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.

Obstacle recognizing device for vehicle

Abstract: PROBLEM TO BE SOLVED: To provide an obstacle-recognizing device which can recognize an obstacle other than a preceding vehicle by accurately distinguishing the obstacle by utilizing its ability of recognizing obstacles in the height direction by on the assumption that it is an obstacle recognizing device of such a type that three-dimensionally recognizes obstacles. SOLUTION: The obstacle recognizing device performs road-side object eliminating processing after the device judges a preceding vehicle based mainly on that the object exists in the same lane as that of its own vehicle. When the center height of an object is higher than 4.0 m ('yes' in S120) or nearly 0 m ('yes' in S130), the device recognizes that the object is not a preceding vehicle (S210). However, when its own vehicle runs on the ending part of an ascent, the device has a possibility of erroneously recognizing a signboard or a mark which is set up at a higher position and rightfully recognized as a road-side object by the device as a preceding vehicle, because such a case that the signboard or mark exists on the road in front of its own vehicle. Therefore, when an object exists at least once in an area, which is not accessible by an ordinary vehicle during a prescribed period of time from two seconds before to the present time, the device judges that the object is not a preceding vehicle (S140-S190).

Evidence for the use of reflected self-generated seismic waves for spatial orientation in a blind subterranean mammal

Abstract: Subterranean mammals like the blind mole-rat (Rodentia: Spalax ehrenbergi ) are functionally blind and possess poor auditory sensitivity, limited to low-frequency sounds. Nevertheless, the mole-rat demonstrates extremely efficient ability to orient spatially. A previous field study has revealed that the mole-rat can assess the location, size and density of an underground obstacle, and accordingly excavates the most efficient bypass tunnel to detour around the obstacles. In the present study we used a multidisciplinary approach to examine the possibility that the mole-rat estimates the location and physical properties of underground obstacles using reflected self-generated seismic waves (seismic `echolocation'). Our field observations revealed that all the monitored mole-rats produced low-frequency seismic waves (250-300 Hz) at intervals of 8±5 s (range: 1-13 s) between head drums while digging a bypass to detour an obstacle. Using a computerized simulation model we demonstrated that it is possible for the mole-rat to determine its distance from an obstacle boundary (open ditch or stone) by evaluating the amplitude (intensity) of the seismic wave reflected back to it from the obstacle interface. By evaluating the polarity of the reflected wave the mole-rat could distinguish between air space and solid obstacles. Further, the model showed that the diffracted waves from the obstacle's corners could give the mole-rat precise information on the obstacle size and its relative spatial position. In a behavioural experiment using a special T-maze setup, we tested whether the mole-rat can perceive seismic waves through the somatosensory system and localize the source. The results revealed that the mole-rat is able to detect low frequency seismic waves using only its paws, and in most cases the mole-rats determined accurately the direction of the vibratory source. In a histological examination of the glabrous skin of the mole-rat's paws we identified lamellate corpuscle mechanoreceptors that might be used to detect low frequency seismic waves. The combined findings from these different approaches lead us to suggest that a specialized seismic `echolocation' system could be used by subterranean mammals to determine the most energy-conserving strategy with which to bypass an obstacle, as well as to estimate their distance from the surface, keeping their tunnels at the optimal depth.

Time-minimal paths among moving obstacles

Abstract: Motion planning for a point robot is studied in a two-dimensional time-varying environment. The obstacle is a convex polygon that moves in a fixed direction at a constant speed. The point to be reached (referred to as the destination point) also moves along a known path. The concept of accessibility from a point to a moving object is introduced, and it is used to define a graph on a set of moving obstacles. The graph is shown to exhibit an important property, that is, if the moving point is able to move faster than any of the obstacles, a time-minimal path is given as a sequence of edges in the graph. An algorithm is described for generating a time-minimal path, and its execution time is analyzed. >

Switching Control of Mobile Robots for Autonomous Navigation in Unknown Environments

Abstract: This paper presents a switching controller for positioning a unicycle-like mobile robot at a desired point with final orientation avoiding obstacles in completely unknown environments. To this aim two complementary algorithms are included: the first decides whether to avoid an obstacle around its right or left side, and the second is intended to detect when an obstacle was successfully avoided. The obstacle avoidance is performed using a laser-based reactive contour-following controller. The switching controllers include the stability analysis at the switching times, using common and multiple Lyapunov functions. Finally, experimental results in a typical unicycle-like mobile robot show the performance of the proposed hybrid control system.

Locomotion among dynamic obstacles for the honda ASIMO

Abstract: We have equipped a Honda ASIMO humanoid with the ability to navigate autonomously in obstacle-filled environments. In addition to finding its way through known, fixed obstacle configurations, the planning system can reason about the future state of the world to locomote through challenging environments when the obstacle motions can be inferred from observation. This video presents work using a vision system to predict the velocities of objects in the scene, allowing ASIMO to safely navigate autonomously through a dynamic environment. Neither obstacle positions nor velocities are known at the start of the trial, but are estimated online as the robot walks. The planner constantly adjusts the footstep path with the latest estimates of ASIMO's position and the obstacle trajectories, allowing the robot to successfully circumnavigate the moving obstacles.