The ASSERT Virtual Machine: A Predictable Platform for Real-Time Systems

The development of real-time control systems is a complex process which has to face often conflicting requirements, especially those related to the performance of the control methods and the real-time behaviour of the system. The ASSERT Virtual Machine provides a reliable execution platform for such systems, which allows developers to cope with functional and real-time aspects separately. In order to guarantee the required real-time properties, the virtual machine only accepts software components which have a predictable temporal behaviour which can be analysed at system design time. Such components can be automatically generated from a high-level description of a system which embodies the functional components (e.g. control algorithms) into a set of containers providing the appropriate concurrent and realtime behaviour. The ASSERT Virtual Machine has been implemented in Ada 2005, using a predictable tasking subset of the language known as the Ravenscar profile. A prototype has been validated on several pilot-scale spacecraft control systems, with good results.