General Evaluation Function Research Articles

An individualized robust stability control strategy for active front steering vehicles

To improve the vehicle stability and driver steering performance, this paper presents an individualized yaw stability control strategy based on H∞ robust control for active front steering (AFS) vehicles. A driver-vehicle system, including a driver steering model and a vehicle dynamics model with AFS, is formed. To analyze the steering characteristics of different drivers, a set of driving data of 36 drivers is collected, and the driver’s characteristics parameters are identified by using the particle swarm optimization (PSO) algorithm. A general evaluation function considering the trajectory tracking performance, vehicle stability, driver workloads, and driver’s characteristics parameters are established to evaluate the comprehensive steering performance. To accomplish the personalized control of vehicle yaw stability, an individualized H∞ robust yaw stability controller is presented by adjusting the gain of the weighting function according to the general evaluation of each driver. Driver-in-the-loop experiment is conducted based on the Matlab/Simulink-CarSim®-Prescan co-simulation platform, and the results demonstrates that the proposed control strategy can provide driver with individualized driving assistance while improving the overall driving performance and reducing the driver’s workloads.

Modeling and simulation of intersection quasi-moving block speed guidance based on connected vehicles

Purpose This study aims to propose a speed guidance model of the CV environment to alleviate traffic congestion at intersections and improve traffic efficiency. By introducing the theory of moving block section for high-speed train control, a speed guidance model based on the quasi-moving block speed guidance (QMBSG) is proposed to direct platoon including human-driven vehicles and connected vehicles (CV) through the intersection coordinately. Design/methodology/approach In this model, the green time of the intersection is divided into multiple block intervals according to the minimal safety headway. Connected vehicles can pass through the intersection by following the block interval using the QMBSG model. The block interval is assigned dynamically according to the traveling relation of HV and CV, when entering the communication range of the intersection. To validate the comprehensive guidance effect of the proposed model, a general evaluation function (GEF) is established. Compared to CVs without speed guidance, the simulation results show that the GEF of QMBSG model has an obvious improvement. Findings Compared to CVs without speed guidance, the simulation results show that the GEF of QMBSG model has an obvious improvement. Also, compared to the single intersection speed guidance model, the GEF value of the QMBSG model improves over 17.1%. To further explore the guidance effect, the impact of sensitivity factors of the CVs’ environment, such as intersection environment, communication range and penetration rate (PR) is analyzed. When the PR reaches 75.0%, the GEF value will change suddenly and the model guidance effect will be significantly improved. This paper also analyzes the impact of the length of block interval under different PR and traffic demands. It is found that the proposed model has a better guidance effect when the length of the block section is 2 s, which facilitates traffic congestion alleviation of the intersection in practice. Originality/value Based on the aforementioned discussion, the contributions of this paper are three-fold. Based on the traveling information of HV/CV and the signal phase and timing plans, the QMBSG model is proposed to direct platoon consisting of HV and CV through the intersection coordinately, by following the block interval assigned dynamically. Considering comprehensively the indexes of mobility, safety and environment, a GEF is provided to evaluate the guidance effect of vehicles through the intersection. Sensitivity analysis is carried out on the QMBSG model. The key communication and traffic parameters of the CV environment are analyzed, such as path attenuation, PR, etc. Finally, the effect of the length of block interval is explored.

Three-way decision on two universes

Rough set models on two universes are important generalizations of Pawlak’s classical model. In most of the two-universe models, the upper and lower approximations are constructed based on inclusion relation. We generalize inclusion relation to the general evaluation function and define the models of three-way decision on two universes. As an important class of evaluation functions, subsethood measures are considered. We compare our models with other five existing two-universe models in rough set theory and point out that the model of three-way decision on two-universe unifies the five two-universe models. Besides, properties of the two-universe model of three-way decision are also given. More importantly, we propose an approach to computing the pair of thresholds α and β. Our approach is based on the maximum value of the accuracy measure with respect to tri-partitions of a universe induced by all thresholds.

New scoring metric for load shedding in multi‐control area systems

Electrical Power Systems should be designed in order to minimise the effects of system disturbances. However, in order to mitigate the damage caused by severe and unexpected contingencies, new special control philosophies such as automatic under frequency load shedding (AUFLS) were developed. The aim of the AUFLS process is to preserve most of the system and avoid situations of widespread blackouts. However, the design of this type of process, including the definition of parameters, is generally based on historical observations or previous experiences without a specific methodological basis. Furthermore, good evaluation methods among AUFLS schemes and the comparison among different load control philosophies play a major role in the overall performance of the system. This study aims to provide a general evaluation function that can be applied to different load shedding schemes, even those with different philosophies and operating principles. For the sake of exemplification, a set of AUFLS schemes were evaluated by the proposed metric.

An information theoretic approach for feature selection

AbstractFeature selection methods play a significant role during classification of data having high dimensions of features. The methods select most relevant subset of features that describe data appropriately. Mutual information (MI) based upon information theory is one of the metrics used for measuring relevance of features. This paper analyses various feature selection methods for (1) reduction in number of features; (2) performance of Naïve Bayes classification model trained on reduced set of features. Research gaps identified are: (1) computation of MI from the whole sample space instead of unclassified sample subspace; (2) consideration of relevance of features only or tradeoff between relevance and redundancy, but class conditional interaction of features is ignored.In this paper, we propose a general evaluation function using MI for feature selection. The proposed evaluation function is implemented which use dynamically computed MI values from unclassified instances. Effectiveness of the proposed feature selection method is done empirically by comparing classification results using KDD 1999 benchmarked dataset of intrusion detection. The results indicate practicability and effectiveness of the proposed method for applications concerned with high accuracy and stability of predictions. Copyright © 2011 John Wiley & Sons, Ltd.

Beam direction of the difference pattern in a monopulse phased array antenna

The beam direction of a monopulse phased array antenna can be changed rapidly by controlling the phase shifters, which is useful in detecting the direction of arrival of radio waves. In monopulse tracking, the null point of the difference pattern is used as the reference for direction determination. However, errors of phase setting, including the quantization error of the phase shifters, give rise to the problem of null shift, that is, the null point shifts from the set direction. This study examines the relation between the phase setting error and the null shift from the statistical point of view and expresses the relation between the two in a simple formula. In the general evaluation function, the position of the element antenna and the excitation amplitude are used as the parameters. Then, an expression is derived by approximating the amplitude distribution over the antenna aperture as a quadratic function, with the result that the evaluation function can be derived without defining the element position. The effectiveness of these expressions is verified by numerical calculation examples. In addition, the minimum change of the beam direction, which determines the angular measurement accuracy of the monopulse phased array antenna, depends on the phase setting accuracy of the digital phase shifters and on the accuracy of the operation unit that calculates the phase to be set in the phase shifters. The accuracies (expressed as numbers of bits) required by the phase shifters and the operation unit so that they can produce the minimum change of the beam direction are investigated, and a simple formula is obtained. In order to verify the results of these investigations, experimental results and numerical calculations are presented. © 2000 Scripta Technica, Electron Comm Jpn Pt 1, 84(1): 68–76, 2001

SIMPLE EVALUATION FUNCTION

The quality of chess programs is based on tree searching; this limits computer chess development. Modern improvements are possible mainly by applying new concepts in a heuristic evaluation of a chess position. While seeking optimal partial solutions to obtain general solutions, one is led to huge programs that solve only a small part of a chess problem. It seems that an optimistic approach is to look for a conceptionally simple and general evaluation function which can be improved by using a computer.