Safety Relevant System Research Articles

Prediction of hydrodynamic characteristics of a venturi scrubber by using CFD simulation

The filtered containment venting system (FCVS) is a safety relevant system, which consists of venturi scrubber and a mesh filter. FCVS needs to be further assessed to improve the existing performance of the venturi scrubber. Therefore, hydrodynamics is an important counter-component needs to be investigated to improve the design of the venturi scrubber. In the present research, Computational Fluid Dynamic (CFD) has been used to predict the hydrodynamic behaviour of a newly designed venturi scrubber. Mesh was developed by gambit 2.4.6 and ansys fluent 15 has been used to predict the pressure drop profile inside the venturi scrubber under various flow conditions. The Reynolds Renormalization Group (RNG) k-ε turbulence model and the volume of the fluid (VOF) were employed for this simulation. The effect of throat gas velocity, liquid mass flow rate, and liquid loading on pressure drop was studied. Maximum pressure drop 2064.34 pa was achieved at the throat gas velocity of 60 m/s and liquid flow rate of 0.033 kg/s and minimum pressure drop 373.51 pa was achieved at the throat gas velocity of 24 m/s and liquid flow rate of 0.016 kg/s. The results of the present study will assist for proper functioning of venturi scrubber.

Diagnostics of an output interface of a safety-related system with safety PLC

Safety programmable logic controllers (S-PLCs) provide broad application options and are being used to perform control but primarily safety functions (SFs) on the process control level. An essential part of control systems based on S-PLC is the sensors and actuators. In order to ensure the SF with high safety integrity level (SIL), the control system performing this SF has to dispose of a suitable failure detection mechanism and a mechanism providing its safe reaction in case of a failure detection. The diagnostics provided by S-PLC is mainly focused on its own components, and the diagnostics of sensors and actuators has to be resolved on the application program level while respecting some specific properties of S-PLC. This paper addresses the analysis of the influence of S-PLC parameters and diagnostic parameters on the safety function SIL, which is performed by a safety relevant electronic system. In the practical part is described the implementation of application diagnostics in S-PLC and the results of diagnostic parameters influence on safety integrity of SF for a selected example connected to a practical application.

Using an Improved Rule Match Algorithm in an Expert System to Detect Broken Driving Rules for an Energy-efficiency and Safety Relevant Driving System

Vehicles have been so far improved in terms of energy-efficiency and safety mainly by optimising the engine and the power train. However, there are opportunities to increase energy-efficiency and safety by adapting the individual driving behaviour in the given driving situation. In this paper, an improved rule match algorithm is introduced, which is used in the expert system of a human-centred driving system. The goal of the driving system is to optimise the driving behaviour in terms of energy-efficiency and safety by giving recommendations to the driver. The improved rule match algorithm checks the incoming information against the driving rules to recognise any breakings of a driving rule. The needed information is obtained by monitoring the driver, the current driving situation as well as the car, using in-vehicle sensors and serial-bus systems. On the basis of the detected broken driving rules, the expert system will create individual recommendations in terms of energy-efficiency and safety, which will allow eliminating bad driving habits, while considering the driver needs.

Common-cause Failures as Major Issue in Safety of Control Systems

In order to gain an improvement of safety or availability measures of the safety-relevant control system through employment of redundancy a redundant system has to comply with the requirement on independence of redundant parts. If the requirements on the independence of redundant parts are unfulfilled, then a common-cause failure can directly cause a hazardous state on a system level through its effects on multiple redundant parts. Identification of sources and quantification of the common-cause failure parameters has been proved to be a formidable task. The latter problem, including other major safety-affecting factors lays in the focus of this paper. Our proposed technical safety analysis concept is extended, so now it partially covers elusive problems related to the common-cause failures.

A New Approach to Input and Output Monitoring for Microcontrollers Supporting Functional Safety

It is very common that a microcontroller is used in a safety relevant system to acquire data from sensors, process the data and then control actuators. With the shrink of technology every few years it becomes ever more common to use digital serial interfaces and high speed PWM links for both inputs and outputs. The microcontroller vendors have responded to the need for functional safety in the CPU cores by lock-stepping them and adding ECC to buses and memories. They are also implementing highly flexible and complex timer peripherals to be able to automate much of the real-time processing of the digital signals. However these timers are becoming significantly large, and many have their own embedded sequence engines or microkernels, which although powerful, often lack the rigorous diagnostic mechanisms required to reach ASILD. Currently the only solution is to use an application level measure to detect timer failures, but the large quantity of signals can lead to a substantial CPU load just for the monitoring tasks. This paper describes how a new I/O Monitoring peripheral can be used to 'lockstep' digital input and output signals, using two redundant or diverse timer peripherals. It will outline the problems, the current state of the art, and the proposed new solution, together with some typical use-cases of braking, electrical power steering and airbag. Language: en

Condition monitoring of Lithium-Ion Batteries for electric and hybrid electric vehicles

Since the early 1990s Lithium-Ion Batteries have stated a key technology in rechargeable batteries due to their high volumetric and gravimetric energy densities and were first introduced in personal devices like camcorders, cellular phones and mobile computers ("3-C applications"). Ongoing evolutionary advances release at present a new spate of research activities to extend the operational area of small-sized batteries with the final aim to achieve reliable energy storage in automotive environments (e.g. hybrid vehicles). High absolute energy amounts of large-scale Lithium-Ion Batteries raise safety and lifetime issues and set demands for methods to monitor the health conditions of batteries for automotive applications. By observing significant system variables, imminent failures of single cells or battery packs are in many cases predictable and suitable counteractions can be initiated. The paper gives a brief introduction to the state-of-the-art of advanced batteries for electric and hybrid electric vehicles. Special focus is put on the monitoring of safety-relevant system parameters like cell-voltage, system temperature and headspace-pressure, their significance on the battery's state-of-health (SOH) and possible cell-failures. Different in-situ, ex-situ and onboard measurement techniques are addressed.