Study On Functional Safety Assessment And Formal Modeling Of FLEDS

Automotive safety has been discussed and studied since the invention of the vehicles.Recently,automotive electronic technology has been increasingly used to improve the performance of vehicles,to enriche the function of the vehicles,making vehicles more intelligent.As a result,more and more Electrical and Electronic(E/E)systems are integrated in vehicles,in order to make sure functional safety of E/E systems and to prevent it from hazard events caused by random failures or systematic failures.Hence,an international standard ISO 26262 was proposed by the International Organization for Standardization(ISO)for the safety of road vehicles.In order to ensure and verify the functional safety of the Fuel Level Estimation and Display System(FLEDS),this dissertation studied the functional safety of FLEDS from following three aspects based on the IS026262.1)A method for ensuring and verifying the functional safety of E/E systems is proposed,and FLEDS is evaluated in conceptual phase based on IS026262.According to this method,firstly,it is necessary to evaluate the E/E systems according to ISO 26262 for generating the evaluation documents.Secondly,we carry out the safety argument of the E/E systems according to the evaluation documents.Finally,the method of formal verification is used to verify the safety argument documents.In order to ensure and verify the functional safety of FLEDS,we need to evaluate the FLEDS in conceptual phase to generate a conceptual evaluation document.2)We prove that FLEDS is acceptable safety and propose a GSN pattern based on IS026262.According to the FLEDS conceptual evaluation document,the GSN method of safety argument is used to demonstrate the safety of the FLEDS,which satisfies all the safety requirements in the argument and then proved the safety of the FLEDS.For the purpose of overcoming the problem that the safety argument graphs are too large to be developed,evaluated,maintained and managed,the GSN pattern based on ISO26262 is proposed.3)We formalize the FLEDS safety argument graphs and ISO26262 pattern,and a conversion algorithm from GSN safety argument graphs to formal model is proposed.In order to facilitate the development and instantiation of ISO26262 pattern and verify the credibility of FLEDS safety argument graphs,FLEDS safety argument graphs and ISO26262 pattern are modeled,and FLEDS safety argument graphs are verified by the formal model.For the sake of modeling and verifying the GSN safety argument graphs automatically,a conversion algorithm from GSN safety argument graphs to formal model is proposed.Based on the study of ISO26262 standard,a method of ensureing and verifying the functional safety of E/E systems is proposed.This method combines ISO26262 standard,safety argument and formal modeling verification to ensure and verify the functional safety of E/E systems.And the method is applied to FLEDS to ensure and verify the safety of FLEDS in concept phase.