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Modern embedded systems have multiple cores available. The CTC++ library is not able to make use of these cores, so a new framework is required to control the robotic setups in our lab. This paper first looks into the available frameworks and compares them to the requirements for controlling the setups. It concludes that none of the available frameworks meet the requirements, so a new framework is developed, called LUNA. The LUNA architecture is component based, resulting in a modular structure. The core components take care of the platform related issues. For each supported platform, these components have a different implementation, effectively providing a platform abstraction layer. High-level components take care of platform-independent tasks, using the core components. Execution engine components implement the algorithms taking care of the execution flow, like a CSP implementation. The paper describes some interesting architectural challenges encountered during the LUNA development and their solutions. It concludes with a comparison between LUNA, C++CSP2 and CTC++. LUNA is shown to be more efficient than CTC++ and C++CSP2 with respect to switching between threads. Also, running a benchmark using CSP constructs, shows that LUNA is more efficient compared to the other two. Furthermore, LUNA is also capable of controlling actual robotic setups with good timing properties.

This paper describes and compares five CSP based and two CSP related process-oriented motion control system implementations that are made for our Production Cell demonstration setup. Five implementations are software-based and two are FPGA hardware-based. All implementations were originally made with different purposes and investigating different areas of the design space for embedded control software resulting in an interesting comparison between approaches, tools and software and hardware implementations. Common for all implementations is the usage of a model-driven design method, a communicating process structure, the combination of discrete event and continuous time and that real-time behaviour is essential. This paper shows that many small decisions made during the design of all these embedded control software implementations influence our route through the design space for the same setup, resulting in seven different solutions with different key properties. None of the implementations is perfect, but they give us valuable information for future improvements of our design methods and tools.

This paper presents two algorithms for analysing gCSP models in order to improve their execution performance. Designers tend to create many small separate processes for each task, which results in many (resource intensive) context switches. The research challenge is to convert the model created from a design point of view to models which have better performance during execution, without limiting the designers in their ways of working. The first algorithm analyses the model during run-time execution in order to find static sequential execution traces that allow for optimisation. The second algorithm analyses the gCSP model for multi-core execution. It tries to find a resource-efficient placement on the available cores for the given target systems. Both algorithms are implemented in two tools and are tested. We conclude that both algorithms complement each other and the analysis results are suitable to create optimised models.

We prove the correctness of a two-way sliding window protocol with piggybacking, where the acknowledgments of the latest received data are attached to the next data transmitted back into the channel. The window size of both parties are considered to be finite, though they can be of different sizes. We show that this protocol is equivalent (branching bisimilar) to a pair of FIFO queues of finite capacities. The protocol is first modeled and manually proved for its correctness in the process algebraic language of muCRL. We use the theorem prover PVS to formalize and to mechanically prove the correctness. This implies both safety and liveness (under the assumption of fairness).

Most motion control systems for mechatronic systems are implemented on digital computers. In this paper we present an FPGA based solution implemented on a low cost Xilinx Spartan III FPGA. A Production Cell setup with multiple parallel operating units is chosen as a test case. The embedded control software for this system is designed in gCSP using a reusable layered CSP based software structure. gCSP is extended with automatic Handel-C code generation for configuring the FPGA. Many motion control systems use floating point calculations for the loop controllers. Low cost general purpose FPGAs do not implement hardware-based floating point units. The loop controllers for this system are converted from floating point to integer based calculations using a stepwise refinement approach. The result is a complete FPGA based motion control system with better performance figures than previous CPU based implementations.

SystemCSP is a graphical modeling language based on both CSP and concepts of component-based software development. The component framework of SystemCSP enables specification of both interaction scenarios and relative execution ordering among components. Specification and implementation of interaction among participating components is formalized via the notion of interaction contract. The used approach enables incremental design of execution diagrams by adding restrictions in different interaction diagrams throughout the process of system design. In this way all different diagrams are related into a single formally verifiable system. The concept of reusable formally verifiable interaction contracts is illustrated by designing set of design patterns for typical fault tolerance interaction scenarios.

gCSP is a graphical tool for creating and editing CSP diagrams. gCSP is used in our labs to generate the embedded software framework for our control systems. As a further extension to our gCSP tool, an occam code generator has been constructed. Generating occam from CSP diagrams gives opportunities to use the Raw-Metal occam eXperiment (RMoX) as a minimal operating system on the embedded control PCs in our mechatronics laboratory. In addition, all processors supported by KRoC can be reached from our graphical CSP tool. The commstime benchmark is used to show the trajectory for gCSP code generation for the RMoX operating system. The result is a simple means for using RMoX in our laboratory for our control systems. We want to use RMoX for future research on distributed control and for performance comparisons between a minimal operating system and our CTC++/RT-linux systems.

