• 제어로봇시스템학회논문지
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• 제17권11호
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• pp.1125-1131
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• 2011

This paper presents a control theoretic approach to realizing fault tolerance in asynchronous sequential circuits. The considered asynchronous circuit is assumed to work in space environment and is subject to faults caused by total ionizing dose (TID) effects. In our setting, TID effects cause permanent changes in state transition characteristics of the asynchronous circuit. Under a certain condition of reachability redundancy, it is possible to design a corrective controller so that the closed-loop system can maintain the normal behavior despite occurrences of TID faults. As a case study, the proposed control scheme is applied to an asynchronous arbiter implemented in FPGA.

• 전기학회논문지
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• 제58권3호
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• pp.591-597
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• 2009

The problem of controlling a finite-state asynchronous sequential machine is examined. The considered machine is governed by input/output control, where access to the state of the machine is not available. In particular, disturbance inputs can infiltrate into the asynchronous machine and provoke unauthorized state transitions. The control objective is to use output feedback to compensate the machine so that the closed-loop system drive the faulty asynchronous machine from a failed state to the original one. Necessary and sufficient condition for the existence of appropriate controllers are presented in a theoretical framework. As a case study, the closed-loop system of an asynchronous machine with the proposed control scheme is implemented in VHDL code.

• 전기학회논문지
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• 제57권8호
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• pp.1440-1446
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• 2008

In this paper, a novel TMR (Triple Modular Redundancy) memory structure is proposed using state feedback control of asynchronous sequential machines. The main ability of the proposed structure is to correct the fault of SEU (Single Event Upset) asynchronously without resorting to the global synchronous clock. A state-feedback controller is combined with the TMR realized as a closed-loop asynchronous machine and corrective behavior is operated whenever an unauthorized state transition is observed so as to recover the failed state of the asynchronous machine to the original one. As a case study, an asynchronous machine modelling of TMR and the detailed procedure of controller construction are presented. A simulation results using VHDL shows the validity of the proposed scheme.

• 한국지능시스템학회논문지
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• 제25권2호
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• pp.139-146
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• 2015

본 논문에서는 교정 제어에 의한 스위칭 비동기 순차 머신의 모델 정합 문제를 다룬다. 스위칭 비동기 순차 머신은 스위칭 신호에 따라서 여러 개의 비동기 순차 머신 특성을 번갈아 가면서 가지는 시스템이라고 정의한다. 이번 연구에서 스위칭 시스템이 가질 수 있는 스위칭 시퀀스(sequence)는 일정하게 고정되어 있다고 가정한다. 제어 목적은 폐루프 시스템의 안정 상태 동작을 주어진 기준 모델과 일치시키는 교정 제어기의 존재조건을 규명하고 제어기를 설계하는 일이다. 이를 위해서 스위칭 비동기 머신이 가지는 도달가능성을 표현하는 새로운 skeleton 행렬을 도입하고 모델 정합 교정 제어기의 존재조건을 기술한다. 또한 사례 연구를 통해 스위칭 신호를 생성하면서 동시에 교정 제어 입력을 변화시키는 새로운 교정 제어 알고리듬을 예시한다.

• 전기학회논문지
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• 제56권9호
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• pp.1655-1664
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• 2007

This paper presents the problem of controlling asynchronous sequential machines in the presence of input disturbances, which may be also regarded as an adversary in a game theoretic setting. The main objective is to develope a new methodology for including unpredictable behavior of input disturbance into models of asynchronous machines. The input disturbance, representing uncontrollable noise input, is embedded into a new model of asynchronous machines in form of input/state finite state machines. It is shown that the proposed modeling preserves the fundamental model and well-pose of asynchronous machines. The reachability matrix, an important performance index of asynchronous machines, is also adapted according to input disturbance and will be used for constructing corrective controllers in the companion paper.

