PICASSOS – Practical Applications of Automated Formal Methods to Safety Related Automotive Systems

PICASSOS was a UK government funded programme to improve the ability of automotive supply chains to develop complex software-intensive systems with high safety assurance and at an acceptable cost. This was executed by a consortium of three universities and five companies including an automotive OEM and suppliers. Three major elements of the PICASSOS project were: use of automated model based verification technology utilising formal methods; application of this technology in the context of ISO 26262; and evaluation to measure the impact of this approach to inform key management decisions on the costs, benefits and risks of applying this technology on live projects. The project spanned system level design and software development. This was achieved by using a unified model based process incorporating SysML at the system level and using Simulink and Stateflow auto-coded into C at the software level. An ISO 26262 compliant development process based on those already used by the commercial partners was used as a baseline, and a modified process using formal methods was developed. Tools that are commercially available were used wherever possible, and technology demonstrators were generated within the programme for enhancement and eventual commercial sale subsequently. A number of trials were undertaken comparing these two processes during simulated development of Electric Vehicle based systems. The paper includes the results of one of the trials, showing that the formal methods-based approach found errors that were missed by a standard model-verification process at software unit level and showing how it can do so with reduced effort.