Myungryun Yoo

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.

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.

A Real-Time Operating System with GNSS-Based Tick Synchronization

The paper presents a real-time operating system (RTOS) with GNSS(Global Navigation Satellite Systems)-based tick synchronization for loosely coupled distributed cyber-physical systems (CPSs) such as distributed control systems connected with wireless networks or wide-area networks. In CPS, computations directly interact with the physical world with the universal physical time. A precisely synchronized system time is required for high performance control of the physical world. We have developed a RTOS that manages application tasks based on a system time, which is precisely synchronized with UTC (Coordinated Universal Time) provided by GNSS. The RTOS has mechanisms for tick rate compensation, tick phase compensation and system time compensation, which utilize GNSS receiver signals. Embedded computers with the RTOS can synchronously execute application tasks according to the precisely synchronized system time. The precise synchronous execution improves the performance of the control of the physical world.

A distributed real-time operating system built with aspect-oriented programming for distributed embedded control systems

The paper presents a method to build a distributed real-time operating system for distributed embedded control systems using aspect-oriented programming. We define aspects to weave distributed computing mechanisms to an existing real-time operating system. By using the aspects, we can build a distributed operating system without modifying the original source code. This improves the maintainability of the source code of a real-time operating system family. We have applied the aspects to an OSEK OS and have got a distributed operating system that provides location-transparent system calls for task management and inter-task synchronization. The evaluation results show that the overhead of aspect-oriented programming is practically small enough.

A Real-Time Operating System with CAN-Based Inter-Node Shared Resource Management and Distributed Shared Memory

The paper presents a real-time operating system (RTOS) that supports location-transparent shared resource management and distributed shared memory for distributed embedded control systems with CAN (Control Area Network) buses. In a distributed embedded control system, location-transparent mechanisms are required because application tasks are distributed to a number of nodes. We have developed a RTOS that supports location-transparent inter-node shared resource management and distributed shared memory. The inter-node resource access protocol is based on the Multiprocessor Priority Ceiling Protocol and inter-node locking is efficiently implemented using the arbitration mechanism of CAN. The distributed shared memory with mutual exclusion is also efficiently implemented. The RTOS is an extension to OSEK OS and supports not only inter-node resource management but also inter-core resource management for multi-core processors and inter-core and inter-node system calls for task management and event control. We have evaluated the performance of the RTOS and have confirmed that the performance is acceptable for practical embedded control systems.