• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.35-42
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• 2004

The control systems with friction cause the steady state error and slow response, because friction is a sensitive to the change of system condition and has highly nonlinear characteristics. To overcome these problems and do precise position control for a ball-screw system, we use Coulomb friction estimator and the sliding mode control(SMC) to compensate its negative effect. The applied SMC for tracking position has a characteristics of robust stability and reducing chattering, and is derived from the Lyapunov stability theorem and reaching condition. Compensating the estimated friction torque to the bounded disturbance term of the SMC's equivalent control input, it has a tracking performance better than the PID from the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.184-191
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• 2002

This paper presents the thermal behavior of a synchronous linear motor with high speed and force. Such a linear motor can successfully replace ball lead screw in machine tools because it has a high velocity, acceleration and good positioning accuracy. On the other hand, low efficiency and high heating up during operation are disadvantage of linear motors. For the application of linear motors to machine tools a water-cooling system is often used. In this research, structure of the linear motor and water cooler is changed to improve the thermal behavior of the linear motor. Some important effects of an integrated cooler, an U-cooler and a thermally symmetrical cooler are presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.387-390
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• 2002

In machine tools, the stiffness of feed drive system is very important for high speed and accurate operation. The ball screw driven feed system has small friction, so the longitudinal and twist stiffness are connected directly and affected by each other. As the longitudinal and twist stiffness are participated in total stiffness of feeding system by about ratio of 4:1, the combined stiffness is necessary to compute when stiffness of feed system is estimated. In this paper, calculation of this combined stiffness is derived and applied for an actual ballscrew fled drive system. The static stiffness and 1 st natural frequency of the feed system is measured, and it is proved the difference between estimation and experiment result is less than 6%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.82-85
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• 2002

Due to various advantages over the conventional linear motion device such as ball-screw, linear motors have been used in wide variety of industrial applications for years. Driven by increased demand for precision machine tools, the importance of high positioning accuracy, high stiffness and high thrust are greatly increasing. In this paper, thrust ripple, detent force and thermal behavior are considered for the development of high performance linear motor whose thrust is up to 4, 000N. This paper presents a comprehensive study for an iron core type linear motor characteristics that include the influence of PM position on thrust thrust ripple by detent farce and motor dynamics as well.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.434-437
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• 2004

This paper presents the development of a new climbing mechanism for inter-block welding in Shipbuilding. The climbing mechanism is that it is career type of robot that can pass over block interval for welding of interblock in shipbuilding. The point part of mechanism is that move ballscrew. The Ballscrew`s capacity account and dynamic analysis of leg part are achieved through this paper. Force and torque analysis were achieved by simulation. This can have strong point in side of cost-cutting and welding amount of work than existent method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.437-441
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• 1995

In this paper, the ultra precision positioning system for servo motor and piezo actuator using dual servo loop control has been developed. For positioning system having long distance with ultra precision, the combination of global stage and micro stage is required. Servo moter and ball screw are used as a master stage and piezo acuator as a fine stage. By using this system, an positional precision witin .+-. 30nm has been achieved at dual servo loop control. When using micro stage, an positional precision within .+-. 10nm has been achieved. This result can be applied to develop semiconductor equipment such as wafer stepper.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.2_2
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• pp.313-321
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• 2020

In this paper, two types of linear actuation methods for the previously proposed adaptive gripper are presented, which includes actual parallelogram inside a five-bar mechanism and has the advantages of smaller actuation torque and larger stroke over the commercial adaptive gripper by RobotiQ. The forward/inverse kinematics and statics analyses for two types of linear actuations are derived. From the inverse kinematics and statics analyses, linear actuation type I is selected and the gripper prototype is designed.

• Coupled systems mechanics
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• v.6 no.2
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• pp.175-187
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• 2017

This paper deals with a uniform cantilever Euler-Bernoulli beam subjected to follower and transversal force at its free end as a model for a pipe conveying fluid under electromagnetic damper force. The electromagnetic damper is composed of a permanent-magnet DC motor, a ball screw and a nut. The main objective of the current work is to reduce the pipe vibration resulting from the fluid velocity and allow it to transform into electric energy. To pursue this goal, the stability and vibration of the beam model was studied using Ritz and Newmark methods. It was observed that increasing the fluid velocity results in a decrease in the motion of the free end of the pipe. The results of simulation showed that the designed semiactive electromagnetic damper controlled by on-off damping control strategy decreased the vibration amplitude of the pipe about 5.9% and regenerated energy nearly 1.9 (mJ/s). It was also revealed that the designed semi-active electromagnetic damper has better performance and more energy regeneration than the passive electromagnetic damper.

• The Journal of Korea Robotics Society
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• v.9 no.4
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• pp.264-271
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• 2014

In this study, we have developed the humanoid joint modules which provide a variety of service while living with people in the future home life. The most important requirement is ensuring the safety for humans of the robot system for collaboration with people and providing physical service in dynamic changing environment. Therefore we should construct the mechanism and control system that each joint of the robot should response sensitively and rapidly to fulfill that. In this study, we have analyzed the characteristic of the joint which based on the target constituting the humanoid motion, developed the optimal actuator system which can be controlled based on each joint characteristic, and developed the control system which can control an multi-joint system at a high speed. In particular, in the design of the joint, we have defined back-drivability at the safety perspective and developed an actuator unit to maximize. Therefore we establish a foundation element technology for future commercialization of intelligent service robots.

• Journal of Powder Materials
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• v.18 no.2
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• pp.181-187
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• 2011

PVDF was used as a polymeric matrix material in this work. Nickel powders with average particles size of 200 nm or 72 nm were used as fillers. PVDF/metal submicro- and nanocomposites were prepared by means of a mixing in twin screw extruder and planetary ball mill, respectively. All samples were prepared by hot pressing method. Their electrical, thermal and morphological properties were examined by dielectric spectroscopy, DSC, FTIR, XRD, optical microscopy and scanning electron microscopy. It was found that all properties of composites were strongly modified depending on the content of metal powders and filler particles size. Particularly, specific volume resistivity of PVDF/Ni composite with 0.2 wt.% of Ni was increased by factor of 1.5~4.