Fail-safe Logic Research Articles

Initiation of enzyme replacement therapy for paediatric Fabry disease: Review of single centre practice and experience

Inherent safety practices rely on emergency shutdown capability as a prime facet in achieving a low-risk facility. This chapter defines these systems and their objectives (i.e., revert to a safe state, prevent inadvertent reactivation, and prevent start until cause is determined). Their design features are also described, which includes activation mechanisms (control room, unit, hardware, and fire and safety system action), levels of shutdown (plant, unit, process train, and individual equipment), reliability and fail-safe logic (SIL levels, failure modes), ESD/DCS interfaces, activation points, activation hardware features, isolation valve requirements, isolation valve features, subsea isolation valves, protection requirements, and system interactions.

Instrumentation and control system architecture of ECRH SST1

The Electron Cyclotron Resonance Heating (ECRH) system is an important heating system for the reliable start-up of tokamak. The 42GHz and 82.6GHz Gyrotron based ECRH systems are used in tokomaks SST-1 and Aditya to carry out ECRH related experiments. The Gyrotrons are high power microwave tubes used as a source for ECRH systems. The Gyrotrons need to be handled with optimum care right from the installation to its Full parameter control operation. The Gyrotrons are associated with the subsystems like: High voltage power supplies (Beam voltage and anode voltage), dedicated crowbar system, magnet, filament and ion pump power supplies and cooling system. The other subsystems are transmission line, launcher and dummy load. A dedicated VME based data acquisition & control (DAC) system is developed to operate and control the Gyrotron and its associated sub system. For the safe operation of Gyrotron, two level interlocks with fail-safe logic are developed. Slow signals that are operated in scale of millisecond range are programmed through software and hardware interlock in scale of microsecond range are designed and developed indigenously. Water-cooling and the associated interlock are monitored and control by data logger with independent human machine interface.

Automata-Based Railway Signaling and Interlocking System Design [Testing Ourselves

Railway signaling has become more important over the years, with the increase in railway traffic and the use of highspeed trains. Since the most important aspect of a railway signaling system is safety, the decision-making "interlocking system" is the critical element of a railway-signaling system. To satisfy the safety standards set for railway-signaling systems, the interlocking software design must be taken into account, using formal methods. In this study, an automata-based railway signaling and interlocking system is introduced and implemented, using a fail-safe programmable logic controller (PLC) on a scale railway model.

차량 주행안정성 제어시스템의 자동안전 로직

This paper describes the fault detection and failsafe logic to be used in an Electronic Stability Program (ESP). The aim of this paper is to prevent of erroneous controls in the ESP. Developed this paper introduces the fault detection logic and evaluation of residual signals. The failsafe logic consists of four redundant sub?models, which can be used for detecting the faults in various sensors (yaw rate, lateral acceleration, steering wheel angle). We present two mathematical residual generation methods: one is a method using the average value and the other is a method using the minimum value of the each residual. We verified a failsafe logic developed using vehicle test results also we compare vehicle model based simulation results with test vehicle results.br/

Motion sensor fault detection and failsafe logic for vehicle stability control systems (VSCs)

The design of a reliable and failsafe control system requires that sensor failures be detected and identified within acceptable time limit so that system malfunction can be prevented. This paper presents a model-based approach to sensor fault detection with applications to vehicle stability control systems. The effectiveness of the proposed method is illustrated through test data-based evaluation. Vehicle test data-based evaluation results show that the proposed fault management scheme can be used for the design of a failsafe VSCs.

A Fuzzy-Logic-Based Programmable Electronic System for the Control of Safety-Critical Processes

The architecture of a fuzzy controller especially suited for safety-critical applications such as temperature control in nuclear reactors is developed. Its main chacteristics are fuzzification by low-resolution analogue-to-digital converters and inference by look-up in a table containing a fuzzy rule set. Although originally based on fuzzy logic, the resulting controller is not “fuzzy” at all in its behaviour. Owing to its simplicity both in hardware and in software, safety-licensing of the controller is facilitated. With regard to software, this can easily be carried out by back translation of the table content. Working in a strictly cyclic fashion, the controller features fully predictable real-time behaviour. The controller’s hardware operation is supervised by a fail-safe logic immediately initiating an emergency shut-down in case of a malfunction.

