Enforcing Temporal Constraints in Embedded Control Systems

Computer control systems are embedded in a large and growing group of products, ranging from consumer entertainment products to large airliners. Products such as automotive vehicles, aircraft, and industrial robots are equipped with advanced computer control systems and have high requirements of reliable and safe operation. A common property of these systems is that the computer systems are becoming increasingly more complex due to the inclusion of more functionality. At the same time, the product cycles are becoming shorter leading to requirements of shorter time to market. To meet this challenging task, the development of computer control systems must be a well-defined and controlled engineering process. One important part in reaching this goal is to find methods for dealing with the complexity of computer systems. A computer control system is typically realized by a set of concurrent activities with inter-dependencies that have to meet a set of pre defined temporal constraints. Because of this, it is difficult to know in advance if the implementation of a design will meet its temporal constraints. Furthermore, it is hard to foresee the consequence of introducing alterations or additional functionality in a system. For a method to be useful it also has to capture all the relevant aspects of the application domain, and in the domain of embedded control systems this includes the ability to express and enforce the temporal constraints of control activities. Moreover, the computer system is a heterogeneous system with many responsibilities. Hence, methods for embedded control systems should support not only control activities but also activities related to e.g., human-machine interaction and communication. The work presented in this thesis contributes with methods for enforcing temporal constraints in embedded control systems. The results include an industrial case study pointing out limitations in classic real-time models and giving indications of engineering needs. Moreover, a method is presented for pre-run-time scheduling of periodic control activities under the interference of sporadic interrupts. Furthermore, a method is presented for enforcement of complex temporal constraints using standard priority based real-time operating systems. Finally, the work includes a method for management of communication resources in distributed systems.