Real-time Issues Research Articles

A Real-Time Negotiation Model and A Multi-Agent Sensor Network Implementation

This paper describes a negotiation model that incorporates real-time issues for autonomous agents. This model consists of two important ideas: a real-time logical negotiation protocol and a case-based negotiation model. The protocol integrates a real-time Belief-Desire-Intention (BDI) model, a temporal logic model, and communicative acts for negotiation. This protocol explicitly defines the logical and temporal relationships of different knowledge states, facilitating real-time designs such as multi-threaded processing, state profiling and updating, and a set of real-time enabling functional predicates in our implementation. To further support the protocol, we use a case-based reasoning model for negotiation strategy selection. An agent learns from its past experience by deriving a negotiation strategy from the most similar and useful case to its current situation. Guided by the strategy, the agent negotiates with its partners using an argumentation-based negotiation protocol. The model is time and situation aware such that each agent changes its negotiation behavior according to the progress and status of the ongoing negotiation and its current agent profile. We apply the negotiation model to a resource allocation problem and obtain promising results.

Viewing urban disruptions from a decision informatics perspective.

Urban infrastructures are the focus of terrorist acts because, quite simply, they produce the most visible impact, if not casualties. While terrorist acts are the most insidious and onerous of all disruptions, it is obvious that there are many similarities to the way one should deal with these willful acts and those caused by natural and accidental incidents that have also resulted in adverse and severe consequences. However, there is one major and critical difference between terrorist acts and the other types of disruptions: the terrorist acts are willful — and therefore also adaptive, if not coordinated. One must counter these acts with the same, if not more sophisticated, willful, adaptive and informed approach. Real-time, information-based decision making — which Tien (2003) has called the decision informatics paradigm — is the approach advanced herein to help make the right decisions at the various stages of a disruption. It is focused on decisions and based on multiple data sources, data fusion and analysis methods, timely information, stochastic decision models and a systems engineering outlook; moreover, it is multidisciplinary, evolutionary and systemic in practice. The approach provides a consistent way to address real-time emergency issues, including those concerned with the preparation for a major disruption, the prediction of such a disruption, the prevention or mitigation of the disruption, the detection of the disruption, the response to the disruption, and the recovery steps that are necessary to adequately, if not fully, recuperate from the disruption. The efforts of the U. S. Department of Homeland Security and its academically-based Homeland Security Centers of Excellence are considered within the proposed types, stages and decisions framework.

An Integrated Memory Array Processor Architecture for Embedded Image Recognition Systems

Embedded processors for video image recognition require to address both the cost (die size and power) versus real-time performance issue, and also to achieve high flexibility due to the immense diversity of recognition targets, situations, and applications. This paper describes IMAP, a highly parallel SIMD linear processor and memory array architecture that addresses these trading-off requirements. By using parallel and systolic algorithmic techniques, despite of its simple architecture IMAP achieves to exploit not only the straightforward per image row data level parallelism (DLP), but also the inherent DLP of other memory access patterns frequently found in various image recognition tasks, under the use of an explicit parallel C language (1DC). We describe and evaluate IMAP-CE, a latest IMAP processor, which integrates 128 of 100MHz 8 bit4-way VLIW PEs, 128 of 2KByte RAMs, and one 16 bit RISC control processor, into a single chip. The PE instruction set is enhanced for supporting 1DC codes. IMAP-CE is evaluated mainly by comparing its performance running 1DC codes with that of a 2.4GHz Intel P4 running optimized C codes. Based on the use of parallelizing techniques, benchmark results show a speedup of up to 20 for image filter kernels, and of 4 for a full image recognition application.

Real-Time Implementation Issues in Passive Automatic Focusing for Digital Still Cameras

Due to consumers' demand for faster picture shot time in the rapidfy expanding digital still camera market, it is of importance to address the real-time implementation issues in the development of passive automatic focusing for digital still cameras. This article discusses such real-time implementation issues that are often overlooked when designing passive contrast sensing automatic focusing on digital still camera processors. Specifically, algorithmic design tradeoffs between automatic focusing speed, accuracy, and power consumption, are addressed. A sample implementation and its performance results on an actual digital still camera hardware platform powered by the Texas Instruments TMS320DM270 processor are presented to further convey these real-time implementation issues.

Minimizing memory requirement of real-time systems with concurrent garbage collector

Garbage collection is a key feature in modern programming languages like Java™. But it also brings some obstacles to real-time issues. Previous work had been put on solving the real-time problems of the garbage collector. Among it there are concurrent collectors that can provide truly real-time guarantees but they rely on a relatively large amount of redundant system memory. This paper concentrates on minimizing the system memory requirement with a new concurrent garbage collector which is based on a deferrable server together with a particular parameter configuration scheme proposed by this paper. The parameter configuration scheme is addressed using two different approaches, that is, the utilization based analysis and exact analysis of the selection of parameters. In this way, the worst-case response time of a garbage collector is minimized, and so is the worst-case system memory requirement, with the schedulability of tasks with hard time constraint not jeopardized. Furthermore, the simulation results demonstrate that, based on the new algorithm, the actual maximum system memory requirement for a given task set also becomes less than that of any previous concurrent collector.

