Design principles for preschool children’s interactive TV

Preschool children have increased access to media via a number of platforms, including digital interactive television. However, the viewing and interaction needs of this user group have not been extensively researched. The project reported in this paper investigates preschoolers’ interactions with a simulated interactive television set-up. The study involved the development of an electronic programme guide prototype and its empirical evaluation. This research was carried out with children in Brazil and in the United Kingdom, aged between three and four. The main issues that arose during the interaction with the prototype application are documented, and a list of design principles is presented to assist in the design of accessible preschool interactive television applications for this age group.     

Design and control of a heavy material handling manipulator for agricultural robots

In this paper, we propose a manipulation system for agricultural robots that handle heavy materials. The structural systems of a mobile platform and a manipulator are selected and designed after proposing new knowledge about agricultural robots. Also, the control systems for these structural systems are designed in the presence of parametric perturbation and uncertainty while avoiding conservative results. The validity of both the structural and control systems is confirmed by conducting watermelon harvesting experiments in an open field. Furthermore, an explicit design procedure is confirmed for both the structural and control systems and three key design tools are clarified.

Implementation and modeling of two-phase locking concurrency control—a performance study

Two-phase locking (2PL) is the concurrency control mechanism that is used in most commercial database systems. In 2PL, for a transaction to access a data item, it has to hold the appropriate lock (read or write) on the data item by issuing a lock request. While the way transactions set their lock requests and the way the requests are granted would certainly affect a system's performance, such aspects have not received much attention in the literature. In this paper, a general transaction-processing model is proposed. In this model, a transaction is comprised of a number of stages, and in each stage the transaction can request to lock one or more data items. Methods for granting transaction requests and scheduling policies for granting blocked transactions are also proposed. A comprehensive simulation model is developed from which the performance of 2PL with our proposals is evaluated. Results indicate that performance models in which transactions request locks on an item-by-item basis and use first-come-first-served (FCFS) scheduling in granting blocked transactions underestimate the performance of 2PL. The performance of 2PL can be greatly improved if locks are requested in stages as dictated by the application. A scheduling policy that uses global information and/or schedules blocked transactions dynamically shows a better performance than the default FCFS.     

Optimal control of saturating linear plants for quadratic performance indices—II†

This paper continues the treatment of the problem of the optimal regulator for linear plants with bounded control variable and quadratic performance index. The optimal controls for this index are singular in a sub-set containing the origin and bang-bang elsewhere. The treatment is extended to the ease where the dimension of the singular sub-space is less than n—l for an nth order plant; the bang-bang mode then has an infinite number of switches. The method of optimal r-switch controls, developed previously for integral-square-error type criteria, is extended to deal with this index. The techniques described here are applicable to any performance index which contains only the state variables.     

Design and performance analysis of RAID based on OSD

Today＇s SAN architectures promise unmediated host access to storage. To keep this promise, however, several issues and opportunities raised by SANs must be addressed, including security, scalability and management. Object storage, such as introduced by the NASD work, is a means of addressing these issues and opportunities. RAID using Object-Based Storage Devices is described, about which some issues are discussed and then its performance by queuing model is investigated.     

Design principles and considerations for the ‘ideal’ silicon piezoresistive pressure sensor: a focused review

Over the past four decades, the field of silicon piezoresistive pressure sensors has undergone a major revolution in terms of design methodology and fabrication processes. Cutting edge fabrication technologies have resulted in improved precision in key factors like dimensions of diaphragm and placement of piezoresistors. Considering the unique nature of each sensor and the trade-offs in design, it is not feasible to follow a standard design approach. Thus, it is useful to derive the specific design from a number of important factors to arrive at the ‘ideal’ design. In this paper, we critically review and analyze the various design considerations and principles for silicon piezoresistive pressure sensor. We also report the effect of these considerations on the sensor output taking help of various CAD tools. Keeping in view the accuracy of state-of-the-art fabrication tools and the stringent demands of the present day market, it has become important to include many of these design aspects. Modelling using analytical expressions for thin plates has also been looked into as it gives a quick guideline and estimation of critical parameters before detailed finite element method analysis. Wherever possible, fabrication imperfections and their effects have been discussed. Dependency of piezoresistive coefficients on temperature and doping concentration, the effect of clamping condition of diaphragms and fabrication using wet bulk micromachining is also analyzed. Silicon-on-insulator based sensors along with innovative design strategies, and future trends have also been discussed. This paper will serve as a quick and comprehensive guide for pressure sensor developers.     

