Time Management of Heterogeneous Distributed Simulation

Cyber-physical systems (CPS), by their very nature, mix continuous and discrete behavior and are modeled by heterogeneous components. Formal analysis cannot always handle such complex systems and simulation is a necessary step. In particular, distributed simulation is very useful for the validation of CPS for two main reasons: either the CPS itself is distributed (e.g., a fleet of UAVs) or the CPS is too complex and/or has too much models (e.g., an aircraft). We discuss in this paper the impact of distributing the simulation of a system: which are the rules that must be applied to guarantee a correct behavior between the different simulators? If a centralized simulation already exists (using Discrete Event simulation), which hypothesis must be made for the Distributed Discrete Event simulation? The co-simulation framework used and discussed in this work is Ptolemy-HLA. It allows a Ptolemy model to be distributed using the high-level architecture (HLA) standard

Development of Economic Water Usage Sensor and Cyber-Physical Systems Co-Simulation Platform for Home Energy Saving

In this thesis, two Cyber-Physical Systems (CPS) approaches were considered to reduce residential building energy consumption. First, a flow sensor was developed for residential gas and electric storage water heaters. The sensor utilizes unique temperature changes of tank inlet and outlet pipes upon water draw to provide occupant hot water usage. Post processing of measured pipe temperature data was able to detect water draw events. Conservation of energy was applied to heater pipes to determine relative internal water flow rate based on transient temperature measurements. Correlations between calculated flow and actual flow were significant at a 95% confidence level. Using this methodology, a CPS water heater controller can activate existing residential storage water heaters according to occupant hot water demand. The second CPS approach integrated an open-source building simulation tool, EnergyPlus, into a CPS simulation platform developed by the National Institute of Standards and Technology (NIST). The NIST platform utilizes the High Level Architecture (HLA) co-simulation protocol for logical timing control and data communication. By modifying existing EnergyPlus co-simulation capabilities, NIST’s open-source platform was able to execute an uninterrupted simulation between a residential house in EnergyPlus and an externally connected thermostat controller. The developed EnergyPlus wrapper for HLA co-simulation can allow active replacement of traditional real-time data collection for building CPS development. As such, occupant sensors and simple home CPS product can allow greater residential participation in energy saving practices, saving up to 33% on home energy consumption nationally

Assessing and augmenting SCADA cyber security: a survey of techniques

SCADA systems monitor and control critical infrastructures of national importance such as power generation and distribution, water supply, transportation networks, and manufacturing facilities. The pervasiveness, miniaturisations and declining costs of internet connectivity have transformed these systems from strictly isolated to highly interconnected networks. The connectivity provides immense benefits such as reliability, scalability and remote connectivity, but at the same time exposes an otherwise isolated and secure system, to global cyber security threats. This inevitable transformation to highly connected systems thus necessitates effective security safeguards to be in place as any compromise or downtime of SCADA systems can have severe economic, safety and security ramifications. One way to ensure vital asset protection is to adopt a viewpoint similar to an attacker to determine weaknesses and loopholes in defences. Such mind sets help to identify and fix potential breaches before their exploitation. This paper surveys tools and techniques to uncover SCADA system vulnerabilities. A comprehensive review of the selected approaches is provided along with their applicability

Distributed Simulation of Heterogeneous and Real-time Systems

This work describes a framework for distributed simulation of cyber-physical systems (CPS). Modern CPS comprise large numbers of heterogeneous components, typically designed in very different tools and languages that are not or not easily composeable. Evaluating such large systems requires tools that integrate all components in a systematic, well-defined manner. This work leverages existing frameworks to facilitate the integration offers validation by simulation. A framework for distributed simulation is the IEEE High-Level Architecture (HLA) compliant tool CERTI, which provides the infrastructure for co-simulation of models in various simulation environments as well as hardware components. We use CERTI in combination with Ptolemy II, an environment for modeling and simulating heterogeneous systems. In particular, we focus on models of a CPS, including the physical dynamics of a plant, the software that controls the plant, and the network that enables the communication between controllers. We describe the Ptolemy extensions for the interaction with HLA and demonstrate the approach on a flight control system simulation

FMI Compliant Approach to Investigate the Impact of Communication to Islanded Microgrid Secondary Control

In multi-master islanded microgrids, the inverter controllers need to share the signals and to coordinate, in either centralized or distributed way, in order to operate properly and to assure a good functionality of the grid. The central controller is used in centralized strategy. In distributed control, Multi-agent system (MAS) is considered to be a suitable solution for coordination of such system. However the latency and disturbance of the network may disturb the communication from central controller to local controllers or among agents or and negatively influence the grid operation. As a consequence, communication aspects need to be properly addressed during the control design and assessment. In this paper, we propose a holistic approach with co-simulation using Functional Mockup Interface (FMI) standard to validate the microgrid control system taking into account the communication network. A use-case of islanded microgrid frequency secondary control with MAS under consensus algorithm is implemented to demonstrate the impact of communication and to illustrate the proposed holistic approach.Comment: Proceedings of the IEEE PES ISGT Asia 2017 conferenc

Coincidence Problem in CPS Simulations: the R-ROSACE Case Study

This paper presents ongoing work on the formalism of Cyber-Physical Systems (CPS) simulations. We focus on a distributed simulations architecture for CPS, where the running simulators exist in concurrent and sequential domains. This architecture of simulation allows the expression of structural and behavioral constraints on the simulation. We call scheduling of simulation the temporal organization of the simulators interconnection. In this paper we address the problem of the interconnected simulations representativity. To do so, we highlight the similarities and differences between task scheduling and simulation scheduling, and then we discuss the constraints expressible over that simulation scheduling. Finally, we illustrate a constraint on simulation scheduling with an extension of the open source case study ROSACE, implemented with CERTI, a compliant High-Level Architecture (HLA) RunTime Infrastructure (RTI). HLA is an IEEE standard for distributed simulation

Coincidence Problem in CPS Simulations: the R-ROSACE Case Study

This paper presents ongoing work on the formalism of Cyber-Physical Systems (CPS) simulations. We focus on a distributed simulations architecture for CPS, where the running simulators exist in concurrent and sequential domains. This architecture of simulation allows the expression of structural and behavioral constraints on the simulation. We call scheduling of simulation the temporal organization of the simulators interconnection. In this paper we address the problem of the interconnected simulations representativity. To do so, we highlight the similarities and differences between task scheduling and simulation scheduling, and then we discuss the constraints expressible over that simulation scheduling. Finally, we illustrate a constraint on simulation scheduling with an extension of the open source case study ROSACE, implemented with CERTI, a compliant High- Level Architecture (HLA) RunTime Infrastructure (RTI). HLA is an IEEE standard for distributed simulation

The Internet of Simulation: Enabling Agile Model Based Systems Engineering for Cyber-Physical Systems

The expansion of the Internet of Things (IoT) has resulted in a complex cyber-physical system of systems that is continually evolving. With ever more complex systems being developed and changed there has been an increasing reliance on simulation as a vital part of the design process. There is also a growing need for simulation integration and co-simulation in order to analyse the complex interactions between system components. To this end we propose that the Internet of Simulation (IoS) as an extension of IoT can be used to meet these needs. The IoS allows for multiple heterogeneous simulations to be integrated together for co-simulation. It's effect on the engineer process is to facilitate agile practices without sacrificing rigour. An Industry 4.0 example case study is provided showing how IoS could be utilized