Reference Point Information Research Articles

Formation Control and Obstacle Avoidance Algorithm of a Multi-USV System Based on Virtual Structure and Artificial Potential Field

This paper proposes a formation generation algorithm and formation obstacle avoidance strategy for multiple unmanned surface vehicles (USVs). The proposed formation generation algorithm implements an approach combining a virtual structure and artificial potential field (VSAPF), which provides a high accuracy of formation shape keeping and flexibility of formation shape change. To solve the obstacle avoidance problem of the multi-USV system, an improved dynamic window approach is applied to the formation reference point, which considers the movement ability of the USV. By applying this method, the USV formation can avoid obstacles while maintaining its shape. The combination of the virtual structure and artificial potential field has the advantage of less calculations, so that it can ensure the real-time performance of the algorithm and convenience for deployment on an actual USV. Various simulation results for a group of USVs are provided to demonstrate the effectiveness of the proposed algorithms.

Meaning and framing: the semantic implications of psychological framing effects

ABSTRACT I use the psychological phenomenon of ‘attribute framing’ as a case study for exploring philosophical conceptions of semantics and the semantics-pragmatics divide. Attribute frames are pairs of sentences that use contradictory expressions to predicate the same property of an individual or object. Despite their equivalence, pairs of attribute frames have been observed to induce systematic variability in hearers’ responses. One explanation of such framing effects appeals to the distinct ‘reference point information’ conveyed by alternative frames. Although this information is taken to be pragmatic, a live debate in the philosophy of language concerns the extent to which pragmatic information can really be held apart from semantics. Therefore, in this article I examine whether – and how – reference point information might be thought to intrude on the semantics of an attribute frame. I describe two ways in which the information might be considered broadly semantic, due to its being directly communicated or conventional. However, I argue that the framing data in fact support a narrower conception of semantics, and a semantics-pragmatics distinction that separates standing sentence meaning from enriched communicated meaning.

A Multi-UAV Formation Maintaining Method Based on Formation Reference Point

In recent years, Unmanned Aerial Vehicles (UAV), have been increasingly utilized by scholars. Efficient control of UAV swarms opens a set of new challenges. There are several formation control methods, however, artificial potential field (APF) method has imperfections in formation maintaining and virtual structure is insufficient in collision avoidance. In this paper, we proposed a multi-UAV formation maintaining method combined artificial potential field method and virtual structure approach. The method uses the concepts of attraction and repulsion in the artificial potential field method, combined with formation reference points inspired by the virtual structure points in the virtual structure approach to control the formation. On the other hand, we express the leaders, the followers, and the formation reference points uniformly. When the formation of UAVs is determined, after the leader arrives at target point and hovers, the followers can track the formation reference points. The method can avoid collision between UAVs and achieve the purpose of formation maintaining. Finally, a UAV swarm consists of four UAVs is used for demonstration and verification, and the results of experiment prove the validity of the algorithm.

2004 Post Tsunami Resilience and Recolonization of Mangroves in South Andaman, India

Mangrove resilience and the scope for new venues of mangrove colonization in the Southern part of south Andaman were studied using satellite interpretation and ground truthing due to after the devastating 26th December 2004 tsunami. 1069.82 ha of Tsunami created wetlands were found in thirty five different villages. Fimbrisstylis littoralis, Acanthus ilicifolius, Acrostichum aureum, Rhizophora spp. and Avicennia spp. were observed in abundance in all the villages. However, Nypa fruticans and Pandanus tectorius were found in four villages alone. Eight venues were found as newly colonized mangrove. Rhizophora mucronata was existing in all the eight new venues whereas Rhizophora apiculata and Avicennia spp. was absent in 3 venues. The present study will act as reference point information for future investigation. The results of the present study provides a huge insight and hope in restorative models for degraded mangrove systems.

