• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.3
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• pp.217-224
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• 2020

The use of a high gain flight control system to achieve high bandwidth performance increase the instability of a helicopter. To investigate these phenomena numerically, high fidelity EC155B1 helicopter model and simplified flight control system that include actuator, digital processor and noise rejection filter was developed. A study conducts an analytical investigation of roll axis stability of the helicopter model as feedback gain increases. And this study analyzes roll-rate and roll-attitude feedback gains limited by rotor flap mode. The results indicate that the phase delays caused by the filter can severely limit the usable values of the roll-rate and roll-attitude feedback gains.

• Tribology and Lubricants
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• v.30 no.3
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• pp.139-145
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• 2014

Nowadays, most micro-patterns are manufactured during flow line production. However, a conventional rotary chemical mechanical polishing (CMP) system has a limited throughput for the fabrication of large and flexible electronics. To overcome this problem, we propose a novel linear roll-CMP system for the planarization of large-area electronics. In this paper, we present a statistical analysis on the linear roll-CMP process of copper-clad laminate (CCL) to determine the impacts of process parameters on the material removal rate (MRR) and its non-uniformity (NU). In the linear roll-CMP process, process parameters such as the slurry flow rate, roll speed, table feed rate, and down force affect the MRR and NU. To determine the polishing characteristics of roll-CMP, we use Taguchi's orthogonal array L16 (44) for the experimental design and F-values obtained by the analysis of variance (ANOVA). We investigate the signal-to-noise (S/N) ratio to identify the prominent control parameters. The "higher is better" for the MRR and "lower is better" for the NU were selected for obtaining optimum CMP performance characteristics. The experimental and statistical results indicate that the down force and roll speed mainly affect the MRR and the down force and table feed rate determine the NU in the linear roll-CMP process. However, over 186.3 N of down force deteriorates the NU because of the bending of substrate. Roll speed has little relationship to the NU and the table feed rate does not impact on the MRR. This study provides information on the design parameter of roll-CMP machine and process optimization.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.91-92
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• 2007

Control of crown and flatness in plate rolling is important not only for enhancement of the structural precision of products, but also for improving the yield and rolling operation. In the heavy plate mill, there have been strong demands for upgrading plate crown and flatness. In order to satisfy these demands, it is essential to develop the high precision numerical models. This paper gives a general description of the crown and flatness preset control model, work roll bender system, simulation result for shape control.

• Journal of the Semiconductor & Display Technology
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• v.17 no.3
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• pp.65-69
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• 2018

In this paper, we have developed a multi-attitude monitoring system for running farm robots for field farming. There are many agricultural robots that can select work modules for various tasks. In order to control the stable attitude of agricultural robots connected to each other, we developed a system for monitoring the roll angle and pitch angle difference by fusing the information of the attitude monitoring system mounted on the robot mainframe and the work module. The developed attitude monitoring system showed resolution below 1 degree. In this paper, roll angle difference of 20 degrees and 60 degrees is measured with a multi - attitude monitoring system.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.9
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• pp.894-898
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• 2009

In a post printing section of roll to roll printing systems, scratch problem is the major defects. The functional qualities such as conductivity, mobility could deteriorate because of the scratch defect. In general, the scratch of the printed pattern on the flexible substrate was induced from a contact between rolls and printed pattern in the post printing section. In this paper, for non-contacting transfer of a moving web, a mathematical tension model has been developed considering strain due to air floatation and the proposed mode has been validated by numerical simulation. Additionally, the correlation between floatation height and speed compensation to control the tension and register are investigated. On the basis of the proposed model, a guide line of speed control in R2R printing system is presented to guarantee the non-contact between rolls and R2R printed pattern on the flexible substrate.

• Journal of Ocean Engineering and Technology
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• v.30 no.1
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• pp.18-24
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• 2016

Stabilizer fins are installed on each side of a ship to control its roll motion. The most common stabilizer fin is a rolling control system that uses the lift force on the fin surface. If the angle of attack of a stabilizer fin is zero or the speed is zero, it cannot control the roll motion. The Coanda effect is well known to generate lift force in marine field. The performance of stabilizer fin that applies the Coanda effect has been verified by model tests and numerical simulations. It was found that a stabilizer fin that applied the Coanda effect at Cj = 0.085 and a zero angle of attack exactly coincided with that of the original fin at α = 26°. In addition, the power needed to generate the Coanda effect was not high compared to the motor power of the original stabilizer fin.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.766-771
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• 1997

In this strip casting,size of the roll separating force is a index representing the solidifying status of the melt. Rolling forces at the start of the casting process can change abruptly due to the overcooling of the leader strip. This inconsistensy leads to machine damage or deficient solidification which results in the failure of the casting. In this study, a mathematical model is derived for the hydraulic servo pressure control system for the twin roll strip caster and its parameters are estimated by the RLS algorithm. Based on the identified model, an one-step ahead predictive control method is applied in order to minimize the transient fluctuation of the rolling force. Its simulation results are compared with those of the conventional PI controllers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.9-15
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• 2013

Roll-to-roll printing technology has lately become a subject of special interests in the field of printed electronics. Since this technology has the advantage that continuous and mass production is possible. And for high precision register control is required in multi-layer printing to produce the electronic devices, this is one of the most important technologies in roll-to-roll printing technology. Register error could be generated by various reasons like eccentricity of roll and thermal deformation due to temperature variation in drying section. In this study, the effect of tension variation on the register was analyzed. The results of these analyses show that it is essential to consider the tension disturbance which is generated by the change of temperature in drying section, and conventional register model has limitation to estimate the register error. In order to overcome the limitation of the register model, advanced register model based on the SI process was developed. Also, the performance of the developed model was verified experimentally.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.85.6-85
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• 2001

This paper describes a 3-DOF attitude control of a small model helicopter in hover through explicit decoupling and adaptive control scheme. A model helicopter mounted on gimbal-stand is considered as a system that has 3 independent SISO systems representing motions about roll, pitch and yaw axis and these subsystems are identified from the test flight data. In this consideration, the contribution of others to yaw channel is neglected since it is relatively small. Two PID controllers based on Ziegler-Nichols method are designed for roll pitch channels independently. Also, adaptive fuzzy tuner is designed and applied to those PID controllers to cope with coupling effects between each channel and system uncertainties due to variation of engine RPM. The experimental results show that the attitude control ...

• International Journal of Aeronautical and Space Sciences
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• v.14 no.3
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• pp.247-255
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• 2013

The flight control of re-entry vehicles poses a challenge to conventional gain-scheduled flight controllers due to the widely spread aerodynamic coefficients. In addition, a wide range of uncertainties in disturbances must be accommodated by the control system. This paper presents the design of a roll channel controller for a non-axisymmetric reentry vehicle model using the trajectory linearization control (TLC) method. The dynamic equations of a moving mass system and roll control model are established using the Lagrange method. Nonlinear tracking and decoupling control by trajectory linearization can be viewed as the ideal gain-scheduling controller designed at every point along the flight trajectory. It provides robust stability and performance at all stages of the flight without adjusting controller gains. It is this "plug-and-play" feature that is highly preferred for developing, testing and routine operating of the re-entry vehicles. Although the controller is designed only for nominal aerodynamic coefficients, excellent performance is verified by simulation for wind disturbances and variations from -30% to +30% of the aerodynamic coefficients.