Research for OSEK/VDX-based Architecture of Vehicular Application Specific Operating System

Transcription

1 Research for OSEK/VDX-based Architecture of Vehicular Application Specific Operating System Yeqing Li Computer Science Department of Career Colleges Inner Mongolia Finance and Economics University Hohhot, China Yuan Sun Information technology school Minzu University of China Beijing, China Abstract The open vehicular industry standard OSEK/VDX is introduced briefly and the OSEK/VDX-based architecture of Vehicular Application Specific Operating System is proposed in this paper. This architecture is based on microkernel mode. Its flexibility, reliability and portability are obvious with the comparison of Monolithic Kernel mode and Exokernel mode which can improve the security and performance of vehicles. At last, the UML is used to model the architecture of Vehicular Application Specific Operating System, and the functions and relationship of different components are analyzed. It is proved that to construct Linux-based Vehicular Application Specific Operating System is feasible. Keywords- OSEK/VDX;Vehicular Application Specific Operating System; UML; embedded operating system I. INTRODUCTION With the rapid progress of modern electronic information technology and the robust growth of automobile manufacturing, modern car technology is integrated with electronic technology and information technology. As a consequence, automobile is no longer a means of transportation only, but also a product and carrier of modern science and technology[1]. The wide application of electronic equipment in automobile is seen as a revolution in the development of vehicular technology as well as the most important technical measure in the improvement of vehicular performance. The employment of integrated circuit and software technology helps better the automobile electronic technology, improves the security and comfortableness, and serves as the foundation of automobile intellectualization, automation and networking. As the automotive electronics develop, electronic control units are being increasingly diversified and complicated. Merely depending on some functional modules to fulfill their respective tasks can no longer satisfy the needs of good performance, real-timing, security and dependability. Thus, it calls for a corresponding operating system to control and coordinate every functional module, so as to make sure that the car performs well and safely. Owing that cars have a high demand in security and realtime performance and there is a corresponding requirement for the vehicular operating system, it is not yet suitable to adopt the general-purpose operating system in the automotive field. Therefore, it is necessary to develop a Vehicular Application Specific Operating System (vasos) according to the specific automotive functions and features. Now some foreign companies have done researches in this field, but there are no systematical studies on it in our country. It is now at the primary stage for the specific operating system, especial vehicular application specific operating system, no matter in theory studies or in technical researches. Though researches have been done by some of the foreign companies and some operating systems have been developed, there are no corresponding standards and systems; hence it is essential to study the architecture, constructive ideology, software engineering, scheduling theory and optimization of the vehicular application specific operating system. Furthermore, the development of vasos theory will guide and speed up the development of automotive electronic engineering[2]. II. BRIEF INTRODUCTION OF OSEK/VDX May 1993, several German automobile manufacturers agreed to cooperate in normalization of a real-time distributed operating system which can be applied to various kinds of cars. The automobile manufacturers were BMW, Bosch, Daimler-Chrysler, Opel, Siemens and VW. Coordinated by University of Karlsruhe, Germany, it was called Offene Systeme und Schnittstellen fur die Elektronik im Kraftfahrzeug or OSEK for short, with the meaning of open systems and the corresponding interfaces for automotive electronics. At the same time, PSA and Renault in France developed a similar system which was called VDX (Vehicle Distributed executive). The two programs were merged in 1994, and one year later, OSEK/VDX was dedicated to the whole world[3]. The purpose of developing OSEK/VDX is to supply the different ECUs with an open, reliable and intercommunicatable software platform. At the present time, this norm has become the open standard for vehicular industry and the basis of long term automotive practicability. Four standards are covered in OSEK/VDX: Operating System (OS), Communication (COM), Network Management (NM) and OSEK Implementation Language (OIL)[3], as shown in Figure 1.

