Obstacle

About: Obstacle is a research topic. Over the lifetime, 9517 publications have been published within this topic receiving 94760 citations. The topic is also known as: impediment & barrier.

The hydraulics of steady two-layer flow over a fixed obstacle

Abstract: This paper reports the results of a theoretical and experimental study of steady two-layer flow over a fixed two-dimensional obstacle. A classification scheme to predict the regime of flow given the maximum height of the obstacle, the total depth of flow, and the density and flow rate of each layer, is presented with experimental confirmation. There are differences between this classification scheme and that derived for flow over a towed obstacle by Baines (1984, 1987). These differences are due to the motion of upstream disturbances in towed obstacle flows. Approach-controlled flows, i.e. flows with an internal hydraulic control in the flow just upstream of the obstacle are studied in detail for the first time. This study reveals that non-hydrostatic forces, rather than a shock solution (called an internal hydraulic drop by previous investigators), need to be considered to explain the behaviour of Approach-controlled flows.

Stereovision approach for obstacle detection on non-planar roads

Abstract: This paper presents a high accuracy stereovision system for obstacle detection and vehicle environment perception in various driving scenarios. The system detects obstacles of all types, even at high distance, outputting them as a list of cuboids having a position in 3D coordinates, size, speed and orientation. For increasing the robustness of the obstacle detection the non-planar road model is considered. The stereovision approach was considered to solve the road-obstacle separation problem. The vertical profile of the road is obtained by fitting a first order clothoid curve on the stereo detected 3D road surface points. The obtained vertical profile is used for a better road-obstacle separation process. By consequence the grouping of the 3D points above the road in relevant objects is enhanced, and the accuracy of their positioning in the driving environment is increased.

Obstacle detection system for motor vehicles

Abstract: An obstacle detection system for a motor vehicle detects obstacles in front of the vehicle and searches for the dynamic relativity between the vehicle and each of the obstacles and on the basis of this an item of information is calculated relating to the level of risk between the vehicle and each obstacle in order to carry out an evaluation of risk. A frequency at which the calculation of the information relating to the level of risk is carried out is changed so as to increase or decrease according to the level of risk of the obstacles.

Autonomous Visual Navigation and Laser-Based Moving Obstacle Avoidance

Abstract: Moving obstacle avoidance is a fundamental re- quirement for any robot operating in real environments, where pedestrians, bicycles and cars are present. In this paper, we propose and validate a framework for avoiding moving obstacles during visual navigation with a wheeled mobile robot. Visual navigation consists of following a path, represented as an ordered set of key images, which have been acquired by an on-board camera in a teaching phase. While following such path, our robot is able to avoid static as well as moving obstacles, which were not present during teaching, and which are sensed by an on- board lidar. The proposed approach takes explicitly into account obstacle velocities, estimated using an appropriate Kalman-based observer. The velocities are then used to predict the obstacle positions within a tentacle-based approach. Finally, our approach is validated in a series of real outdoor experiments, showing that when the obstacle velocities are considered, the robot behaviour is safer, smoother, and faster than when it is not.

A reciprocity theorem for the electromagnetic field scattered by an obstacle

Abstract: When a time-harmonic plane electromagnetic wave is incident upon a scattering obstacle of finite dimensions, the far-zone scattered field satisfies a reciprocity relation. This reciprocity relation is derived with the aid of H. A. Lorentz’s theorem. The result is valid under rather general assumptions as far as the electromagnetic properties of the obstacle are concerned. As a special case, the result for a perfectly conducting obstacle is obtained.