Optimal control of saturable linear plants for minimum integral-square-error and similar performance criteria†

The paper deals with the problem of minimizing integral–square–error and similar performance indices for linear single–variable plants with saturating control input. It is shown that the optimal control can be obtained by treating it as the limit as υ→∞ of the Sequence of controls which minimize the performance index on the class of all bang–bang controls containing not more than υ switches. These optimal υ switch controls are shown to satisfy a modified maximum principle.The method enables the computation of optimal controls from any given initial plant state. The particular problems of minimizing integral–modulus–error for a two–integrator plant and integral–square–error for a three–integrator plant are worked out in detail so as to illu3trata the techniques involved.     

Perceptual control architecture for cyber–physical systems in traffic incident management

Based on Perceptual Control Theory, we study the problem of unified modeling for incompatible approaches of Cyber–Physical Systems (CPSs). Inspired by the effective organization of living systems structure accommodating heterogeneous information processing and environmental interaction, we propose Perceptual Control Architecture of CPSs, and take Traffic Incident Management systems as the modeling research carrier. Throughout the structure of Traffic Incident Management systems, the hierarchical negative feedback is constituted by perceptual and behavioral loops to ensure a mechanism of intelligence behavior. The internal representation is categorized into two intelligent spaces: physical-reflex space and cyber-virtual space. In physical-reflex space, the sensing-actuation mapping of objective world is built, through four levels of distributed traffic infrastructure. In cyber-virtual space, subjective decision using Bayesian reasoning network is defined by three levels: principles, interrelated factors and situation assessment. Through evaluation of field operation in Dalian, the Traffic Incident Management under the developed architecture shows a considerable reduction in response time as well as assessment inaccuracy. The test results explicated the effectiveness of the architecture on integrating complex Cyber–Physical functions. Besides transportation systems, the modeling approach could be a well-defined unified architecture applied to other CPSs.     

Design and performance analysis of tracking controller for uncertain nonlinear composite system using neural networks

Based on high order dynamic neural network, this paper presents the tracking problem for uncertain nonlinear composite system, which contains external disturbance, whose nonlinearities are assumed to be unknown. A smooth controller is designed to guarantee a uniform ultimate boundedness property for the tracking error and all other signals in the dosed loop. Certain measures are utilized to test its performance. No a priori knowledge of an upper bound on the “optimal” weight and modeling error is required; the weights of neural networks are updated on-line. Numerical simulations performed on a simple example illustrate and clarify the approach.     

Analysis of the performance characteristics of controllers’ strategies in en route air traffic control tasks

For addressing human factor issues in the air traffic control (ATC) domain, further comprehension of controllers’ working methods during actual work is required. The objective of the present research is to analyze the performance characteristics of control strategies, which can be a major means to manage a traffic situation and workload for controllers, by using our process visualization tool of ATC tasks called COMPASi (COMPAS in interactive mode/COMPAS: COgnitive system Model for simulating Projection-based behaviors of Air traffic controllers in dynamic Situations). The computer-based simulation using COMPASi has clearly demonstrated the performance differences in the types of control strategies derived from a high-fidelity human-in-the-loop simulation (HITLS) for safety, efficiency of completing ATC tasks, and fuel economy of aircraft in a specific situation, and also differences in their tolerance of situational variability. The analysis results have been supported by performance evaluations carried out by ATC training instructors. In addition, a comparative analysis between simulation results under several simulation conditions by COMPASi and evaluation results by the instructor has strongly implied that the tolerance for the variability of situations might be a major factor in selection of control strategies by a controller. These contributions of the present research may be useful for practical purposes such as further improvement of education and training for controllers.     

Optimal control for chatter mitigation in milling—Part 1: Modeling and control design

Active structural methods constitute a promising way to mitigate chatter vibrations in milling. This paper presents an active system integrated into a spindle unit. Two different optimal control strategies are investigated. The first one only considers the dynamics of the machine structure in the controller design and minimizes the influence of cutting forces on tool tip deviations. The second one takes explicitly the process interaction into account and attempts to guarantee the stability of the overall closed-loop system for specific machining conditions. The modeling and formulation used for both strategies are presented in this first part. A simulation allows the comparison of their respective working principle. The validation of the proposed concept in experimental conditions is described in the second part.     

