A layered fuzzy logic controller for nonholonomic car-like robot

A system for real time navigation of a nonholonomic car-like robot in a dynamic environment consists of two layers is described: a Sugeno-type fuzzy motion planner; and a modified proportional navigation based fuzzy controller. The system philosophy is inspired by human routing when moving between obstacles based on visual information including right and left views to identify the next step to the goal. A Sugeno-type fuzzy motion planner of four inputs one output is introduced to give a clear direction to the robot controller. The second stage is a modified proportional navigation based fuzzy controller based on the proportional navigation guidance law and able to optimize the robot's behavior in real time, i.e. to avoid stationary and moving obstacles in its local environment obeying kinematics constraints. The system has an intelligent combination of two behaviors to cope with obstacle avoidance as well as approaching a target using a proportional navigation path. The system was simulated and tested on different environments with various obstacle distributions. The simulation reveals that the system gives good results for various simple environments

Linear, Deterministic, and Order-Invariant Initialization Methods for the K-Means Clustering Algorithm

Over the past five decades, k-means has become the clustering algorithm of choice in many application domains primarily due to its simplicity, time/space efficiency, and invariance to the ordering of the data points. Unfortunately, the algorithm's sensitivity to the initial selection of the cluster centers remains to be its most serious drawback. Numerous initialization methods have been proposed to address this drawback. Many of these methods, however, have time complexity superlinear in the number of data points, which makes them impractical for large data sets. On the other hand, linear methods are often random and/or sensitive to the ordering of the data points. These methods are generally unreliable in that the quality of their results is unpredictable. Therefore, it is common practice to perform multiple runs of such methods and take the output of the run that produces the best results. Such a practice, however, greatly increases the computational requirements of the otherwise highly efficient k-means algorithm. In this chapter, we investigate the empirical performance of six linear, deterministic (non-random), and order-invariant k-means initialization methods on a large and diverse collection of data sets from the UCI Machine Learning Repository. The results demonstrate that two relatively unknown hierarchical initialization methods due to Su and Dy outperform the remaining four methods with respect to two objective effectiveness criteria. In addition, a recent method due to Erisoglu et al. performs surprisingly poorly.Comment: 21 pages, 2 figures, 5 tables, Partitional Clustering Algorithms (Springer, 2014). arXiv admin note: substantial text overlap with arXiv:1304.7465, arXiv:1209.196

The wicked and complex in education: developing a transdisciplinary perspective for policy formulation, implementation and professional practice

The concept of 'wicked issues', originally developed in the field of urban planning, has been taken up by design educators, architects and public health academics where the means for handling 'wicked issues' has been developed through 'reflective practice'. In the education of teachers, whilst reflective practice has been a significant feature of professional education, the problems to which this has been applied are principally 'tame' ones. In this paper, the authors argue that there has been a lack of crossover between two parallel literatures. The literature on 'wicked issues' does not fully recognise the difficulties with reflective practice and that in education which extols reflective practice, is not aware of the 'wicked' nature of the problems which confront teachers and schools. The paper argues for a fresh understanding of the underlying nature of problems in education so that more appropriate approaches can be devised for their resolution. This is particularly important at a time when the government in England is planning to make teaching a masters level profession, briefly defined by the Quality Assurance Agency for Higher Education (QAA) benchmark statement as 'Decision-making in complex and unpredictable situations'. The paper begins by locating the argument and analysis of 'wicked problems' within the nature of social complexity and chaos. The second part of the paper explores implications for those involved in policy formation, implementation and service provision. Given the range of stakeholders in education, the paper argues for a trans-disciplinary approach recognising the multiple perspectives and methodologies leading to the acquisition of reticulist skills and knowledge necessary to boundary cross. © 2009 Taylor & Francis

The external action paradox of the Lisbon treaty: reconciling integration with delimitation

Ever since its creation the CFSP constituted a deliberately separate category of EU cooperation. The Lisbon Treaty largely undoes this and takes a significant leap towards integrating the CFSP and former Community elements in a streamlined external action system. It abolishes the pillar structure, accords a single legal personality to the Union and puts in place a common external action framework governed by a single set of principles and objectives. Yet, at the same time the CFSP remains overtly separate from the other external competences and is still governed by specific rules and procedures. This concurrent emphasis on integration and delimitation places the Union for a genuine paradox that may put the accountability of the Lisbon Treaty’s institutional novelties significantly to the test and force the EU judiciary as well as policy-makers to look for creative ways of adjudicating on and conducting external policy