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Ulrik Schultz

Syddansk Universitet, Technology, Faculty Member

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Papers by Ulrik Schultz

PReGO: a generative methodology for satisfying real-time requirements on COTS-based systems: definition and experience report

Proceedings of the 19th ACM SIGPLAN International Conference on Generative Programming: Concepts and Experiences, 2020

Satisfying real-time requirements in cyber-physical systems is challenging as timing behaviour de... more Satisfying real-time requirements in cyber-physical systems is challenging as timing behaviour depends on the application software, the embedded hardware, as well as the execution environment. This challenge is exacerbated as realworld, industrial systems often use unpredictable hardware and software libraries or operating systems with timing hazards and proprietary device drivers. All these issues limit or entirely prevent the application of established real-time analysis techniques. In this paper we propose PReGO, a generative methodology for satisfying real-time requirements in industrial commercial-off-the-shelf (COTS) systems. We report on our experience in applying PReGO to a use-case: a Search & Rescue application running on a fixed-wing drone with COTS components, including an NVIDIA Jetson board and a stock Ubuntu/Linux. We empirically evaluate the impact of each integration step and demonstrate the effectiveness of our methodology in meeting real-time application requirements in terms of deadline misses and energy consumption.

Energy-Aware Design of Vision-Based Autonomous Tracking and Landing of a UAV

2020 Fourth IEEE International Conference on Robotic Computing (IRC), 2020

In this paper, we present the design and evaluation of a vision-based algorithm for autonomous tr... more In this paper, we present the design and evaluation of a vision-based algorithm for autonomous tracking and landing on a moving platform in varying environmental conditions. We use an energy-aware approach, where the design of the algorithm is based on an evaluation of the energy consumption and Quality of Service (QoS) of each computational component. We evaluate our approach with an agricultural use case where a moving platform is tracked using a landing marker and the YOLOv3tiny CNN is used to detect ground-based hazards. We perform all computations onboard using an NVIDIA Jetson Nano and analyse the impact on the flight time by profiling the energy consumption of the marker detection and the CNN. Experiments are conducted in Gazebo simulation using an energy modeling tool to measure the computational energy cost as a function of QoS. We test the energy efficiency and robustness of our system in various dynamic wind disturbances. We show that the marker detection algorithm can be run at the highest QoS with only a marginal energy overhead whereas adapting the QoS level of CNN results in a considerable power saving. The power saving is significant for a system executing on a fixed-wing UAV.

Object-Oriented Software Engineering using Partial Evaluation

Object-oriented programming languages facilitate mapping an abstract characterization of a proble... more Object-oriented programming languages facilitate mapping an abstract characterization of a problem into a generic, extensible implementation built from reusable program components. However, a well-designed object-oriented program may be overly general when used for a specific purpose, and hence be inefficient in terms of speed and size. To enhance performance and reduce program size, the program can be adapted to encompass only the specific functionality required in a specific situation. Partial evaluation is an automatic program specialization technique, that adapts a program to a given execution context. In the object-oriented software development process, a program is developed by mapping a problem characterization into a generic implementation. Partial evaluation provides an additional stage in the object-oriented software development process: it maps a general implementation into a dedicated implementation. It is our thesis that partial evaluation can be integrated into the obj...

DSLs in Robotics: A Case Study in Programming Self-reconfigurable Robots

Lecture Notes in Computer Science

Robotic systems blend hardware and software in a holistic way that intrinsically raises many cros... more Robotic systems blend hardware and software in a holistic way that intrinsically raises many crosscutting concerns such as concurrency, uncertainty, and time constraints. These concerns make programming robotic systems challenging as expertise from multiple domains needs to be integrated conceptually and technically. Programming languages play a central role in providing a higher level of abstraction. This briefing presents a case study on the evolution of domain-specific languages based on modular robotics. The case study on the evolution of domain-specific languages is based on a series of DSL prototypes developed over five years for the domain of modular, self-reconfigurable robots.