2 III. ARCHITECTURE OF VASOS Figure 1. Architecture of OSCK/VDX OSEK/VDX OS describes the standards of OSEK/VDX operating system, which adopt the concept classification and define a scalable operating system. Tasks, alarming, resources, events and inside information are clearly defined in this part. Communication (COM) describes the standards of OSEK/VDX communications, which stipulate the process and inter-process communications. Network Management (NM) sets up the standards of OSEK/VDX network regulations, which lay out the ways to identify all the node states of the network[3]. OIL is the implementation language of OSEK/VDX, which can be applied to realize the portability of the software[5]. As an open standard of vehicular industry, the prominent merits of OSEK/VDX lie in[6]: High portability OSEK provides the standard API interface. Designing the software according to it guarantees the high portability and reusability. Minor changes are needed when being transferred between different microcontrollers, which will lower the cost greatly. High reliability OSEK operating system is designed statically and the functions and requirements of the application programs are also static. Accordingly, compared with the dynamic operating system, it avoids the uncertainty and randomness brought by the dynamic system, and thereby, has higher security and reliability. So the automotive operating system based on OSEK/VDX guarantees the stable and safe performance to a greater extent. At the present time, the real-time operating systems which meet the criteria of OSEK/VDX are: Oscan system by Vector Informatik, ProOSEK system by 3SOFT, OSEKWorks by Wind River, RTA3 by LiveDevices Limited Innovation Centre and OSEKTrubo by Metrowerks[7]. A. Features of vasos The automotive specific embedded operating system vasos is an extension of the specific embedded real-time operating system (ASOS). It is in line with a series of system features of ASOS. Apart from the basic functions of multi-task handling, file processing and device driving, it possesses the following system features as well[8]: Simplified system call interface for specific application which can support a certain kind or a certain category of embedded application; The smallest kernel processing set with low system overhead and high efficiency which can also be applied to various kinds of non-computing equipments Scalable and reducible system architecture which applies multilevel system architecture; Various kinds of plug-and-play device drive interfaces; Network access functions like Internet or radio access which provide TCP/UDP/IP/PPP and unified access layer interface and reserve the interfaces for various types of mobile computing devices. Compared with the general RTOS, ASOS emphasizes: first, the functional specificity which is application-oriented, such as, partial function sets with high reliability which can carter to a certain kind (or category) of application, rather than the system generality and the configurability of the system resource in RTOS; second, good real-time performance which is application-oriented, rather than the overall system efficiency in RTOS; third, the connections of the Internet, especially the radio access interfaces. vasos is a specific application of ASOS, which, though shares the similarity with ASOS, has its own characteristics: High real-time capability and high speed in task switching which can make a quick response to any interruptions and sudden events. Modularization which can achieve the high scalability and reducibility. Wireless-communication-supported, which can realize the internal and external information transfer. High security which can alarm and monitor correctly. B. Architecture of vasos Three main architectures of embedded operating system are[2]: Monolithic Kernel Mode, Microkernel Mode and Exokernel Mode. Based on the features of high real-time capability, modularization and high reliability, vasos is designed as the microkernel mode, whose architectural model is shown in Figure 2: Why do we adopt the microkernel mode? Compared with the monolithic kernel mode and exokernel mode, the microkernel enjoys the advantages as follows[9]:

3 Unified interface: microkernel mode is designed to provide unified interface for process requests. Extendibility: new services are allowed to be added and multiple services are provided in the same functional area. Portability: all or most of the specific processor codes are included in the microkernel, and only minor changes are needed while being transferred. Reliability: by using just a few application programming interfaces, it generates high quality code for the external operating system of the kernel. Flexibility: relevant to extendibility, it not only allows the new functions to be added to the operating system, but also allows deleting the existed functions. Microkernel is delicate, and it shifts many parts of the traditional operating system kernels out, whose functions are respectively realized by the server mode. By employing this method, vasos enhances the extendibility, portability and flexibility greatly. Meanwhile, taking the microkernel as an information forwarding center helps to realize the isolation of every module, which means that the operating system will not be broken down when one of the module goes wrong, which is quite different from the monolithic kernel. By doing this, the reliability is strengthened, as is quite important to the automobiles. In addition, the necessary module will not be loaded into memory, which will in turn help to make better use of memory. monolithic kernel functions by the way of IPC (inter-process communication). In connection with the real-time capability of Vehicular Application Specific Operating System, the microkernel meets all the real-time features, including fast task switching, interruption support, and preemptive scheduling. Microkernel design lowers the system