Showing papers on "Obstacle published in 2011"

Chance-Constrained Optimal Path Planning With Obstacles

Abstract: Autonomous vehicles need to plan trajectories to a specified goal that avoid obstacles. For robust execution, we must take into account uncertainty, which arises due to uncertain localization, modeling errors, and disturbances. Prior work handled the case of set-bounded uncertainty. We present here a chance-constrained approach, which uses instead a probabilistic representation of uncertainty. The new approach plans the future probabilistic distribution of the vehicle state so that the probability of failure is below a specified threshold. Failure occurs when the vehicle collides with an obstacle or leaves an operator-specified region. The key idea behind the approach is to use bounds on the probability of collision to show that, for linear-Gaussian systems, we can approximate the nonconvex chance-constrained optimization problem as a disjunctive convex program. This can be solved to global optimality using branch-and-bound techniques. In order to improve computation time, we introduce a customized solution method that returns almost-optimal solutions along with a hard bound on the level of suboptimality. We present an empirical validation with an aircraft obstacle avoidance example.

Room evacuation in the presence of an obstacle

Abstract: The investigation of human behaviour while trying to escape from a room under panic is an important issue in complex systems research. Several authors have called attention to the fact that placing an obstacle near the exit improves the evacuation time of the room (Helbing et al. (2000, 2005) [2] , [8] , Hughes (2003) [6] , Johansson and Helbing (2005) [16] , Piccoli and Tosin (2009) [5] ). We studied this effect in the context of the “social force model” (Helbing et al. (2000) [2] ). We show that placing an obstacle does not guarantee, by itself, better chances of survival for all pedestrians. The way they choose to avoid the obstacle is critical for their own performance. We found not only that the faster they try to escape, the slower they get out (“faster is slower” effect), but also, the short cut they might take in order to get to the exit will probably do no better (“clever is not always better” effect).

Probabilistic Collision Checking With Chance Constraints

Abstract: Obstacle avoidance, and by extension collision checking, is a basic requirement for robot autonomy. Most classical approaches to collision-checking ignore the uncertainties associated with the robot and obstacle's geometry and position. It is natural to use a probabilistic description of the uncertainties. However, constraint satisfaction cannot be guaranteed, in this case, and collision constraints must instead be converted to chance constraints. Standard results for linear probabilistic constraint evaluation have been applied to probabilistic collision evaluation; however, this approach ignores the uncertainty associated with the sensed obstacle. An alternative formulation of probabilistic collision checking that accounts for robot and obstacle uncertainty is presented which allows for dependent object distributions (e.g., interactive robot-obstacle models). In order to efficiently enforce the resulting collision chance constraints, an approximation is proposed and the validity of this approximation is evaluated. The results presented here have been applied to robot-motion planning in dynamic, uncertain environments.

Autonomous obstacle avoidance and maneuvering on a vision-guided MAV using on-board processing

Abstract: We present a novel stereo-based obstacle avoidance system on a vision-guided micro air vehicle (MAV) that is capable of fully autonomous maneuvers in unknown and dynamic environments. All algorithms run exclusively on the vehicle's on-board computer, and at high frequencies that allow the MAV to react quickly to obstacles appearing in its flight trajectory. Our MAV platform is a quadrotor aircraft equipped with an inertial measurement unit and two stereo rigs. An obstacle mapping algorithm processes stereo images, producing a 3D map representation of the environment; at the same time, a dynamic anytime path planner plans a collision-free path to a goal point.

A vision-based obstacle detection system for Unmanned Surface Vehicle

Abstract: This paper describes a vision-based obstacle detection system for Unmanned Surface Vehicle (USV) towards the aim of real-time and high performance obstacle detection on the sea surface. By using both the monocular and stereo vision methods, the system offers the capacity of detecting and locating multiple obstacles in the range from 30 to 100 meters for high speed USV which runs at speeds up to 12 knots. Field tests in the real scenes have been taken and the obstacle detection system for USV is proven to provide stable and satisfactory performance.

Autonomous mobile body

Abstract: Provided is an autonomous mobile body capable of moving in an autonomously set waiting-position direction without presetting a stop zone so that a movable obstacle can safely pass through. The autonomous mobile body (1) comprises: a storage unit (22) for storing the size (D2) of the autonomous mobile body (1); a laser range finder (12) for obtaining obstacle information; an obstacle specifying unit (233) for, on the basis of the obtained obstacle information, specifying edge points (86) indicating the positions of both ends of a region where an interference obstacle (66) is present, which are in a direction substantially orthogonal to the movement target direction (72) of the autonomous mobile body (1) in a plane parallel to a passage plane; a direction setting unit (237) for, on the basis of the size (D2) of the autonomous mobile body (1) and the edge points (86), setting the waiting-position direction; and a movement control unit (25) for performing control so that the autonomous mobile body (1) heads in the waiting-position direction.

