Knut Åkesson

Chalmers University of Technology · Department of Signals and Systems

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...

To explore safe interactions between a mobile robot and dynamic obstacles, this paper presents a comprehensive approach to collision-free navigation in dynamic indoor environments. The approach integrates multimodal motion predictions of dynamic obstacles with predictive control for obstacle avoidance. Multimodal Motion Prediction (MMP) is achieved...

In this paper, we present an efficient approach to ensuring real-time, collision-free navigation for mobile robots. By integrating deep reinforcement learning with model predictive control, our aim is to achieve both collision avoidance and computational efficiency. The methodology begins with training a preliminary agent using deep Q-learning, ena...

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...

The aim of this technical report is to investigate the effect of input parameters on the falsification of cyber-physical systems (CPSs).

Cyber-physical systems (CPSs) are usually complex and safety-critical; hence, it is difficult and important to guarantee that the system's requirements, i.e., specifications, are fulfilled. Simulation-based falsification of CPSs is a practical testing method that can be used to raise confidence in the correctness of the system by only requiring tha...

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...

A framework for data collection and visualization of operational deviation at a Volvo truck manufacturing plant implementing Volvo Group’s production system, Volvo Production System (VPS), is presented. This includes visualisation of daily quality performance indicators to support decision making and improvement actions at the shop foor team level....

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...

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...

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 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...

This paper presents an approach to collision-free, long-range trajectory generation for a mobile robot in an industrial environment with static and dynamic obstacles. For the long range planning a visibility graph together with A* is used to find a collision-free path with respect to the static obstacles. This path is used as a reference path to th...

This paper presents an approach to collision-free, long-range trajectory generation for a mobile robot in an industrial environment with static and dynamic obstacles. For the long range planning a visibility graph together with A* is used to find a collision-free path with respect to the static obstacles. This path is used as a reference path to th...

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...

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...

Cyber-Physical Systems (CPSs) are systems with both physical and software components, for example cars and industrial robots. Since these systems exhibit both discrete and continuous dynamics, they are complex and it is thus difficult to verify that they behave as expected. Falsification of temporal logic properties is an approach to find counterex...

The manufacturing industry resumes operations after the COVID-19 pandemic supported by return-to-work guidelines, which are mostly personal protection measures for the workers and employees. In this paper, we propose a framework for assessing risk at the workstation level by linking the risk levels to possible mitigation strategies that can be impl...

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...

Cyber-Physical Systems (CPSs) are systems with both physical and software components, for example cars and industrial robots. Since these systems exhibit both discrete and continuous dynamics, they are complex and it is thus difficult to verify that they behave as expected. Falsification of temporal logic properties is an approach to find counterex...

We propose a new logic of valued Booleans for writing properties which are not just true or false but compute how severely they are falsified. The logic is reminiscent of STL or MTL but gives the tester control over what severity means in the particular problem domain. We use this logic to simplify failing test inputs in the context of random testi...

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...

Configurable products, like vehicles, face the challenge of handling all possible variants which are needed to answer the various customer needs. For these configurable products the support of all variants need to be addressed both by the design phase and the production phase. The product design phase and the production phase are linked together vi...

Product configuration is when an artifact from a product family is assembled from a set of predefined components that can only be combined in certain ways. These ways are defined by configuration rules. The product developers inspect the configuration rules when they develop new configuration rules or modify the configuration rules set. The inspect...

In some recent work, we proposed a binary decision diagram (BDD-) based approach for the development of the maximally permissive deadlock avoidance policy (DAP) for complex resource allocation systems (RAS), that is based on the identification and the explicit storage of a set of critical states in the underlying RAS state-space. The work presented...

In order to develop a computationally efficient implementation of the maximally permissive deadlock avoidance policy (DAP) for complex resource allocation systems (RAS), a recent approach focuses on the identification of a set of critical states of the underlying RAS state-space, referred to as minimal boundary unsafe states. The availability of th...

The state-space explosion problem, resulting from the reachability computations in controller synthesis, is one of the main obstacles preventing supervisory control theory from having an industrial breakthrough. To alleviate this problem, a strategy is to symbolically perform the synthesis procedure using binary decision diagrams. Based on this pri...

