Martin Fabian

Chalmers University of Technology · Department of Electrical Engineering

The Conflict-Free Electric Vehicle Routing Problem (CF-EVRP) is a combinatorial optimization problem of designing routes for vehicles to execute tasks such that a cost function, typically the number of vehicles or the total travelled distance, is minimized. The CF-EVRP involves constraints such as time windows on the tasks’ execution, limited opera...

This survey gives an overview of the current research on compositional algorithms for verification and synthesis of modular systems modelled as interacting finite-state machines. Compositional algorithms operate by repeatedly simplifying individual components of a large system, replacing them by smaller so-called abstractions, while preserving crit...

The original version of this paper contains errors in many tables and equations mistakes and has been submitted by mistake. This has been corrected.

This paper presents an algorithm for synthesizing a supervisor for timed automata (TA) using the conventional supervisory control theory. The algorithm is directly applicable to TA without explicit transformation into finite automata, and iteratively strengthens the guards of edges labeled by controllable events and invariants of locations where th...

This method generates input signals to a simulation of the system under test and uses quantitative semantics that plays the role of objective functions to minimize the distance to falsify a specification. This paper presents and evaluates differently structured parameterizations of input generators: pulse, sinusoidal, and piecewise with different i...

The Conflict-Free Electric Vehicle Routing Problem (CF-EVRP) is a combinatorial optimization problem of designing routes for vehicles to visit customers such that a cost function, typically the number of vehicles or the total travelled distance, is minimized. The CF-EVRP involves constraints such as time windows on the delivery to the customers, li...

Smart contracts are programs that are stored on a blockchain ledger with code immutable after deployment. Thus, verifying the correct behavior of smart contracts before deployment is vital. This paper demonstrates how a security vulnerability verification in a casino smart contract can be transformed to non-blocking verification. To this end, the c...

Supervisory control theory provides an approach to synthesize supervisors for cyber-physical systems using a model of the uncontrolled plant and its specifications. These supervisors can help guarantee the correctness of the closed-loop controlled system. However, access to plant models is a bottleneck for many industries, as manually developing th...

The safety of automated driving systems must be justified by convincing arguments and supported by compelling evidence to persuade certification agencies, regulatory entities, and the general public to allow the systems on public roads. This persuasion is typically facilitated by compiling the arguments and the compelling evidence into a safety cas...

Cyber-physical systems are often safety-critical and their correctness is crucial, as in the case of automated driving. Using formal mathematical methods is one way to guarantee correctness. Though these methods have shown their usefulness, care must be taken as modeling errors might result in proving a faulty controller safe, which is potentially...

Safety critical systems are typically subjected to hazard analysis before commissioning to identify and analyse potentially hazardous system states that may arise during operation. Currently, hazard analysis is mainly based on human reasoning, past experiences, and simple tools such as checklists and spreadsheets. Increasing system complexity makes...

The automation system of the future will consist of an increasing amount of complex resources, such as collaborative robots and/or autonomously roaming robots for material handling. To control these devices in an environment shared with human operators require state of the art computer perception and motion planning algorithms to be used as part of...

Cyber-physical systems are often safety-critical and their correctness is crucial, as in the case of automated driving. Using formal mathematical methods is one way to guarantee correctness. Though these methods have shown their usefulness, care must be taken as modeling errors might result in proving a faulty controller safe, which is potentially...

italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Compositional Optimization (CompOpt) was recently proposed for optimization of discrete-event systems of systems. A modular optimization model allows CompOpt to divide the optimization into separate sub-problems, mitigating the state space explosion pr...

The Conflict-Free Electric Vehicle Routing Problem (CF-EVRP) is an extension of the Vehicle Routing Problem (VRP), a combinatorial optimization problem of designing routes for vehicles to visit customers such that a cost function, typically the number of vehicles or the total travelled distance, is minimized. The problem finds many logistics applic...

This paper proposes a method to synthesise controllers for cyber-physical systems such that the controlled systems satisfy specifications given as linear temporal logic formulas. The focus is on systems with disturbance, where future states cannot be predicted exactly due to uncertainty in the environment. The approach used to solve this problem is...

This paper presents a framework that tackles the challenges met in the development of automation systems featuring collaborative robotics and other machines that have some degree of autonomy. These machines rely on online algorithms for both sensing and acting in order to achieve a very high level of flexibility. To take advantage of these new mach...