Reversible Object-Oriented Programming with Region-Based Memory Management - Work-in-progress Report

This paper presents the design and implementation Joule\(^R\), a reversible object-oriented langu... more This paper presents the design and implementation Joule\(^R\), a reversible object-oriented language in the style of Janus, that supports common object-oriented programming patterns such as factories, iterators, and the definition of abstract datatypes. Memory management is performed using a simple notion of regions, enabling the full power of object-oriented programming to be used, while remaining completely garbage-free. The language is implemented by translation to Janus.

Component-based computation-energy modeling for embedded systems

Proceedings Companion of the 2019 ACM SIGPLAN International Conference on Systems, Programming, Languages, and Applications: Software for Humanity, 2019

Computational energy-efficiency is a critical aspect of many modern embedded devices as it impact... more Computational energy-efficiency is a critical aspect of many modern embedded devices as it impacts the level of autonomy for numerous scenarios. We present a component-based energy modeling approach to abstract per-component energy in a dataflow computational network executed according to a given scheduling policy. The approach is based on a modeling tool and ultimately relies on battery state to support a wider range of energy-optimization strategies for power-critical devices.

Reversible Control of Robots

Programming industrial robots is challenging due to the difficulty of precisely specifying genera... more Programming industrial robots is challenging due to the difficulty of precisely specifying general yet robust operations. As the complexity of these operations increases, so does the likelihood of errors. Certain classes of errors during industrial robot operations can however be addressed using reverse execution, allowing the robot to temporarily back out of an erroneous situation, after which the operation can be automatically retried. Moreover reverse execution permits automatically deriving programs that physically reverse the operations of an industrial robot. This can be useful in industrial assembly, where a disassembly program can be automatically derived from the assembly program.

Can Some Programming Languages Be Considered Harmful?

Programming languages are not uniformly perceived by the software engineering community: some are... more Programming languages are not uniformly perceived by the software engineering community: some are respected, others are hated, some have a devoted following, others are viewed as a necessary evil. However, is it true that using some languages on a regular basis or even being exposed to them to a significant extent, can harm coders’ minds? Can a programming language be blamed for limiting a software engineer’s ability to form proper abstractions, communicate them to other members of the programming social unit, choose correctly among tools, techniques and constructs within the solution spaces, and altogether for boosting or ruining an engineer’s career? If we knew, we could ensure language designers use methods that are least harmful when making new libraries, protocols and domain-specific languages. In this paper we raise a number of questions concerning language safety and design sociotechnical experiments to answer them. CCS Concepts • Human-centered computing → Computer supported...

Towards a Robust Spatial Computing Language for Modular Robots (Position Paper)

Self-reconfigurable, modular robots are distributed mechatronic devices that can autonomously cha... more Self-reconfigurable, modular robots are distributed mechatronic devices that can autonomously change their physical shape. Self-reconfiguration from one shape to another is typically achieved through a specific sequence of actuation operations distributed across the modules of the robot. More generally, control of self-reconfigurable robots requires individual modules to act in specific ways in response to sensor input, and these actions need to be coordinated across the modules of the robot. Robust sequential control and role-based control of individual modules has been experimentally demonstrated using the DynaRole language. DynaRole however only allows simple sequences of distributed operations to be executed, which is suitable for self-reconfiguration sequences but lacks the generality needed to implement more complex behaviors. In this position paper we present initial ideas on generalizing the DynaRole language to support a wider range of modular robot control scenarios, while...

Towards Interactive, Incremental Programming of ROS Nodes

ArXiv, 2014

Writing software for controlling robots is a complex task, usually demanding command of many prog... more Writing software for controlling robots is a complex task, usually demanding command of many programming languages and requiring significant experimentation. We believe that a bottom-up development process that complements traditional component- and MDSD-based approaches can facilitate experimentation. We propose the use of an internal DSL providing both a tool to interactively create ROS nodes and a behaviour-replacement mechanism to interactively reshape existing ROS nodes by wrapping the external interfaces (the publish/subscribe topics), dynamically controlled using the Python command line interface.

HELENA Stage 2—Danish Overview

Product-Focused Software Process Improvement

Since the early days of software engineering, a number of methods, processes, and practices to de... more Since the early days of software engineering, a number of methods, processes, and practices to design and develop software systems have been proposed and applied in industry, e.g., the Rational Unified Process, Agile Software Development, etc. However, since no silver bullet exists, organizations use rich combinations of agile and/or traditional methods and practices, rather than following a single process by the book. To investigate this reality, an international exploratory multistage research project named HELENA (Hybrid DEveLopmENt Approaches in software systems development) was initiated. Currently, the HELENA survey is conducted globally (second stage of HELENA project). This short paper presents and discusses the results of the survey in Danmark compared to the global results based on the data from August 15, 2017.

