Takanori Yokoyama

A Distributed Computing Environment for Embedded Control Systems with Time-Triggered and Event-Triggered Processing

The paper presents a distributed computing environment for embedded control systems with time-triggered and event-triggered distributed processing. We have already presented a time-triggered distributed object model and a time-triggered distributed computing environment for embedded control systems. However, there are many embedded control systems with time-triggered and event-triggered processing. In this paper, we present two kinds of event-triggered distributed object models, a pure event-triggered distributed object model and a data-triggered distributed object model, in addition to the time-triggered distributed object model. We also present a distributed object computing environment based on a time-division scheduling for the mixed architecture with time-triggered and event-triggered distributed processing. The time division scheduling divides an execution cycle into a time-triggered processing segment and a non-time-triggered processing segment. The time-triggered distributed processing is executed in the former segment, and the event-triggered distributed processing is executed in the latter segment. The distributed object computing environment consists of a real-time operating system with the time division scheduling and distributed computing middleware to support the three kinds of distributed object models. We provide a development environment that generates stubs and configuration data to build distributed control systems.

A Distributed Real-Time Operating System with Location-Transparent System Calls for Task Management and Inter-task Synchronization

The paper presents a distributed real-time operating system (DRTOS) for hard real-time embedded systems such as automotive control systems. A real-time control application program is usually designed as a set of tasks that cooperate with each other through the mechanism of a real-time operating system. In a distributed embedded control system, location-transparent mechanisms are required because the tasks are allocated to multiple nodes. We have developed a DRTOS that provides location-transparent system calls for task management and inter-task synchronization. The DRTOS is an extension to OSEK OS, which is a standard operating system in the automotive control domain. The DRTOS manages distributed tasks based on the global time supported by the clock synchronization of Flex Ray, which is a real-time network based on a TDMA (Time Division Multiple Access) protocol. By using the DRTOS, we can develop a distributed control application program with location-transparent system calls. We can also reallocate the tasks of the application program just by reconfiguration, without rewriting the source code. The worst case response time of a remote system call of the DRTOS is predictable if the Flex Ray communication is well configured.

A Distributed Real-Time Operating System with Distributed Shared Memory for Embedded Control Systems

The paper presents a distributed real-time operating system (DRTOS) that provides a distributed shared memory (DSM) service for distributed control systems. Model-based design has become popular in embedded control software design and the source code of software modules can be generated from a controller model. The generated software modules exchange their input and output values through shared variables. We develop a DRTOS with a real-time DSM service to provide a location-transparent environment, in which distributed software modules can exchange input and output values through the DSM. The DRTOS is an extension to OSEK OS. We use a real-time network called FlexRay, which is based on a TDMA (Time Division Multiple Access) protocol. The consistency of the DSM is maintained according to the order of data transfer through FlexRay, not using inter-node synchronization. The worst case response time of the DSM is predictable if the FlexRay communication is well configured.

Embedded Control Software Design with Aspect Patterns

The paper presents an aspect-oriented design for embedded control software such as automotive control. In the control logic design phase, we build a control model with a CAD/CAE tool such as MATLAB/Simulink, in which “zero-time execution” is assumed. In the software design phase, we design timing issues such as task structures and mechanisms for data integrity to execute the control software in the preemptive multi-task environment. We represent mechanisms for timing design as reusable aspect patterns. We define aspect patterns of triggering methods, synchronizations and inter-task communications. We also provide a model weaver to weave the aspect patterns into the base model incrementally. In the timing design, we only have to select the aspect patterns and weave them into the functional model with the model weaver.

