Research On New Safety Assurance Technology Of Distributed Control System--Safety Kernel

Since software is being used largely in the control systems, the possibility of serious damage resulting from a software defect is considerable and growing, and then the control systems are plunging into safety crisis. In fact, control systems are in urgent need of new safety assurance technologies. Safety kernel is a new concept of safety assurance. It emerges, as the times require. This dissertation is devoted to the subject on how to bring the safety kernel into practice in the complex distributed control system, and has achieved several useful results, in addition to some breakthroughs in this field. From the perspective of the service quality, the present paper at first comprehensively discusses the nature of safety research, summarizes the research results of the decade, points out the trends in the future, and raises some ideas for safety research and developing high dependable computer systems. Then this paper explores the multi-layer and syntheses of the dependability evaluation of the distributed control system, and points out, in accordance with the fact that the field multiple-computer system has an obvious need for availability and reliability, a model for evaluating the system dependability. This model, based on the systematical function, can combine availability and reliability. Based on the analyses above, and from two new perspectives (software safety and introducing monitor), this paper comprehensively analyzes the concept of safety kernel. Furthermore, it analyses the reasons for which the current safety kernel project can抰 be applied to complex distributed control system, puts forward new ideas for setting up the safety structure of distributed control system, discusses the designing aims for the safety structure and the possibility of being put into practice, and sets up SSBSK (Safety Structure Based on Safety Kernel). The difficulties for the SSBSK to meet are also studied in this paper. The first difficulty is the proving of safety kernel consistency. The present method is test. By defining the concept of ideal safety policy and setting up abstract III models of control system, a solution based on formal description and proving has been put forward. Taking the control system in the traffic lights as example, the whole process has been achieved. The second difficulty is the realization of the safety kernel mechanism. Since there are a lot of shortcomings in the current methods of realizing safety kernel by applying software, this paper advances a program for RTOS to supply safety kernel mechanism, and designs it from three aspects of construction, reuse and supporting circumstances in safety kernel mechanism. Prototype experiment of SSBSK has been done on the RT-Linux platform in the lab, and this experiment has proved the validity of the realization program of the safety kernel mechanism and SSBSK. The third difficulty is the evaluation of the reliability of safety kernel. This paper does a comprehensive research and study on the choice of software reliability model and the problem that it is difficult to decide the model evaluation precision. A practical model of evaluating errors has been established, and by using it to analyze the influence which the safety kernel developing circumstances produces on reliability evaluating results, the reliability of safety kernel can be somewhat accurately predicted. The st...