overhead so that it guarantees a quick and appropriate response to external events. Primary systemic functions are provided in the system service layer: process management, network management, device management, file system, drivers and graphic/window support, etc. Generally, the server needs to cooperate with each other, and exercises the functions supplied by the microkernel with the calling of the system. Open and convenient communication interfaces, such as CAN bus interface and wireless network communication interface, should be supplied in the platform design. Accordingly, drivers of various kinds of communication interfaces should be provided in the system service layer to satisfy the needs of application development of automobile instruments, communication and navigation, and automobile safety. C. Architecture of vasos based on OSEK/VDX In view of the features of automobile hardware, vasos focuses on the control of internal key ECU (electronic control unit) software platform. The key ECU software platform includes electronic control ECU, vehicle-mounted ECU, automobile alarm ECU and automobile gateway ECU. All the internal ECUs are connected by CAN/LIN bus lines. OSEK/VDX supports CAN bus protocol, develops CANsupported hardware for embedded automobile software platform and ECU hardware for driving assistance and safety monitoring, studies the application layer protocol and develops the corresponding application layer software, and then sets up the internal network. OSEK/VDX defines ways of multitasking, interrupt handling and scheduling and the standard interface function. According to these specifications, we need to follow OSEK/VDX and set up the corresponding standard interface while designing vasos. According to OSEK/VDX, we design the overall architecture of vasos, as shown in Figure 3. Figure 2 the architectural modal of vasos In the designing of this architecture, we just keep the task scheduling,inter-process communication, memory management, and interrupt handling for the microkernel, and try to separate the advanced functions such as device management and file system from the kernel, and make them into the independent non-kernel processes, so as to simplify and stabilize the function of kernel. The independent modules existing in the privileged mode of user process will have their own operating space, and accomplish the calling of identical

4 Microkernel, Internal Service, External Services, API and Client. Figure 3 Architecture of vasos based on OSEK/VDX In this architecture, user layer is provided with the standard API function through the system service layer based on microkernel. Task monitoring, inter-process communication, memory management and interrupt handling are introduced in B., while OSEK/VDX also establishes relevant regulations for these four aspects[10]: It stipulates the preemptive and non-preemptive mixed scheduling strategy for static priority, which guarantees the high efficiency and real-time capability of the system. It adopts the PCP protocol and shares the mutually exclusive resources, which will avoid system deadlock and guarantee security. It supports three types of ISR, realizes the fast interrupt, and satisfies the real-time requirements of different units. It adopts the ways of message management to obtain the internal process communication, which guarantee the safe transfer of information. It allocates memory statically to ensure the stability of the system. In the designing of the vasos microkernel, we do our best to follow the standards of OSEK/VDX and generate the vasos microkernel based on it. Meanwhile, we design the API function interface according to the standards provided by OSEK while we are designing the system service layer, so as to supply the application layer with the standard API function and make sure that the system will have a good portability and the car can perform well and safely. D. Modeling of UML Based on the above analysis, architecture of vasos will be modeled by UML, as shown in Figure 4. In this model, the microkernel mechanism mode with five parts is adopted[11]: Figure 4 UML model of the architecture of vasos Microkernel components which provide the core service have five main components. The scheduler component offers the service of task creating, deleting and scheduling. IPC component provides the internal process communication service. Memory management component is in charge of memory management services such memory allocating and freeing and information recycling. Interrupt redirector component deals with the internal and external fast interrupt. Hardware abstraction component helps the interlinking of device drivers. The internal service components which rely on the microkernel components and their interface service also have five main components. Network management component provides the web service based on TCP/IP protocol, which can exchange messages between the network nodes as well as conduct the remote file operations by using file service components. Process management component renders the coordinating and managing service for user process and system process. File service component supports several kinds of file systems and offers the service of file creating, deleting, reading and writing. Drivers component supplies the drivers for the device. Devices management component provides the managing and coordinating service for the internal devices. The external service components offer a series of optional services, which can use both the internal components and the microkernel. Two parts are designed here file compression component which provides the service of compression and helps make better use of the limited resources, and event logging component which renders the service of monitoring and recording[11]. Application program interfaces are a group of interfaces from microkernel components, internal service components and external service components.

