An Improved Continuous Integral Variable Structure Systems with Prescribed Control Performance for Regulation Controls of Uncertain General Linear Systems

Jung-Hoon Lee(이정훈) 대한전기학회 2017 전기학회논문지 Vol.66 No.12

In this paper, an improved continuous integral variable structure systems(ICIVSS) with the prescribed control performance is designed for simple regulation controls of uncertain general linear systems. An integral sliding surface with an integral state having a special initial condition is adopted for removing the reaching phase and predetermining the ideal sliding trajectory from a given initial state to the origin in the state space. The ideal sliding dynamics of the integral sliding surface is analytically obtained and the solution of the ideal sliding dynamics can predetermine the ideal sliding trajectory(integral sliding surface) from the given initial state to the origin. Provided that the value of the integral sliding surface is bounded by certain value by means of the continuous input, the norm of the state error to the ideal sliding trajectory is analyzed and obtained in Theorem 1. A corresponding discontinuous control input with the exponential stability is proposed to generate the perfect sliding mode on the every point of the pre-selected sliding surface. For practical applications, the discontinuity of the VSS control input is approximated to be continuous based on the proposed modified fixed boundary layer method. The bounded stability by the continuous input is investigated in Theorem 3. With combining the results of Theorem 1 and Theorem 3, as the prescribed control performance, the pre specification on the error to the ideal sliding trajectory is possible by means of the boundary layer continuous input with the integral sliding surface. The suggested algorithm with the continuous input can provide the effective method to increase the control accuracy within the boundary layer by means of the increase of the G₁ gain. Through an illustrative design example and simulation study, the usefulness of the main results is verified.

An Improved Continuous Transformed Integral Sliding Mode Control(ICTISMC) with Prescribed Control Performance for Regulation Controls of Uncertain General Linear Systems

Jung-Hoon Lee(이정훈) 대한전기학회 2019 전기학회논문지 Vol.68 No.6

In this paper, an improved continuous transformed integral sliding mode control(ICTISMC) with the prescribed control performance is designed for simple regulation controls of uncertain general linear systems, as an alternative approach of [51] with the same performance. An transformed integral sliding surface with an integral state having a special initial condition is adopted for removing the reaching phase and predetermining the ideal sliding trajectory from a given initial state to the origin in the state space. The ideal sliding dynamics of the transformed integral sliding surface is dynamically obtained and the solution of the ideal sliding dynamics can predetermine the ideal sliding trajectory(transformed integral sliding surface) from the given initial state to the origin. Provided that the value of the transformed integral sliding surface is bounded by certain value by means of the continuous input, the norm of the state error to the ideal sliding trajectory is analyzed and obtained in Theorem 1. A corresponding discontinuous control input with the exponential stability is proposed to generate the perfect sliding mode on the every point of the pre-selected transformed integral sliding surface. The existence condition of the sliding mode together with the closed loop stability is proved in Theorem 2 for the complete formulation. For practical applications, the discontinuity of the VSS control input is approximated to be continuous based on the modified fixed boundary layer method. The bounded stability by the continuous input is investigated in Theorem 3. With combining the results of Theorem 1 and Theorem 3, as the prescribed control performance, the pre specification on the error to the ideal sliding trajectory is possible by means of the fixed boundary layer continuous input with the transformed integral sliding surface. The suggested algorithm with the continuous input can provide the effective method to increase the control accuracy within the boundary layer by means of the increase of the G₁ gain. Through an illustrative design example and simulation study, the usefulness of the main results is verified.

