Safety Diagnostics and Degraded Operational Modes

Unmanned ground combat vehicles (UGCV) promise numerous ultimate military, civilian, and space applications. The focus of this research mainly deals with how a non-geometric hazard scenario may potentially lead to a mission ending situation and a non geometric hazard can be considered as any terrain feature or object that is adjudged to be non-traversable by virtue of its physical properties. The novelty of this research lies in how a UGCV in a military applications can overcome the challenges of traversing through ever changing natural obstacles when compared to the reinforcing obstacles which are encountered by autonomous vehicle in a conventional structured scenario (see Figure 1).Figure 1. Traversal across an off-road terrain facing uneven terrain and obstacles.An operational design domain (ODD) can help specify potential unsafe situations and restrict the vehicle’s operation within them. A complete ODD will guarantee that the safety arguments can be dealt in a streamlined manner and in scenarios of restricting the ODD, the overall availability of the system gets reduced. With a semantic ODD structure for the UGVC, the standard development of the safety process for an automotive system is achieved and with the already created safety protocols, the overall situation space is reduced during critical situations.DISTRIBUTION A. Approved for public release; distribution unlimited. OPSEC5045The process of identifying reduced operational domain (ROD) starts with the quantificationand analysis of maneuvers and further leads to the identification of critical situations. Criticalareas are conditions of the environment that cause unintentional behaviour which eventuallyleads to an accident. A state machine constituting nominal behaviour will form the basis for acomponent fault tree (CFT) which is used to identify conditions that cause critical situations.Subsequently, the corresponding risk of an identified critical situation is assessed as a part ofthis process.The safety diagnostics mainly depends on a probabilistic model-based controller examining adynamic environment in which the stochastic evolution depends on the input of observationsand the current behaviour of the UGCV. In order to model the real-life performance of safetycritical systems realistically and accurately, Markov chain and Bayesian filters are highlyuseful. The finite state essence of the discrete controller may possibly lead to incorrectbehaviour of the complete system if an unforeseen situation occurs and for which there is alack of any predefined contingency. For this purpose, it becomes important to have a sense ofa complete set of admissible scenarios and also to develop a structured decision-making processfor each of the previously mentioned scenarios. State machine and failure propagation treescan help in determining the failure probabilities which keep updating based on changes incircumstances and this would help define if a mission should continue. As a part of thisresearch, Markov decision process which forms the basis for decision making process isemployed to identify and compare a set of state sequences and this in turn would help inrealizing better maneuverability of the vehicle.The assignment of ROD can be accomplished with the complete risk assessment of the criticalsituations. By assigning the ROD, the aim of increasing the overall availability of the systemwhich degraded from the nominal driving behaviour is fulfilled and this would allow for thesafe operation of UGCV.

Criticality Analysis Based on Reliability and Failure Propagation Effect for a Complex Wastewater Treatment Plant

Wastewater treatment is a critical and necessary task every human settlement is obligated to address. If not, the consequences might be catastrophic, not just for humans but for the ecosystems as well, pushing research into finding new ways to improve wastewater treatment processes to make them safer and more efficient. Hence, there is a need to address matters, such as reliability and maintainability of Wastewater Treatment Plants (WWTP), when analyzing the availability and operational conditions. These should be addressed by analyzing the plant operational effectiveness impact (P-OEI), and in this article specifically, a WWTP study case to identify design flaws or improvement opportunities. A vital aspect of a complex system is to determine the contribution to resilience, reliability, and availability of every element embedded in the system. This is performed by adapting and applying the P-OEI methodology and real data of a WWTP located in Chile. This methodology breaks down the system into several levels of disaggregation similar to RBD methodology, analyzing the upstream for availability and the downstream for the P-OEI analysis from the system itself to the individual elements within subsystems. The potential impact on the overall system’s lack of efficiency is also quantified by an Expected Operational Impact (EOI) index, which is also calculated by the methodology. The P-OEI and EOI analyses performed in this study are powerful tools to assess the design and performance of complex systems and WWTP in particular.

A Failure Propagation Analysis Method Based on 3 X 3 Hierarchical Model

In recent years, with the increasing complexity of equipment, system design and safety analysis for the equipment are becoming more and more difficult. In this paper, we make a more comprehensive analysis of the hierarchical relationship of the system from the vertical and horizontal angles and put forward the 3 × 3 Hierarchical Model. Then, we propose a failure propagation analysis method based on 3 × 3 Hierarchical Model. At the same time, SysML is used to build the models, which is convenient for different people to learn and modify the models. Finally, a hydraulic transmission system is taken as an example to illustrate the feasibility of the method.

Dynamical Recovery of Complex Networks under a Localised Attack

In real systems, some damaged nodes can spontaneously become active again when recovered from themselves or their active neighbours. However, the spontaneous dynamical recovery of complex networks that suffer a local failure has not yet been taken into consideration. To model this recovery process, we develop a framework to study the resilience behaviours of the network under a localised attack (LA). Since the nodes’ state within the network affects the subsequent dynamic evolution, we study the dynamic behaviours of local failure propagation and node recoveries based on this memory characteristic. It can be found that the fraction of active nodes switches back and forth between high network activity and low network activity, which leads to the spontaneous emergence of phase-flipping phenomena. These behaviours can be found in a random regular network, Erdős-Rényi network and Scale-free network, which shows that these three types of networks have the same or different resilience behaviours under an LA and random attack. These results will be helpful for studying the spontaneous recovery real systems under an LA. Our work provides insight into understanding the recovery process and a protection strategy of various complex systems from the perspective of damaged memory.

Influence of Geometry on Failure Modes of Hybrid Metal-Composite Protruding Bolted Joints

This article presents the influence of joint geometry on the damage mode in the CFRP (Carbon Fiber Reinforced Polymer) composite plate of the single-lap, protruding, hybrid metal-composite joints. A detailed 3D finite element model incorporating geometric, material and friction-based contact full nonlinearities is developed to numerically investigate the geometry effects on the progressive damage analysis (PDA) of the orthotropic material model. The PDA material model integrates the nonlinear shear response, Hashin-tape failure criteria and strain-based continuum degradation rules being developed using the UMAT user subroutine in Nastran commercial software. In order to validate the geometry effects on the failure modes of the joints with hexagonal head bolts, experiments were conducted using the SHM (Structural Health Monitoring) technique. The results showed that the plate geometry is an important parameter in the design process of an adequate bolted joint and its effects on damage initiation and failure modes were quite accurately predicted by the PDA material model, which proved to be computational efficient and can predict failure propagation and damage mechanism in hybrid metal-composite bolted joints.

spaceAPPS – A modular approach for on-board software

Software modularity and partial qualification capabilities are key enablers to produce cost efficient software in highly regulated domains. The modular concept (called spaceAPPS) described in this paper has been developed in the frame of the OPS-SAT project aiming at missions where flexibility is one of the success factors. spaceAPPS implements a novel software architecture for satellites inspired by the Apps concept of modern smartphones. In the European space domain the operation of a satellite is based on a set of 18 services. Accordingly, in spaceApps these services are mapped to individual Apps. This is not a one-to-one mapping which means that one App implements one or more services. During OPS-SAT ground testing it was demonstrated that functionality could be easily added through a new App or updated through replacing an existing App. Also during OPS-SAT ground testing it could be shown that a failing UserApp did not impact the basic apps to operate the satellite. Thus, it is possible to run applications of different criticality on the same platform. With operating systems supporting time and space separation the risk of failure propagation can be further reduced. The implementation of a partial validation approach, i. e. testing of third-party Apps in a representative environment and not running the validation on the target platform is feasible but was not demonstrated.