5 Meanwhile, the model also shows the relations between different components, among which is that the internal components rely on the external ones, as shown in Figure 4. The figure shows how each part of the internal components depend on the microkernel components, for example, the process management component, which is a kind of internal component, depends on the process communication component, task scheduling component and memory management component, which are microkernel components. Besides, Figure 4 demonstrates dependence among the internal components as well, for example, network management component s dependence on file service component. Moreover, the dependence between external component and microkernel, between external component and internal component, and the dependence of clients on the whole operating system are shown in this figure. E. Construction of vasos The constructors of ASOS are the application-oriented reduction-and-generation method and mode-based generation method[10]. When constructing the vasos, we modify the Linux embedded operating system into the one which meets the standard of OSEK/VDE through custom-built cutting and basing on the microkernel mode introduced above. To satisfy some real-time requirements of automotive electronics, general kernels of Linux are also modified into dual-kernel operating mechanism with both real-time kernel and general kernel. Interrupt handling, task scheduling algorithm and synchronous processing mechanism should meet the real-time requirement of the system. At the same time, we develop a computer-aided development system for vasos, and offer more convenient mode to the clients. Real-time kernel of Linux is designed to satisfy real-time extended standard of POSIX. Though there are similarities between POSIX and OSEK/VDS in the description of real-time system, differences exist. POSIX covers most of the contents of OSEK/VDX in defining the real-time system, so it can be seen that it is feasible to modify the real-time Linux into the automotive exclusive embedded operating system based on OSEK/VDX. IV. CONCLUSION With the development and application of wireless communication and global positioning technology, vehiclemounted box with the combination of communication, information, navigation, entertainment and various kinds of automotive electronic safety system will be the leading direction in next generation and future vehicle design. Since there is a strong market demand, vehicle-mounted box will be hot in the recent development[10]. As a vehicular operating system which controls and coordinates the internal ECUs and guarantees the safe and efficient performance, vasos, the core technology of automotive electronics will enjoy the increasingly wide application in the market. The open vehicular industry standard OSEK/VDX is introduced briefly and the OSEK/VDX-based architecture of Vehicular Application Specific Operating System is proposed in this paper. The feasibility will be verified in the future work, and insufficiency will be improved, so as to realize the function of each module and finally construct the OSEK/VDX-based operating system of vasos. REFERENCES [1] x.shtm [2] Zhu, Lixin, Study on Application Specific Embedded Operating (ASOS)Systems[D], Lab of Complex Systems and Intelligence Science, Institute of Automation,Chinese Academy of Sciences, 2004(In Chinese) [3] Lemieux J., Luo, Kelu et al. (trans.) Programming in the OSEK/VDX Environment [M], Beijing: Beijing University of Aeronautics and Astronautics Press, 2004, 2~6 (In Chinese) [4] OSEK/VDX Operation System, Version 2.2.2, OSEK Group, July, 2004 [5] OSEK Implementation Language, Version 2.5, OSEK Group, July, 2004 [6] Michael O Donnell. OSEK/VDX:Driving the standard for optimized embedded systems. Embedded Computing Design [7] [8] [9] [10] [11] Douglass, B. P., Mai, Zhongfan & Tao, Wei (trans) Developing Real- Time Systems with UML, Objects, Frameworks, and Patterns [M], Beijing: Beijing University of Aeronautics and Astronautics Press, 2004,120~124 (In Chinese)