Modelling reversible execution of robotic assembly

Robotica

SUMMARYProgramming robotic assembly for industrial small-batch production is challenging; hence, ... more SUMMARYProgramming robotic assembly for industrial small-batch production is challenging; hence, it is vital to increase robustness and reduce development effort in order to achieve flexible robotic automation. A human who has made an assembly error will often simply undo the process until the error is undone and then restart the assembly. Conceptually, robots could do the same. This paper introduces a programming model that enables robot assembly programs to be executed in reverse. We investigate the challenges in running robot programs backwards and present a classification of reversibility characteristics. We demonstrate how temporarily switching the direction of program execution can be an efficient error recovery mechanism. Moreover, we demonstrate additional benefits arising from supporting reversibility in an assembly language, such as increased code reuse and automatically derived disassembly sequences. As a default approach to reversibility, we use program inversion and sta...

Elements of a Reversible Object-Oriented Language

Reversible Computation, 2016

This paper presents initial ideas for the design and implementation of a reversible object-orient... more This paper presents initial ideas for the design and implementation of a reversible object-oriented language based on extending Janus with object-oriented concepts such as classes that encapsulate behavior and state, inheritance, virtual dispatching, as well as constructors. We show that virtual dispatching is a reversible decision mechanism easily translatable to a standard reversible programming model such as Janus, and we argue that reversible management of state can be accomplished using reversible constructors. The language is implemented in terms of translation to standard Janus programs.

Increasing Safety by Combining Multiple Declarative Rules in Robotic Perception Systems

Advanced cyber-physical systems such as mobile, networked robots are increasingly finding use in ... more Advanced cyber-physical systems such as mobile, networked robots are increasingly finding use in everyday society. A critical aspect of mobile robotics is the ability to react to a dynamically changing environment, which imposes significant requirements on the robot perception system. The perception system is key to maintaining safe navigation and operation for the robot and is often considered a safety-critical aspect of the system as a whole. To allow the system to operate in a public area the perception system thus has to be certified. The key issue that we address is how to have safety-compliant systems while keeping implementation transparency high and complexity low. In this paper we present an evaluation of different methods for modelling combinations of simple explicit computer vision rules designed to increase the trustworthiness of the perception system. We utilise the best-performing method, focusing on keeping the models of the perception pipeline transparent and underst...

Object-Oriented Software Engineering Using Partial Evaluation

... Object-Oriented Software Engineering Using Partial Evaluation (2000) [7 citations 5 self]. ... more

Towards Error Handling in a DSL for Robot Assembly Tasks

Lambda-Lifting in Quadratic Time

Jflp, 2004

Page 1. BRICS Basic Research in Computer Science Lambda-Lifting in Quadratic Time Olivier Danvy U... more

Towards Automatic Migration of ROS Components from Software to Hardware

ABSTRACT The use of the ROS middleware is a growing trend in robotics in general, ROS and hard re... more ABSTRACT The use of the ROS middleware is a growing trend in robotics in general, ROS and hard real-time embedded systems have however not been easily uniteable while retaining the same overall communication and processing methodology at all levels. In this paper we present an approach aimed at tackling the schism between high-level, flexible software and low-level, real-time software. The key idea of our approach is to enable software components written for a high-level publish-subscribe software architecture to be automatically migrated to a dedicated hardware architecture implemented using programmable logic. Our approach is based on the Unity framework, a unified software/hardware framework based on FPGAs for quickly interfacing high-level software to low-level robotics hardware.