The challenges in providing convincing arguments for safe and correct behavior of automated driving (AD) systems have so far hindered their widespread commercial deployment. Conventional development approaches such as testing and simulation are limited by non-exhaustive analysis, and can thus not guarantee correctness in all possible scenarios. For...

This paper presents an approach to reduce the number of test cases, and hence testing time for the safe input-output conformance simulation relation (safe-IOCOS). The safe-IOCOS relation requires the implementation to be trace equivalent with respect to the specification only for traces composed of safety behaviors, which makes safe-IOCOS a suitabl...

The Conflict-Free Electric Vehicle Routing Problem (CF-EVRP) is an extension of the Vehicle Routing Problem (VRP), a combinatorial optimization problem of designing routes for vehicles to visit customers such that a cost function, typically the number of vehicles or the total travelled distance, is minimized. The problem finds many logistics applic...

The correctness of autonomous driving software is of utmost importance, as incorrect behavior may have catastrophic consequences. Formal model-based engineering techniques can help guarantee correctness and thereby allow the safe deployment of autonomous vehicles. However, challenges exist for widespread industrial adoption of formal methods. One o...

The challenges in providing convincing arguments for safe and correct behavior of automated driving (AD) systems have so far hindered their widespread commercial deployment. Conventional development approaches such as testing and simulation are limited by non-exhaustive analysis, and can thus not guarantee safety in all possible scenarios. Formal m...

This paper presents an approach to automatically amend an erroneous model of an implementation using a safety specification as the basis to ensure safety. Industrially, safety PLCs are common to ensure safe operations. However, before its commissioning, the implemented safety code must be tested for faults caused by spurious transitions and missing...

Cyber-physical systems (CPSs) are complex and exhibit both continuous and discrete dynamics, hence it is difficult to guarantee that they satisfy given specifications, i.e., the properties that must be fulfilled by the system. Falsification of temporal logic properties is a testing approach that searches for counterexamples of a given specification...

To avoid the state-space explosion problem, a set of supervisors may be synthesized using divide and conquer strategies, like modular or multilevel synthesis. Unfortunately, these supervisors may be conflicting, meaning that even though they are individually non-blocking, they are together blocking. Abstraction-based compositional nonblocking verif...

A tool, MIDES, for automatic learning of models and supervisors for discrete event systems is presented. The tool interfaces with a simulation of the target system to learn a behavioral model through interaction. There are several different algorithms to choose from depending on the intended outcome. Moreover, given a set of specifications, the too...

div>Cyber-physical systems (CPSs) are complex and exhibit both continuous and discrete dynamics, hence it is difficult to guarantee that they satisfy given specifications, i.e., the properties that must be fulfilled by the system. Falsification of temporal logic properties is a testing approach that searches for counterexamples of a given specifica...

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. This paper proposes a format for the requirements and a method...

The Vehicle Routing Problem (VRP) is the combinatorial optimization problem of designing routes for vehicles to visit customers in such a fashion that a cost function, typically the number of vehicles, or the total travelled distance is minimized. The problem finds applications in industrial scenarios, for example where Automated Guided Vehicles ru...

div>Cyber-physical systems (CPSs) are complex and exhibit both continuous and discrete dynamics, hence it is difficult to guarantee that they satisfy given specifications, i.e., the properties that must be fulfilled by the system. Falsification of temporal logic properties is a testing approach that searches for counterexamples of a given specifica...

div>Cyber-physical systems (CPSs) are complex and exhibit both continuous and discrete dynamics, hence it is difficult to guarantee that they satisfy given specifications, i.e., the properties that must be fulfilled by the system. Falsification of temporal logic properties is a testing approach that searches for counterexamples of a given specifica...

div>Cyber-physical systems (CPSs) are complex and exhibit both continuous and discrete dynamics, hence it is difficult to guarantee that they satisfy given specifications, i.e., the properties that must be fulfilled by the system. Falsification of temporal logic properties is a testing approach that searches for counterexamples of a given specifica...

The Vehicle Routing Problem (VRP) is the combinatorial optimization problem of computing routes to serve customers while minimizing a cost function, typically the travelled distance or the number of vehicles required for a given performance. Industrial applications of the problem in manufacturing plants is the scheduling and routing of Automated Gu...