Fuzzy-Sliding Mode Control of a Polishing Robot Based on Genetic Algorithm

Go, Seok-Jo,Lee, Min-Cheol,Park, Min-Kyu The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.5

This paper proposes a fuzzy-sliding mode control which is designed by a self tuning fuzzy inference method based on a genetic algorithm. Using the method, the number of inference rules and the shape of the membership functions of the proposed fuzzy-sliding mode control are optimized without the aid of an expert in robotics. The fuzzy outputs of the consequent part are updated by the gradient descent method. It is further guaranteed that the selected solution becomes the global optimal solution by optimizing Akaikes information criterion expressing the quality of the inference rules. In order to evaluate the learning performance of the proposed fuzzy-sliding mode control based on a genetic algorithm, a trajectory tracking simulation of the polishing robot is carried out. Simulation results show that the optimal fuzzy inference rules are automatically selected by the genetic algorithm and the trajectory control result is similar to the result of the fuzzy-sliding mode control which is selected through trial error by an expert. Therefore, a designer who does not have expert knowledge of robot systems can design the fuzzy-sliding mode controller using the proposed self tuning fuzzy inference method based on the genetic algorithm.

Finite Time Robust Controller Design for Microbial Fuel Cell in the Presence of Parametric Uncertainty

Fu Li,Fu Xiuwei,Imani Marrani Hashem 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

Microbial fuel cells are one of the most important elements in the renewable energy supply chain. To increase the effi ciency and performance of the fuel cell, designing a suitable control method is essential to achieve reliable performance and output stability. By considering the parametric uncertainties on the microbial fuel cell model as well as nonlinear terms, this paper presents a novel fi nite time adaptive sliding mode control method that achieves optimal performance of fuel cell in a fi nite time and also ensures the stability of the closed loop system. Sliding mode method without linearization or elimination of nonlinear terms has been used as a robust method to overcome uncertainty eff ects and guarantees proper operation of the fuel cell in the presence of the eff ects. The fi nite time convergence of the states is also assured by using of the proposed method. Furthermore, it uses an adaptive method to determine the sliding mode control coeffi cients which eliminates the necessity to know the upper bound of uncertainty. Finally, the simulation results show the effi ciency and stability of the proposed method in diff erent operating conditions.

방법과 유한요소법에 의한 붕괴 토류벽의 거동차이 분석

정상섬,김영호 한국지반공학회 2009 한국지반공학회논문집 Vol.25 No.4

In this study, a numerical analysis was performed to predict the sequential behavior of anchored retaining wall where the failure accident took place, and verified accuracy of prediction through the comparisons between prediction and field measurement. The emphasis was given to the wall behaviors and the variation of sliding surface based on the two different methods of elasto-plastic and finite element (shear strength reduction technique). Through the comparison study, it is shown that the bending moment and the soil pressure at construction stages produce quite similar results in both the elasto-plastic and finite element method. However, predicted wall deflections using elasto-plastic method show underestimate results compared with measured deflections. This demonstrates that the elasto-plastic method does not clearly consider the influence of soil-wall-reinforcement interaction, so that the tension force (anchor force and earth pressure) on the wall is overestimated. Based on the results obtained, it is found that finite element method using shear strength reduction method can be effectively used to perform the back calculation analysis in the anchored retaining wall, whereas elasto-plastic method can be applicable to the preliminary design of retaining wall with suitable safety factor.

동해항 방파제를 대상으로 한 신뢰성 설계법의 비교 연구.

김승우(Kim, Seung-Woo),서경덕(Suh, Kyung-Duck),오영민(Oh, Young-Min) 한국해안해양공학회 2006 한국해안해양공학회 논문집 Vol.18 No.2