Object-Oriented Software Engineering Using Partial Evaluaion

... Object-Oriented Software Engineering Using Partial Evaluation (2000) [7 citations 5 self]. ... more

A unified simulator for Self-Reconfigurable Robots

2008 Ieee Rsj International Conference on Intelligent Robots and Systems, Sep 1, 2008

Abstract Generic simulation platforms such as Player/Stage are an essential tool in mobile robot... more

PReGO: a generative methodology for satisfying real-time requirements on COTS-based systems: definition and experience report

Proceedings of the 19th ACM SIGPLAN International Conference on Generative Programming: Concepts and Experiences, 2020

Satisfying real-time requirements in cyber-physical systems is challenging as timing behaviour de... more Satisfying real-time requirements in cyber-physical systems is challenging as timing behaviour depends on the application software, the embedded hardware, as well as the execution environment. This challenge is exacerbated as realworld, industrial systems often use unpredictable hardware and software libraries or operating systems with timing hazards and proprietary device drivers. All these issues limit or entirely prevent the application of established real-time analysis techniques. In this paper we propose PReGO, a generative methodology for satisfying real-time requirements in industrial commercial-off-the-shelf (COTS) systems. We report on our experience in applying PReGO to a use-case: a Search & Rescue application running on a fixed-wing drone with COTS components, including an NVIDIA Jetson board and a stock Ubuntu/Linux. We empirically evaluate the impact of each integration step and demonstrate the effectiveness of our methodology in meeting real-time application requirements in terms of deadline misses and energy consumption.

Energy-Aware Design of Vision-Based Autonomous Tracking and Landing of a UAV

2020 Fourth IEEE International Conference on Robotic Computing (IRC), 2020

In this paper, we present the design and evaluation of a vision-based algorithm for autonomous tr... more In this paper, we present the design and evaluation of a vision-based algorithm for autonomous tracking and landing on a moving platform in varying environmental conditions. We use an energy-aware approach, where the design of the algorithm is based on an evaluation of the energy consumption and Quality of Service (QoS) of each computational component. We evaluate our approach with an agricultural use case where a moving platform is tracked using a landing marker and the YOLOv3tiny CNN is used to detect ground-based hazards. We perform all computations onboard using an NVIDIA Jetson Nano and analyse the impact on the flight time by profiling the energy consumption of the marker detection and the CNN. Experiments are conducted in Gazebo simulation using an energy modeling tool to measure the computational energy cost as a function of QoS. We test the energy efficiency and robustness of our system in various dynamic wind disturbances. We show that the marker detection algorithm can be run at the highest QoS with only a marginal energy overhead whereas adapting the QoS level of CNN results in a considerable power saving. The power saving is significant for a system executing on a fixed-wing UAV.

Object-Oriented Software Engineering using Partial Evaluation

Object-oriented programming languages facilitate mapping an abstract characterization of a proble... more Object-oriented programming languages facilitate mapping an abstract characterization of a problem into a generic, extensible implementation built from reusable program components. However, a well-designed object-oriented program may be overly general when used for a specific purpose, and hence be inefficient in terms of speed and size. To enhance performance and reduce program size, the program can be adapted to encompass only the specific functionality required in a specific situation. Partial evaluation is an automatic program specialization technique, that adapts a program to a given execution context. In the object-oriented software development process, a program is developed by mapping a problem characterization into a generic implementation. Partial evaluation provides an additional stage in the object-oriented software development process: it maps a general implementation into a dedicated implementation. It is our thesis that partial evaluation can be integrated into the obj...

DSLs in Robotics: A Case Study in Programming Self-reconfigurable Robots

Lecture Notes in Computer Science

Robotic systems blend hardware and software in a holistic way that intrinsically raises many cros... more Robotic systems blend hardware and software in a holistic way that intrinsically raises many crosscutting concerns such as concurrency, uncertainty, and time constraints. These concerns make programming robotic systems challenging as expertise from multiple domains needs to be integrated conceptually and technically. Programming languages play a central role in providing a higher level of abstraction. This briefing presents a case study on the evolution of domain-specific languages based on modular robotics. The case study on the evolution of domain-specific languages is based on a series of DSL prototypes developed over five years for the domain of modular, self-reconfigurable robots.

Reversible Object-Oriented Programming with Region-Based Memory Management - Work-in-progress Report

This paper presents the design and implementation Joule\(^R\), a reversible object-oriented langu... more This paper presents the design and implementation Joule\(^R\), a reversible object-oriented language in the style of Janus, that supports common object-oriented programming patterns such as factories, iterators, and the definition of abstract datatypes. Memory management is performed using a simple notion of regions, enabling the full power of object-oriented programming to be used, while remaining completely garbage-free. The language is implemented by translation to Janus.

