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REVIEW OF REAL-TIME MICRO-OPERATING SYSTEMS THEORY


Astapkovitch A. M., Kasatkin A. A.


(State University of Aerospace Instrumentation, Saint-Petersburg)



Abstract

The review of actual state of Real-time micro-Operating Systems theory is presented. This applied theory is focused on subclass of embedded multi-channel control systems for hard real-time applications and oriented tobe a theoretical base for next-generation software integrated development environments (IDE). Article concerns hierarchy of programming methods, probabilistic behavior of real-time control systems and new approaches for describing algorithms of multi-channel real-time control system functioning with developed formalism and high-level language. Initial objects of theory are introduced. It‘s shownthat response time for multi-channel real-time systems has to be interpreted as probabilistic value. A new formalism provides possibilities for two-dimensioned algorithm description with address-time maps (AT-map). Classification of conflict in concurrent space was introduced: AT-conflict, A-conflict, T-conflict. Formal criterion was introduced to provide possibilities for automatic solution ofcritical section analysis problem. Basic definitions for AT-formalism operations were introduced. Structure of next generation IDE is discussed.

I. INTRODUCTION

Real-time micro-operating systems (RTmOS) theory was introduced in [1]. This theory is focused on subclass of embedded multi-channel control systems for hard real-time applications. The structure of theory is illustrated on fig. 1.1.Fig. 1.1. RTmOS theory structure






Typical structure of multi-channel control system is represented on Fig. 1.2.





































Fig. 1.2. Typical structure of a control system




Classical theory defines RealTime Control System (RTCS) as a system that provides response on object state changing during time Tri that not exceeds specified time Tspi for every controlled channel.
Tri < Tsp i i=1…Nch (1.1)
For specified controller’s performance number of controlled channels is a complex function of different factors. Controller’s performance is a most significant systemparameter that forces to fix it while examining others.
Nch = f (Ns, Na, Tr, …) (1.2)
RTCS class can be divided into two subclasses: a subclass of control systems for Soft Real Time Application (SRTA) and subclass of control systems for Hard Real Time Application (HRTA). HRTA subclass consists of very reliable control systems, because it is supposed that every fault of control system of thissubclass leads to loose of control object.
As applied to control software it has to be outlined that for HRTA control systems fault can occur if mistakes are exist in control algorithm for some channel or if specified response time is exceeded due to interference between channels.
To reduce probability of mistakes for real time applications a special programming technology has to be used.Hierarchy of software developing methods for embedded control systems was proposed in [1]. It is represented on fig. 1.3.
























Fig. 1.3. Hierarchy of modern software developing methods for embedded control systems


It can be concluded, that RTmOS is a key element of modern software development technology. RTmOS are to be used as standardizedstructure of modern embedded control systems’ software that responds for task scheduling and inter-task communications. Also, RTmOS is a core of modern Integrated Development Environments (IDE).
It was pointed out [1] that embedded control systems has some special features as:
– known number of control channels;
– well determined control algorithms for every channel;
– this system...