• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.317-320
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• 1999

A robust end time optimal conかof strategy for dual-stage servo system is presented. The time optimal trajectory for a mass-damper system is determined and given os a reference input to the servo system. The feedback controller is constructed so that the fine stage tracks the coarse stage errors and robustly designed as the“perturbation compensated sliding mode control(PCSMC)”law, a combination of slid-ing mode controller(SMC) and perturbation observer(PO). In addition, a null motion controller which regulates the fine stage at its neutral position is designed based on the“dynamic consistency”So, the overall dual-stage servo system exhibits the robust and time-optimal performance. The inherent merit and performance of the dual-stage system will be shown.

• 한국생산제조학회지
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• 제22권2호
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• pp.206-215
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• 2013

In this paper, a synchronization control technique of dual-servo motor driven press system is proposed. An independent cascade PID control technique has been applied to the conventional press system for advancement of control stability. However, it is not easy to reduce synchronous error using the independent cascade PID control technique when some different load disturbances are involved in each motor. The eccentric error of the slide caused by the problem degrade the control performance of the BDC(Bottom Dead Center). In order to achieve reduction of the synchronous error between two servo motors and accurate position control simultaneously, a new control scheme comprised with cascade PID control loop and cross-coupling loop is proposed. In simulation using Matlab SIMULINK, the AC servo system is designed. The control performance of proposed technique is compared with conventional control technique to the model of AC servo system. Also, the sub-scale model of dual-servo motor driven press system which can replicate the slide motion is constructed for experimental verification for the performance of the proposed control technique. The cross-coupling control technique reveals more precise and stable performances in the position and synchronization controls.

• 한국정밀공학회지
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• 제23권2호
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• pp.43-50
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• 2006

Recently, with rapid development of semiconductor and flat panel display, the manufacturing equipments are required to have large travel range, high productivity, and high accuracy. In this paper, an ultra precision decoupled dual servo (DDS) system is proposed to meet these requirements. And a control scheme for the DDS is studied. The proposed DDS consists of a $XY{\Theta}$ fine stage for handling work-pieces precisely and a XY coarse stage for large travel range. The fine stage consists of four voice coil motors (VCM) and air bearing guides. The coarse stage consists of linear motors and air bearing guides. The DDS is mechanically decoupled between coarse stage and fine stage. Therefore, both stages must be controlled independently and the performance of the DDS is mainly determined by the fine stage. For high performance tracking, the controller of fine stage consists of time delay control (TDC) and perturbation observer while the controller of coarse stage is TDC alone. With these individual controllers, two kinds of dual-servo control strategies are suggested: master-slave type and parallel type. By simulations and experiments, the performances of two dual-servo control strategies are compared.

• Journal of Electrical Engineering and Technology
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• 제2권1호
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• pp.50-54
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• 2007

In this paper, a dual-servo type VCM (Voice Coil Motor) for the measuring of nano-level displacement and small thrust is proposed and developed. The shape of VCM for improving the resolution of displacement and ensuring a large displacement are presented. The FEM (finite element method) is utilized to analyze the characteristics of VCM that produces linear driving thrust and satisfies the thrust that the measurement system requires. The Prototype is fabricated and an experiment is performed in order to measure displacement. As a result of simulation and testing, the proposed VCM shows the applicable possibility for a nano-level measurement system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2013년도 춘계학술대회 논문집
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• pp.817-818
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• 2013

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.46-51
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• 2001

To reach high areal density, less track pitch is expected and more servo bandwidth is required. One approach to overcoming the problem is by using dual stage servo system. In this system, a voice coil motor (VCM) is used as the primary stage while a milliactuator is used as the secondary stage. We have suggested new milliactuator based on the shear mode of piezoelectric elements to drive the head suspension assembly. In this paper, we introduce controller design method, PQ method. PQ method reduces the controller design problem for DISO(dual-input/single-output) systems to two standard controller design problems for SISO(single-input/single-output) problems. The first part of PQ method directly address the issue of actuator output contribution, and the second part allows the use of traditional loop shaping to achieve the overall system performance. This paper shows how to employ the PQ method to meet aggressive close-loop performance specifications for a disk drive system with a VCM and piezoelectric milliactuator.

• 한국정밀공학회지
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• 제24권2호
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• pp.86-94
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• 2007

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve control performances such as small rise time, small overshoot, small settling time, small stabilization error etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving responses and attenuating the disturbance response related with dynamic coupling.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.37-38
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• 2012

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.175-178
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• 1991

The drive system of servo motor is requested to have robustness of disturbance and parameter variation. However, the dynamics of PMSM drive change significantly by forced disturbance and parameter variation. Moreover, the state error caused by them should be suppressed completely and rapidly. In this paper, the vector-control system of PMSM using dual adaptive control loop is investigated. In the proposed system, linear adaptive control loop rapidly recovers the state error caused by both disturbance and parameter variation. In the dual adaptive control loop, the inner loop reduces the system sensitivity of parameter variation and disturbance, and the outer loop suppresses the state error caused by them completely. The proposed servo system is verified through a computer simulations and experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.2087-2092
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• 2005

Using disturbance observer (DOB) is effective in enhancing the performance of dynamic system in the presence of disturbances. Recently the definition of disturbance has been expanded to modeling uncertainty including parameter variation, internal disturbance. Various structures of DOB have been proposed to improve sensitivity of system for better disturbance rejection performance. However in the case of improvement of sensitivity function, it tends to bring poor transient response due to cross-coupling and phase lag. Furthermore it could be very sensitive to measurement noise due to increased peak of complementary sensitivity function. In this paper, a dual disturbance observer (Dual-DOB) is proposed to reduce the effect of such cross-coupling. It is possible for us to improve the sensitivity function with additional external DOB with hardly affecting complementary sensitivity function. Thus it is able to have robustness against measurement noise. Since we are able to design DOBs of internal and external loop independently, we could prevent transient response quality from degrading while improving the sensitivity function. The proposed Dual-DOB is applied to a commercial optical disk drive tracking servo system. The experimental result shows that the Dual-DOB is an effective method in rejecting the disturbance as well as improving the tracking performance.