Johannes F. Broenink

20-sim software for hierarchical bond-graph/block-diagram models

We discuss the modeling and simulation package 20-sim, a tool for modeling and simulation of dynamic behavior of engineering systems. Engineering systems as application domain means that we focus on systems that span multiple physical domains and the information domain. The 20-sim software is an interactive tool, where model entry and model processing are fully integrated. This means that already during model entry and editing, models can be checked on their consistency. 20-sim has its own simulator, using sophisticated numerical integration methods, taken from. internationally accepted numerical libraries. The use of 20-sim is demonstrated by an example, in which a 3-dof scara robot with controller is modeled and simulated.

Libraries of Reusable Models: Theory and Application

Setting up a simulation model is more than writing down state equations and running them on a computer. A lot of conceptual information about the physics and engineering aspects of the system must be taken into account to construct a useful simulation model. The role of a model library is to manage this information and to make model fragments reusable. This is especially important if models are reused and shared in cooperative work groups. In this article, we discuss the architecture of a library of reusable models. The practical application is demonstrated by reviewing an actual modeling problem in the machine tool domain.

Constitutive Hybrid Processes: a Process-Algebraic Semantics for Hybrid Bond Graphs

Models of physical systems have to be based on physical principles such as conservation of energy and continuity of power. These principles are inherently enforced by the bond graph modeling formalism. Often, however, physical components may be best modeled as piecewise continuous with discrete mode changes, which leads to a violation of continuity principles. To support such hybrid models, bond graphs can be extended by facilitating a dynamic model structure, resulting in hybrid bond graphs. Behavior generation then requires computing continuous-time evolution, detecting the occurrence of events, executing the discrete state changes and re-initializing the continuous-time state. This paper presents a comprehensive representation of these different aspects of behavior using hybrid process algebra. The behavior of a hybrid bond graph can then be studied using a uniform representation while a direct correspondence with the elements of the bond graph is maintained. Additionally, non-determinism can be included in hybrid bond graph semantics which may alleviate the modeling task without being detrimental to the required analyses.

A co-modelling method for solving incompatibilities during co-design of mechatronic devices

The design process of mechatronic devices, which involves experts from different disciplines working together, has limited time and resource constraints. These experts normally have their own domain-specific designing methods and tools, which can lead to incompatibilities when one needs to work together using these those methods and tools. Having a proper framework which integrates different design tools is of interest, as such a framework can prevent incompatibilities between parts during the design process. In this paper, we propose our co-modelling methodology and co-simulation tools integration framework, which helps to maintain the domain specific properties of the model components during the co-design process of various mechatronic devices. To avoid expensive rework later in the design phase and even possible system failure, fault modelling and a layered structure with fault-tolerance mechanisms for the controller software are introduced. In the end, a practical mechatronic device is discussed to illustrate the methods and tools which are presented in this paper in details.

Controller system design trajectory

This paper structures existing modelling techniques and theories into a systematic stepwise design trajectory with the goal to facilitate a less error-prone path from model to realization. It is a model-driven approach, whereby simulation is used to check whether refinement updates leave the model compliant with the requirements. Via various “in-the-loop simulations”, the design trajectory runs from complete simulation to full realization. Tests on a basic experimental set up showed that the design trajectory is feasible, although it is expected that all stages are really necessary when complex controller behavior is to be implemented on distributed embedded computers.

Model-driven robot-software design using integrated models and co-simulation

The work presented here is on a methodology for design of hard real-time embedded control software for robots, i.e. mechatronic products. The behavior of the total robot system (machine, control, software and I/O) is relevant, because the dynamics of the machine influences the robot software. Therefore, we use two appropriate Models of Computation, which represent continuous-time equations for the machine / robot part, and discrete event / discrete time equations for the control software part.

Thinking Tracks for Multidisciplinary System Design

Systems engineering is, for a large part, a process description of how to bring new systems to existence. It is valuable as it directs the development effort. Tools exist that can be used in this process. System analysis investigates existing and/or desired situations. However, how to create a system that instantiates the desired situation depends significantly on human creativity and insight; the required human trait here is commonly called systems thinking. In literature, this trait is regularly used, but information on how to do systems thinking is scarce. Therefore, we have introduced earlier twelve thinking tracks that are concrete and help system designers to make an optimal fit between the system under design, the identified issue, the user, the environment and the rest of the world. The paper provides the scientific rationale for the thinking tracks based on literature. Secondly, the paper presents three cases of application, leading to the conclusion that the tracks are usable and effective

On a directed tree problem motivated by a newly introduced graph product

In this paper we introduce and study a directed tree problem motivated by a new graph product that we have recently introduced and analysed in two conference contributions in the context of periodic real-time processes. While the two conference papers were focussing more on the applications, here we mainly deal with the graph theoretical and computational complexity issues. We show that the directed tree problem is NP-complete and present and compare several heuristics for this problem.

Collaborative Development of Embedded Systems

This chapter presents motivation for taking a collaborative multi-disciplinary approach to the model-based development of embedded systems. Starting from a consideration of the ubiquity of embedded systems in daily life it identifies challenges faced by industry in developing products in a timely manner, but to sufficient quality to merit the reliance of their users. Using a fictional story of product development, it presents the perspectives of both the control engineer and the software designer. We describe an approach—realised using the Crescendo tool—that promotes collaborative modelling and co-simulation, taking account of existing technology and current industry practice

Design-time improvement using a functional approach to specify GraphSLAM with deterministic performance on an FPGA

SLAM is a fundamental problem in robotics that can be solved by a set of algorithms that are known to have large computational complexity. GraphSLAM contains a rapidly growing system of equations which are often solved by sparse evaluation techniques. This paper proposes a technique to evaluate sparse equations on an FPGA by restricting the maximum amount of items in the system. The implementation is done using CλaSH which allows a transformation from mathematical descriptions to a hardware design. The results show a scalable hardware design that can be used to solve small and large systems with dynamic parallelism.