An object-oriented simulation framework for real-time control of automated flexible manufacturing systems

This paper describes an object-oriented simulation approach for the design of a flexible manufacturing system that allows the implementation of control logic during the system design phase. The object-oriented design approach is built around the formal theory of supervisory control based on Finite Automata. The formalism is used to capture inter-object relationships that are difficult to identify in the object-oriented design approach. The system resources are modeled as object classes based on the events that have to be monitored for real-time control. Real-time control issues including deadlock resolution, resource failures in various modes of operation and recovery from failures while sustaining desirable logical system properties are integrated into the logical design for simulating the supervisory controller.

ロボット制御プログラムの無停止更新手法

This paper presents a method to update running RTLinux robot controller programs (RTU) on the fly. The proposed method exploits thread swapping. This paper focuses on the safety conditions of thread swapping, platform requirements, realtime issues, and uncertainties in RTU completion time. This paper introduces RTU-able software design by layered modules which enable the update of servo functions and robot model global variables. We have developed a RTU-able mobile manipulator controller, evaluated its performance by worst case results, and shown its practical applicability.

Real time implementation of acoustical beamforming

Sensor networks are gaining great attention because of their large range of applications. The main purpose of a sensor network is to monitor an area including detecting, identifying, localizing, and tracking one or more objects of interest. These networks may be used by the military in surveillance, reconnaissance, and combat scenarios or around the perimeter of a manufacturing plant for intrusion detection. Such systems should be very ready to catch and signal the event. Real time issues are critical. Fortunately, nowadays the integrated circuit technology provides low-cost sensor nodes with signal processing and wireless communication capabilities. In this paper, we consider the use of simple PDAs (Personal Digital Assistant) equiped with built-in microphones and external IEEE802.11b wireless cards for radio communication. The purpose is to realize an audio localization system with some real-time constraints in term of computational delay.

A six-legged robot: real-time issues and architecture

Mobile robot systems often operate under real-time constraints imposed by the interactions with the world in which they act. Such timing constraints are typically assigned to the various software activities (acquisition, control and actuation tasks) that run on the robot controller, and need to be enforced by the operating system that support the application. To reduce weight and power consumption, however, battery-operated robots are usually controlled by small microcontrollers with little computational power and memory capacity. As a consequence, predictability as well as high efficiency is required from the real-time kernel to enforce timing constraints on application tasks. In this paper we describe a robot control architecture specifically developed for supporting real-time applications in small mobile robots with limited resources. The proposed real-time system has been used to control the behavior of a six-legged walking robot, where the motion of each leg has to be synchronized with the other based on the walking parameters.

A real-time system for tracking and catching moving targets

In this paper we describe the real-time issues related to the development of a control system for tracking and catching moving targets by vision. After describing the main hardware and software components of the system, we discuss a number of interesting scheduling problems that arise in these kind of control applications. A possible solution to these problems is also outlined and has been implemented on top the Shark operating system. used to develop the real-time application. The experimental results obtained on the system prototype show the effectiveness of our approach and encourage further research on the specific scheduling problems.

Model predictive control: Real-time issues and RBF-ANN implementation

Model predictive controls are control strategy in which the effect of the control actions are evaluated many steps in the future to gain an optimal control action. According to this the number of calculations made is very big and it needs some simplifications to use it in real time control tasks. That’s why some recurrent formulas will be used. The GPC was realized with ANN using gradient descent algorithm which adjust the parameters of the ANN regulator with RBF.

An Object-oriented Methodology for Embedded Real-time Systems

The usage of object-oriented methodologies in conjunction with formal description techniques has arisen as a promising way of dealing with the increasing complexity of embedded real-time systems. These methodologies are currently well supported by a set of tools that allow the specification, simulation and validation of the functional aspects of these systems. However, most of these methodologies do not take into account non-functional aspects such as hardware interaction and real-time constraints, which are especially important in the context of this kind of system. Based on our experiences in developing embedded real-time systems, we present a new methodology to design them. This methodology is based on a combination of ideas from different existing methodologies (UML, OCTOPUS, etc.) together with the integration of rate-monotonic analysis in the context of the SDL formal description technique development cycle. Additionally, in order to get this integration, a real-time execution model for SDL is presented to allow us to express hard real-time constraints. The methodology pays special attention to the transition from the object model to the task model, taking into account real-time and hardware integration issues. We also illustrate our proposal by applying it to the development of a multi-handset cordless telephone.

Applying active learning at the graduate level: merger issues at Newco

Most of the active learning literature focuses on approaches in undergraduate courses. However, active learning also can benefit students in public relations and integrated communication courses at the graduate level. This case report describes how three active learning approaches—research and field work, student accountabilities for learning, and student reflection and reflexive exercises—were used in a graduate class project to help a Fortune 50 consumer products company identify and address real-time merger communication issues.