Conventional supervisory control theory assumes full synchronization between the supervisor and the plant. This assumption is violated in a networked-based communication setting due to the presence of delays, and this may result in incorrect behavior of a supervisor obtained from conventional supervisory control theory. This paper presents a techni...

Considering real-valued clocks in timed automata (TA) makes it a practical modeling framework for discrete-event systems. However, the infinite state space brings challenges to the control of TA. To synthesize a supervisor for TA using the conventional supervisory control theory, existing methods abstract TA to finite automata (FA). For many applic...

The correctness of autonomous driving software is of utmost importance as incorrect behaviour may have catastrophic consequences. Though formal model-based engineering techniques can help guarantee correctness, challenges exist in widespread industrial adoption. One among them is the model construction problem. Manual construction of formal models...

Bin packing and bin covering are important optimization problems in many industrial fields, such as packaging, recycling, and food processing. The problem concerns a set of items, each with its own value, that are to be sorted into bins in such a way that the total value of each bin, as measured by the sum of its item values, is not above (for pack...

Development of safety critical systems requires a risk management strategy to identify and analyse hazards, and apply necessary actions to eliminate or control them as malfunctions could be catastrophic. Fault Tree Analysis (FTA) is one of the most widely used methods for safety analysis in industrial use. However, the standard FTA is manual, infor...

Supervisory control theory provides means to synthesize supervisors for cyber-physical systems from models of the uncontrolled plant and models of the control requirements. It has been shown that in general supervisory control synthesis is NP-hard. However, for several industrial systems supervisory control synthesis verifies that the provided cont...

The technological advancements of recent years have increased the complexity of manufacturing systems, and the ongoing transformation to Industry 4.0 will further aggravate the situation. This is leading to a point where existing systems on the factory floor get outdated, increasing the gap between existing technologies and state-of-the-art systems...

This paper proposes an approach to synthesize a modular discrete-event supervisor to control a plant, the behavior model of which is unknown, so as to satisfy given specifications. To this end, the Modular Supervisor Learner (MSL) is presented that based on the known specifications and the structure of the system defines the configuration of the su...

Model-based techniques are these days being embraced by the industry in their development frameworks. While model-based approaches allow for offline verification and validation of the system, and have other advantages over existing methods, they do have their own challenges. One of the challenges is to obtain a model describing the behavior of the...

This paper proposes an approach to synthesize a modular discrete-event supervisor to control a plant, the behavior model of which is unknown, so as to satisfy given specifications. To this end, the Modular Supervisor Learner (MSL) is presented that based on the known specifications and the structure of the system defines the configuration of the su...

Automated vehicles need a safe back-up solution in the presence of system degradations since a driver cannot be expected to take control on short notice. In the event of a degradation, the vehicle is required to reach a minimal risk condition via a minimal risk maneuver. The activation of such maneuvers is safety critical, and a correct implementat...

A transition system represented by guards and actions can be amended by new guards computed in order to satisfy some specification. If the transition system is the result of composing smaller state machines, guard extraction can be used to put the new guards onto the guards the original state machines. Planning and verification can then be performe...

Real-valued clocks make the state space of timed automata (TA) infinite. Conventional supervisory control synthesis techniques are only applicable to finite automata (FA). Therefore, to synthesize a supervisor for TA using conventional techniques, an abstraction of TA to FA is required. For many applications, the abstraction of real-time values res...

Cyber-physical systems are typically safety-critical, thus it is crucial to guarantee that they conform to given specifications, that are the properties that the system must fulfill. Optimization-based falsification is a model-based testing method to find counterexamples of the specifications. The main idea is to measure how far away a specificatio...

Model-based techniques are these days being embraced by the industry in their development frameworks. While model-based approaches allow for offline verification and validation of the system, and have other advantages over existing methods, they do have their own challenges. One of the challenges is to obtain a model describing the behavior of the...

In this paper, limitations of the IOCOS testing relation in regard to testing safety PLC code is examined and a modification of the current IOCOS relation, called safe-IOCOS is proposed. In the IOCOS testing relation, an implementation is IOCOS with respect to a specification, if it emits a subset of the specified outputs and a super-set of the spe...

This paper presents an approach for testing safety PLC logic in a virtual environment, using the IOCO testing relation as validation criteria. Manufacturing companies more and more rely on virtual commissioning to reduce the physical commissioning time by testing and debugging the PLC logic of the nominal behavior prior to physical commissioning. H...