The Role of Inference in Attribute Framing Effects

AbstractPrevious research has shown that a speaker's choice between logically equivalent frames is influenced by reference point information, and that listeners draw accurate inferences based on the frame. Less clear, however, is whether these inferences play a causal role in generating attribute framing effects. Two experiments are reported, which suggest that frame‐dependent inferences are sufficient to generate attribute framing effects, and that blocking such inferences may block framing effects. Experiment 1 decomposed the typical framing design into two parts: One group of participants saw a target described in one of two attribute frames and reported their estimates (inferences) of the typical attribute value. These estimates were then given to a second group of yoked participants, who evaluated the target. Although this latter group was not exposed to different attribute frames, they nevertheless exhibited a “framing effect” as a result of receiving systematically different inferences. In contrast, Experiment 2 shows that experts—who are familiar with an attribute's distribution and are therefore less likely to draw strong frame‐based inferences—exhibit a diminished framing effect. Together, these findings underscore the role of inferences in the generation and attenuation of attribute framing effects. Copyright © 2017 John Wiley & Sons, Ltd.

Bioinspired Coordinated Path Following for Vessels with Speed Saturation Based on Virtual Leader.

This paper investigates the coordinated path following of multiple marine vessels with speed saturation. Based on virtual leader strategy, the authors show how the neural dynamic model and passivity-based techniques are brought together to yield a distributed control strategy. The desired path following is achieved by means of a virtual dynamic leader, whose controller is designed based on the biological neural shunting model. Utilizing the characteristic of bounded and smooth output of neural dynamic model, the tracking error jump is avoided and speed saturation problem is solved in straight path. Meanwhile, the coordinated path following of multiple vessels with a desired spatial formation is achieved through defining the formation reference point. The consensus of formation reference point is realized by using the synchronization controller based on passivity. Finally, simulation results validate the effectiveness of the proposed coordinated algorithm.

Research on the Cooperative Control of a Group of Autonomous Underactuated Vessels

This paper considers the cooperative control of a group of autonomous underactuated vessels (AUV). The control objective for each vessel is to maintain its position in the formation while Formation Reference Point (FRP) tracks a predefined spatial path. In order to achieve this goal, we use vectorial backstepping to solve two subproblems: one is geometric task, anther is dynamic task. The former guarantees that the FRP tracks the spatial path, while the later ensures accurate speed control along the path. A dynamic guidance system with feedback from the state of all AUV ensures that they have the same priority (no leader) when moving along the path. The controller is proposed basically based on Lyapunov direct method and backstepping technique. Simulation results are presented and discussed.

The Common Warthog and Its Parasites in the Free State Province (South Africa) Cannot be used to Test the ‘Enemy Release’ Hypothesis for an Introduced Species: The Value of Reference Point Information for Testing Hypotheses of Change

Given the conservation concerns raised by invasive species, testing hypotheses dealing with invasion biology are crucial to understanding the mechanisms and drivers of invasiveness. Central to this though is a clear zoogeographical foundation regarding areas where a species is indigenous, and upon which an experimental design can be based. Recently Matthee et al. (2013) sampled ectoparasites of the common warthog, Phacochoerus africanus, in the Free State Province (South Africa), with the express intention of testing the hypothesis that 'non-indigenous species leave their natural parasites behind in their natural range, and would thus have lower parasite species richness in introduced [sic] areas' (Matthee et al. 2013: 260). Their experimental design rests on the assumption that the common warthog is an introduced species in the Free State. They base this assumption on two publications (D'Huart & Grubb 2001; Skead 2007), neither of which focus on warthogs in the Free State, and both of which have been superseded by a more recent and relevant study (Boshoff & Kerley 2013), which just postdates Matthee et al. (2013). This more recent work, however, has implications for the validity of the Matthee et al. (2013) study and these are addressed below.

