• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.249-253
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• 2016

In this study, a harmonic-pulsation-compensator (HPC) is presented to reduce a periodic speed ripple in IPMSM. A proportional-integral compensator in HPC is proposed instead of the existing integral compensator to reduce the speed ripple more rapidly. A formula to calculate a rotation angle is also proposed, making compensation optimal in sensored and sensorless controls. The validity of the proposed algorithm is verified by experiments.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1198-1205
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• 2000

A two-degrees-of-freedom servosystem for step-type reference signals has been preposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. this paper considers robust stability of the servosystem incorporating an observer against both structured and unstructured uncertainties of the plant. A condition is obtained as a linear matrix inequality, under which the servosystem is robustly stable independently of the gain of the integral compensator. This result implies that we can tune the gain to achieve a desirable transient response of the servpsystem preserving robust stability. An example is presented to demonstrate that under the robust stability condition, the transient response can be improved by increasing the gain of the integral compensator.

• Journal of Institute of Control, Robotics and Systems
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• v.2 no.4
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• pp.318-323
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• 1996

The speed of SR(Switched Reluctance) motor can be controlled by switching angle. However, since the relation between speed and switching is nonlinear, it is difficult for simple adjustment schemes to achieve the desired performances. In this paper, an error.feedback nonlinear compensator with robustness is proposed for improving the performances of the switching angle controlled SR motor. The proposed controller consists of integral type control and relay type control. The integral type controller which operates regulation, is derived by the steady.state I/O(input/output) map and the relay type controller which works tracking, is designed by Lyapunov stability theory. The validities of the proposed controller are confirmed with the experimental results.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1298-1307
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• 2017

The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

• Journal of Ocean Engineering and Technology
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• v.26 no.1
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• pp.70-77
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• 2012

In this study, a numerical analysis of offshore installation using a floating crane with heave compensator is carried out in time domain. The motion analysis of crane vessels is based on floating body dynamics using convolution integral and the crane wire is treated as simple spring. The lifted structure is assumed as a rigid body with 3 degree-of-freedom translational motion. The heave compensator is numerically modelled by the generalized spring-damper system. Firstly, forced motion simulations of crane wire system are carried out to figure out the basic principle of heave compensator. The transfer function of crane wire system is obtained and effective wave period of heave compensator are found. Then, coupled analysis of crane vessel, crane wire, and lifted structure are performed in regular and irregular sea conditions. Two different crane vessels and two lifted structures (suction pile and manifold) are considered in this study. Through a series of numerical calculations, the effective zone of heave compensator is investigated with respect to wave period and crane wire length.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.1
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• pp.10-15
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• 2004

We present a state-space approach to make non-square linear systems strictly passive by using an input-dimensional parallel feedforward compensator. A necessary and sufficient condition for the existence of the parallel feedforward compensator is given by the static output feedback formulation, which enables to utilize linear matrix inequality. By modifying the structure of the compensator the additional technical assumption in the previous result [1] is removed. The effectiveness of the proposed method is illustrated by some numerical examples which can be stabilized by the proportional-derivative (PD) and proportional-derivative-integral (PID) control laws. The proposed control scheme can successfully replace the measurements of derivative terms in the control laws.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.1066-1071
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• 1992

A new scheme of OFVSC(Output Feedvack Variable Structure Controller) is proposed for the servo control system. The main structure of proposed control scheme is composed of servo compensator and dynamic switiching function. By the use of dynamic switiching function the assumption of full state availability can be removed and the disturbances which does not satisfy the matching condition cna be rejected. And the servo compensator which is designed for each output variable the robustness for the all type of disturbances. And the performances of proposed control system are evaluated through simulation studies for a numerical example.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.722-726
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• 2007

In this paper we deal with a design of the integral sliding mode controller to suppress the disturbance force acting on the suspension system of the magnetically levitated train system. One of the important factors that cause the disturbance force acting on the suspension system comes from the low propulsion speed of linear induction motor. In this paper integral sliding mode controller is employed to reject the disturbance force produced by the propulsion system of the linear induction motor. In order to show the effectiveness of the designed controller a dynamic simulation is utilized and the sliding mode controller without integral compensator is compared with the proposed integral sliding mode controller to suppress the disturbance force.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.1-8
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• 1997

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, if the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem incorporating an observer to the structured and unstructured uncertainties of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is written in a linear matrix inequality (LMI) and independent of the gain of the integral compensator. This result impies that if the plant uncertainty is in the allowable set defined by the LMI condition, a high-gain integral compensation can be carried preserving robust stability to accelerate the tracking response.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.125-125
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• 1996

In order to reject the steady-state tracking error, it is common to introduce integral compensators in servosystems for constant reference signals. However, the mathematical model of the plant is exact and no disturbance input exists, the integral compensation is not necessary. From this point of view, a two-degree-of-freedom(2DOF) servosystem has been proposed, in which the integral compensation is effective only when there is a modeling error or a disturbance input. The present paper considers robust stability of this 2DOF servosystem to the unstructured uncertainty of the controlled plant. A robust stability condition is obtained using Riccati inequality, which is independent of the gain of the integral compensator. An example is presented, which demonstrates that the tracking response of the 2DOF servosystem with uncertainty becomes faster when the integral gain made larger under the robust stability condition.