• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제34권3호
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• pp.74-80
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• 2006

This paper deals with the control and fault monitoring of a DDV hydraulic actuation system. A hydraulic servo system has a nonlinear dynamics of an orifice flow through a valve spool. A full nonlinear model for a DDV actuation system is driven, and linearized to a simple model which is convenient for a control loop and fault monitor design. A top level requirement on the performance and safety for the actuation system is introduced. A control system and fault monitoring structure which can meet these requirements are discussed. A simulation package for a DDV actuation system which has a triplex redundant structure is developed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.405-413
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• 2006

In general mechanical servo systems, friction deteriorates the performance of controllers by its nonlinear characteristics. Especially, friction phenomenon causes steady-state tracking errors and limit cycles in position and velocity control systems, even though gains of controllers are tuned well in linear system model. Even if sensor is used higher accuracy level, it is difficult to improve tracking performance of the position to the same level with a general control method such as PID type. Therefore, many friction models were proposed and compensation methods have been researched actively. In this paper, we consider that the variation of mover's mass is various by loading and unloading. The normal force variation occurs by it an other parameters. Therefore, the proposed control system is composed of main position controller and a friction compensator. A parameter estimator for a nonlinear friction model is designed by adaptive control law and adaptive backstepping control method.

• Journal of Navigation and Port Research
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• 제31권1호
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• pp.55-64
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• 2007

In general mechanical servo systems, friction deteriorates the performance of controllers by its nonlinear characteristics. Especially, friction phenomenon causes steady-state tracking errors and limit cycles in position and velocity control systems, even though gains of controllers are tuned well in linear system model. Even if sensor is used higher accuracy level, it is difficult to improve tracking performance of the position to the same level with a general control method such as PID type. Therefore, many friction models were proposed and compensation methods have been researched actively. In this paper, we consider that the variation of mover's mass is various by loading and unloading. The normal force variation occurs by it and other parameters. Therefore, the proposed control system is composed of main position controller and a friction compensator. A parameter estimator for a nonlinear friction model is designed by adaptive control law and adaptive backstepping control method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• 제15권3호
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• pp.93-101
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• 2016

This study presents a simple genetic algorithm to systematically design a PID controller for a hydraulic positioning system operated by a proportional solenoid valve. The inverse dead-zone compensator with nonlinear characteristics is used to cancel out the dead-zone phenomenon in the hydraulic system. The object function considering overshoot, settling time, and control input is adopted to search for optimal PID gains. The designed PID controller is compared with the LQG/LTR controller to check the performance of the hydraulic positioning system in the time and frequency domains. The experimental results show that the hydraulic servo system with the proposed PID controller responds effectively to the various types of reference input.

• Journal of the Korean Society for Precision Engineering
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• 제18권6호
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• pp.133-140
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• 2001

This paper suggests another system for a cutting force measuring tool in a milling process. Generally, tool dynamometer is taken into account for the most appropriate cutting force measuring tool in the analysis of cutting mechanism. However, high price and limited space make it difficult to be in-situ system for controllable milling process. Although an alternative method using AC current of servo-motor has been suggested, it is unsuitable for cutting force control because of small upper frequency limit and noise. The cutting force measuring system is composed of two load cells placed between the moving table bracket and the nut flange part of ballscrew. It has many advantages such as low cost and wide range measurement than tool dynamometer because of the built-in moving table and the low cost load cell. The static and dynamic model of the measuring system using imbeded load cell is introduced. Various Experiments are carried out to validate both models. By comparing the cutting forces from a series of end milling experiments on the tool dynamometer and the system developed in this paper, the accuracy of the cutting force measuring system is verified. Upper frequency limit is measured by the experiment of dynamic characteristics.

• Proceedings of the KIEE Conference
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1027-1030
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• 1996

The purpose of this study was to develop systematic diagnostic system testing easily, rapidly vestibular function of patients suffered from vestibular syndrome such as nausea vomiting, dizzness, ataxia. Diagnostic system composed of rotatory chair system which rotated sinusoidally patients against their vertical axis for purpose of invoking eye movement by vestibulo-ocular reflex and the softwares which storaged eye movement into computer and analyzed eye movement. Rotatory chair system consisted of comfortable chair and DC servomotor with reducer(1:80) by controlled servo in field of nonlinear motor control, double feedback loops system containing velocity feedback loop and position feedback loop was applied to this sever controlled rotatory chair system. Maximum rotatory velocity of rotatory chair was upto 60 degree per second and frequency range was 0.01 to 0.64 Hz. These above results suggest that clinical rotatory chair system may test easily, rapidly vestibular function and diagnose etiology of dizziness, thus giving effective assistance on the treatment of dizziness patients.