Autonomous movement system

Abstract: A route decision system is provided to avoid an obstacle existing in a traceably moving direction for tracing a reference route from a current location of an autonomous movable body. The system computes traffic distance and a traffic width as a traffic region having a given traffic width and does not allow an obstacle to intrude in each of a plurality of moving The moving direction of the autonomous movable body is decided on the basis of the traceably moving direction and the traffic region. A speed decision device decides a moving speed allowing the autonomous movable body to stop before it collides with the obstacle in response to the braking condition of the autonomous movable body and the location and the speed of the obstacle.

Beyond visual range obstacle avoidance and infrastructure inspection by an autonomous helicopter

Abstract: This paper demonstrates the feasibility of accomplishing real-world inspection tasks beyond visual range with an autonomous helicopter using simple but effective methods. We propose a LIDAR-based perception and guidance system that enables a helicopter to perform obstacle detection and avoidance, terrain following, and close-range inspection. The system has been implemented on board the CSIRO unmanned helicopter and flight tested in a number of different mission scenarios in unknown environments. We have successfully completed 37 missions and recorded more than 14 hours of autonomous flight time. Missions beyond visual range were executed without a backup pilot. The system has achieved a high success rate and has proven to be dependable.

Lidar based off-road negative obstacle detection and analysis

Abstract: In order for an autonomous unmanned ground vehicle (UGV) to drive in off-road terrain at high speeds, it must analyze and understand its surrounding terrain in realtime: it must know where it intends to go, where are the hazards, and many details of the topography of the terrain. Much research has been done in the way of obstacle avoidance, terrain classification, and path planning, but still so few UGV systems can accurately traverse off-road environments at high speeds autonomously. One of the most dangerous hazards found off-road are negative obstacles, mainly because they are so difficult to detect. We present algorithms that analyze the terrain using a point cloud produced by a 3D laser range finder, then attempt to classify the negative obstacles using both a geometry-based method we call the Negative Obstacle DetectoR (NODR) as well as a support vector machine (SVM) algorithm. The terrain is analyzed with respect to a large UGV with the sensor mounted up high as well as a small UGV with the sensor mounted low to the ground.

Stepping back to see the big picture: when obstacles elicit global processing

Abstract: Can obstacles prompt people to look at the "big picture" and open up their minds? Do the cognitive effects of obstacles extend beyond the tasks with which they interfere? These questions were addressed in 6 studies involving both physical and nonphysical obstacles and different measures of global versus local processing styles. Perceptual scope increased after participants solved anagrams in the presence, rather than the absence, of an auditory obstacle (random words played in the background; Study 1), particularly among individuals low in volatility (i.e., those who are inclined to stay engaged and finish what they do; Study 4). It also increased immediately after participants encountered a physical obstacle while navigating a maze (Study 3A) and when compared with doing nothing (Study 3B). Conceptual scope increased after participants solved anagrams while hearing random numbers framed as an "obstacle to overcome" rather than a "distraction to ignore" (Study 2) and after participants navigated a maze with a physical obstacle, compared with a maze without a physical obstacle, but only when trait (Study 5) or state (Study 6) volatility was low. Results suggest that obstacles trigger an "if obstacle, then start global processing" response, primarily when people are inclined to stay engaged and finish ongoing activities. Implications for dealing with life's obstacles and related research are discussed.

Stereo vision-based vehicle detection using a road feature and disparity histogram

Abstract: This paper presents stereo vision-based vehicle detection approach on the road using a road feature and disparity histogram. It is not easy to detect only vehicles robustly on the road in various traffic situations, for example, a nonflat road or a multiple-obstacle situation. This paper focuses on the improvement of vehicle detection performance in various real traffic situations. The approach consists of three steps, namely obstacle localization, obstacle segmentation, and vehicle verification. First, we extract a road feature from v-disparity maps binarized using the most frequent values in each row and column, and adopt the extracted road feature as an obstacle criterion in column detection. However, many obstacles still coexist in each localized obstacle area. Thus, we divide the localized obstacle area into multiple obstacles using a disparity histogram and remerge the divided obstacles using four criteria parameters, namely the obstacle size, distance, and angle between the divided obstacles, and the difference of disparity values. Finally, we verify the vehicles using a depth map and gray image to improve the performance. We verify the performance of our proposed method by conducting experiments in various real traffic situations. The average recall rate of vehicle detection is 95.5%.

Coverage robot navigating

Abstract: A method of navigating an autonomous coverage robot on a floor includes controlling movement of the robot across the floor in a cleaning mode, receiving a sensor signal indicative of an obstacle, rotating the robot away from the sensed obstacle, determining a change in the received sensor signal during at least a portion of the rotation of the robot away from the sensed obstacle, and identifying the sensed obstacle based at least in part on the determined change in the received sensor signal.

