Polar Histogram Research Articles

탑-뷰 변환과 빔-레이 모델을 이용한 영상기반 보행 안내 시스템

본 논문은 야외 환경에서 하나의 카메라를 이용한 시각 장애인을 위한 보행 안내 시스템을 제안한다. 기존의 스테레오 비전을 이용한 보행 지원 시스템과는 다르게 제안된 시스템은 사용자의 허리에 고정된 하나의 카메라를 이용하여 꼭 필요한 정보만을 얻는 것을 목표로 하는 시스템이다. 제안하는 시스템은 먼저 탑-뷰 영상을 생성하고, 생성된 탑-뷰 영상 내 지역적인 코너 극점을 검출한다. 검출된 극점에서 방사형의 히스토그램을 분석하여 장애물을 검출한다. 그리고 사용자 움직임은 사용자에 가까운 지역 안에서 옵티컬 플로우를 사용하여 추정한다. 이렇게 영상으로부터 추출된 정보들을 기반으로 음성 메시지 생성 모듈은 보행 지시 정보를 합성된 음성을 통해 시각 장애인에게 전달한다. 다양한실험 영상들을 사용하여 제안한 보행 안내 시스템이 일반 인도에서 유용한 안내 지시를 제공하는 것이 가능함을 보인다. This paper presents a walking guidance system for blind pedestrians in an outdoor environment using just one single camera. Unlike many existing travel-aid systems that rely on stereo-vision, the proposed system aims to get necessary information of the road environment by using just single camera fixed at the belly of the user. To achieve this goal, a top-view image of the road is used, on which obstacles are detected by first extracting local extreme points and then verified by the polar edge histogram. Meanwhile, user motion is estimated by using optical flow in an area close to the user. Based on these information extracted from image domain, an audio message generation scheme is proposed to deliver guidance instructions via synthetic voice to the blind user. Experiments with several sidewalk video-clips show that the proposed walking guidance system is able to provide useful guidance instructions under certain sidewalk environments.

Algorithm for Threat Area Avoidance in Military Unmanned Ground Vehicles

In addition to the conventional obstacle avoidance capabilities, the Unmanned Ground Vehicles (UGVs) used in military environments should be capable of avoiding certain areas which could inflict damage to the UGVs or result in the failure of the mission. The threat area could be minefields or an area vulnerable to enemy fire or detection. In this paper we have proposed and implemented an algorithm for ‘Threat Area Avoidance (TAA)’. Our algorithm was incorporated in two of the obstacle avoidance methods, Vector Polar Histogram (VPH) and the Enhanced VPH. The performance of our algorithm was evaluated in terms of distance overhead, navigation time, computational time and UGV Orientation Angle Variation Index. Through simulations, we observed that the proposed algorithm avoids a potential threat area (even though it is free of any obstacles) and takes a safe path while navigating between the start and goal points, with minimum overhead in computation.

Visually-extended vector polar histogram applied to robot route navigation

This paper presents a visual extension of the vector polar histogram (VVPH) for safe and fast real-time obstacle avoidance and navigation in route environments. VVPH is based on an enhanced vector polar histogram method (VPH+). VPH+ is a powerfully performing method in obstacle avoidance and navigation. It depends on highly accurate sensors, such as a laser range finder. The accuracy of visual data for route environments is enhanced using the hidden Markov model (HMM) and extended Kalman filter (EKF). HMM yields faster estimation results in route environments, preventing the smoothing effect of the EKF causing unexpected errors in a situation where features disappear suddenly. The performance of the proposed method, VVPH, is verified via computer simulations and experimental setups, in terms of the total travelling time and the accuracy of the visual histogram.