Embedded control software design with aspect patterns

This article presents an aspect-oriented design method for embedded control software. Model-based control design has become popular in embedded control systems such as automotive control systems. In the control logic design phase, a control model is built with a CAD/CAE tool such as MATLAB/Simulink, in which ‘zero-time execution’ is assumed. Then, in the software design phase, we design the software to meet timing constraints and to execute control logic correctly in the preemptive multi-task environment. We design task structures and then add mechanisms for data integrity. To make the timing design more efficient, we represent the mechanisms for the timing design as reusable aspect patterns. We define aspect patterns of triggering methods, synchronizations, and inter-task communications. We also provide a model weaver to weave the aspect patterns into the base model incrementally. In the timing design, we only have to select the aspect patterns and weave them into the functional model with the model weaver.

A real-time operating system with location-transparent inter-core and inter-node system calls for distributed embedded control systems

The paper presents a real-time operating system (RTOS) with location-transparent system calls that supports multi-core parallel processing and distributed computing in embedded control systems. An application program of an embedded control system is usually designed as a set of tasks that cooperate with each other through the mechanism of a RTOS. Location-transparent mechanisms are required for multi-core and distributed embedded control systems because the tasks are allocated to multiple CPU cores or multiple nodes. We have extended an OSEK OS to provide location-transparent inter-core and inter-node system calls for task management and event control. We have also confirmed that the performance of the RTOS is practical for embedded control systems.

Aspect-Oriented Customization of the Scheduling Algorithm and the Resource Access Protocol of a Real-Time Operating System

Tasks of an embedded system application are managed by a real-time operating system (RTOS). Most RTOSs adopt just fixed priority scheduling, which is not optimal in all cases. Some applications require earliest deadline first (EDF) scheduling, which is an optimal scheduling algorithm. In order to develop an efficient real-time embedded system, the scheduling algorithm of a RTOS should be selectable. The paper presents a method to customize the scheduling algorithm and the resource access protocol of an OSEK OS using aspect-oriented programming. We define aspects to replace the fixed priority scheduling mechanism of the OSEK OS with an EDF scheduling mechanism. We also define aspects to replace the resource access protocol of the OSEK OS with the resource access protocol for EDF scheduling. By using the aspects, we can customize the scheduling algorithm and the resource access protocol without modifying the original source code. This improves the maintainability of the source code of a RTOS. We have applied the aspects to the OSEK OS and have got a customized RTOS with EDF scheduling. The evaluation results show that the overhead of aspect-oriented programming is small enough.

A Real-Time Operating System Supporting Distributed Shared Memory for Embedded Control Systems

The paper presents a real-time operating system (RTOS) that supports distributed shared memory (DSM) for distributed embedded control systems. The RTOS provides a location-transparent environment, in which distributed software modules can exchange input and output values through the DSM. The RTOS is an extension to OSEK OS and it utilizes a real-time network called FlexRay. The consistency of the DSM is maintained according to the order of data transfer through FlexRay, not using inter-node synchronization. The worst case response time of the DSM is predictable if the FlexRay communication is well configured.

A Simulink to UML model transformation tool for embedded control software development

The paper presents a tool to transform Simulink models into UML models. The embedded control software design process can be divided into the control logic design phase and the software design phase. MATLAB/Simulink is widely used to build a controller model in the control logic design phase. On the other hand, UML is widely used in the software design phase. We have developed a model transformation tool to automatically transform Simulink models with state transitions, conditional selection of data flows or conditional selection of control flows. The model transformation tool analyzes the data flows and control flows of Simulink models and generates UML models with efficient control flows. We have applied the model transformation tool to a number of Simulink models and have confirmed its usefulness for embedded control software design.

A Real-Time Operating System with Location-Transparent Shared Resource Management for Multi-core Processors

This paper presents a real-time operating system (RTOS) that supports location-transparent shared resource management for multi-core embedded control systems. We modify the Multiprocessor Stack Resource Policy (MSRP) for the fixed priority scheduling of OSEK OS and extend an OSEK OS to provide location-transparent resource management based on the modified MSRP. Application tasks access local (intra-core) shared resources and inter-core shared resources using the same system calls. The RTOS also provides location-transparent inter-core and inter-node task management and event control. We have also confirmed that the performance of the RTOS is acceptable for practical embedded control systems.