Smart stick for Blind: Obstacle Detection, Artificial vision and Real-time assistance via GPS

Abstract: 31 ABSTRACT The paper presents a theoretical model and a system concept to provide a smart electronic aid for blind people. The system is intended to provide overall measures – Artificial vision and object detection ,real-time assistance via global positioning system(GPS).The system consist of proximity sensors, ultrasonic sensors , gps module, stereo cameras and dual feedback systemauditory as well as vibratory circuit. The aim of the overall system is to provide a low cost and efficient navigation aid for blind which gives a sense of artificial vision by providing information about the environmental scenario of static and dynamic objects around them.

Stereo obstacle detection in challenging environments: The VIAC experience

Abstract: Obstacle detection by means of stereo-vision is a fundamental task in computer vision, which has spurred a lot of research over the years, especially in the field of vehicular robotics. The information provided by this class of algorithms is used both in driving assistance systems and in autonomous vehicles, so the quality of the results and the processing times become critical, as detection failures or delays can have serious consequences. The obstacle detection system presented in this paper has been extensively tested during VIAC, the VisLab Intercontinental Autonomous Challenge [1], [2], which has offered a unique chance to face a number of different scenarios along the roads of two continents, in a variety of conditions; data collected during the expedition has also become a reference benchmark for further algorithm improvements.

Methods and systems for avoiding a collision between an aircraft on a ground surface and an obstacle

Abstract: The disclosed embodiments relate to methods and systems for avoiding a collision between an obstacle and a vehicle, such as an aircraft, on a ground surface. A processor receives a detection signal from one of a plurality of proximity sensors. The detection signal indicates that the obstacle has been detected. In response to receiving the detection signal, a video image signal is transmitted from the processor to a display in the cockpit of the aircraft. The video image signal corresponds to a particular video imager that is associated with the particular proximity sensor that detected the obstacle. A video image, of a particular region around the aircraft that includes the obstacle is displayed on a display. In response to receiving the detection signal, the processor can also transmit an alert signal, and a brake activation signal to activate a braking system to prevent the aircraft from colliding with the obstacle.

Mobile robots cooperative control and obstacle avoidance using potential field

Abstract: Formation control of mobile robots based on the virtual and behavioral structures is proposed in this paper. To achieve this goal, each robot is modeled by an electric charge, and a trajectory is defined to move the robots toward a circle. Because of the repulsive force between the identical charges, each robot finds its desired position in the formation, and the regular polygon formation of the robots will be realized. For swarm formation, a moving virtual robot is located at the center of the circle, and the formation keeping is guaranteed. An approach for obstacle avoidance of mobile robots based on the behavioral structure is proposed as well. When a robot approaches an obstacle, a force obtained based on a rotational potential field makes it avoid collision and also locating in local minima positions. The illustrative examples and numerical simulations confirm the feasibility of the proposed approaches.

Analytical Solution for Long-Wave Reflection by a Rectangular Obstacle with Two Scour Trenches

Abstract: In this paper, linear long-wave reflection by a rectangular obstacle with two scour trenches of power function profile is explored. A closed-form analytical solution in terms of the first and second kinds of Bessel functions is obtained, which finds two classic analytical solutions as its special cases, i.e., the wave reflection from a rectangular obstacle and from an infinite step. The phenomenon of zero reflection coefficient for a single rectangular obstacle with the same depths in front of and behind the obstacle still remains for a rectangular obstacle with two scour trenches as long as the bathymetry is symmetrical about the obstacle. The periodicity of the reflection coefficient as a function of the relative length of the middle rectangular obstacle disappears if two scour trenches are attached to the middle rectangular obstacle. Finally, the wave reflection by a rectangular obstacle with two scour trenches generally increases when the trenches become wide and deep. The wave reflection by a degener...

Electric vehicle and method for controlling the same

Abstract: An electric wheelchair (11) includes a body portion (12), an operating section (13) to detect an operation by an operator, an obstacle sensor (14) to detect an obstacle existing in the vicinity of the body portion (12), an obstacle determination section (15) to form a search region (21) extending from the body portion (12) in an operating direction, and to determine an obstacle existing in the search region (21), as the obstacle to be avoided, a virtual repulsive force calculation section (16) to calculate a virtual repulsive force to move the body portion away from the obstacle determined by the obstacle determination section, a resultant force calculation section (17) to calculate a resultant force composed of an operating force and the virtual repulsive force, and a control section (18) to control a movement of the body portion so that the body portion is moved in a direction of the resultant force.