Inferring product healthfulness from nutrition labelling. The influence of reference points

Despite considerable research on nutrition labelling, it has proven difficult to find a front-of-pack label which is informative about product healthfulness across various situations. This study examines the ability of different types of nutrition labelling schemes (multiple traffic light label, nutrition table, GDA, logo) to communicate product healthfulness (a) across different product categories, (b) between options from the same product category, and (c) when viewed in isolation and in comparison with another product. Results of two experiments in Germany and The Netherlands show that a labelling scheme with reference point information at the nutrient level (e.g., the traffic light label) can achieve all three objectives. Although other types of labelling schemes are also capable of communicating healthfulness, labelling schemes lacking reference point information (e.g., nutrition tables) are less effective when no comparison product is available, and labelling schemes based on overall product healthfulness within the category (e.g., logos) can diminish consumers’ ability to differentiate between categories, leading to a potential misinterpretation of product healthfulness. None of the labels affected food preferences.

Aksjologia kształcenia w perspektywie pedagogiki dialogu

Standardisation is the feature of modern school education. Its result is a replacement of goals described in value categories with the goals expressed in the form of competences. This understanding may lead the pedagogy to the so called axiological heteronomy. The present article calls for the need of connection between the schools educational activity and pedagogical axiology. The sources of pedagogical axiology should not be rooted in the external codes of values or norms, but in the experience of educational reality. The meaning of the pedagogy of dialogue is presented from this perspective. The analysis of dialogical structure of human being describes the experience of presence of the other human not only in phenomenological, but also in hermeneutical categories – exposure of the meaning of ethical foundation of human being belongs to its essence. The dialogical ‘hermeneutics of presence’ can be understood as the existential reference point for formation of individual moral sensibility, ethical convictions and for pedagogical axiology.

Scalable Sensing, Estimation, and ControlArchitecture for Large Spacecraft Formations

A decentralized estimation architecture for large formations of spacecraft is introduced that, when coupled with a local controller, parameterizes the degree to which a node is a leader or a follower, eliminating the rigid classification of nodes as strictly leaders and followers. Measurements are provided by a single range/bearing sensor similar to the autonomous formation flying sensor. A reference point calculation is introduced that automatically compensates for noise in the estimation and sensing subsystems. A scheduling algorithm is developed that maximizes the information collected across the formation. The scheduling problem is posed as an infinite horizon optimization of either the formation information or covariance matrices, or the reference point information or covariance matrices. The resulting architecture is compared via simulation to a system in which each spacecraft has full knowledge of the fleet. Results show that performance degradation (root mean square position error and fuel usage) is very small compared to the ideal, full knowledge solution, and that the system performs better than the traditional leader-follower architecture.

A novel watermarking algorithm for resistant geometric attacks using feature points matching

PurposeAims to report a novel method of estimating the geometric manipulation to which present day data hiding is subjected.Design/methodology/approachComputes the feature points matching measure for the geometric manipulation using shape‐specific points. The feature points matching is realized by simulated annealing algorithm.FindingsFinds that the purposed scheme does not require the original image because reference point information on the original image has been contained in the secret key.Originality/valueExperiments herein have proved the method's robustness in face of geometric attacks and a new way of designing a better blind secret message decodes has been revealed.

Complexity of convex optimization using geometry-based measures and a reference point

Our concern lies in solving the following convex optimization problem: where P is a closed convex subset of the n-dimensional vector space X. We bound the complexity of computing an almost-optimal solution of GP in terms of natural geometry-based measures of the feasible region and the level-set of almost-optimal solutions, relative to a given reference point xr that might be close to the feasible region and / or the almost-optimal level set. This contrasts with other complexity bounds for convex optimization that rely on data-based condition numbers or algebraic measures, and that do not take into account any a priori reference point information.

Complexity of Convex Optimization Using Geometry-Based Measures and a Reference Point

Our concern lies in solving the following convex optimization problem: minimize cx subject to Ax=b, x \in P, where P is a closed convex set. We bound the complexity of computing an almost-optimal solution of this problem in terms of natural geometry-based measures of the feasible region and the level-set of almost-optimal solutions, relative to a given reference point x^r that might be close to the feasible region and/or the almost-optimal level set. This contrasts with other complexity bounds for convex optimization that rely on data-based condition numbers or algebraic measures, and that do not take into account any a priori reference point information.