Verification and Validation Methods for TDMA Based “by Wire” Systems

This paper addresses techniques and tools used for verification and validation (V&V) of safety critical systems that utilize Time Division Multiple Access (TDMA) bus technology to communicate between subsystems. Presentation of an example solution for safety critical systems and software will include descriptions for use of the solution at multiple stages of product development. Stages include:• Software or model verification and validation• Prototype evaluation• Hardware and software integration• System testing• Software regression testing• Data collection during stress, exploratory, or field testingIn the process of implementing the above V&V process goals, we found it was necessary to create simulations of certain software subsystems. These simulations allowed for the implementation of V&V strategies prior to the actual completion of the system software itself. Substituting a test resource for one or more elements on the bus solves two problems. These bus based simulations relieve some project schedule dependencies and allow testing of subsystem elements prior to the availability of the other system elements on the TDMA bus. The simulations also allow injection of data that is typically impossible to evoke from a properly functioning subsystem element. These simulations are sometimes a simplification of the real subsystem they represent but are still extremely useful because they allow the bus to function exactly as it would in the target system and allow total control of the data consumed by the subsystem under test.The solution is scalable from a single computer deployment to a distributed system that allows significant abstraction in defining tests, scenarios, or exploratory algorithms and flexibility in software and hardware implementation of the abstractions. Flexibility in integrating with other technologies is achieved through coupling to a scripting environment that supports controlling other physical or electronic stimuli and collecting data from instrumentation.