• 드라이브 ㆍ 컨트롤
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• 제19권1호
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• pp.51-61
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• 2022

This paper presents a model-free system based on a framework of a backstepping sliding mode control (BSMC) with a radial basis function neural network (RBFNN) and adaptive mechanism for electro-hydraulic systems (EHSs). First, an EHS mathematical model was dedicatedly derived to understand the system behavior. Based on the system structure, BSMC was employed to satisfy the output performance. Due to the highly nonlinear characteristics and the presence of parametric uncertainties, a model-free approximator based on an RBFNN was developed to compensate for the EHS dynamics, thus addressing the difficulty in the requirement of system information. Adaptive laws based on the actor-critic neural network (ACNN) were implemented to suppress the existing error in the approximation and satisfy system qualification. The stability of the closed-loop system was theoretically proven by the Lyapunov function. To evaluate the effectiveness of the proposed algorithm, proportional-integrated-derivative (PID) and improved PID with ACNN (ACPID), which are considered two complete model-free methods, and adaptive backstepping sliding mode control, considered an ideal model-based method with the same adaptive laws, were used as two benchmark control strategies in a comparative simulation. The simulated results validated the superiority of the proposed algorithm in achieving nearly the same performance as the ideal adaptive BSMC.

• 로봇학회논문지
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• 제16권2호
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• pp.79-85
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• 2021

Soft fluidic actuators (SFAs) are widely utilized in various areas such as wearable systems due to the inherent compliance which allows safe and flexible interaction. However, SFA-driven systems generally require a large pump, multiple valves and tubes, which hinders to develop a miniaturized system with small range of motion. Thus, a highly integrated soft actuator needs to be developed for implementing a compact SFA-driven system. In this study, we propose an electro-hydraulic soft zipping actuator that can be used as a miniature pump. This actuator exerts tactile force as a dielectric liquid contained inside the actuator pressurized its deformable part. In addition, the proposed actuator can estimate the internal dielectric liquid thickness by using its self-sensing function. Besides, the electrical characteristics and driving performance of the proposed system were verified through experiments.

• 한국정밀공학회지
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• 제12권12호
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• pp.139-148
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• 1995

In this paper an electro-hydraulic servo system is designed by using a fuzzy control algorithm. In order to drive an optimal fuzzy control system, a simulation program for the control system has been developed. By this program the fuzzifier and defuzzifier, a fuzzy inference method, a fuzzy relational matrix, and a fuzzy inference method are investigated. As a result, Larsen inference method, 9*9 fuzzy relational matrix, and center of area defuzzifier are turned out the best as parameters. Finally this method is compared with the conventional PID algotithm, and showed that the fuzzy control performs better than PID algorithm. The fuzzy control performs very well adap- tation against uncertain disturbances.

• 유공압시스템학회논문집
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• 제6권4호
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• pp.1-8
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• 2009

Nowadays with the high fuel prices, the demands for energy saving and green emission of construction machinery have highly been increased without sacrifice of working performance, safety and reliability. The aim of this paper is to propose a new energy saving hybrid excavator system using an electro-hydraulic actuator driven by an electric motor/generator for the regeneration of potential energy. A 5 ton class excavator is analyzed, developed with the boom for the evaluation of the designed system. The hardware implementation is also presented in this paper. A control strategy for the hybrid excavator is proposed to operate the machine with a highest efficiency. The energy saving ability of the proposed excavator is clearly verified through simulation and experimental results in comparison with a conventional hydraulic excavator.

• 드라이브 ㆍ 컨트롤
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• 제18권3호
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• pp.16-22
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• 2021

The variable structure controller has the characteristic that while in sliding mode, the system moves along the switching plane in the vicinity of the switching plane, so it is robust to 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 exposed to disturbances. To solve this problem, a sliding mode controller based on the IVSC approach excluding an integrator is proposed in this study. The proposed sliding mode control was applied to the position control of a hydraulic cylinder piston. 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 the modeling and controller was reviewed by comparing it with a conventional proportional control through computer simulation using MATLAB software and experiment in the presence of significant plant parameter fluctuations and disturbances.