단일 카메라를 이용한 VFH기반의 실시간 주행 기술 개발

본 논문에서는 단일 카메라로부터 주어진 영상을 실시간으로 장애물과 비장애물 영역으로 분류 한 후 VFH를 이용하여 안전한 경로를 선정하는 실시간 주행 시스템을 개발한다. 제안된 시스템은 배경 분류기, 점유 그리드맵 생성기와 VFH기반의 선정기로 구성된다. 배경 분류기는 입력된 <TEX>$320{\times}240$</TEX> 영상의 색조와 명도 정보를 이용하여 실시간으로 배경파 장애물 영역을 분류한다. 점유 그리드맵 생성기는 이를 바탕으로 위험도에 따라 10개의 그레이 레벨을 가지는 <TEX>$32{\times}24$</TEX>의 점유 그리드맵을 생성한다. VFH를 이용하여 폴라 히스토그램을 작성한 후 밀도가 낮은 곳으로 주행 경로를 결정 한다. 제안된 기술의 효율성을 증명하기 위하여 다양한 형태의 장애물을 포함하는 실내 및 실외 환경에서 평가하였으며 센서 기반의 그 결과는 기존의 센서기반의 주행시스템과 비교 되었다. 그 결과 제안된 시스템은 88%의 정확도를 보였으며, 기존의 시스템보다 실시간으로 빠르고 안전한 주행을 수행할 수 있음이 증명되었다. In this paper, a real-time monocular vision based navigation system is developed for the disabled people, where online background learning and vector field histogram are used for identifying obstacles and recognizing avoidable paths. The proposed system is performed by three steps: obstacle classification, occupancy grid map generation and VFH-based path recommendation. Firstly, the obstacles are discriminated from images by subtracting with background model which is learned in real time. Thereafter, based on the classification results, an occupancy map sized at <TEX>$32{\times}24$</TEX> is produced, each cell of which represents its own risk by 10 gray levels. Finally, the polar histogram is drawn from the occupancy map, then the sectors corresponding to the valley are chosen as safe paths. To assess the effectiveness of the proposed system, it was tested with a variety of obstacles at indoors and outdoors, then it showed the a'ccuracy of 88%. Moreover, it showed the superior performance when comparing with sensor based navigation systems, which proved the feasibility of the proposed system in using assistive devices of disabled people.

Development of a navigation system for heterogeneous mobile robots

Navigation systems often play an important role in mobile robot control. Many existing mobile robot navigation systems have been implemented and tested for particular types of robots. However, in some implementations, such as heterogeneous multi-robot systems, a generic navigation system can offer potential advantages. In such applications, a generic navigation system should be able account for robots with varying size, shape, drive type and sensor quantities. Additionally, it should be capable of offering a high degree of flexibility for navigation in known and unknown environments. Hence, a single generic navigation system that combines the benefits of reactive and deliberative control has been developed for heterogeneous mobile robots. The design of the hierarchical hybrid navigation system is based on the A* algorithm, a polar histogram and a modified dynamic window approach. Simulation experiments with three heterogeneous robots in a range of environments have been conducted. Performance of reactive navigation and hybrid reactive-deliberative navigation in known and unknown environments is evaluated. Favourable results are achieved with the developed reactive system. Hybrid reactive-deliberative navigation offers improved performance over reactive navigation in known environments. Deliberative control does not affect performance significantly in unknown environments. Initial hardware experiments demonstrate that the navigation system can work on real robots.

Construction of Fisheye Lens Inverse Perspective Mapping Model and Its Applications of Obstacle Detection

In this paper, we develop a vision based obstacle detection system by utilizing our proposed fisheye lens inverse perspective mapping (FLIPM) method. The new mapping equations are derived to transform the images captured by the fisheye lens camera into the undistorted remapped ones under practical circumstances. In the obstacle detection, we make use of the features of vertical edges on objects from remapped images to indicate the relative positions of obstacles. The static information of remapped images in the current frame is referred to determining the features of source images in the searching stage from either the profile or temporal IPM difference image. The profile image can be acquired by several processes such as sharpening, edge detection, morphological operation, and modified thinning algorithms on the remapped image. The temporal IPM difference image can be obtained by a spatial shift on the remapped image in the previous frame. Moreover, the polar histogram and its post-processing procedures will be used to indicate the position and length of feature vectors and to remove noises as well. Our obstacle detection can give drivers the warning signals within a limited distance from nearby vehicles while the detected obstacles are even with the quasi-vertical edges.

StereoBox: A Robust and Efficient Solution for Automotive Short-Range Obstacle Detection

This paper presents a robust method for close-range obstacle detection with arbitrarily aligned stereo cameras. System calibration is performed by means of a dense grid to remove perspective and lens distortion after a direct mapping between image pixels and world points. Obstacle detection is based on the differences between left and right images after transformation phase and with a polar histogram, it is possible to detect vertical structures and to reject noise and small objects. Found objects' world coordinates are transmitted via CAN bus; the driver can also be warned through an audio interface. The proposed algorithm can be useful in different automotive applications, requiring real-time segmentation without any assumption on background. Experimental results proved the system to be robust in several envitonmental conditions. In particular, the system has been tested to investigate presence of obstacles in blind spot areas around heavy goods vehicles (HGVs) and has been mounted on three different prototypes at different heights.

Peripheral Polar-Graphic Displays for Signal/Failure Detection

The object of this series of studies was to examine the utility of multivariate polar-graphic iconic displays, placed in the parafoveal or near-peripheral regions of the visual field, for the presentation of multiple indices of subsystem performance in an aircraft system context. Results of the first study suggest that (a) such a display, circumscribed about a primary flight instrument, could be used readily to detect performance deviations that exceeded defined normal bounds; and (b) polygons arc more effective than polar histograms. The second study was used to examine the hypothesis that the superior performance obtained with polar formats was not merely a function of reductions in visual scanning requirements but stemmed from the organization and symmetry found in the iconic display. In addition, index markings lacking in the first study were added to the polar histogram to determine if these would materially affect speed and accuracy of judgments. Performance using polar histograms in the second st...

