• Journal of the Korean Society for Precision Engineering
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• v.32 no.3
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• pp.263-268
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• 2015

This paper describes lost motion analysis for a novel 6-DOF ultra-precision positioning stage. In the case of flexure hinge based precision positioning stage, lost motion is generated when the displacement of actuator is not delivered completely to the end-effector because of the elasticity of flexure hinge. Consequently, it is need to compute amount of lost motion to compensate the motion or to decide appropriate control method for precision positioning. Lost motion analysis for the vertical actuation unit is presented. The analysis results are presented in two ways: analytic and numerical analyses. It is found that they closely coincide with each other by 1% error. In finite element analysis result, the amount of lost motion is turned out to be about 3%. Although, the amount is not so large, it is necessary procedure to check the lost motion to establish the control method.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.926-931
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• 2012

Since robot industry growing, the machine that could move with multi-DOF has been studied in many industrial fields. Spherical motor is one of the multi-DOF machine that doesn't need gear for multi-DOF motion. Unlike conventional motor, spherical motor can not only rotate on the shaft axis (rotating motion), but tilt the shaft with 2-DOF motion (positioning motion). In the typical type of spherical motor, one coil took part in positioning motion and rotating motion at the same time. As the result, the control algorithm was complex. To solve this problem, this study proposed a novel type of coil on the stator. The coils were separated for positioning motion and rotating motion. Thus the linkage flux of rotating coil didn't be affected the positioning angle. In this paper, comparing the back-EMF of typical and novel type was conducted and the driving experiment was carried out as the positioning angle. From the experiment result, the performance of proposed spherical motor could be verified.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.247-250
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• 1996

In this paper, we have examined the impedance characteristics of a tipper link of human being in a positioning motion. Firstly, we have shown the characteristics of the human arm using a bilinear model. From the bilinear model, we have observed that both the driving torque of the forearm and the visco-elasticity of the elbow joint can be controlled by muscles, respectively. Then, we have defined several indexes to show the impedance characteristics. Using the proposed indexes, we have examined the impedance characteristics in the positioning operation. As a result, we can not observe the difference of the impedance characteristics, even if the ease of the positioning motion is varied.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.275-284
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• 2011

The accuracy simulation technology of linear motion system is introduced in this paper. Motion errors and positioning errors are simulated using informations on the design parameters of elements of linear motion system. 5 Degree-of-freedom motion error analysis algorithm utilizing the transfer function method and positioning error analysis algorithm which are main frame of accuracy simulation are introduced. Simulated motion errors are compared with experimental results for verifying the effectiveness. Then, using the proposed algorithms, simulation is performed to investigate the effects of ballscrew and linear motor on the motion errors. Finally, the influence of feedback sensor position on the positioning error is also discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.986-992
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• 2014

This research investigates experimentally and numerically the tilting angle, eccentricity ratio, flying height of axial direction, friction torque, and critical mass of the HDD disk-spindle system due to HDD positioning angle. The tilting angle and the eccentricity ratio are the maximum when the HDD positioning angle is $90^{\circ}$ respect to horizontal position because the external force in radial direction and the torque applied to the rotating part are the maximum when the HDD positioning angle is $90^{\circ}$. The flying height increases with the increase of the HDD positioning angle because the direction of gravity applied to the rotating part changes. The friction torque increases with the increase of the HDD positioning angle until it becomes $60^{\circ}$, and decreases with the increase of the HDD positioning angle after it becomes $60^{\circ}$. The stability is the maximum when the HDD positioning angle is $90^{\circ}$.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.129-137
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• 2016

In the present study we verified performance of feed-forward control algorithm using short term prediction of ship motion information by taking advantage of developed numerical simulation model of FPSO motion. Up until now, various studies have been conducted about thrust control and allocation for dynamic positioning systems maintaining positions of ships or marine structures in diverse sea environmental conditions. In the existing studies, however, the dynamic positioning systems consist of only feedback control gains using a motion of vessel derived from environmental loads such as current, wind and wave. This study addresses dynamic positioning systems which have feedforward control gain derived from forecasted value of a motion of vessel occurred by current, wind and wave force. In this study, the future motion of vessel is forecasted via Brown's Exponential Smoothing after calculating the vessel motion via a selected mathematical model, and the control force for maintaining the position and heading angle of a vessel is decided by the feedback controller and the feedforward controller using PID theory and forecasted vessel motion respectively. For the allocation of thrusts, the Lagrange Multiplier Method is exploited. By constructing a simulation code for a dynamic positioning system of FPSO, the performance of feedforward control system which has feedback controller and feedforward controller was assessed. According to the result of this study, in case of using feedforward control system, it shows smaller maximum thrust power than using conventional feedback control system.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.1
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• pp.82-89
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• 2003

A robust motion control method is proposed fur the point-to-point position control of a XY positioning system which consists of a base cart, elastic ben and moving mass. The horizontal motion controller consists of the feedforward controller to suppress the single mode vibration of the elastic beam and the feedback controller to get the high-accuracy positioning performance of the base cart. Input preshaping vibration suppression method based on system modeling with analytic frequency equation is proposed and integrated into the robust internal-loop compensator(RIC) to increase the robustness of the whole closed-loop system The vertical motion controller is proposed based on the dual RIC structure. Through experiments, it is shown that the proposed method can stabilize the system and suppress the vibration in the presence of uncertainties and disturbances.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.117-118
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• 2007

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.212-217
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• 1993

In this paper, characteristics of the motions of a human arm are investigated experimentally. When the conditions of the target point are restricted, human adjusts its trajectory and velocity pattern of the arm to fit the conditions skillfully. The purpose of this work is to examine the characteristics of the trajectory, velocity pattern, and the size of the duration in the following cases. First, we examine the case of point-to-point motion. The results are consistent with the minimum jerk theory. However, individual differences in the length of the duration can be observed in the experiment. Second, we examine the case which requires accuracy of positioning at the target point. It is found that the velocity pattern differs from the bell shaped pattern explained by the minimum jerk theory, and has its peak in the first half of the duration. When higher accuracy of the positioning is required, learning effects can be observed. Finally, to examine the case which requires constraint of the arm posture at the target point, we conduct experiments of a human trying to grasp a cup. It is considered that this motion consists of two steps : one is the positioning motion of the person in order to start the grasping motion, the other is the grasping motion of the human's hand approaching toward the cup and grasping it. In addition, two representative velocity patterns are observed : one is the similar velocity pattern explained in the above experiment, the other is the velocity pattern which has its relative maximum in the latter half of the duration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.539-542
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• 1997

We present a micro-positioning stage that has minimized geometrical error and can drive in the 4-axis. This stage divided into two parts: $Z\theta_x$ $\theta_y$, motion stage and$\theta_z$ motion stage. These stages are constructed in flexure hinges, piezoelectric actuators and displacement scnsors. The dynamic model for each stage is obtained and their FE (finite element) models are made. Using the Lagrange's equation, the motion of equation is found. Through the parametric analysis and FE analysis, sensitiv~ty of the design parameters is executed. Finally, fundamental frequencies, maximum stress, and displacement sensitivity for each stage are obtained. We expect that this micro-positioning stage be a useful micro-alignment device for various applications.