SHaDe, a new 3-DOF haptic device

This paper presents a new type of haptic device using spherical geometry. The basic idea of haptic devices is to provide users with feedback information on the motion and/or force that he or she generates. Haptic devices have several potential applications such as, for example, fine compliant assembly, VR environment simulation, and high-precision teleoperation, especially in hazardous or hostile areas. The particular architecture of the spherical haptic device developed here will be presented and its advantages will be highlighted. Then, its basic kinematic properties, which shall be used for control and geometric optimization purposes, will be reviewed. The design optimization itself will then highlight some important features of the mechanism. The control scheme and real-time force feedback issues will then be presented. Finally, the results obtained with the prototype will be discussed.

Distributed Mining of Classification Rules

Many successful data-mining techniques and systems have been developed. These techniques usually apply to centralized databases with less restricted requirements on learning and response time. Not so much effort has yet been put into mining distributed databases and real-time issues. In this paper, we investigate issues of fast-distributed data mining. We assume that merging the distributed databases into a single one would either be too costly (distributed case) or the individual fragments would be non-uniform so that mining only one fragment would bias the result (fragmented case). The goal is to classify the objects O of the database into one of several mutually exclusive classes Ci. Our approach to make mining fast and feasible is as follows. From each data site or fragment dbk, only a single rule rik is generated for each class Ci. A small subset {ri1,.....,rih} of these individual rules is selected to form a rule set Ri for each class Ci. These rule subsets represent adequately the hidden knowledge of the entire database. Various selection criteria to form Ri are discussed, both theoretically and experimentally.

Auction-based distributed scheduling in a dynamic job shop environment

Developments in computing and communication technology coupled with the inability to address real-time issues in scheduling algorithms based on central control, has led to an interest in solving the problem of a distributed decision-making environment. This paper presents a new job shop formulation that schedules jobs using auctions for distributing control. A theoretical basis is presented for problem decomposition, bid construction, and bid evaluation for the auction using standard mathematical programming tools. Numerical results show that the auction-based approach outperforms the distributed dispatching approaches and can be used to create schedules for a wide range of scheduling objectives.

Ground-based GPS water vapour estimation: potential for meteorological forecasting

In order to assess the impact of ground-based GPS water vapour estimates in meteorological forecasting applications, estimates must be available within near real time and must be produced with an accuracy comparable with that of existing meteorological measurement techniques. Before the potential benefit of GPS-integrated water vapour (IWV) estimates in numerical weather prediction (NWP) models could be determined, extensive tests were performed to examine the effect of various process error models, constraints and estimation techniques involved within GPS processing procedures in order to devise a recommended processing strategy. Ten months of GPS data from a selection of stations, which are co-located with radiosonde launch sites, within the UK permanent GPS network, have been processed to validate these findings. Near real-time estimation issues have subsequently been examined, primarily using a sliding-window processing approach to demonstrate the feasibility of producing accurate GPS IWV estimates within the required time frame. Additionally, preliminary simulation work has been performed to assimilate GPS IWV into the UK Meteorological Office (UKMO) numerical weather prediction models, in preparation for impact assessments on the quality of mesoscale weather forecasts.

Deadlock detection, prevention, and avoidance for automated tool sharing systems

Automated tool sharing systems provide a technological response to the high cost of tools in flexible manufacturing systems. These systems allow different machines to use the same tools by automatically transferring them from machine to machine as tooling needs evolve. With these systems, tool allocation is a real-time issue that requires sophisticated control techniques to make the right allocation decisions. An essential property that tool sharing policies must guarantee is deadlock-free operation. Although manufacturing researchers have investigated the performance aspects of tool sharing through simulation, no work has yet addressed deadlock handling strategies for these real-time systems. In this paper, we characterize the structural and computational properties of the tooling deadlock problem. We develop polynomial algorithms that detect and avoid deadlock, and we investigate the safety implications of special structures appearing in tool sequences.

Genetic adaptive control for an inverted wedge: experiments and comparative analyses

The inverted wedge is a planar robot with two degrees of freedom and a single control input (i.e., it is “underactuated”). The goal is to develop a digital controller that can balance the wedge in the inverted position by shifting a weight on the top of the wedge. Because it is underactuated and has complicated nonlinear dynamics, the inverted wedge is a good testbed for the development of nonconventional advanced control techniques and comparative analysis between control methods. We begin with the development of a nonlinear state feedback controller and direct and adaptive fuzzy controllers, that we will later use as a baseline comparison to show what type of performance is possible for this testbed. Control routines based on the GA have been found to apply to several practical applications in simulation and off-line optimization. Here, we will show that a GA can be used on-line in real-time to produce a particularly effective adaptive control method and this is the main contribution of this work. Computational and real-time implementation issues will be discussed and the genetic adaptive strategy will be compared with the state feedback and fuzzy control methods.

A real-time Java server for real-time mach

We have developed a real-time Java1 server on the Real-Time Mach micro-kernel which is suitable for embedded systems and distributed real-time systems. By implementing it as a user-level server on Real-Time Mach, applications such as WWW browsers and embedded applications can both execute Java byte codes. In this paper, we describe the real-time issues in Java and the architecture of our Java server. The real-time extension of the Java server and Java threads using kernel-level threads was also evaluated.