Component-based computation-energy modeling for embedded systems

Proceedings Companion of the 2019 ACM SIGPLAN International Conference on Systems, Programming, Languages, and Applications: Software for Humanity, 2019

Computational energy-efficiency is a critical aspect of many modern embedded devices as it impact... more Computational energy-efficiency is a critical aspect of many modern embedded devices as it impacts the level of autonomy for numerous scenarios. We present a component-based energy modeling approach to abstract per-component energy in a dataflow computational network executed according to a given scheduling policy. The approach is based on a modeling tool and ultimately relies on battery state to support a wider range of energy-optimization strategies for power-critical devices.

Reversible Control of Robots

Programming industrial robots is challenging due to the difficulty of precisely specifying genera... more Programming industrial robots is challenging due to the difficulty of precisely specifying general yet robust operations. As the complexity of these operations increases, so does the likelihood of errors. Certain classes of errors during industrial robot operations can however be addressed using reverse execution, allowing the robot to temporarily back out of an erroneous situation, after which the operation can be automatically retried. Moreover reverse execution permits automatically deriving programs that physically reverse the operations of an industrial robot. This can be useful in industrial assembly, where a disassembly program can be automatically derived from the assembly program.

Can Some Programming Languages Be Considered Harmful?

Programming languages are not uniformly perceived by the software engineering community: some are... more Programming languages are not uniformly perceived by the software engineering community: some are respected, others are hated, some have a devoted following, others are viewed as a necessary evil. However, is it true that using some languages on a regular basis or even being exposed to them to a significant extent, can harm coders’ minds? Can a programming language be blamed for limiting a software engineer’s ability to form proper abstractions, communicate them to other members of the programming social unit, choose correctly among tools, techniques and constructs within the solution spaces, and altogether for boosting or ruining an engineer’s career? If we knew, we could ensure language designers use methods that are least harmful when making new libraries, protocols and domain-specific languages. In this paper we raise a number of questions concerning language safety and design sociotechnical experiments to answer them. CCS Concepts • Human-centered computing → Computer supported...

Towards a Robust Spatial Computing Language for Modular Robots (Position Paper)

Self-reconfigurable, modular robots are distributed mechatronic devices that can autonomously cha... more Self-reconfigurable, modular robots are distributed mechatronic devices that can autonomously change their physical shape. Self-reconfiguration from one shape to another is typically achieved through a specific sequence of actuation operations distributed across the modules of the robot. More generally, control of self-reconfigurable robots requires individual modules to act in specific ways in response to sensor input, and these actions need to be coordinated across the modules of the robot. Robust sequential control and role-based control of individual modules has been experimentally demonstrated using the DynaRole language. DynaRole however only allows simple sequences of distributed operations to be executed, which is suitable for self-reconfiguration sequences but lacks the generality needed to implement more complex behaviors. In this position paper we present initial ideas on generalizing the DynaRole language to support a wider range of modular robot control scenarios, while...

Towards Interactive, Incremental Programming of ROS Nodes

ArXiv, 2014

Writing software for controlling robots is a complex task, usually demanding command of many prog... more Writing software for controlling robots is a complex task, usually demanding command of many programming languages and requiring significant experimentation. We believe that a bottom-up development process that complements traditional component- and MDSD-based approaches can facilitate experimentation. We propose the use of an internal DSL providing both a tool to interactively create ROS nodes and a behaviour-replacement mechanism to interactively reshape existing ROS nodes by wrapping the external interfaces (the publish/subscribe topics), dynamically controlled using the Python command line interface.

HELENA Stage 2—Danish Overview

Product-Focused Software Process Improvement

Since the early days of software engineering, a number of methods, processes, and practices to de... more Since the early days of software engineering, a number of methods, processes, and practices to design and develop software systems have been proposed and applied in industry, e.g., the Rational Unified Process, Agile Software Development, etc. However, since no silver bullet exists, organizations use rich combinations of agile and/or traditional methods and practices, rather than following a single process by the book. To investigate this reality, an international exploratory multistage research project named HELENA (Hybrid DEveLopmENt Approaches in software systems development) was initiated. Currently, the HELENA survey is conducted globally (second stage of HELENA project). This short paper presents and discusses the results of the survey in Danmark compared to the global results based on the data from August 15, 2017.