A Comparison of Shape/Object Displays, Quasi Shape Displays, and Conventional Univariate Indicators: Integration Benefits or the “Nearer to Thee” Effect?

The performance of a complex task, such as piloting an aircraft, requires an operator to effectively process and integrate information from numerous sources. Recent efforts (Beringer, 1985; 1986) have examined the combining of integrated displays to provide both continuous-system-control information and secondary system status/rate information. The present effort reported herein is an attempt to determine the origin of benefits that accrue from shape/object displays; specifically whether they stem from cognitively based integration of information or merely physical proximity of the information. This study examined several formats of information display using conventional (univariate needle indicators) and nonconventional (polar histograms and polar polygons) formats for presenting multiple univariate indices. Some flight control parameters and out-of-tolerance detection rates were affected by the format of the peripheral display while these performance measures plus processing rate of a digit-cancelling side task were affected by flight difficulty (two axes versus three axes; effect in the expected direction). Performance with the polar histogram display was superior in all cases followed closely by performance with the polar polygons, the multiple nonpolar univariate indicators (needles) being least effective for the differentiation task. This suggests that the shape/object displays do allow integration of information beyond that found with simple physical proximity of univariate indicators. A continuation of this research is addressing the problem of system diagnostics using these formats.

Letter: A digital computer method for revealing directional information in images.

At each point in the image, the direction of the line of greatest rate of change in intensity is calculated and quantized to the required accuracy. For each quantized angle a tally is kept of the total number of occurrences of that angle over the whole image. The results are presented as a polar histogram.

Paleocurrent Analysis of Trough Cross Stratification

ABSTRACT Additional documentation of the economy and superiority as a paleocurrent indicator of trough-axis orientation data in contrast to cross-set orientations is provided from studies of Cambrian sandstones around Baraboo, Wisconsin. Separate concentric polar histogram portrayals of both types of data allowed direct comparison of cross-set and trough-axis distributions, and several interpretable patterns emerged. In many cases bimodal cross-set distributions are bisected by axis azimuths; these reflect symmetrical filling of troughs. In other cases, a single dominant cross-set mode is perpendicular to the axes, indicating asymmetrical filling of troughs, which is commonly observable in cross-section views. In both of these cases, an error of 90° in paleocurrent interpretation is possib e if the trough-origin of such sets goes unrecognized. Sets with a single mode parallel to the axes reflect readings of cross-set dips mainly from the heads of the troughs. Most puzzling are bimodal trough-axis distributions, which are common in Wisconsin. Reflecting the great complexity of sand-wave bedforms, they represent the fillings of canoe-shaped depressions whose counterparts can be seen in modern sediments. Even the bimodal trough-axis data tends to yield better orientation results than do associated cross sets.

Longitude Effects in Jovian Decametric Radio Emission.

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Longitude Effects in Jovian Decametric Radio Emission. Smith, Harlan J. Abstract The essential impossibility of directly resolving Jupiter's surface by any radio technique, other than microwave interferometry, forces decameter radio astronomers to use inferential approaches in localizing radio phenomena. The principal technique has been to determine a precise radio rotation period from the data, then to use this period to establish the frequency or probability of detection of decameter noise storms as a function of Jupiter's longitude of central meridian (LCM). Three principal LCM regions associated with (not necessarily the source of) emission have been suspected for some time. Douglas (Astron. J. 65, 487, 1960) has specified these as Regions 1 and 3 (A111= 1100 and 2800, respectively) and the principal Region 2 (2120). If emission frequency as a function of longitude is plotted as a polar histogram centered on Jupiter, the longitude-associated character of the decameter radiation stands out clearly as a lobe pattern the appearance of which supports the view that these regions correspond to integrated cones of emission. This paper summarizes evidence, from our own and other observers' data and conclusions, that: (a) for each cone, the emission cone angle is nearly independent of the intensity of the storm, (b) the basically trilobed character is strongly marked over the entire span of existing observations, (c) at a given frequency the three principal cones tend to be stable in position and angular width with time, (d) subsidiary cones may occasionally be observed, (e) certain phenomena are characteristic of phase with respect to the principal lobe, in particular the sense of frequency drift, and the polarization reversals and magnetic field inclination both of which are approximately aligned with the major lobe. These phenomena are generally consistent with models such as Warwick's in which the decameter radiation is produced at the local gyrofrequency in an obliquely rotating magnetic field. This work has been supported by the National Science Foundation and the National Aeronautics and Space Agency. Publication: The Astronomical Journal Pub Date: 1962 DOI: 10.1086/108662 Bibcode: 1962AJ.....67S.586S full text sources ADS |