• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.71-79
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• 2008

In the manufacture of flat panel display devices, there is a strong demand for contactless glass panel handling devices that can manipulate a glass panel without contaminating or damaging it. To fulfill this requirement, an electrostatic suspension device far glass panels where the glass panel is supported by electrostatic forces without any mechanical contact is proposed. To implement the system with low cost and compactness, switched-voltage control scheme that is based on the relay feedback control is utilized. Relay feedback control method deploys only a single high-voltage power supply that can deliver a DC voltage of positive and/or negative polarity and thus high voltage amplifiers that are costly and bulky are not needed any more. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping originating from the electrodes and levitated object. Using this scheme, a $100{\times}100mm^2$ glass panel was levitated stably with airgap variation decreasing down to $1\;{\mu}m$ at an airgap of $100\;{\mu}m$.

• International Journal of Automotive Technology
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• v.3 no.1
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.229-234
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• 2005

A novel method to measure the interaction movement, focusing direction and tracking direction in an optical pick-up, is proposed and the decoupling control for it is discussed. First, the basic principle of the coupline analysis method using back electromotive farce is introduced. Second, the interaction analysis between focusing direction and tracking direction fur commercial slim type actuator is performed using the proposed method. Finally, the coupling analysis and decoupling control for the slim type optical pick-up are discussed. From the brief simulation, we shows that the effectiveness and validity of the proposed method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.229-232
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• 2002

This paper describes the development of robot's finger 3-axis force sensor that detects the Fx, Fy, and Fz simultaneously fur stably grasping an unknown object. In order to safely grasp an unknown object using the robot's fingers, they should detect the force of gripping direction and the force of gravity direction, and perform the force control using the detected farces. The 3-axis force sensor that detects the Fx, Fy, and Fz simultaneously should be used for accurately detecting the weight of an unknown object of gravity direction. Thus, in this paper, robot's finger for stably grasping an unknown object is developed. And, the 3-axis farce sensor that detects the Fx, Fy, and Fz simultaneously fur constructing a robot's finger is newly modeled using several parallel-plate beams, and is fabricated. Also, it is calibrated, and evaluated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.431-434
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• 2002

In this study, the dynamic absorbing system using MR damper for the multiple structure system with high-level-impact force has been investigated. Based on the experiment and analysis of short recoil system, the dynamic absorbing system has been constructed by using MR damper and stroke-dependent variable damper. Through a series of experimental works with the devised test bench, the absorbing system with MR damper using reverse control is effective for reduction of the transmitted force, furthermore, for implementation to the multi-structure impulsive force system.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.226-228
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• 1994

In this paper, a moving iron core type LOA is designed and analyzed electro-magnetically and is applied to the active control of structural vibration as an active mass driver. Structural vibration is sensored by the accelerometer attached the structure and reduced by the optimally controlled motion of active mass of LOA giving anti-phase inertia farce to the structure. As a result, the basement of the application of LOA as an active mass driver is successfully established.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.80-91
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• 2008

Electrostatic forces have an advantage of directly levitating not only non-ferromagnetic metals but also semiconductors, such as silicon wafers, and dielectric materials like glass. This paper describes the characteristics of electrostatic forces and electrostatic suspension system, followed by the basic principle of 1-DOF(degree of freedom) electrostatic suspension system, and the structures of electrodes-for-suspension and voltage supplying methods to the electrodes in 1-DOF model. This paper also discuss about the minimum number of electrodes needed to control n-DOF motion of the suspended object and represents some desirable electrode patterns to stabilize the 6-DOF motion of the object. In the near future, electrostatic suspension system is expected to be applied to industrial manufacturing processes, for example, to the manufacture of semiconductor devices and/or flat panel display devices.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.96-99
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• 2001

The fatigue life of support bearings is one of the most critical factors for the performance of a control rod driving mechanism. They are operated at high temperature and high pressure and especially lubricated with dramatically low viscosity water. The support bearing is made of standardized 440C stainless steel, and it supports thrust load including the weight of the driving system and external force. Friction and wear characteristics of this material operating under severe lubrication condition is not well known yet, although it is expected to be changed with respect to temperature and boundary pressure. So the friction characteristics are investigated in sliding conditions using the reciprocating tribometer which can simulate the operating conditions. Highly purified water is used as lubricant, and the water is heated up and pressurized. Friction farce on the reciprocating specimens is monitored by the load cells. The results of the experiments are presented in this paper.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.4
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• pp.350-356
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• 2004

This paper presents a farce manipulability analysis of multi-legged walking robots, which calculates force or acceleration workspace attainable from joint torque limits of each leg. Based on the observation that the kinematic structure of the multi-legged walking robots is basically the same as that of multiple cooperating robots, we derive the proposed method of analyzing the force manipulability of walking robot. The force acting on the object in multiple cooperating robot systems is taken as reaction force from ground to each robot foot in multi-legged walking robots, which is converted to the force of the body of walking robot by the nature of the reaction force. Note that each joint torque in multiple cooperating robot systems is transformed to the workspace of force or acceleration of the object manipulated by the robots in task space through the Jacobian matrix and grasp matrix. Assuming the torque limits are given in infinite norm-sense, the resultant dynamic manipulability is derived as a polytope. The validity of proposed method is verified by several examples, and the proposed method is believed to be useful for the optimal posture planning and gait planning of walking robots.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.5
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• pp.451-456
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• 2005

This paper describes three kinds of experiments and analysis of their results related to human tactile sensitivity using an integrated tactile display system. The device can provide vibration, normal pressure and lateral slip/stretch which are important physical quantities to sense texture. We have tried to find out the efficient method of stimulating, limitation of surface discrimination by kinesthetic farce feedback and the effectiveness of the combination of kinesthetic force and tactile feedback. Seven kinds of different stimulating methods were carried out and they are single or combination of the kinesthetic force, normal static pressure, vibration, active/passive shear and moving wave. Both prototype specimen and stimulus using tactile display were provided to all examinees and they were allowed to answer the most similar sample. The experimental results show that static pressure is proper stimulus for the display of micro shape of the surface and vibrating stimulus is more effective for the display of fine surface. And the sensitivities of active touch and passive touch are compared. Since kinesthetic force feedback is appropriate to display shape and stiffness of an object, but roughness display has a limitation of resolution, the concurrent providing methods of kinesthetic and tactile feedback are applied to simulate physical properties during touching an object.