performance is evaluated, both experimentally and by visualization techniques. The design of the thermosyphon system proposed is aimed to cool multichip modules (MCM) upto heat flux of 8 W/cm². The results indicate that in the loop thermosyphon system, cooling heat flux is capable of 12 W/cm² with two condensers under the forced convection cooling of the condenser section with acetone or FC-87 as the working fluid. The instability of the working fluid flow within the loop is observed using the visualization techniques and temperature fluctuation is stabilized with orifice insertion.     

A pressure output feedback control of turbo compressor surge with a thrust magnetic bearing actuator

This paper presents a pressure output feedback control of turbo compressor surge using tip clearance actuation with a thrust magnetic bearing actuator. First, static and dynamic compressor models were obtained for a commercial turbocharger, and the surge point was found through local stability analysis. Then, the effect of tip clearance on the compressor pressure rise was derived, and Lyapunov analysis was used to establish a limit of stability with tip clearance modulation. After that, a linear quadratic (LQ) state feedback control was designed considering the limit established by the Lyapunov analysis. In addition, an extended Kalman filter (EKF) was designed to estimate the mass flow rate from the measured compressor pressure. Finally, the pressure output feedback controller was built by combining the LQ state feedback control and EKF. Control simulation proved the effectiveness of the output feedback controller. This paper was recommended for publication in revised form by Associate Editor Dong Hwan Kim Dr. Ahn earned Ph.D. from Seoul National University in 2001. He was a research associate of University of Virginia. He is currently an assistant professor of department of mechanical engineering at Soongsil University and serving as an editor of international journal of rotating machinery. His research interests are rotordynamics, control and mechatronics. Mr. Park is a junior research engineer in Doosan infracore. He received his master from Seoul National University. His research area is on dynamics and control of rotating machinery. Dr. Sanadgol is an assistant Professor of Physics and Engineering at Sweet Briar College. She earned her PhD in Mechanical and Aerospace Engineering with a focus in controls from the University of Virginia in 2006. Her research interests are in controlling flow instabilities in compressors and application of nonlinear control theories to mechatronics systems. Dr. Park received his PhD degree from the Seoul National University, Korea in 2007. He is currently director of research institute at KMB&SENSOR company. His research interests include the precision machine design, rotor dynamics, and magnetic actuators. Dr. Han received the Dipl.-Ing. and Dr.-Ing. in mechanical engineering from University of Karsruhe, Germany in 1975 and 1979, respectively. In 1982, he joined the school of mechanical and aerospace engineering, Seoul National University as an assistant professor. He is currently an honorary professor of mechanical engineering. His research interests are in machine element design, magnetic bearing, lubrication engineering and Bio-MEMS devices. Dr. Maslen is a Professor of Mechanical and Aerospace Engineering at the University of Virginia. He earned his Bachelor of Science in 1980 from Cornell University and his doctorate from the University of Virginia in 1991. His research focuses on application of automatic controls to electromechanical systems with a concentration in magnetic bearings.     

Development of rapid mixing fuel nozzle for premixed combustion

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel. This paper was recommended for publication in revised form by Associate Editor Ohchae Kwon Masashi Katsuki received his B.E. degree in Mechanical Engineering from Osaka University, Japan, in 1965. He received his Dr. Eng. from O. U. in 1985. Dr. Katsuki is currently a Visiting Professor at the Department of Environmental Engineering at Hoseo University in Chungnam, Korea. He was a Vice President of the Japan Society of Mechanical Engineers. Dr. Katsuki’s research interests include combustion, computational thermo-fluid dynamics, and molecular dynamics. Jin-Do Chung received his B. S., M.S. and Ph.D. degrees in Mechanical Engineering from Chungnam University, Korea in 1983, 1985 and 1990. He then received another Ph.D. in Environmental Engineering from Kanazawa University, Japan in 1996. After that he worked as Post-doc researcher for 1,6 year at KIMM and Senior researcher for 6years at KEPCO Research Center. Dr. Chung is currently a Professor at the Department of Environmental Engineering at Hoseo University in Asan, Korea. Dr. Chung’s research interests include thermal-fluid and environmental engineering. Jang-Woo Kim received his B. S. degree in Mechanical Engineering from Chungnam University, Korea, in 1990. He then received his M. S. and Ph. D. degrees from Kyushu University, Japan in 1994 and 1998, respectively. Dr. Kim is currently a Professor at the School of Display Engineering at Hoseo University in Asan, Korea. Dr. Kim’s research interests include CFD, aerodynamics, and display equipment technology. Seung-Min Hwang received the Ph.D. degree in Mechanical Engineering at Osaka University in 2005. After that he worked as visiting researcher for 3 years at CRIEPI (central research institute of electric power industry) and Osaka University in Japan. He is currently a Professor at the Graduate School of Venture at Hoseo University in Korea. His major research is thermal-fluid, energy issue and environment. Seung-Mo Kim received his Ph. D. degrees in Mechanical engineering from Osaka University, Japan, in 2004. Dr. Kim is currently a research Professor at Pusan Clean Coal Center at Pusan National University in Pusan, South Korea. Dr. Kim’s research interests include coal combustion, oxy-fuel combustion, coal gasification, coal de-watering, power generation plant system and energy issues. Chul-Ju Ahn received his B.S. degree in Mechanical Engineering from Hanyang University, Korea, in 1998. He then received his M.S. and Ph.D. degrees from Osaka University, Japan, in 2001 and 2006, respectively. Dr. Ahn is currently a Senior Research Engineer at Samsung Techwin CO. LTD. in Changwon, Korea. Dr. Ahn’s research interests include gas turbine engine, biomass gasification, and power system.     