본 논문은 동해항 방파제를 대상으로 신뢰성 설계법을 비교하는 한 쌍의 논문의 두 번째 부분이다. 제 2부인 본 논문에서는 케이슨의 활동을 다룬다. 사석 마운드 위에 케이슨을 거치한 직립방파제의 파괴모드는 케이슨의 활동 및 전도, 그리고 사석 마운드 또는 지반의 파괴 등이 있는데, 그 중 케이슨의 활동에 의한 파괴가 가장 많이 발생한다. 케이슨 활동 파괴에 대한 기존의 결정론적 설계법은 저항이 하중보다 일정 배수(예를 들어 1.2배) 커야 한다는 안전율 개념으로 접근한다. 그러나 안전율의 개념으로는 구조물의 안정성을 정량적으로 평가할 수 없다. 한편 최근 활발한 연구가 진행되고 있는 신뢰성 설계법은 구조물의 파괴확률을 산정함으로써 안정성에 대한 정량적인 평가를 가능케 한다. 신뢰성 설계법은 사용되는 확률적 개념의 정도에 따라 Level 1, 2 및 3의 세가지로 분류된다. 본 연구에서는 기존의 결정론적 방법으로 설계, 시공된 후 1987년 피해를 입었던 동해항 방파제의 케이슨 활동에 대하여 피해 전과 보강 후의 단면에 대해서 각각 신뢰성 해석을 수행하였다. 그 결과 피해 전 단면의 파괴확률은 허용파괴확률을 크게 초과하여 케이슨이 과소 설계되었음을 나타내는 반면, 보강 후 단면의 파괴확률은 허용파괴확률과 비슷한 값을 보임으로써 보강 후 안정한 구조물이 되었음을 나타냈다. 한편, 서로 다른 세 가지 신뢰성 설계법의 결과가 대체로 잘 일치하는 것을 보임으로써 각 방법을 이용한 해석 결과 사이에는 큰 차이가 없음을 확인하였다. This is the second of a two-part paper which describes comparison of reliability design methods by application to Donghae Harbor Breakwaters. In this paper, Part 2, we deal with sliding of caissons. The failure modes of a vertical breakwater, which consists of a caisson mounted on a rubble mound, include the sliding and overturning of the caisson and the failure of the rubble mound or subsoil, among which most frequently occurs the sliding of the caisson. The traditional deterministic design method for sliding failure of a caisson uses the concept of a safety factor that the resistance should be greater than the load by a certain factor (e.g. 1.2). However, the safety of a structure cannot be quantitatively evaluated by the concept of a safety factor. On the other hand, the reliability design method, for which active research is being performed recently, enables one to quantitatively evaluate the safety of a structure by calculating the probability of failure of the structure. The reliability design method is classified into three categories depending on the level of probabilistic concepts being employed, i.e., Level 1, 2, and 3. In this study, we apply the reliability design methods to the sliding of the caisson of the breakwaters of Donghae Harbor, which was constructed by traditional deterministic design methods to be damaged in 1987. Analyses are made for the breakwaters before the damage and after reinforcement. The probability of failure before the damage is much higher than the allowable value, indicating that the breakwater was under-designed. The probability of failure after reinforcement, however, is close to the allowable value, indicating that the breakwater is no longer in danger. On the other hand, the results of the different reliability design methods are in fairly good agreement, confirming that there is not much difference among different methods.

직립방파제의 케이슨 활동에 대한 확률과정에 기반한 시간의존 신뢰성 설계법 개발

김승우(Kim, Seung-Woo),천세현(Cheon, Sehyeon),서경덕(Suh, Kyung-Duck) 한국해안해양공학회 2012 한국해안해양공학회 논문집 Vol.24 No.5

직립 케이슨 방파제에 대한 기존의 성능설계법은 임의의 시간 동안의 평균활동량을 산정하지만 허용활동량을 최초로 초과하는 사건의 발생확률(최초통과확률)은 계산하지 못한다. 설계자는 구조물이 최초로 피해를 입을 확률에 대한 정보를 구조물의 설계 단계뿐 아니라 관리 및 운영에서도 필요로 한다. 따라서 본 연구에서는 케이슨 활동의 최초통과확률을 산정하기 위해 확률과정에 기반한 시간의존 신뢰성 설계법을 개발하였다. 방파제의 활동을 일으키는 폭풍파는 발생 시간과 강도의 임의성의 특징이 있기 때문에 Poisson spike process를 사용하여 케이슨 활동을 정식화할 수 있다. 여기서 방파제의 활동을 일으키는 폭풍파의 발생률은 활동량분포함수와 폭풍파의 평균발생률로 표현된다. 성능설계법으로 모의된 이들은 설계변수들의 다변량 회귀함수로 나타내진다. 결과적으로 활동량분포함수와 폭풍파의 평균발생률은 유의파고, 케이슨 폭, 수심의 함수로 표현되어 케이슨 활동에 대한 최초통과확률을 손쉽게 산정할 수 있다. Although the existing performance-based design method for the vertical breakwater evaluates an average sliding distance during an arbitrary time, it does not calculate the probability of the first occurrence of an event exceeding an allowable sliding distance(i.e. the first-passage probability). Designers need information about the probability that the structure is damaged for the first time for not only design but also maintenance and operation of the structure. Therefore, in this study, a time-dependent reliability design method based on a stochastic process is developed to evaluate the first-passage probability of caisson sliding. Caisson sliding can be formulated by the Poisson spike process because both occurrence time and intensity of severe waves causing caisson sliding are random processes. The occurrence rate of severe waves is expressed as a function of the distribution function of sliding distance and mean occurrence rate of severe waves. These values simulated by a performance-based design method are expressed as multivariate regression functions of design variables. As a result, because the distribution function of sliding distance and the mean occurrence rate of severe waves are expressed as functions of significant wave height, caisson width, and water depth, the first-passage probability of caisson sliding can be easily evaluated.