• 전기학회논문지
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• 제58권12호
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• pp.2484-2491
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• 2009

This paper proposes robust state feedback control of asynchronous sequential machines with model uncertainty. The considered asynchronous machine is deterministic, but its state transition function is partially known before executing a control process. The main objective is to derive the existence condition for a corrective controller for which the behavior of the closed-loop system can match a prescribed model in spite of uncertain transitions. The proposed control scheme also has learning ability. The controller perceives true state transitions as it undergoes corrective actions and reflects the learned knowledge in the next step. An adaptation is made such that the controller can have the minimum number of state transitions to realize a model matching procedure. To demonstrate control construction and execution, a VHDL and FPGA implementation of the proposed control scheme is presented.

• 전자공학회논문지SC
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• 제45권4호
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• pp.1-10
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• 2008

본 논문에서는 비동기 순차 머신의 교정 제어 문제를 다룬다. 교정 제어는 머신의 동작을 주어진 모델의 동작과 일치시키도록 하는 모델 매칭을 실현하는 제어를 말한다. 본 논문의 주요 목적은 비동기 순차 머신이 추종해야 하는 모델의 형태가 비결정적일 때, 즉 여러 개의 결정적 모델의 합으로 주어질 때 교정 제어기를 설계하는 일이다. 본 논문에서는 먼저 비동기 순차 머신을 위한 교정 제어 시스템의 형태와 동작 원리를 설명하고 비결정 모델의 표현 방법을 제안한다 또한 교정 제어기 존재 조건을 표현하기 위해서 비동기 순차 머신과 비결정적 모델에 대한 도달가능성을 분석하고 예제를 통해서 분석 방법을 검증한다.

• 제어로봇시스템학회논문지
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• 제15권10호
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• pp.967-973
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• 2009

The model matching problem of asynchronous sequential machines is to design a corrective controller such that the stable-state behavior of the closed-loop system matches that of a prescribed model. In this paper, we address model matching when the external input set consists of controllable inputs and uncontrollable ones. Like in the frame of supervisory control of Discrete-Event Systems (DES), uncontrollable inputs cannot be disabled and must be transmitted to the plant without any change. We postulate necessary and sufficient conditions for the existence of a corrective controller that solves model matching despite the influence of uncontrollable events. Whenever a controller exists, the algorithm for its design is outlined. To illustrate the physical meaning of the proposed problem, the closed-loop system of an asynchronous machine with the proposed control scheme is implemented in VHDL code.

• 전자공학회논문지SC
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• 제47권5호
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• pp.9-17
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• 2010

교정 제어는 비동기 순차 머신의 안정 상태 동작을 원하는 목적에 맞게 바꾸어주는 역할을 한다. 본 논문에서는 교정 제어를 이용하여 영구 고장이 존재하는 비동기 순차 머신의 고장 극복 기법을 제안한다. 비동기 순차 머신에서 영구 고장이 발생하면 머신은 원래 상태로 영원히 회복되지 못하고 제한된 상태 집합 내에서만 동작하게 된다. 하지만 비동기 순차 머신이 줄어든 작동 범위 안에서도 정상적인 동작을 계속할 수 있는 여유도를 가지고 있다면 교정 제어 기법을 이용하여 고장 극복 문제를 해결할 수 있다. 본 논문에서는 영구 고장을 탐지할 수 있는 조건과 함께 고장 극복 문제를 푸는 교정 제어기가 존재할 필요충분조건을 밝힌다. 또한 사례 연구를 통해서 제안된 제어기의 설계 과정을 예시한다.

• 전기학회논문지
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• 제60권1호
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• pp.93-99
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• 2011

A PRT vehicle's control method is presented in this paper. In the asynchronous vehicle control system, vehicles follow their leading vehicles. Leading vehicles are defined differently among the different types of track. The main topic of this paper is to present a method to define the leading vehicle among different types of track and the calculation algorithm of the safety length the following vehicle must maintain. Simulation program is developed using the algorithm and the results of the test run are presented. An asynchronous PRT vehicle control algorithm was presented by Szillat in the paper "A low level PRT Microsimulation, Dissertation, University of Bristol, 2001". But it is different from the algorithm in this paper. In the algorithm proposed by Markus, vehicles in the merging track are controlled synchronously, and its safety distance between the leading and the following car is evaluated after the establishment of the complicated future time-location table instead of simple equations proposed in this paper.