In the automotive industry in general, but in particular for trucks, the vehicle can be configured to fit specific needs of every customer. For trucks, this means that one truck physically can be very different from another truck, for example one truck may be configured to support long-distance transportation, another will be used for inner-city di...

We symbolically compute a nonblocking, controllable, and minimally restrictive supervisor for timed discrete event systems (TDESs), in the supervisory control theory context. We model TDES based on timed extended finite automata (TEFAs): an augmentation of extended finite automata (EFAs) by incorporating discrete time into the model. EFAs are ordin...

This paper presents an empirical study of control logic specifications used to document industrial control logic code in manufacturing applications. More than one hundred input/output related property specifications from ten different reusable function blocks were investigated. The main purpose of the study was to provide understanding of how the s...

Product platforms are commonly used in industries with complex products and high competition like the car and truck industry to allow a customer to order a product that satisfy its unique needs. A consequence of product variety is that manufacturing and assembly processes need to deal with this variety as well. If the variety is low and changes of...

Discrete event systems (DES) are typically man-made reactive systems such as manufacturing, traffic control and embedded systems. DES behaviours are modelled in terms of states and events; states represent certain situations under which specific properties hold, while events represent significant occurrences that change those properties. A DES occu...

A generic state-vector transition (SVT) model is suggested, including a flexible synchronous composition involving both shared variables and events. This model is analyzed, focusing on properties that are important for supervisor synthesis. A synthesis procedure is then developed for the SVT model, where supervisor guards are generated that guarant...

In this paper, we symbolically represent timed discrete-event systems (TDES), which can be used to efficiently compute the supervisor in the supervisory control theory context. We model a TDES based on timed extended finite automata (TEFAs): an augmentation of extended finite automata (EFAs) by incorporating discrete time into the model. EFAs are o...

This paper addresses a visual tracking and analysis method for automatic monitoring of an industrial manual assembly process, where each worker sequentially picks up components from different boxes during an a ssembling process. Automatic surveillance of assembling process would enable to reduce assembling errors by giving early warning. We propose...

Supervisory Control Theory (SCT) is a model-based framework for automatically synthesizing a supervisor that minimally restricts the behavior of a plant such that given specifications is fulfilled. The main obstacle which prevents SCT from having a major industrial breakthrough is that the supervisory synthesis, consisting of a series of reachabili...

In this paper, we symbolically compute a minimally restrictive nonblocking supervisor for timed discrete event systems, in the supervisory control theory context. The method is based on Timed Extended Finite Automata, which is an augmentation of extended finite automata (EFAs) by incorporating discrete time into the model. EFAs are ordinary automat...

In this paper, we settle some problems that are encountered when modeling and synthesizing complex industrial systems by the supervisory control theory. First, modeling such huge systems with explicit state-transition models typically results in an intractable model. An alternative modeling approach is to use extended finite automata (EFAs), which...

Formal methods for specification and verification are promising in developing programmable logic controller (PLC) programs in manufacturing industry. Particularly this holds for safety PLCs, used to protect humans and equipment from injuries and damages. An important challenge though, is the development of formal specifications, typically a tough t...

In supervisory control theory, a supervisor restricts the plant in order to fulfill given specifications. A problem for larger industrial applications is that the resulting supervisor is not easily implemented and comprehensible for the users. To tackle this problem, an efficient method has recently been introduced to characterize a supervisor by t...

The state-space explosion problem, resulting from the reachability computation of the synthesis task, is one of the main obstacles preventing the supervisory control theory (SCT) from having an industrial breakthrough. To alleviate this problem, a well-known strategy is to utilize binary decision diagrams (BDDs) to compute supervisors symbolically....

In the development of complex products product configuration systems are often used to support the development process. Item Usage Rules (IURs) are conditions for including specific items in products bills of materials based on a high-level product description. Large number of items and significant complexity of IURs make it difficult to maintain a...

The sequential behavior of a manufacturing system results from several constraints introduced during the product, manufacturing, and control logic development. This paper proposes methods and algorithms for automatically representing and visualizing this behavior from various perspectives throughout the development process. A new sequence planning...

