• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.147-155
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• 2001

A new displacement type web position control system for cold mills using QFT is presented. The control system features an inner-outer cascaded system in which the inner loop provides the position tracking control of the hydraulic system and the outer loop provides the position regulation control of the web. By the sensitivity analysis and computer simulation, it is verified that the proposed control system has better robust stability and performance than the conventional control system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.385-389
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• 1992

The position control of the electro-hydraulic servo indexing system in a flexible forging machine was investigated. The role of an Electro-hydraulic servoindexing system is to rotate a workpiect fast and accurately to a desired position. Since the inertia of a workpiece changes during each forging step, an adapt control scheme could be adopted to the position control of the workpiece. A generalized predictive control method which depends on predicting the plant output over several steps ahead based on the assumption about future control actions is proposed. The perormance of the proposed GPC algorithm is investigated experimentally and compared with that of PID control. Experimental results show that the proposed GPC algorithm is satisfactory for the position control of the workpiece of an electrohydraulic indexing system.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.155-163
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• 1996

This paper presents vibration and position tracking control of a smart structure using shape memory alloy(SMA) actuators. A governing equation of motion of the proposed structure is obtained via Hamilton's princeple. The dynamic characteristics of the SMA actuator are experimentally identified and incorporated with the governing equation to furnish a control system model. Subsequently, a sliding mode controller which has inherent robustness to external disturbances is formulated on the basis of the sliding mode conplacement, and also for the position tracking control of desired trajectories with low-frequency sine and square waves.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.344-344
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• 2000

Recently, the demand for high precision and large stroke in linear positioning systems is increasing in industry. A coarse-fine position control system composed of a linear motor and a piezoelectric actuator has such characteristics. Many optimal control laws have been applied to the position control of coarse-fine actuators but most of them did not take account into constraints. In this study, model predictive control (MPC) method with constraints is applied to the position control of the coarse-fine actuator and the performance of MPC is compared with those of conventional control laws.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.383-388
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• 2004

A piezoelectric actuator yields hysteresis effect due to its composed ferroelectric. Hysteresis nonlinearty is neglected when a piezoelectric actuator moves with short stroke. However when it moves with long stroke and high frequency, the hysteresis nonlinearty can not be neglected. The hysteresis nonlinearty of piezoelectric actuator degrades the control performance in precision position control. In this paper, in order to improve the control performance of piezoelectric actuator, an inverse modeling scheme is proposed to compensate the hysteresis nonlinearty problem. And feedforward - feedback controller is proposed to give a good tracking performance. The Feedforward controller is inverse hysteresis model, Nueral network and PID control is used as a feedback controller. To show the feasibility of the proposed controller and hysteresis modeling, some experiments have been carried out. It is concluded that the proposed control scheme gives good tracking performance

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.349-352
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• 1997

A Piezoelectric actuator yields hysteresis effect due to its composed ferroelectric. Hysteresis nonlinearity is neglected when a piezoelectric actuator moves with short stroke. However when it moves with long stroke and high frequency, the hysteresis nonlinearity can not be neglected. The hysteresis nonlinearity of piezoelectric actuator degrades the control performance in precision position control. In this paper, in order to improve the control performance of piezoelectric actuator, an inverse modeling scheme is proposed to compensate the hysteresis nonlinearity problem. And feedforward-feedforward-feedback controller is proposed to give a good tracking performance. The Feedforward controller is inverse hysteresis model, and PID control is sued as a feedback controller. To show the feasibility of the proposed controller and hysteresis modeling, some experiments have been carried out. It is concluded hat the proposed control scheme gives good tracking performance.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.2
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• pp.48-56
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• 2001

This paper presents the position tracking control of a closed-loop cylinder system using electro-rheological (ER) valve actuators. After manufacturing three sets of cylindrical ER valves on the basis of Bingham model of ER fluid, a 3 dof(degree-freedom) closed-loop cylinder system having the heave, roll and pitch motions is constructed. The governing equations of motion are derived using Lagrange's equation and a control model is formulated by considering nonlinear characteristics of the system, Sliding mode controllers are the designed for these ER valve actuators in order to achieve position tracking control. The effectiveness of trajectory tracking control performance of the proposed cylinder system is demonstrated through computer simulation and experimental implementation of the sliding mode controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.225-229
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• 1996

This paper presents an active position control of a moving table utilizing ER(electro-rheological) brake and ER clutch. A transformer oil-based ER fluid is composed and its Bingham properties are evaluated with respect to electric fields. The dynamics of the actuators : ER brake and ER clutch, are identified through experiments, and subsequently the governing equation of motion of the moving table system is formulated from the governing equation, a sliding mode controller is designed to achieve an accurate position control. Both simulation and experimental results and presented in order to demonstrate the effectiveness of the proposed control methodology.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.432-438
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• 2005

In this paper, the high precision position control of AC Servo motor for semiconductor equipment is studied. The control system was implemented using TI DSP TMS320F2812 which has 150 MIPS speed for next generation motor control. The controlled 100W PMSM motor has 2,500 ppr optical incremental encoder. The control system has speed controller and current controller to control the motor position. The encoder pulses are divided into 4 times, which has 10,000 ppr and the motor system has the position accuracy of 1/10,000. If the resolution of the encoder is increased, the resolution of the position control will be increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.260-264
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• 2005

This paper describes the ultra precise position control of servo motor using sinusoidal encoder based on 'Arcsine Interpolation Method'. First, the paper theoretically analyzes and verify throughout experiments, the relationship between A/D converter input ripple and the total resolution to measure the precise position. Second, this paper presents a way to compensate the total gain and offset error by utilizing a low cost programmable differential amp, by which without any special expensive equipments they are easily on-line tuned and effectively compensated. Lastly, it was compared to servomotor position control characteristics using digital incremental 50,000ppr encoder. The test results show that, with much cheaper sinusoidal encoder, the proposed method exhibits better performance both in position control and ASD applications than the 50,000ppr optical encoder.