Determination of Johnson-Cook constitutive equation for Inconel 601

Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values.     

Wetting characteristics of a water droplet on solid surfaces with various pillar surface fractions under different conditions

A numerical study was carried out using a molecular dynamics program to examine the wetting characteristics of nano-sized water droplets on surfaces with various pillar surface fractions under different conditions. Square-shaped pillars had surface fractions that increased from 11.1 % to 69.4 %. The pillars had 4 different heights and 3 different surface energies. When the pillar surface fraction changed, the contact angle of a water droplet also changed due to the attraction between the droplet and the pillar surface or the inner attraction of the water molecules. The pillar height also has different effects on the water droplet depending on the magnitude of surface energy.     

The canonical stewart platform as a six DOF pose sensor for automotive applications

The growing demand for prolonged fatigue life of automotive parts and components requires elaboration of their motion in Cartesian space having six degrees of freedom (DOF). Recently, the canonical Steward platform, consisting of six displacement sensors mounted on two parallel platforms, was introduced to comply with this request. In order to apply this pose sensor to automotive applications, the following two important matters are investigated in this study. First, update Jacobian is proposed as a faster and more stable numerical method to solve the forward kinematic problem without any iteration process. Second, the attachment position and initial configuration of the Stewart platform must be adjustable to avoid the interference with other components due to space constraints under the hood of automotive vehicle. In this case, however, the Jacobian matrix which converts six displacement components into a six DOF pose vector is prone to be ill-conditioned so that the converting accuracy becomes worse. The L₁-norm of each row in the Jacobian matrix quantifies how much the error would be provoked according to the given kinematic geometry. Hence, it can be used here as a reliable error indicator. Furthermore, several numerical examples are discussed to demonstrate what to consider when designing a six DOF pose sensor for automotive applications.     

A novel inverse modeling control for piezo positioning stage

Journal of Mechanical Science and Technology - This paper focuses on the application of a novel inverse nonlinear autoregressive with exogenous input (NARX) structure and a fuzzy inference system...     

Process modeling of hybrid machining system consisted of electro discharge machining and end milling

This paper presents a novel hybrid machining process (HMP) that combines cutting action with machining using discharge pulses. Working conditions for a machine tool capable of combining micro-electro discharge machining (EDM) with milling is still an ill-defined problem relying on heuristics because there is insufficient knowledge of the discharge mechanism and the effects of machining parameters. The proposed HMP that combines micro-EDM and milling processes was applied to a steel alloy (AISI 1045) as the workpiece and end mill tungsten carbide as the tool electrode. Test results obtained from a number of experiments showed that the developed HMP yields reasonable machining time and surface roughness. Significant controlling variables for the machining response were identified and ranked using the Taguchi method. Furthermore, the response surface method was used to develop an empirical model based on the correlation between input variables and output responses.     

Direct 3D mask modeling for nonplanar workpieces in microabrasive jet machining

Recently, a new microengraving technology, microabrasive jet machining, has been studied as a machining technology for highly brittle materials. The technology implements the machining by using an abrasive jet and it uses mask structures to achieve microscale geometrical accuracy. The mask structure selectively blocks the abrasive jet at the portions of the surface that are not to be machined. Modeling and fabrication of the mask structure are thus key processes in microabrasive jet machining. Microstereolithography is believed to be a better means of mask fabrication for general planar and nonplanar workpieces. However, it is not easy to model a precise 3D mask structure from a given pattern image. Because of inconsistencies between the computer-aided design (CAD) model and the actual workpiece, mask structures modeled from workpiece CAD models often fall off. We therefore propose an automated modeling algorithm for the corresponding 3D nonplanar mask structure by using measured geometry directly. The algorithm takes the workpiece geometry as section images acquired from computer tomography and generates the CAD mask model directly from the section and mask images. Application software was developed to verify the algorithm and was tested by verification and actual cases.