In the supervisory control theory, a supervisor is generated based on given plant and specification models. The supervisor restricts the plant in order to fulfill the specifications. A problem that is typically encountered in industrial applications is that the resulting supervisor is not easily comprehensible for the users. To tackle this problem,...

Deadlock avoidance for resource allocation systems (RAS) is a well-established problem in the Discrete Event System (DES) literature. This paper is mainly concerned with modeling the class of Conjunctive / Disjunctive sequential resource allocation systems (C/D RAS) as finite automata extended with variables. The proposed modeling approach allows f...

In this paper, we settle some problems that are encountered when modeling and synthesizing complex indus- trial systems by the supervisory control theory. First, modeling such huge systems with explicit state-transition models typi- cally results in an intractable model. An alternative modeling approach is to use extended finite automata (EFAs), wh...

Extended Finite Automata (EFA), i.e., finite automata extended with variables, are a suitable modeling framework for discrete event systems owing to their compactness, resulting from the use of variables. In this paper, we propose a symbolic algorithm that efficiently synthesizes a supervisor for a plant modeled by an EFA and a specification define...

Models of configurable products can have hundreds of variables and thousands of configuration constraints. A product engineer usually has a limited responsibility area, and thus is interested in only a small subset of the variables that are relevant to the responsibility area. It is important for the engineer to have an overview of possible product...

Supervisory Control Theory (SCT) is a model based framework for automatically synthesizing a supervisor that minimally restricts the behavior of a plant such that a given specification is fulfilled. A problem, which prevents SCT from having a major breakthrough industrially, is that the supervisory synthesis often suffers from the state-space explo...

The supervisory control theory (SCT) is a model-based framework, which automatically synthesizes a supervisor that restricts a plant to be controlled based on specifications to be fulfilled. Two main problems, typically encountered in industrial applications, prevent SCT from having a major breakthrough. First, the supervisor which is synthesized a...

In order to obtain a unified information flow from early product design to final production, an integrated framework for product, process and automation design is presented. The framework is based on sequences of operations and includes a formal relation between product properties and process operations. This relation includes liaisons (interfaces)...

The sequential behavior of a manufacturing system results from a number of constraints introduced both in product, manufacturing and control logic development. Sequence planning is therefore an important activity throughout the complete development process. This paper proposes a sequence planning approach using self-contained manufacturing operatio...

Formal verification, using model checking tools, is promising in developing (IEC 61131) industrial control logic. Formal verification requires a formal specification of the properties to be verified. Specifications in model checking tools are typically expressed using temporal logic. However, the standard temporal logic dialects are not well suited...

For Discrete Event Systems (DES) modeled as Finite Automata, supervisory control theory has been extensively studied. Extended Finite Automata (EFA), i.e., finite automata extended with variables, are a suitable modeling framework for discrete event systems owing to their compactness, resulting from the use of variables. In this paper, we propose a...

Component-based programming frameworks for industrial control logic development promise to shorten development and modification times, and to reduce programming errors. To get these benefits, it is, however, important that the components are specified and verified to work properly. This work introduces Reusable Automation Components (RACs), which c...

IEC 61499 is a standard architecture, based on function blocks, for developing distributed control and measurement applications. However, the standard has no formal semantics and different interpretations of the standard have emerged. As a consequence, it is harder to transfer applications between different standard compliant platforms. This paper...

IEC 61499 is a standard architecture, based on function blocks, for developing distributed control and measurement applications. However, the standard has no formal semantics and different interpretations of the standard have emerged. As a consequence, the execution behavior of applications running on different platforms may exhibit different behav...

In this chapter a study of PLC programming and use of library components at two Swedish car manufacturers is presented. Both companies used several programs for each PLC, implemented mainly in LD and SFC. These programs included lots of instances of reusable function blocks, FBs. Some of the most frequent FBs were used for automatic control of actu...

When supervisory control theory is applied to industrial problems the need for a more expressive modeling formalism than plain event based automata is crucial. The models are typically built in a bottom-up structure where multiple sub-plant and sub-specifications together compose the full plant and specification, respectively. Typically, the enabli...

A method for solving the forbidden state problem in the Supervisory Control Theory framework is presented. In many real-world applications both the plant and specification is given as a set of interacting automata or processes. In this work, we enable specification of forbidden states within such a modular structure. The aim with the method is to m...