• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.56-64
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• 2009

This paper presents a parallel typed walking robot which can walk in omni-direction and climb from a floor to a wall. We design a six D.O.F leg mechanism composed of three legs, which form a parallel mechanism with a base and a ground to generate arbitrary poses. Optimal design is conducted to maximize the walking space and the dexterity, which are normalized by the stroke of leg. Kinematic parameters are found to maximize the weighted optimal objectives. We design a triple parallel mechanism robot by inserting Stewart platform between the upper leg mechanism and the lower leg mechanism and examine the gaits when the robot walks on the ground and climbs from a floor to a wall. The analysis of walking space and dexterity for each gait shows that the triple parallel walking robot has a large walking space with a large stability region. We explore the possibility that the robot can climb from a floor to a wall. Investigating the gaits for the six steps proves that the robot can lift the foot up to the wall by combining the orientational walking space generated by three parallel mechanisms.

• Journal of Aerospace System Engineering
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• v.9 no.4
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• pp.55-61
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• 2015

In this study, we peformed optimal design of a composite skid landing gear, one of the solid spring shock absorbers, for light vertical takeoff and landing aircraft. Although a solid spring type has poor energy dissipation capability, it is commonly used for light aircraft where sink speeds are low and shock absorption is non-critical in terms of simplicity, low cost and weight reduction. In this paper, design parameters of solid spring such as sink speed, gear leg length, deflection and landing load factor were reviewed. In order to meet structural requirements such as deflection and strength, finally, we conducted optimal design of the composite skid landing gear for VTOL UAV using genetic algorithm and pattern search algorithm.

• Steel and Composite Structures
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• v.31 no.6
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• pp.629-640
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• 2019

The investigation of retaining wall structures behavior under dynamic loads is considered as one of important parts for designing such structures. Generally, the performance of these structures is under the influence of the environment conditions and their geometry. The aim of this research is to design retaining wall structures based on smart and optimal systems. The use of accuracy and speed to assess the structures under different conditions is one of the important parts sought by designers. Therefore, optimal and smart systems are able to have better addressing these problems. Using numerical and coding methods, this research investigates the retaining wall structure design under different dynamic conditions. More than 9500 models were constructed and considered for modelling design. These designs include height and thickness of the wall, soil density, rock density, soil friction angle, and peak ground acceleration (PGA) variables. Accordingly, a neural network system was developed to establish an appropriate relationship between data to obtain safety factor (SF) of retaining walls under different seismic conditions. Different parameters were analyzed and the effect of each parameter was assessed separately. According to these analyses, the structure optimization was performed to increase the SF values. The optimal and smart design showed that under different PGA conditions, the structure performance can be appropriately improved while utilization of the initial (or basic) parameters leads to the structure failure. Therefore, by increasing accuracy and speed, smart methods could improve the retaining structure performance in controlling the wall failure. The intelligent design process of this study can be applied to some other civil engineering applications such as slope stability.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.36-43
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• 2003

In machining of ceramic materials, they are very difficult-to cut materials because of there high strength and hardness. Machining of ceramics are characterized by cracking and brittle fracture. Generally, ceramics are machined using conventional method such as finding and polishing. However these processes are generally costly and have low MRR(material removal rate). This paper focuses on determining the optimal levels of process parameters for products with CNC machining center. For this purpose, the optimization of cutting parameters is performed based on experimental design method. A design and analysis of experiments is conducted to study the effects of these parameters on the surface roughness by using the S/N ratio, analysis of ANOVA and F-test. Cutting parameters, namely, cutting speed, feed and depth of cut are optimized with consideration of the surface roughness.

• Korean Chemical Engineering Research
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• v.51 no.1
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• pp.87-92
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• 2013

Microalgae have been suggested as a promising feedstock for producing biofuel because of their potential of lipid production. In this study, a first principles ODE model for microalgae growth and neutral lipid synthesis proposed by Surisetty et al. (2010) is investigated for the purpose of maximizing the rate of microalgae growth and the amount of neutral lipid. The model has 6 states and 12 parameters and follows the assumption of Droop model which explains the growth as a two-step phenomenon; the uptake of nutrients is first occurred in the cell, and then use of intra-cellular nutrient to support cells growth. In this study, optimal input design using D-optimality criterion is performed to compute the system input profile and sensitivity analysis is also performed to determine which parameters have a negligible effect on the model predictions. Furthermore, model predictive control based on successive linearization is implemented to maximize the amount of neutral lipid contents.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.172.2-172.2
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• 2005

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.11-16
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• 2001

It is not easy to apply a small-sized centrifugal fan to the duct used for the thermal management of home electronic appliances due to complex design parameters of its blades and scroll. The main objective of this study was to develop the systematic process to design an optimal centrifugal fan based on the 3-dimensional configuration of blades obtained from the conceptual design program self-developed with the given design constraints such as the flow rate, the total pressure loss, the size of fan, and the number of rotation. The design process to find an optimal centrifugal fan for refrigerator was technologically linked in many ways. The complex grid generation system of the fan model included scroll was adopted for the numerical simulation. The FVM CFD code, FLUENT, was used to investigate the three dimensional flow pattern at the coordinate system of rotating frame and to check the optimal performance of the fan. By using this design process, a selected centrifugal fan was designed, numerically simulated, manufactured and experimentally tested in the wind tunnel. The performance curve of fan manufactured by NC process was compared with numerically obtained characteristic curve. The developed design method was proved into being excellent because these two curves were well matched.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.101-109
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• 2005

Ultra-precision positioning systems basically require high natural frequency and sufficient workspace. To cope with this requirement, flexure hinge mechanisms have been proposed. However, previous designs are hard to satisfy the functional requirements of the system due to difficulty in modeling and optimizing process applying an independent axiomatic design. Therefore, this paper proposes a new design and design-order based on semi-coupled axiomatic design. A planar 3 DOF parallel type micro mechanism is chosen as an exemplary device. Based on preliminary kinematic analysis and dynamic modeling of the system, an optimal design has been carried out. To check the effectiveness of the optimal parameters obtained from theoretical approach, simulation is performed by FEM. The simulation result shows that a natural frequency of 200.53Hz and a workspace of $2000{\mu}m{\times}2000{\mu}m$ can be ensured, which is in very close agreement with the specified goal of design.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.645-648
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• 1998

We used a three-dimensional inductance extraction program, Fasthenry for optimal design of the spiral inductors on silicon substrate. The inductance and quality factor of the spiral inductors with various design parameters were calculated so that the optimal parameter value was determined. The spiral inductors then were fabricated using different foundary processes and were measured using the network analyzer and microwave probes. The pad and other parasitics of measurement system were de-embedded using the y-parameter calibration technique. the inductors fabricated using the LG 0.8um process and HP 0.5um process showed the quality factor of 5.8 and 3, respectively. Finally the equivalent circuit farameters of the spiral inductors on silicon substrate were extracted from the measurement data using the matlab.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.500-503
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• 2003

The tool geometry parameters and cutting process have complex relationships. Until now, various cutting test were needed to acquire optimal design of end mill for the purpose of high speed machining, due to the insufficient knowledge about cutting process in high speed machining. Using various tools with different geometry, relationships between tool geometry parameter (rake angle, clearance angle, length of cutter) and cutting process (cutting force, surface accuracy, surface roughness) have been studied. Acquired data can be used to design optimal tool for high speed machining