• International Journal of Automotive Technology
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• 제8권5호
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• pp.555-562
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• 2007

The Variable Valve Timing(VVT) system for high performance is a key technology used in newly developed engines. The system realizes higher torque, better fuel economy, and lower emissions by allowing an additional degree of freedom in valve timing during engine operation. In this study, a model-based control method is proposed to enable a fast and precise VVT control system that is robust with respect to manufacturing tolerances and aging. The VVT system is modeled by a third-order nonlinear state equation intended to account for nonlinearities of the system. Based on the model, a controller is designed for position control of the VVT system. The sliding mode theory is applied to controller design to overcome model uncertainties and unknown disturbances. The experimental results suggest that the proposed sliding mode controller is capable of improving tracking performance. In addition, the sliding mode controller is robust to battery voltage disturbance.

• 드라이브 ㆍ 컨트롤
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• 제18권4호
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• pp.52-58
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• 2021

The variable structure controller is designed such that in sliding mode, the system moves along the switching plane in the vicinity of the switching plane, thus it is robust because it is not affected by the parameter fluctuations of the plant. However, a controller based on a variable structure may not meet the desired performance when it is commanded to track any input or is exposed to disturbances. This study proposes a sliding mode controller that follows the IVSC (Integral Variable Structure Control) approach with ELO (Extended Luenberger observer) to solve this problem. The proposed sliding mode control is applied to the velocity control of the hydraulic motor. The sliding plane was determined by the pole placement, and the control input was designed to ensure the existence of the sliding mode. The feasibility of modeling and controller are reviewed by comparing with conventional proportional-integral control through computer simulation using MATLAB software and experimenting on the cases of significant plant parameter fluctuations and disturbances.

• 설비공학논문집
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• 제8권1호
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• pp.65-75
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• 1996

A pilot plant, which is simplified the hot water heating control system of a large scale residential building, is used to investigate the effects of control methods and operating conditions on the system performance and to compare control characteristics. Digital variable structure controller(DVSC) and digital PI controller are implemented to control the speed of the circulating pump for the pilot plant using PC. For the DVSC, a control algorithm is suggested, which using a nonlinear sliding surface and a PID sliding surface outside and inside of output error boundary layer, respectively. Smith predictor algorithm is used for the compensation of long dead time. The suggested DVSC yields improved control performance compared with existing DVSC using linear sliding surface only. the system responses with the suggested DVSC shows good responses without overshoot for various operating conditions and robust under external disturbances compared with digital PI controller.

• 한국정밀공학회지
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• 제16권8호
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• pp.79-87
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• 1999

In this study, a new type of flow control valve which is SMA actuated flow control valve is presented. The flow control valve is actuated by a small motion of shape memory alloy. The performance of this valve as a position control component is analyzed by computer simulation. A variable structure control technique is applied for the position control by the flow control valve. The position control performance of the valve is evaluated on the step responses of a PID control by a electrohydraulic servo valve. For the simulation study, first, the mathematical model of a hydraulic system, which is consisted of the flow control valve and a hydraulic cylinder, is formulated. This mathematical model and the designed variable structure control algorithm are then combined by the MATLAB software. The same sequence of work is carried out for the PID position control system with a electrohydraulic servo valve. The simulation results show the validity of the new type of flow control valve as a variable position control component.

• 동력기계공학회지
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• 제22권1호
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• pp.18-24
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• 2018

This paper focuses on systematic design about the membership ranges of the main design factors such as control error, control error rate, and sampling time for the fuzzy logic control of the variable speed drive refrigeration cycle. The upper and the lowest limit of the membership ranges are set up from the data of static characteristics obtained by experiments. Three kinds of membership ranges on the control error and the control error rate are tested by experiments. Especially, an effect of sampling time on control performance is also investigated in the same way. Experimental data showed the control error rate and the sampling time strongly effected on the control performance of the refrigeration cycle with a variable speed drive.

• 제어로봇시스템학회논문지
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• 제5권2호
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• pp.166-173
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• 1999

Reference models are used in many control algorithms for improvement of transient response characteristics. They provide desired trajectories that the plant should follow Most control systems have bounded control inputs to avoid saturation of the plant. If we design the reference models that do not account for limits of the control inputs, control performance of the system may be deteriorated. In this paper a new approach of avoiding saturation by varying the reference model for TDC(time delay control) based systems subject to step changes in the reference input. In this scheme, the variable reference model is determined based on the information on control inputs and the size of the step changes in the reference inputs. This scheme was verified by application to the BLDC motor position control system in simulations and experiments. The responses of the TDC with the variable reference model showed better tracking performance than that with the fixed reference model.

• 설비공학논문집
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• 제13권6호
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• pp.532-540
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• 2001

The objectives of this study are to analyze the control variables according to condensation occurrence, to find the range in floor surface temperature and frequency of condensation, and to evaluate the control methods through simulations when the radiant heating system is used for cooling. Through the simulation analysis the control methods such as on/off control, variable flow control and outdoor reset with indoor temperature feedback control are evaluated and compared. The results show that the lowest floor surface temperature is around $23^{\circ}C$, the surface condensation can be prevented by controlling indoor humidity within 20g/kg(DA0, and that outdoor reset with indoor temperature feedback control is more appropriate than on/off control and variable flow control with regard to prevention of the condensation and thermal comfort.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.548-551
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• 1991

The Sliding Mode Control of Variable Structure System is applied to robot manipulators or servo system for its merits of robustness to variable system parameters and disturbances. But Switching frequency of control input is excessively high during sliding mode operation. In this paper, a new control algorithm usings fuzzy logic is proposed to solve this problem. With the proposed algorithm, a dc motor speed control system has been simulated and the result shows expected performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.742-744
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• 1995

In position control system using variable structure control, the velocity of control object is controlled to approach the desired specified velocity patterns, and eventually the position of control object is correctly at reference position. Here, this intention can be success by means of variable structure control. In this paper, the PI velocity feedback control is also used sliding mode controller. The design of position controller under specified velocity profiles in variable structure control's constraints is studied.

• 한국자동차공학회논문집
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• 제10권4호
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• pp.114-121
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• 2002

This paper describes the control system of the toroidal traction driver continuously variable-speed transmission(CVT) fur a tractor. The instrumentation system, the hydraulic power control system and the principle control scheme were introduced. Experimental tests in the bench and the tractor were conducted to validate the performance of the CVT utilizing the proposed controller. The speed of the vehicle was continuously changed to follow the speed set by driver under various operating conditions. Given the reduction ratio of the variator from 2.0 to 1.0, the settling time was about just 0.52 seconds which was satisfactory value for working with the tractor. It was also proved that the tractor could work with continuously variable speed under heavy load disturbances.