• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1841-1844
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• 2005

A linear motor makes a long stroke by accumulating short steps, which is based on the quasistatic deformation of a magnetostrictive material in a magnetic field. It's also called as inchworm effect. The application areas of linear motors are an adaptive and active optics, X-Y positioning, precision alignment, etc. It is found that control of the frequency and current inputs are all that is necessary to control the speed handling ability of the linear motor. In inchworm mode, linear speeds of up to $500{\mu}m/s$ are achieved resulting from the accumulation of $25{\mu}m$ steps at 1.4A.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.785-789
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• 2001

Piezoelectric actuators are characterized by non-linear dynamics and high frequency oscillations of the piezocrystal. Both properties have to be taken into consideration when optimizing real time systems. Taking benefit of the almost linear behaviour between charge and strain, current source fed piezoelectric actuators are given preference for high dynamic applications. Here special emphasis is put on current sources for multi-actuator systems and the controller design for optimal system integration of the actuator. It is shown that sliding mode operation of the converter system offers good possibilities to guaranty high accuracy and dynamics of the actuators system. The presented multi-actuator system is used for positioning and vibration damping in flexible mechanical systems.

• 한국정밀공학회지
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• 제23권5호
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• pp.184-189
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• 2006

This research presents the performance analysis of the linear type pneumatic actuators that are used in semi-conductor assembly line to transfer some product with high accuracy. To increase positioning and repetitive accuracies, a cross roller guide is implemented inside the pneumatic actuator. The finite element method is used to verify the force against working moments, and reliability analysis is performed to classify the breakdown cases. Also, reliability, failure rate, probability density function, and $B_{10}$ to life are estimated under the boundary of thrust or air leakage conditions. In this study, the failure probabilistic function of the pneumatic actuators is analyzed using Weibull distribution.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.997-1005
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• 2008

Linear motor stage is a useful device in precision engineering field because of its simple power transmission mechanism and accurate positioning. Even though linear motor stage shows fine positioning accuracy along travel axis, geometric dependent errors which relay on machining and assembling accuracy should be addressed to increase total positioning performances. In this paper, we suggests a cost effective yaw error compensation servo-system which is mounted on platform of the stage and nullify travel position dependent yaw error. This paper also provides a method of designing a sliding mode control which is robust to existing friction disturbance and model uncertainties. The reachability condition of slinding mode control for the yaw error compensating servo-system has been established. From some experimental results by using an experimental set-up, the sliding mode control showed its effective in disturbance rejection and its performance was superior to conventional linear controls.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.131-132
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• 2006

This paper presents a micro-positioning platform based on the unique parallel mechanism recently developed by the authors. The platform has a meso-scale rectangular shape whose size is $20{\times}23m$. The stroke is 5 mm for both the x- and y-axis and 100 degrees for the ${\alpha}$-axis(the rotational axis along the x-axis). The platform is actuated by the three sets of two-stage linear actuators: a linear motor for rough positioning and a piezo actuator for fine positioning. The platform is already assembled. Experimental results of the positioning measurements and control performance are presented.

• International Journal of Control, Automation, and Systems
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• 제2권3호
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• pp.279-288
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• 2004

This paper presents a novel design for a tubular linear brushless permanent-magnet motor. In this design, the magnets in the moving part are oriented in an NS-NS―SN-SN fashion which leads to higher magnetic force near the like-pole region. An analytical methodology to calculate the motor force and to size the actuator was developed. The linear motor is operated in conjunction with a position sensor, three power amplifiers, and a controller to form a complete solution for controlled precision actuation. Real-time digital controllers enhanced the dynamic performance of the motor, and gain scheduling reduced the effects of a nonlinear dead band. In its current state, the motor has a rise time of 30 ms, a settling time of 60 ms, and 25% overshoot to a 5-mm step command. The motor has a maximum speed of 1.5 m/s and acceleration up to 10 g. It has a 10-cm travel range and 26-N maximum pull-out force. The compact size of the motor suggests it could be used in robotic applications requiring moderate force and precision, such as robotic-gripper positioning or actuation. The moving part of the motor can extend significantly beyond its fixed support base. This reaching ability makes it useful in applications requiring a small, direct-drive actuator, which is required to extend into a spatially constrained environment.