Modelling reversible execution of robotic assembly

Robotica

SUMMARYProgramming robotic assembly for industrial small-batch production is challenging; hence, ... more SUMMARYProgramming robotic assembly for industrial small-batch production is challenging; hence, it is vital to increase robustness and reduce development effort in order to achieve flexible robotic automation. A human who has made an assembly error will often simply undo the process until the error is undone and then restart the assembly. Conceptually, robots could do the same. This paper introduces a programming model that enables robot assembly programs to be executed in reverse. We investigate the challenges in running robot programs backwards and present a classification of reversibility characteristics. We demonstrate how temporarily switching the direction of program execution can be an efficient error recovery mechanism. Moreover, we demonstrate additional benefits arising from supporting reversibility in an assembly language, such as increased code reuse and automatically derived disassembly sequences. As a default approach to reversibility, we use program inversion and sta...

Elements of a Reversible Object-Oriented Language

Reversible Computation, 2016

This paper presents initial ideas for the design and implementation of a reversible object-orient... more This paper presents initial ideas for the design and implementation of a reversible object-oriented language based on extending Janus with object-oriented concepts such as classes that encapsulate behavior and state, inheritance, virtual dispatching, as well as constructors. We show that virtual dispatching is a reversible decision mechanism easily translatable to a standard reversible programming model such as Janus, and we argue that reversible management of state can be accomplished using reversible constructors. The language is implemented in terms of translation to standard Janus programs.

Increasing Safety by Combining Multiple Declarative Rules in Robotic Perception Systems

Advanced cyber-physical systems such as mobile, networked robots are increasingly finding use in ... more Advanced cyber-physical systems such as mobile, networked robots are increasingly finding use in everyday society. A critical aspect of mobile robotics is the ability to react to a dynamically changing environment, which imposes significant requirements on the robot perception system. The perception system is key to maintaining safe navigation and operation for the robot and is often considered a safety-critical aspect of the system as a whole. To allow the system to operate in a public area the perception system thus has to be certified. The key issue that we address is how to have safety-compliant systems while keeping implementation transparency high and complexity low. In this paper we present an evaluation of different methods for modelling combinations of simple explicit computer vision rules designed to increase the trustworthiness of the perception system. We utilise the best-performing method, focusing on keeping the models of the perception pipeline transparent and underst...

Object-Oriented Software Engineering Using Partial Evaluation

... Object-Oriented Software Engineering Using Partial Evaluation (2000) [7 citations 5 self]. ... more

Towards Error Handling in a DSL for Robot Assembly Tasks

Lambda-Lifting in Quadratic Time

Jflp, 2004

Page 1. BRICS Basic Research in Computer Science Lambda-Lifting in Quadratic Time Olivier Danvy U... more

Towards Automatic Migration of ROS Components from Software to Hardware

ABSTRACT The use of the ROS middleware is a growing trend in robotics in general, ROS and hard re... more ABSTRACT The use of the ROS middleware is a growing trend in robotics in general, ROS and hard real-time embedded systems have however not been easily uniteable while retaining the same overall communication and processing methodology at all levels. In this paper we present an approach aimed at tackling the schism between high-level, flexible software and low-level, real-time software. The key idea of our approach is to enable software components written for a high-level publish-subscribe software architecture to be automatically migrated to a dedicated hardware architecture implemented using programmable logic. Our approach is based on the Unity framework, a unified software/hardware framework based on FPGAs for quickly interfacing high-level software to low-level robotics hardware.

Object-Oriented Software Engineering Using Partial Evaluaion

... Object-Oriented Software Engineering Using Partial Evaluation (2000) [7 citations 5 self]. ... more

A unified simulator for Self-Reconfigurable Robots

2008 Ieee Rsj International Conference on Intelligent Robots and Systems, Sep 1, 2008

Abstract Generic simulation platforms such as Player/Stage are an essential tool in mobile robot... more