A visualization tool of en route air traffic control tasks for describing controller’s proactive management of traffic situations

Improvements of aviation systems are now in progress to ensure the safety and efficiency of air transport in response to the rapid growth of air traffic. For providing theoretical and empirical basis for design and evaluation of aviation systems, researches focusing on cognitive aspects of air traffic controllers are definitely important. Whereas various researches from cognitive perspective have been performed in the Air Traffic Control (ATC) domain, there are few researches trying to illustrate ATCO’s control strategies and their effects on task demands in real work situations. The authors believe that findings from these researches can contribute to reveal why ATCOs are capable of handling air traffic safely and efficiently even in the high-density traffic condition. It can be core knowledge for tackling human factors issues in the ATC domain such as development of further effective education and training program of ATCO trainees. However, it is difficult to perform such kinds of researches because identification of ATC task from a given traffic situation and specification of effects of ATCO’s control strategies on task demands requires expert knowledge of ATCOs. The present research therefore aims at developing an automated identification and visualization tool of en route ATC tasks based on a cognitive system simulation of an en route controller called COMPAS (COgnitive system Model for simulating Projection-based behaviors of Air traffic controller in dynamic Situations), developed by the authors. The developed visualization tool named COMPASⁱ (COMPAS in interactive mode) equips a projection process model that can simulate realistic features of ATCO’s projection involving setting extra margins for errors of projection. The model enables COMPASⁱ to detect ATC tasks in a given traffic situation automatically and to identify Task Demand Level (TDL), that is, an ATC task index. The basic validity of COMPASⁱ has been confirmed through detailed comparison between TDLs given by a training instructor and ones by COMPASⁱ in a simulation-based experiment. Since TDL corresponds to demands of ATC tasks, temporal sequences of TDLs can reflect effectiveness of ATCO’s control strategies in terms of regulating task demands. By accumulation and analysis of such kind of data, it may be expected to reveal important aspect of ATCO’s skill for achieving the safety and efficiency of air traffic.     

Microcomputer control of high dynamic performance ac-drives—A survey

Alternating current machines, in particular induction motors, are of simple mechanical construction but have a nonlinear, highly interacting multivariable control structure. This has made it difficult in the past to design controlled ac-drives with high dynamic performance, similar to converter-fed dcdrives. A satisfactory solution of this problem has not been available until Blaschke formulated the principle of field orientation, where the machine is controlled in a moving frame of reference. This paper presents a survey of controlling acmachines for use in high dynamic performance drives including different types of machines and converters with their specific control characteristics. It is shown that by combining a suitable machine model with the principle of rotor- or field-orientation a unifying basis for the design of ac-drives is created. The complicated signal structure of the control systems can very effectively be handled by microelectronics, i.e. by using software instead of elaborate hardware. This is shown in the paper with the help of examples.     

Effects of output display and control—display gain on human performance in interactive systems

Abstract

Human performance comparisons on interactive systems were drawn between output displays (CRT and LCD) across settings of control-display gain. Empirical evidence was sought in light of the common feeling in the user community that motor-sensory tasks are more difficult on a system equipped with an LCD display vs. a CRT display. In a routine target acquisition task using a mouse, movement times were 34% longer and motor-sensory bandwidth was 25% less when the output display was an LCD vs. a CRT. No significant difference in error rates was found. Control-display (C-D) gain was tested as a possible confounding factor; however, no interaction effect was found. There was a significant, opposing main effect for C-D gain on movement lime and error rates, illustrating the difficulty in optimizing C-D gain on the basis of movement time alone.     

Design,control, and performance of the ‘weed’ 6 wheel robot in the UK MOD grand challenge

A new locomotion method for unmanned (autonomous) ground vehicles (UGV) is proposed based around six independently driven wheels mounted on three separate modules. Each module is attached to the overall robot via a pivot point and capable of independently controlling its orientation and velocity. This configuration allows the UGV to perform maneuvers conventional vehicles cannot perform, and in particular to control the body orientation separately from the movement direction. The locomotion method is mathematically analyzed to develop appropriate control algorithms and to demonstrate the vehicle performance criteria. A vehicle was constructed according to the proposed configuration and experimentally tested in the UK Ministry Of Defense grand challenge. The performance of the developed locomotion schemes helped the robot make it to the finale of the competition.     

Improving the performance of pipelined query processing with skipping—and its comparison to document-wise partitioning

Web search engines need to provide high throughput and short query latency. Recent results show that pipelined query processing over a term-wise partitioned inverted index may have superior throughput. However, the query processing latency and scalability with respect to the collections size are the main challenges associated with this method. In this paper, we evaluate the effect of inverted index skipping on the performance of pipelined query processing. Further, we introduce a novel idea of using Max-Score pruning within pipelined query processing and a new term assignment heuristic, partitioning by Max-Score. Our current results indicate a significant improvement over the state-of-the-art approach and lead to several further optimizations which include dynamic load balancing, intra-query concurrent processing and a hybrid combination between pipelined and non-pipelined execution. Lastly, we show how the state of term-wise partitioning relates to the industry standard document-wise partitioning. Even though there are situations pipelined query processing is advantegous, document-wise partitioning is still the road to follow.