Annual Review in Automatic Programming最新文献

The methods and environments for developing real-time systems have become an important factor encouraging the rapidly increasing role of real-time systems in everyday life. In spite of the remarkable success in applying software engineering tools to real-time systems, the analysis of timing properties and the consistency proofs of time-constraints is still in its infancy.

This paper suggests a solution which improves the ability to study and prove time-correctness of real-time systems. CONRAD (CONtrol software Requirements, Analysis and Design) is a set of tools which allows formal specification and analysis of timing properties (the EDITOR), and informal analysis (animation) starting from the early stages of the requirements specification. This paper describes the possibilities provided by the EDITOR.

We present a novel technique for establishing a highly accurate global time in fault-tolerant, large-scale distributed real-time systems. Unlike the usual clock synchronization approaches, our clock validation technique provides a precise system time that also relates to an external time standard like UTC with high accuracy. The underlying idea is to validate time information of external time sources like GPS-receivers against a global time maintained by the local clocks in the system. As an example, a promising interval-based clock validation algorithm ICV that exhibits excellent fault-tolerance properties is outlined and analyzed. It requires only a few high-accurate external time sources and provides each node with the actual accuracy of its clock.

Soft real-time techniques are needed for continuous multimedia communication systems. It is the intention of MMOSS, a real-time multimedia operating system supporting environment under development, to promote the integration of real-time techniques into such systems. MMOSS tries to support multimedia communications and applications by exploiting their special “soft” features, which are not present in or are not typical of other kinds of real-time applications. Some of these features are soft real-time guarantee, periodicity, error-tolerance, adaptability, etc. Feasible real-time models for these special features are provided. To run on a multiprocessor communication subsystem, MMOSS tries to support multimedia applications by providing them with a soft real-time execution environment.

A general scheme for signal sampling is presented, which is based on requirements of real-time systems. Instead of the ideal low-pass filter in Shannon's sampling theorem, alternative filters are derived from wavelet theory. To evaluate the filters, digital simulations have been carried out. The results of these simulations are briefly discussed in this paper. Finally, some remarks are made on the implementation of the alternative sampling methods and their usage for process control systems.

The ability of reasoning about temporal data, representing past, current and expected application states is an important function to be accomplished by Real-Time Knowledge-Based Systems (RTKBS). The application of Knowledge-based systems to real-time problems has to deal with dynamic time-constrained environments and assess two of the most important requirements in real-time systems: the ability to react rapidly to changes in the environment and the guarantee of a bound on the response time. This paper presents a temporal framework for reasoning about the future behaviour of a dynamic time-constrained problem. The proposed mechanism is integrated into a multiagent blackboard architecture and will provide a perspective of the temporal functionalities offered in the REAKT tool

This paper describes the use of neural networks in diferent domains of robot control. Three robot control problems, relevant to a broad range of robotics applications, are analyzed, with a review of the state of the art and a description of current research by the authors, highlighting the advantages of the use of neural networks with respect to conventional techniques.

Designing and reasoning about real-time systems are difficult activities, in which timing and reactive behaviour requirements add significant complexity to system validation. In this paper, a new technique for distributed prototyping of real-time systems is presented. It enables system prototypes to be concurrently developed and tested by a geographically distributed team, in such a way that each developer can validate his or her part of the system against the other parts which are being built in other development sites. A set of tools has been implemented that supports validation of functional and time behaviour through distributed animation of graphical prototypes with a consistent vision of simulated time.

In the paper a realistic approarh to fuzzy control of urban road traffic lights is described. Fuzzy application is encouraging since the design procedure of vehicle actuated traffic light systems is very transparently, and an adaptation to changing situations of traffic is easily to accomplish. The paper presents simulation results obtained for an intersection with 12 main direction traffic flows. The fuzzy controller proposed switches to a two-state, a three-state or a four-state control. The results with respect to the average loss of traveltime are very promising in comparison with other controllers applied to the same simulation example.

This paper describes the application of a real time fuzzy controller to a column flotation pilot plant. The objective of this controller is to regulate three important process variables: air holdup, level of collection zone/froth zone interface in the column and bias water flow rate that are related with the product quality (concentrate grade) and recovery. The fuzzy controller was developed based on heuristic rules and it was tuned by a trial and error approach. The controller is coupled with a real-time graphics interface providing an easy process monitoring, with on line set point changes of all the controlled variables.

A local guidance control method for wheeled mobile vehicles equipped with low-cost sensors is presented. This method uses fuzzy logic to provide a smooth path which is not necessarily optimal in distance and/or power consumption but allows guidance, obstacle avoidance and docking using few ultrasound sensors. The module that implements this method receives objectives from a Global Path Generation module as points that the robot should pass by at a specified orientation and speed. An important aspect of this method is that it does not require expensive sensors to create a good map of its surrounding because it relies only on range information provided by inexpensive sensors. Using only this range information also provides real-time performance at low cost.