Managing complex temporal requirements in real-time control systems

Design and implementation of motion control applications includes the transition from control design to real-time system implementation. To make this transition smooth, the specification model for the real-time system should allow also for temporal requirements other than deadlines, e.g., deviation from nominal period time of an activity, end-to-end timing constraints, temporal correlation between different sampling tasks and constraints on temporal variations in output. Many real-time systems in industry today are based on pre-emptive priority based run-time systems, and hence, the temporal requirements should be fulfilled by correctly assigning attributes such as priorities and offsets to the tasks executing in such systems. Assigning priorities and offsets in order to fulfill complex temporal requirements originating from control design and computer system design is a hard task that should be supported by powerful methods and tools. In this paper we propose a method which, by assigning priorities and offsets to tasks, guarantees that complex timing constraints can be met. In addition to the complex timing constraints, the method supports sporadic tasks, shared resources, and varying execution times of tasks. We present the idea and implementation, which is based on a genetic algorithm, and illustrate the method by an example