A single camera based rear obstacle detection system

Abstract: This paper presents a rear obstacle detection system by using a single rear view camera. The system can detect various static and moving obstacles behind the cars. An efficient hierarchical detecting strategy is used to achieve high detection rate and low false positives. The temporal Inverse perspective mapping difference image based coarse detection is used to estimate whether there are obstacles in the predetermined warning area at first stage. Then a novel integral image based segmentation algorithm is developed for fine obstacle segmentation. Finally, the blob analysis is utilized for obstacle representation and verification. Our system achieves 94.2% detection rate and 16% false positives rate on 125 challenging video sequences. The average processing speed of the system is 25fps on a standard laptop.

Parking space detection device and method thereof

Abstract: A parking space detection device and method thereof, wherein, firstly, store a plurality of border data relating to moved distance of a vehicle, and distance between vehicle and an obstacle for reverse transmission of ultrasonic waves; then determine if said border data satisfy evaluation conditions, such that it is in a first detecting parking space then obstacle state, or in a first detecting obstacle then parking space state. Wherein, in case that any of evaluation conditions is satisfied, start to calculate a first difference between each of said border data and their average, to determine if it is grater than a standard deviation; in case that answer is positive, fetch at least two data points, a first data point and a second data point, corresponding to border data, then calculate their difference to adjust weights of first data point and second data point, in obtaining a highly accurate parking space.

Method and apparatus for mining vehicle safety arrangements

Abstract: The present invention relates to a method for a safety system of a mining vehicle. The method comprises scanning the surroundings of the mining vehicle while the mining vehicle is driven and giving a collision warning if an obstacle is detected in a safety zone of the mining vehicle.In the system, there is stored obstacle information comprising at least location information of predetermined obstacles. Location information of the obstacle detected on the basis of the scanning is compared with the location information determined in the obstacle information. Stopping of the mining vehicle, caused by the safety system due to the detected obstacle, is prevented in response to the detected obstacle being determined safe on the basis of checking the obstacle information.

Visual navigation with obstacle avoidance

Abstract: We present and validate a framework for visual navigation with obstacle avoidance. The approach was originally designed in [1], but major improvements and real outdoor experiments are added here. Visual navigation consists of following a path, represented as an ordered set of key images, that have been acquired in a preliminary teaching phase. While following such path, the robot is able to avoid new obstacles which were not present during teaching, and which are sensed by a range scanner. We guarantee that collision avoidance and navigation are achieved simultaneously by actuating the camera pan angle, in the presence of obstacles, to maintain scene visibility as the robot circumnavigates the obstacle. The circumnavigation verse and the collision risk are estimated using a potential vector field derived from an occupancy grid. The framework can also deal with unavoidable obstacles, which make the robot decelerate and eventually stop.

ODE-based obstacle avoidance and trajectory planning for unmanned surface vessels

Abstract: A new method for real-time obstacle avoidance and trajectory planning of underactuated unmanned surface vessels is presented. In this method, ordinary differential equations (ODEs) are used to define transitional trajectories that can avoid obstacles and reach a final desired target trajectory using a robust tracking control law. The obstacles are approximated and enclosed by elliptical shapes. A transitional trajectory is then defined by a set of ordinary differential equations whose solution is a stable elliptical limit cycle defining the nearest obstacle on the vessel's path to the target. When no obstacle blocks the vessel's path to its target, the transitional trajectory is defined by exponentially stable ODE whose solution is the target trajectory. The planned trajectories are tracked by the vessel through a sliding mode control law that is robust to environmental disturbances and modeling uncertainties and can be computed in real time. The method is illustrated using a complex simulation example with a moving target and multiple moving and rotating obstacles and a simpler experimental example with stationary obstacles.

Study of effects of obstacle on non-line-of-sight ultraviolet communication links

Abstract: This paper studies the effects of the obstacle on non-line-of-sight ultraviolet communication links using multiple-scatter model based on a Monte Carlo method. On the condition that transmitter beam and receiver FOV just pass the top of the obstacle, and ranges is fixed, the received energy density is at its maximum. The path loss increases when the transmitter or the receiver is much near to the obstacle, because the nearby common scattering volumes decrease intensively. The optimal received range decreases with the increasing of the distance between transmitter and obstacle. The predictions are validated with experimental measurements. This work can be used for the guidance of UV system design and network technology to apply in complex surroundings, such as mountain, buildings, etc.

Robot crowd navigation using predictive position fields in the potential function framework

Abstract: A potential function based path planner for a mobile robot to autonomously navigate an area crowded with people is proposed. Path planners based on potential functions have been essentially static, with very limited representation of the motion of obstacles as part of their navigation model. The static formulations do not take into account the possibility of using predicted workspace configuration to augment the performance of the path planner. The use of an elliptical region signifying the predicted position and direction of motion of an obstacle is proposed in this paper. The repulsive potential caused by an obstacle is defined relative to this elliptical field. An analytic switch is made when the robot enters this predicted elliptical zone of the obstacle. The development of navigation functions makes it possible to design a potential-based planner which is guaranteed to converge to the target.