Development and Validation of Functional Model of a Cruise Control System

Modern automobiles can be considered as a collection of many subsystems working with each other to realize safe transportation of the occupants. Innovative technologies that make transportation easier are increasingly incorporated into the automobile in the form of functionalities. These new functionalities in turn increase the complexity of the system framework present and traceability is lost or becomes very tricky in the process. This hugely impacts the development phase of an automobile, in which, the safety and reliability of the automobile design should be ensured. Hence, there is a need to ensure operational safety of the vehicles while adding new functionalities to the vehicle. To address this issue, functional models of such systems are created and analysed. The main purpose of developing a functional model is to improve the traceability and reusability of a system which reduces development time and cost. Operational safety of the system is ensured by analysing the system with respect to random and systematic failures and including safety mechanism to prevent such failures. This paper discusses the development and validation of a functional model of a conventional cruise control system in a passenger vehicle based on the ISO 26262 Road Vehicles - Functional Safety standard. A methodology for creating functional architectures and an architecture of a cruise control system developed using the methodology are presented.Comment: In Proceedings FESCA 2016, arXiv:1603.0837

Lessons learned in the application of formal methods to the design of a storm surge barrier control system

The Maeslantkering is a key flood defense infrastructural system in the Netherlands. This movable barrier protects the city and harbor of Rotterdam, without impacting ship traffic under normal circumstances. Its control system, which operates completely autonomously, must be guaranteed to work correctly even under extreme weather conditions, although it closes only sporadically. During its development in the 1990's, the formal methods Z and Spin were used to increase reliability. As the availability of industrial expert knowledge on these formal methods declines, maintaining the specifications defined back then has become cumbersome. In the quest for an alternative mathematically rigorous approach, this paper reports on an experience in applying supervisory control synthesis. This formal method was recently applied successfully to other types of infrastructural systems like waterway locks, bridges, and tunnels, with the purpose to ensure safe behavior by coordinating hardware components. Here, we show that it can also be used to coordinate several (controller) software systems. Additionally, we compare the lessons learned from the originally used formal methods and link Z to supervisory control synthesis

Structuring Multilevel Discrete-Event Systems With Dependence Structure Matrices

Despite the correct-by-construction property, one of the major drawbacks of supervisory control synthesis is state-space explosion. Several approaches have been proposed to overcome this computational difficulty, such as modular, hierarchical, decentralized, and multilevel supervisory control synthesis. Unfortunately, the modeler needs to provide additional information about the system's structure or controller's structure as input for most of these nonmonolithic synthesis procedures. Multilevel synthesis assumes that the system is provided in a tree-structured format, which may resemble a system decomposition. In this paper, we present a systematic approach to transform a set of plant models and a set of requirement models provided as extended finite automata into a tree-structured multilevel discrete-event system to which multilevel supervisory control synthesis can be applied. By analyzing the dependencies between the plants and the requirements using dependence structure matrix techniques, a multilevel clustering can be calculated. With the modeling framework of extended finite automata, plant models and requirements depend on each other when they share events or variables. We report on experimental results of applying the algorithm's implementation on several models available in the literature to assess the applicability of the proposed method. The benefit of multilevel synthesis based on the calculated clustering is significant for most large-scale systems

Model Properties for Efficient Synthesis of Nonblocking Modular Supervisors

Supervisory control theory provides means to synthesize supervisors for systems with discrete-event behavior from models of the uncontrolled plant and of the control requirements. The applicability of supervisory control theory often fails due to a lack of scalability of the algorithms. We propose a format for the requirements and a method to ensure that the crucial properties of controllability and nonblockingness directly hold, thus avoiding the most computationally expensive parts of synthesis. The method consists of creating a control problem dependency graph and verifying whether it is acyclic. Vertices of the graph are modular plant components, and edges are derived from the requirements. In case of a cyclic graph, potential blocking issues can be localized, so that the original control problem can be reduced to only synthesizing supervisors for smaller partial control problems. The strength of the method is illustrated on two case studies: a production line and a roadway tunnel.Comment: Submitted to Journal of Control Engineering Practice, revision

DSM-based analysis for the recognition of modeling errors in supervisory controller design

The design of supervisory controllers for cyber-physical systems is steadily becoming harder as increasingly more functionality needs to be automated, the systems become larger, and safe operation becomes more important. Model-based systems engineering incorporating formal methods such as supervisory control synthesis can be used to synthesize these supervisory controllers based on models of the uncontrolled system components and models of the control requirements. Although synthesis is an automatic procedure, creating these models is still a manual activity prone to modeling errors. In this paper, we propose to use several DSM-supported analysis techniques to identify potential modeling errors. Analyzing the dependencies between uncontrolled system component models and requirement models with both a domain mapping matrix and a dependency structure matrix reveals potential modeling errors. We present several examples of models from literature to show the potential effectiveness of the DSM-supported analysis of the uncontrolled system and the associated control requirements.</p

Integration of supervisory control synthesis in model-based systems engineering

Due to increasing system complexity, time-to-market and development costs reduction, there are higher demands on engineering processes. Model-based engineering processes can play a role here because they support system development by enabling the use of various model-based analysis techniques and tools. As a result, they are able to cope with complexity and have the potential to reduce time-to-market and development costs. Moreover, supervisory control synthesis can be integrated in this setting, which can contribute to the development of control systems. This paper gives an overview of recently developed supervisor synthesis techniques and tools. To evaluate the applicability of these techniques and to show how they can be integrated in an engineering process, a few industrial cases are discussed. The supervisors synthesized for these cases have successfully been implemented and integrated in the existing resource-control platform

Integration of supervisory control synthesis in model-based systems engineering

Due to increasing system complexity, time-to-market and development costs reduction, there are higher demands on engineering processes. Model-based engineering processes can play a role here because they support system development by enabling the use of various model-based analysis techniques and tools. As a result, they are able to cope with complexity and have the potential to reduce time-to-market and development costs. Moreover, supervisory control synthesis can be integrated in this setting, which can contribute to the development of control systems. This paper gives an overview of recently developed supervisor synthesis techniques and tools. To evaluate the applicability of these techniques and to show how they can be integrated in an engineering process, a few industrial cases are discussed. The supervisors synthesized for these cases have successfully been implemented and integrated in the existing resource-control platform