This paper proposes an approach to synthesize a discrete-event supervisor to control a plant, the behavior model of which is unknown, so as to satisfy a given specification. To this end, the $L^*$ algorithm is modified so that it can actively query a plant simulation and the specification to hypothesize a supervisor. The resulting hypothesis is the...

In conventional supervisory control theory, a plant and supervisor are supposed to work synchronously such that enabling an event by the supervisor, execution of it in the plant, and observation of the executed event by the supervisor all occur at once. Therefore, these occurrences are all captured by means of a single event. However, when a superv...

Correctness of autonomous driving systems is crucial as incorrect behaviour may have catastrophic consequences. Many different hardware and software components (e.g. sensing, decision making, actuation, and control) interact to solve the autonomous driving task, leading to a level of complexity that brings new challenges for the formal verification...

In this paper, an approach based on the IOCOS testing relation to test safety PLC code using the tool QuickCheck is presented. Testing and validation of the safety PLC code is typically carried out on a physical system using checklists. These checklists are developed by engineers using system specification. However, due to the manual nature of chec...

This paper contains a link to my pages on Chalmers Univerity's website for research dissemination, where (allmost) all of the papers co-authored by me are available in full-text. The link is https://research.chalmers.se/organisation/?tab=publications&query=martin+fabian

The need for tools to help guide decision making is growing within the manufacturing industry. The analysis performed by these tools will help operators and engineers to understand the behavior of the manufacturing stations better and thereby take data-driven decisions to improve them. The tools use techniques borrowed from fields such as Data Anal...

In this paper, an approach to incorporate a digital twin for legacy production systems is presented. Hardware-in-the-loop setups are routinely used by manufacturing companies to carry out virtual commissioning. However, manufacturing companies having online legacy production systems are still struggling to incorporate a digital twin due to the abse...

Model-based techniques are, these days, being embraced by the manufacturing industry in their development frameworks. While model-based approaches allow for offline verification and validation before physical commissioning, and have other advantages over existing methods, they do have their own challenges. Firstly, models are typically created manu...

Unexpected incorrect behavior of autonomous vehicles can have catastrophic outcomes. But, as with any large-scale software development, correctness of the system is not easily guaranteed. As the system is made up of multiple sub-modules that interact with each other, unexpected behavior can arise from incorrect interactions between the modules. In...

Evaluation of manufacturing systems requires large amounts of accurate data from the factory floor. This data is then processed to calculate Key Performance Indicators (KPIs), evaluation metrics used within the manufacturing industry by engineers and managers in order to make data-driven decisions. Mechanisms to capture large scales of usable data,...

This paper presents a method where the behavior of a robot cell is automatically modeled based on existing robot programs and a simulation model of the cell. Robot programs from the shop floor are uploaded into a virtual manufacturing tool, and a formal model is then generated from the robot programs. Then, control logic is automatically calculated...

It is essential to understand the operation sequences of a production system when designing or changing it. This paper will demonstrate how the software tool Sequence Planner (SP) not only supports this understanding by sequence visualization, but also improves the solution using optimization and verification. SP is a tool for modeling and analyzin...

Testing of cyber-physical systems (CPSs) is a complex task, mainly due to the presence of continuous dynamics. In industry, CPSs are typically safety-critical and their complexity is rapidly increasing. Thus, it is important to know how well the tests perform. One common approach to ensuring test quality is to use coverage criteria, for example the...

Supremica is a tool for the modelling and analysis of discrete-event control functions based on state machine models of the uncontrolled plant and specification of the desired closed-loop behaviour. The modelling framework in Supremica is based on finite-state machines extended with variables, guard conditions, and action functions. In order to han...

The Eleventh Annual IEEE International Conference on Automation Science and Engineering (CASE 2015) was held on August 24–28, at Elite Park Avenue Hotel in Gothenburg, Sweden. IEEE CASE represents the Flagship Automation Conference of the IEEE Robotics and Automation Society and constitutes the primary forum for cross-industry and multidisciplinary...

This paper investigates the compositional abstraction-based synthesis of least restrictive, controllable, and nonblocking supervisors for discrete event systems that are given as a large number of finite-state machines. It compares a previous algorithm that synthesises modular supervisors in the form of state machines, with an alternative that reco...