A Study on Test Method for Water Resistance of Slide Fasteners

이민희,홍성돈,이선희 한국섬유공학회 2019 Fibers and polymers Vol.20 No.5

Breathable waterproof performance fabrics have been developed to protect the human body from externalmoisture, and it is used in various forms. So, there are various test methods for evaluating these, and those are utilized forquality control. However, the test method for evaluating the functionality of slide fasteners is extremely limited in realitybeside physical characteristics. In the reason, it is true that the assurance of functionality cannot be guaranteed in terms offinished products. Especially in military goods, the penetration of a small amount of moisture or water through sub-materialsin extreme cold conditions has also caused fatal consequences. So it has become an urgent task of developing evaluationmethod in order to prevent these situations. In this research, we investigated the waterproof evaluation method used in thepast and wanted to develop an appropriate test method so that these can be applied to slide fasteners. Therefore, byinvestigating the test method through preparation of samples, use of protective jigs, it was possible to develop adiscriminating test method. Finally, it was expected that it could contribute to the improvement of product quality by applyingto future munitions related standards.

SLIDING-MODE-BASED PARAMETER IDENTIFICATION WITH APPLICATION TO TIRE PRESSURE AND TIRE–ROAD FRICTION

D.-J. LEE,Y.-S. PARK 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.4

This paper presents a method of simultaneous estimation of tire pressure and tire–road friction. A sliding-mode scheme is designed to identify the system state and the parameter variation of a torsional tire system, which greatly depend on the change in tire pressure. Then, the recursive least-squares method with a forgetting facto is used to estimate the parameter variations of the tire system and the tire–road friction force without a friction model using the information retrieved from the equivalent input for sliding motion. A simulation study is performed to illustrate the effectiveness of the proposed method.

New Method for Analysis of Sliding Cable Structures in Bridge Engineering

Xiang-min Yu,De-wei Chen,Zhi-zhou Bai 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11

The Sliding Cable Structure (SCS) is widely used in bridge construction by cable crane method. The SCS generally consists of cables and fixed pulleys and the cables will slide around the pulleys when the cables are loaded until the balanced state is achieved. In this paper, an efficient Angle Bisector Method (ABM) is proposed for the mechanical analysis of SCS. The constraint effect of pulley on the cable is simulated by fixed hinge and the constraint force perpendicular to the angle bisector of cable elements adjacent to the pulley is therefore zero at balanced state. By utilizing “Unit Length Influence Matrix” (ULIM), the adjustment of unstressed length of each sub-cable can be determined. As the angle bisector at each pulley will change when the unstressed lengths of cables are changed, iterative procedures are necessary to find the convergence solutions. The proposed method is firstly verified by two examples and then applied to the analysis of cable crane during construction of the world’s longest steel truss cable-stayed bridge, namely Yachihe Bridge. Satisfactory numerical solutions can be obtained only with several iterations and are in good agreement with field measurements from the cable crane load tests, which confirms the accuracy and validity of the proposed method.