• Journal of Institute of Control, Robotics and Systems
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• 제6권11호
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• pp.1022-1032
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• 2000

We propose a sliding mode controller tracking the states of a time-varying reference model. The reference model generates the desired trajectories of the states, and the sliding mode controller regulates robustly the errors between the desired states and the measured states. We apply this controller to the overhead crane. Its reference model generates the trajectories of the damped-out swing angle and the swing angular velocity to suppress the swinging motion caused by the acceleration and the deceleration of crane transportation. Also, this model generates the desired trajectories of the position and velocity of the crane. The crane model is identified from the experimental data using an orthogonal function. Kalman filtering is applied to estimate the crane states. The designed controller is simulated on a computer and is tested through a 2-ton industrial overhead crane using the vector-controlled servo motor system. It is verified that, from the simulated and experimental results, the sliding mode controller tracking a time-varying reference model works well.

• The Transactions of the Korean Institute of Power Electronics
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• 제3권3호
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• pp.214-221
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• 1998

A new control approach using neural network for the robust position control of a BRUSHLESS direct drive(BLDD) motor is presented. The linear quadratic controller plus feedforward neural network is employed to obtain the robust BLDD motor system approximately linearized using field-orientation method for an AC servo. The neural network is trained in on-line phases and this neural network is composed by a feedforward recall and error back-propagation training. Since the total number of nodes are only eight, this system will be easily realized by the general microprocessor. During the normal operation, the input-output response is sampled and the weighting value is trained by error back-propagation at each sample period to accommodate the possible variations in the parameters or load torque. And the state space analysis is performed to obtain the state feedback gains systematically. In addition, the robustness is also obtained without affecting overall system response.

• Journal of the Korean Society for Precision Engineering
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• 제13권2호
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• pp.133-145
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• 1996

This paper presents an indirect cutting force measuring system, which uses the current signals from the AC servo drive units of the horizontal machining center, with its applications to the adaptive regulation of the cutting forces in various milling processes and to the on-line monitoring of tool breakage. A typical model for the feed-drive control system of a horizontal machining center is developed to analyze cutting force measurement from the drive motor. The pulsating milling forces can be measured indirectly within the bandwidth of the current feedback control loop of the feed-drive system. It is shown that the indirectly measured cutting force signals can be used in the adaptive controller for cutting force regulation. The whole scheme has been embedded in the commercial machining center and a series of cutting experiments on the face cutting processes are performed. The adaptive controller reveals reliable cutting force regulating capability against the various cutting conditions. It is also shown that the tool breakage in milling can be detected within one spindle revolution by adaptively filtering the current signals. The effect of the cutter run-out has been considered for the reliable on-line detection of tool breakage.

• The Transactions of the Korean Institute of Power Electronics
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• 제20권5호
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• pp.456-463
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• 2015

Nowadays, small quantity batch production, which is so-called a flexible manufacturing system, is a major trend in the modern factory automation industry. The demands for new transportation system are increased gradually, with which multiple passive carriers carrying materials and semi-products are precisely and individually controlled along a single closed rail. Thus, a new type of permanent magnet linear synchronous motor (PMLSM), which consists of state coils on a single rail and PM movers as many as carriers, is proposed in this paper. The rail can be segmented as modules with pairs of coils and a current amplifier, which makes the transportation system simple; therefore, the rail can be easily extended and repaired. A design method of the new PMLSM with a single carrier is proposed, which can be thought as a new version of PMLSM, a coil-segmented coreless PMLSM (CS-CLPMLSM). Experimental setup for it is made, and propulsion results show that with the help of a new effective coil selection and switching algorithms, the conventional current-based vector control is sufficient to fulfill the position and velocity control of the new PMLSM. The proposed PMLSM is expected to fulfill seamless servo-control of multiple carriers also in process line, such as a new generation of flat panel display manufacturing line.