• 한국정밀공학회지
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• 제21권12호
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• pp.174-181
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• 2004

Ultra precision positioning mechanism has widely been used on semiconductor manufacturing equipments, optical spectrum analyzer and cell manipulations. Ultra precision positioning mechanism is consisted of several actuators, sensors, guides and control systems. Its efficiency depends on each performance of components. The object of this study is to design, analysis and manufacture all of the inchworm linear motor system, which is one of the equipments embodied in ultra precision positioning mechanism. Inchworm linear motor system is consisted of a controller system and an inchworm linear motor, and its driving form is similar to a motion of spanworm. A design and manufacture of inchworm linear motor, which is consisted of three PZT actuators, a rod, two columns and a guide plate, are performed. Minimizing the von-Mises stress of the hinge using Taguchi method and simulation by FEM software optimizes the structural design in a column of flexure hinge. The designed columns and guide plates are manufactured by a W-EDM and NC-milling. A controller system, which is an apparatus to drive inchworm linear motor, can easily adjust driving conditions by varying resonance frequency and input-output voltage of actuators and amplifiers. The performance of manufactured inchworm linear motor system is verified and valuated. In the future, inchworm linear motor system will be used to make a more precision positioning by reinforcing a sensor and feedback system.

• 한국정밀공학회지
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• 제22권7호
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• pp.102-111
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• 2005

In this paper, we address a position control for a parallel stage, which is levitated and driven by electric magnetic force. This consists of a levitating object (called platen) with 4 permanent magnetic linear synchronous motors in parallel. Each motor generates vertical force for suspension against gravity and propulsion force horizontally as well. This stage can generate six degrees of freedom motion by the vertical and horizontal force. A dynamic equation of the stage system is derived based on Newton-Euler method and it's special Jacobian matrix describing a relation between the limited velocity and Cartesian velocity is done. There are proposed two control methods for positioning which are Cartesian space controller and Actuator space controller. The control performance of the Cartesian space controller is better than the Actuator space controller in task space trajectory while the Actuator space controller is simpler than the Cartesian space controller in controller realization.

• 한국정밀공학회지
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• 제19권12호
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• pp.163-170
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• 2002

The quality of a precision product, in general, relies on the accuracy and precision of its manufacturing and inspection process. In many cases, the level of precision in the manufacturing and inspection system is also dependent on the positioning capability of tool with respect to the work piece in the process. Recently the positioning accuracy level has reached to the level of submicron and long range of motion is required. For example, for 1 GDARM lithography, 20nm accuracy and 300mm stroke needs. This paper refers to the lithography stage especially to fine stage. In this study, for long stroke and high accuracy, the dual servo system is proposed. For the coarse actuator, LDM (Linear DC Motor) is used and for fine one VCM is used. In this study, we propose the new structure of VCM for the fine actuator. It is 3 axis precision positioning stage for an aligner system. After we perform the optimal design of the stage to obtain the maximum force, which is related to the acceleration of the stage to accomplish throughput of product. And we controlled this fine stage with TDC. So we obtained 50nm resolution. So later more works will be done to obtain better accuracy.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권1호
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• pp.33-39
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• 2005

In this paper, we propose a slider servo-mechanism driven by electro-magnetic actuator to improve straightness of linear motor stages. Based on axial-position dependent deterministic characteristics of the straightness error, a feedforward compensation control is appled to reduce the straightness error. In the consideration of uncertain properties of friction and its effects on positioning accuracy, a sliding mode control is applied. The effectiveness of the suggested mechanism and the control performances are illustrated along with some experimental results.