• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.687-692
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• 2015

LAM (Laser-Assisted Machining) is an effective method for processing difficult-to-cut workpieces. The focal length of a LAM system is changed by the change of the workpiece shape during laser preheating; this problem is solved by changing the lens of the laser module. Linear- and rotary-type lens changers were developed to change the laser lens of a LAM system. The linear-type lens changer is operated by a motor with a ball-screw, and the rotary type is operated by a stepping motor. The natural frequency and structural stability of the laser lens changers were confirmed by using a finite element analysis; in addition, the functions of the lens changers were verified by measuring the iterative accuracy. The measured results show that the rotary-type lens changer is more accurate than the linear-type changer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.981-984
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• 2004

This paper is about the development of Automatic FPC punching instrument. FPC(flexible printed circuit) is used to detect the contact position of K/B and button like a cellular phone. Depending on the quality of the printed ink and position of reference punching point to the FPC, the resistance and current are varied to the malfunctioning values. The size of reference punching point is 2mm and the above. Because the punching operation is done manually, the accuracy of the punching degree is varied with operator's condition. Recently, The punching accuracy has deteriorated severely to the 2mm punching reference hall so that assembly of the K/B has hardly done. To improve this manual punching operation to the FPC, automatic FPC punching system is introduced. Precise mechanical parts like a 5-step stepping motor and ball screw mechanism are designed and tested and low cost PC camera is used for the sake of cost down instead of using high quality vision systems for the FA. Test algorithm shows good results to the designed automatic punching system.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.2
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• pp.343-350
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• 2008

In this paper, a six degree-of-freedom robot arm which is very light but capable of delivering heavy loads was studied. The proposed robot arm has much higher load capacity than conventional robot arms actuated by motors with speed reducers such as the harmonic drive since a new type of robot actuator based on a closed chain mechanism driven by the ball screw was adopted. Analysis on the design scheme and on the mechanism of the joint actuator of the robot arm were made. Since the robot arm was designed very light, it has deflection in the links. To analyze this, a finite element analysis on the structure of the designed robot links was made using ANSYS software. Verifying experiments on the performance of high load capacity of the robot arm was performed by loading heavy weights on the robot arm. Through experiments. the correctness of the numerical analysis was also verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.435-442
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• 2010

The analysis of rigid body traveling along the rotating Timoshenko shaft has been a topic of interest. The problem arose from the observations that as a structure is subjected to moving loads, dynamic deflection as well as stresses can be significantly higher than those for static loads. The establishment of analytical method for the development and maintenance of performance is required in the fields of the machining operations and the position control using ball screw. The equations of motion for the rotating shaft subjected to the two moving forces are derived by using Hamilton's principle. Influence of system parameters such as the speed ratio, the mass ratio and the Rayleigh coefficient is discussed on the response of the moving system.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.621-625
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• 2005

This paper presents a new hybrid serial-parallel robot(HSPR), which has six degrees of freedom driven by ball screw linear actuators and motored joints. This hybrid robot design presents a compromise between high rigidity of fully parallel manipulators and extended workspace of serial manipulators. The hybrid robot has a large, singularity-free workspace and high stiffness. Therefore, the presented kinematic structure of the hybrid robot is particularly suitable for multi-tasking machining processes such as milling, drilling, deburring and grinding. In addition to the machining processes, the hybrid robot can be used for welding, fixturing, material handling and so on. The study on design of the hybrid robot is performed. A kinematic analysis and mechanism description of the hybrid robot with six-controlled degree of freedom is presented. In the virtual design works by DADS, workspace and force analysis are discussed. A numerical model is treated to demonstrate our analysis and to determine the range of permissible extension of the struts. Also, we determine some important design parameters for the hybrid robot.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.81-87
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• 2020

A stable rotational-to-linear motion transformation structure using a driving mechanism with 2 degrees of freedom was developed for an orthogonal mechanism to prevent the interference of each axis in 2D motion. In this mechanism, a step motor was used for precise position control. This structure was developed to maneuver workparts in micro particle blast machining experiments. To determine the real-time performance of micro particle blast machining, the control, input, and output were operated simultaneously and precise position control was implemented, using a timer interrupt with multiple execution codes. The two step motors obtained precise position control by removing backlash with a ball-screw mechanism. The device has menu-type control codes for user-friendliness, and real-time sequence control was simultaneously adopted for user control input.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.55-61
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• 2000

In this paper we have discussed on the characteristics and modeling of machined geometry which was established for the case of round shape machining also the effects of externally machined profile are analyzed and its modeling realia-bility was verified by the experiments of roundness testing especially in lathe operation. In this study we established a harmonic geometric model with the parameter harmonic function. In general we can calculate the theoretical roundness profile with an arbitrary multilobe parameter. But in real experiments only 2-5 lobe profile was frequently measured, The most frequently measured ones are 3 and 5 lobe profile in experiments. With these results we can predict that these results may be applied to round shape machining such as turning drilling boring ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. in this study simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling methods in real process for the predic-tion of part profile behaviors machined such as in round shape machining operation.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1221-1227
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• 2012

As demands on micro-products increase significantly with raising functional integration and increasing complexity, microfoming attracts a lot of attention in the manufacture of micro-products. Since the conventional big forming systems are not adequate to achieve sufficient tolerances of micro-scale parts, it is necessary to reduce the scale of the forming equipment and devices. In addition, understandings on the size effects, which exist in the material behavior and process characterization of microforming processes, need to be expanded. In this study, a miniaturized forming system based on the ball screw and servo motor actuator was developed for the efficient micro-parts production. In addition, tensile tests and cylindrical upsetting experiments were performed to evaluate the performance of the microforming system and to investigate the flow stress and friction size effects in microforming processes.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.41-49
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• 2010

Two promising control candidates have been selected to test the sinusoidal reference tracking performance for a brush-type polishing machine having strong nonlinearities and disturbances. The controlled target system is an oscillating mechanism consisting of a common positioning stage of one degree-of-freedom with a screw and a ball nut driven by a servo motor those can be obtained commercially. Beside the strong nonlinearity such as stick-slip friction, the periodic contact of the polishing brush and the work piece adds an external disturbance. Selected control candidates are a Sliding Mode Control (SMC) and a variant of a feedback linearization control called Smooth Robust Nonlinear Control (SRNC). A SMC and SRNC are selected since they have good theoretical backgrounds, are suitable to be implemented in a digital environment and show good disturbance and modeling uncertainty rejection performance. It should be also noted that SRNC has a nobel approach in that it uses the position information to compensate the stickslip friction. For both controllers analytical and experimental studies have been conducted to show control design approaches and to compare the performance against the strong nonlinearity and the disturbances.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1755-1762
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• 2004

Friction phenomenon can be described as two parts, which are the pre-sliding and sliding regions. In the motion of the sliding region, the friction force depends on the velocity of the system and consists of the Coulomb, stick-slip, Streibeck effect and viscous frictions. The friction force in the pre-sliding region, which occurs before the breakaway, depends on the position of the system. In the case of the motion of the friction in the sliding region, the LuGre model describes well the friction phenomenon and is used widely to identify the friction model, but the motion of the friction in the pre-sliding such as hysteresis phenomenon cannot be expressed well. In this paper, a modified friction model for the motion of the friction in the pre-sliding region is suggested which can consider the hysteresis phenomenon as the Preisach model. In order to show the effectiveness of the proposed friction model, the sliding mode controller (SMC) with hysteresis friction compensator is synthesized for a ball-screw servo system.