Enforcing Temporal Constraints in Embedded Control Systems

University dissertation from Stockholm : Maskinkonstruktion

Abstract: Computer control systems are embedded in a large and growing group of products, rangingfrom consumer entertainment products to large airliners. Products such as automotive vehicles,aircraft, and industrial robots are equipped with advanced computer control systems and havehigh requirements of reliable and safe operation. A common property of these systems is thatthe computer systems are becoming increasingly more complex due to the inclusion of morefunctionality. At the same time, the product cycles are becoming shorter leading torequirements of shorter time to market. To meet this challenging task, the development ofcomputer control systems must be a well-defined and controlled engineering process. Oneimportant part in reaching this goal is to find methods for dealing with the complexity ofcomputer systems.A computer control system is typically realized by a set of concurrent activities with inter-dependenciesthat have to meet a set of pre defined temporal constraints. Because of this, it isdifficult to know in advance if the implementation of a design will meet its temporalconstraints. Furthermore, it is hard to foresee the consequence of introducing alterations oradditional functionality in a system. For a method to be useful it also has to capture all therelevant aspects of the application domain, and in the domain of embedded control systemsthis 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 alsoactivities related to e.g., human-machine interaction and communication.The work presented in this thesis contributes with methods for enforcing temporalconstraints in embedded control systems. The results include an industrial case study pointingout 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 activitiesunder the interference of sporadic interrupts. Furthermore, a method is presented forenforcement of complex temporal constraints using standard priority based real-time operatingsystems. Finally, the work includes a method for management of communication resources indistributed systems.