A Fail‐safe Logic Operator Using an Insulated Planar Transformer

AbstractA fail‐safe logic circuit must switch the output signal to the logical value “0” when an operation circuit fails. A transformer has such favorable characteristics for fail‐safe logic circuits as only the magnetic flux change is transmitted and a superposition of magnetic flux is realized. Thus those characteristics arc applied to a failsafe logic operator.A new fail‐safe logic operator using an insulated planar transformer was developed for a fail‐safe majority operation and a fail‐safe interlocking. In this paper, the principle, structure, design and fundamental characteristics of the new fail‐safe logic operator are described.

A Fail-Safe Logic Operator Using an Insulated Planar Transformer.

A fail-safe logic circuit must switch the output signal to the logical value “0” when an operation circuit fails. A transformer has such favorable characteristics for fail-safe logic circuits as only the magnetic flux change is transmitted and a superposition of magnetic flux is realized. Thus those characteristics arc applied to a failsafe logic operator. A new fail-safe logic operator using an insulated planar transformer was developed for a fail-safe majority operation and a fail-safe interlocking. In this paper, the principle, structure, design and fundamental characteristics of the new fail-safe logic operator are described.

Discussion and realization of safety device for stop-hold robot operation.

The machine of the man-machine system must be fail-safe to assure the safety of the human and a fail-safe interlock must be provided to allow the machine to perform the intended operation only when the human absent in the work area of the machine. But, as the matter of fact, a human operation such as trouble-shooting or maintenance is conducted under stop-hold condition of the machine. This paper addresses, such a system that a human operation can safely work with an industrial robot stop-holding in the common work area. The paper first shows a principle of safe work in a man-machine (robot) system. Described next is a prototype safety device (safety hold device) that actuates when the human works in close proximity to the movable part of robot in the stop-hold condition. Described last is fail-safe construction of the device. On the basis of the fail-safe logic, the safety device is so constructed that an erroneous operation signal produced by the safety device cannot permit the stop-hold operation and any malfunction of the device make a shut-off of the power source.

Realization of a fail-safe train wheel sensor using electromagnetic induction

A wheel detector is described as a method for detecting the approach of a train on a railroad without using any vehicle-mounted devices. Wheels of the train are detected as the change in the magnetic coupling between two coils located on either side of the rail. The coils are placed on one metal plate so that high sensitivity and reliability can be achieved. The wheel detector produces two fail-safe output signals having different characteristics when it fails. One output signal indicates the wheel detection state by the failure of any detector component, while the other indicates the wheel nondetection state by the failure of any detector component. Fail-safe window comparators are used to obtain these characteristics. The two binary output signals are related as mutually negative information and are produced as complementary output signals with double rails. The output signals allow fail-safe logic operations, including logic negations. >

窓特性をもつフェイルセーフ論理素子を使ったインタロックシステムの一構成法

窓特性をもつフェイルセーフ論理素子を使ったインタロックシステムの一構成法

Fail-Safe Logic Elements for Use with Reactor Safety Systems

A complete fail-safe trip circuit is described which utilizes fail-safe logic elements. The logic elements1 used are analog multipliers and active bandpass filter networks. These elements perform Boolean operations on a set of AC signals from the output of a reactor safety-channel trip comparator.

METHOD OF PROGRAM SYNTHESIS FOR FAILSAFE INTERLOCKING DEVICE IN RAILWAY SIGNALLING

The functions are analyzed of conventional interlocking relay devices used for train control. It is indicated which parts should be designed on the failsafe basis. A method is also proposed for synthesizing a failsafe logic system which is fed with non-failsafe inputs. A universal digital computer program using an interlocking matrix is proposed for the failsafe logic system. The effectiveness of the proposed method has been confirmed by field tests and 20,000-hour test operations.

Failsafe Logic Nets

The basic properties and realization of failsafe combinational logic nets and failsafe sequential machines are discussed. The present note concerns totally asymmetric faiiure nets which are composed only of (+) elements and/ or (-) elements, where a (+) element is an asymmetric failure element which never fails to logical zero and a (-) element is defined similarly.

Fail-Safe Circuits for Nuclear Protective Systems

The article describes a new set of fail-safe logic blocks particularly suited to safety systems. The input information is normally +5V; in case of alarm, the input drops to 0V. Fundamental blocks (AND, OR, NOT, etc.) are pulse-modulated, so as to achieve 0V output voltage in case of failure. More complex logic function can be synthesized and redundancy can be employed in order to avoid erroneous action.