Sandeep Patil

Neutralizing Semantic Ambiguities of Function Block Architecture by Modeling with ASM

The Function Blocks Architecture of the IEC 61499 standard is an executable component model for distributed embedded control systems combining block-diagrams and state machines. The standard aims at the portability of control applications that is however hampered by ambiguities in its execution semantics descriptions. In recent years several execution models have been implemented in different software tools that generate mutually incompatible code.

Formal Modelling and Verification of IEC61499 Function Blocks with Abstract State Machines and SMV - Execution Semantics

IEC 61499 Standard for Function Blocks Architecture is an executable component model for distributed embedded control system design that combines block-diagrams and state machines. This paper proposes approach to formal modelling of IEC61499 function block execution semantics for popular model checking environment of SMV using Abstract State Machines. An operational semantics of IEC 61499 application with two-stage synchronous execution model is presented using this framework. This paper first introduces the importance of model checking function block applications in different execution semantics. It highlights the uses of formal verification, such as, verifying portability behavior of component based control applications across different implementation platforms compliant with the IEC 61499 standard. The formal model is applied on an example IEC 61499 application. The paper compares the verification results of this IEC 61499 application with two-stage synchronous execution model and the same application with cyclic execution model presented in the earlier work. With this comparison, we verify the portability of the IEC61499 applications across different platforms.

Cloud-Based Framework for Practical Model-Checking of Industrial Automation Applications

In this paper we address practical aspects of applying the model-checking method for industrial automation systems verification. Several measures are proposed to cope with the high computational complexity of model-checking. To improve scalability of the method, cloud-based verification tools infrastructure is used. Besides, closed-loop plant controller modelling and synchronization of transitions in the SMV (input language for symbolic model checking) model aim at complexity reduction. The state explosion problem is additionally dealt with by using an abstraction of the model of the plant with net-condition event systems, which is then translated to SMV. In addition, bounded model-checking is applied, which helps to achieve results in cases when the state space is too high. The paper concludes with comparison of performance for different complexity reduction methods.

IEC 61499 distributed control enhanced with cloud-based web-services

This paper presents a framework for employing cloud- deployable web services in the design of distributed control systems in industrial automation. The paper demonstrates how a part of the control logic can be developed as a web service and deployed in the cloud to improve reusability and flexibility. In order to demonstrate the use of the framework we consider an example of Pick-and-Place Manipulator, which was originally designed as IEC 61499 function block application with a distributed control consisting of a high level and a low-level control logic. Firstly the high level control and its functionality is converted to a web services and deployed to a cloud. Secondly the application is modified such that the low level control interacts with these newly developed web services. The paper also presents an interface between low level control and web service using dynamic linked library that bridges communication between the two components It concludes with the simulation results of the of Pick-and-Place Manipulator implemented using the proposed framework.

Reconstruction of function block logic using metaheuristic algorithm: Initial explorations

This paper presents an approach for automatic reconstruction of automation logic from execution scenarios using a metaheuristic algorithm. The IEC 61499 basic function blocks is chosen as implementation language and reconstruction of Execution Control Charts for basic function blocks is addressed. The synthesis method is based on a metaheuristic algorithm most closely related to ant colony optimization and evolutionary computation. Execution scenarios can be recorded from testing legacy software solutions. At this stage results are only limited to generation of basic function blocks having only Boolean input/output variables.

Cyber-physical components for heterogeneous modelling, validation and implementation of smart grid intelligence

This paper presents a practical framework to bring the cyber-physical block diagram models, such as Ptolemy, to the practice of industrial automation. Cyber-Physical Component (CPC) architecture is suggested. CPC aims at the improvement of design, verification and validation practices in automation of Smart Grid. IEC 61499 standard is used as a basis for this architecture. This architecture addresses several design software and system engineering challenges: right equilibrium between abstract representation and “executability” and round-trip engineering. An CPC exhibit such properties as portability, interoperability and configurability thanks to the reliance on open standards. The use of time stamp based execution paradigm adds determinism and predictability at the run-time.

Counterexample-guided simulation framework for formal verification of flexible automation systems

This paper proposes a framework for formal verification of industrial automation software in an intuitive way. The IEC 61499 function block architecture is assumed to be the input language, and the Intelligent Mechatronic Components (IMC) architecture is assumed as an underlying design pattern for the applications, which implies autonomous control logic in each IMC and their compositions to systems in a plug-and-play way. Then the system is automatically verified using model checking and the counter examples for the failed model checking properties are played back step-by-step and state-by-state in the simulation model that most industrial automation control systems would have built as the basis for initial testing. Net Condition Event Systems formalism (a modular extension of Petri net) is used to model the decentralized control logic and discrete-state dynamics of the plant. The model is then subjected to model checking using the ViVe/SESA tool chain. The methods application is illustrated using a simple pick and place manipulator. A closed loop model of Plant and Controller is used. Controller is extensively verified for safety, liveliness and functional properties of the robot. We then show how a counter example for deadlock detected by the model checker is played back in the simulation model for visualizing how exactly the system deadlocked.

Towards formal verification of smart grid distributed intelligence: FREEDM case

This paper presents a model-checking framework for the purpose of design and implementation of robust smart grid applications based on distributed intelligence. The paper first introduces distributed grid intelligence approach to smart grid automation and related challenges of their verification. We then introduce the case study example and how model-checking can be applied to the presented system implemented in IEC 61499 standard. In the end we present the initial results of our model-checking application to smart grid applications. The paper will conclude with some issues faced during the research and corrective steps to address these issues in future.

Formal verification of cyber-physical automation systems modelled with timed block diagrams

In this paper a new modelling approach is presented to be used for formal-verification of block-diagram executable specifications of distributed industrial cyber-physical systems following the IEC 61499 standard. The approach allows usage of timers and arithmetic operations in the controller code. SMV model-checker is used as the target tool. The function block modelswith multiple communicating plant-controller closed-loops are transformed to the SMV modelling language using a dedicated model-generator tool. The paper first deals with SMV modelling of the IEC 61499 specific timer function block types. In particular, modelling of hierarchical function block systems with timers located at different levels of hierarchy is addressed. The paper then presents plant abstraction techniques so that the complexity of cyber-physical systems models is reduced. The abstraction uses discrete-timed state machine model implemented in UPPAAL. Delays in the plant model are interpreted as model time constraints. The approach is illustrated with an example of formal verification of a modular mechatronic automated system. The achieved results extend the abilities in validation of real cyber-physical automation systems. The paper also demonstrates how this result helps in counterexample guided simulation in Ciros 3D simulation environment, which improves practical usability of formal verification.

Orchestration of Arrowhead services using IEC 61499: Distributed automation case study

This paper presents a novel approach to automation of flexible manufacturing systems with mechatronic intelligence and distributed control. The mechatronic intelligence layer is implemented using a combination of wireless sensor/actuator networks with service-oriented architecture, where services are located at the device level, as well as in local and global Clouds following the Arrowhead framework.