In this paper a data sharing framework for multi-threaded, distributed control programs is described that is realized in C++ by means of only a few, powerful classes and templates. Fast data exchange of entire data structures is supported using sockets as communication medium. Access methods are provided that preserve data consistency and synchronize the data exchange. The framework has been successfully used to build a distributed robot soccer control system running on as many computers as needed.

For broad acceptance of an engineering paradigm, a graphical notation and a supporting design tool seem necessary. This paper discusses certain issues of developing a design environment for building systems based on CSP. Some of the issues discussed depend specifically on the underlying theory of CSP, while a number of them are common for any graphical notation and supporting tools, such as provisions for complexity management and design overview.

Closed loop control systems typically contain multitude of spatially distributed sensors and actuators operated simultaneously. So those systems are parallel and distributed in their essence. But mapping this parallelism onto the given distributed hardware architecture, brings in some additional requirements: safe multithreading, optimal process allocation, real-time scheduling of bus and network resources. Nowadays, fault tolerance methods and fast even online reconfiguration are becoming increasingly important. All those often conflicting requirements, make design and implementation of real-time distributed control systems an extremely difficult task, that requires substantial knowledge in several areas of control and computer science. Although many design methods have been proposed so far, none of them had succeeded to cover all important aspects of the problem at hand. [1] Continuous increase of production in embedded market, makes a simple and natural design methodology for real-time systems needed more then ever.

We use several formal methodologies for developing control applications at our Control Engineering research group. An important methodology we use for designing and implementing control software architecture is based on CSP concepts. These concepts allow us to glue multidisciplinary activities together and allow for formal stepwise refinement from design down to its implementation. This paper illustrates a trajectory and shows the usefulness of CSP diagrams for a simple mechatronic system. The simulation tool 20-SIM is used for creating the control laws and our CTC++ package is used for coding in C++.

Sampling and timing is considered a responsibility of the environment of controller software. In this paper we will illustrate a concept whereby an environmental process and multi-way events play an important role in applying timing for untimed CSP software architectures. We use this timing concept for building our control applications based on CSP concepts and with our CSP for C++ (CTC++) library. We present a concept of sampling of control applications that is orthogonal to the application. This implies global timing on the basis of timed events. We also support traditional local timing on the based of timed processes.

This JIWY demonstrator is constructed in the context of the development of a design framework and software tools to efficiently support mechatronic engineers in developing sophisticated control computer code out of a set control laws. We use the CSP-based Communicating Threads -CT- library as the software communication layer, our hard real-time "virtual machine". JIWY (just a soundful name) is a little tabletop robot with 2 rotational degrees of freedom and a camera as its "end effector", controlled via a joystick on a PC running Real-Time Linux. The control laws are stepwise refined to obtain the control software, enhancing the control-law block diagrams to CSP-diagrams, showing the communication and composition properties of the control software. Enhancements like adding homing and end stops for safety can easily be added in the CSP-diagrams, without adapting the control law design. This shows the orthogonality of the design steps. State charts were not needed to express all functionality, which leaves the design simple. The prize of this elegance, namely performance, has as yet not been investigated.

The CSP paradigm is known as a powerful concept for designing and analysing the architectural and behavioural parts of concurrent software. Although the theory of CSP is useful for mathematicians, the programming language occam has been derived from CSP that is useful for any engineering practice. Nowadays, the concept of occam/CSP can be used for almost every object-oriented programming language. This paper describes a tree-based description model and prototype tool that elevates the use of occam/CSP concepts at the design level and performs code generation to Java, C, C++, and machine-readable CSP for the level of implementation. The tree-based description model can be used to browse through the generated source code. The tool is a kind of browser that is able to assist modern workbenches (like Borland Builder, Microsoft Visual C++ and 20-SIM) with coding concurrency. The tool will guide the user through the design trajectory using support messages and several semantic and syntax rule checks. The machine-readable CSP can be read by FDR, enabling more advanced analysis on the design. Early experiments with the prototype tool show that the browser concept, combined with the tree-based description model, enables a user-friendly way to create a design using the CSP concepts and benefits. The design tool is available from our URL, http://www.rt.el.utwente.nl/javapp.

The incorporation of multithreading in Java may be considered a significant part of the Java language, because it provides udimentary facilities for concurrent programming. However, we belief that the use of channels is a fundamental concept for concurrent programming. The channel approach as described in this paper is a realization of a systematic design method for concurrent programming in Java based on the CSP paradigm. CSP requires the availability of a Channel class and the addition of composition constructs for sequential, parallel and alternative processes. The Channel class and the constructs have been implemented in Java in compliance with the definitions in CSP. As a result, implementing communication between processes is facilitated, enabling the programmer to avoid deadlock more easily, and freeing the programmer from synchronization and scheduling constructs. The use of the Channel class and the additional constructs is illustrated in a simple application.