• 한국항공우주학회지
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• 제41권4호
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• pp.291-298
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• 2013

본 논문에서는 압력보상형 사판식 유압 피스톤 펌프와 밸브 제어형 실린더를 결합한 EHA에 대하여 유압 실린더의 소비 유량이 작으면 펌프 회전 속도를 낮추는 새로운 개념의 하이브리드형 제어 시스템을 제안하였다. 펌프 내 압력조절기의 사판각 제어와 간섭을 피하기 위해 위치 명령 신호의 속도 성분 평균치를 이용하여 펌프의 회전속도를 조절하였고, 시스템 압력이 기준치 이하로 낮아지는 것을 방지하기 위해 압력 스위치 기능을 추가하였다. 시뮬레이션과 실험 결과에 의하면, EHA의 동적인 응답 특성에 영향을 주지 않는 조건에서 하이브리드 제어를 통해 공전 모드에서의 펌프 회전속도를 1,800rpm에서 600rpm로 낮춤으로써 하이브리드 제어를 안 할 경우에 비해 펌프 구동 동력을 약 44%까지 절감시킬 수 있음을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.436-440
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• 1996

In this study, underdeveloping heavy-load driving servo control system, which are composed of controller, electro-hydraulic servo-valve, hydraulic motor, reduction gear box, turret slew bearing and turret structure, are investigated to simplify the control system. To estimate the effect of each component, modeling and simulation of linear and nonlinear system are carried out. In the first stage, to prove the reliability of performance estimation program, simulation results are compared with experimental results. In the second stage, the effect of each component of control system is evaluated and then a simplified control system is suggested.

• 전력전자학회논문지
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• 제15권4호
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• pp.335-341
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• 2010

전기제동 시스템(Electric braking system)은 기존 자동차 시스템에서 사용된 유압 브레이크를 대신하여 전동기를 이용하여 제동력을 얻게 된다. 전기제동은 기존 유압식에 비해 부품의 수가 감소되며 ABS, ESC 등의 응답성 향상 및 제동거리 감소효과를 얻을 수 있다. 본 논문에서는 EMB(Electro-Magnetic Brake)용 BLAC 전동기의 제어기를 개발하였다. 제어 시스템은 BLAC 전동기 구동을 위한 전력변환장치와 속도제어를 위한 디지털제어기로 구성되었으며, 빠른 토크 응답특성을 위해 벡터제어 기법을 적용하였다. 또한 Matlab/Simulink를 이용한 시뮬레이션 및 실험 결과를 제시하여 EMB용 BLAC 전동기의 성능을 검증하였다.

• 한국자동차공학회논문집
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• 제2권3호
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• pp.62-74
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• 1994

This paper addresses on the model synthesis and performance analysis of an engine mount featuring electro-rheological(ER) fluids which undergo a phase change when subjected to electric fields. A novel type of ER fluid-filled engine mount is devised and its hydraulic model is constructed. An equivalent mechanical model is subsequently obtained from the governing equation of the hydraulic model. The model parameters associated with the ER fluids are distilled from experimental investigations on the Bingham properties of the fluids. The distilled data are then incorporated into the governing model to undertake feasible work through computer simulations,. It is shown that the proposed engine mount has an inherent capability of controlling both the damping force and the resonance frequency. Other superior performance characteristics accrued from the proposed methodology are also evaluated.

• 유공압시스템학회논문집
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• 제1권4호
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• pp.15-21
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• 2004

High speed on-off electro-magnetic valves have been used for pressure control or flow control in automotive or construction machine servomechanisms. These systems require quicker valve switching speed to improve control preciseness. The authors designed and manufactured an electric valve driver with quick response characteristics by using 3 power source type valve driver concept. In experiments by using a hydraulic system incorporating the new valve driver, the new driver shortened the switching lag time from 5 ms to 1.3 ms. And also the new driver showed excellent position tracking control performances.