Showing papers on "Obstacle published in 1989"

Real-time obstacle avoidance for fast mobile robots

Abstract: A real-time obstacle avoidance approach for mobile robots has been developed and implemented. It permits the detection of unknown obstacles simultaneously with the steering of the mobile robot to avoid collisions and advance toward the target. The novelty of this approach, entitled the virtual force field method, lies in the integration of two known concepts: certainty grids for obstacle representation and potential fields for navigation. This combination is especially suitable for the accommodation of inaccurate sensor data as well as for sensor fusion and makes possible continuous motion of the robot with stopping in front of obstacles. This navigation algorithm also takes into account the dynamic behavior of a fast mobile robot and solves the local minimum trap problem. Experimental results from a mobile robot running at a maximum speed of 0.78 m/s demonstrate the power of the algorithm. >

Computing metric and topological properties of configuration-space obstacles

Abstract: The author describes an algorithm that takes two polygons as input, and computes a representation of their corresponding configuration-space obstacle, including contact information. The algorithm's output includes a full metric and topological description of the obstacle surface, as well as the set of polygon features that are in contact for each point of the surface. The representation is exact, up to the limits of floating-point arithmetic. The algorithm has been implemented and test-run on over 40 input pairs; run times varied between 12 and 135 s. >

Navigating vehicles through an unstructured environment with sonar

Abstract: A procedure to navigate a vehicle from a source to a destination through an unstructured environment using only a sonar sensor is described. The environment considered is a two-dimensional floor plan, consisting of line segments of arbitrary size that is extended into the third dimension. To ensure that a sonar-guided vehicle does not collide with an obstacle, it is necessary to consider an obstacle that produce the weakest echoes and determine the conditions under which these obstacles can be detected. In this environment, the smallest echo is produced by the line that defines the boundary between the two planes, or the edge; and distant edges become invisible. This physical principle then becomes the basis for the navigation strategy, indicating the necessary scanning pattern and maximum step size that guarantee that no collision will occur. The approach is illustrated with results produced by a vehicular robot equipped with a Polaroid sensor. A representative floor plan and the automatically determined path are shown; a blind alley was included to observe the behavior of the algorithm. >

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. >

Cuba: The Test of Time

Abstract: Describes the mixture of achievement and obstacle that makes up modern Cuba, concentrating on the issues and dilemmas facing ordinary Cubans: availability of consumer goods, motivation at work, civil rights and decision-making and the country's involvement in war overseas.

Equations for boundaries of joint obstacles for planar robots

Abstract: Parameterized equations for the boundaries of joint space obstacles for planar robots are derived. The boundary of a joint obstacle prescribes the link motion of the closed chain formed by the robot in contact with a given obstacle. The theory of kinematic mappings is used to represent the link motion as a set of points in a projective three space. The link positions that are feasible to the arm define a manifold in this space, termed its reachable manifold. The link positions satisfying contact conditions define another manifold in the same space called the contact manifold. Their intersection is mapped to joint space to obtain equations defining the obstacle boundary. While the theory applies to general planar robots, the authors focus on the 3R robot arm. An example is also provided in which the boundaries of joint obstacles are computed. >

Process and apparatus for locating an obstacle

Abstract: An unmanned movable and steerable vehicle has a device for locating obstacles in relation to a coordinate system which moves along with the vehicle. Ultrasonic waves transmitted by transmitters on the vehicle in the driving direction thereof and ultrasonic waves reflected back to the vehicle by obstacles and received by receivers on the vehicle produce information whereby vehicle steering and/or braking signals function to prevent a collision. For the purpose of an interference-free, accurate location determination of an obstacle in relation to the coordinate system moved along with an unmanned movable and steerable vehicle, a single pulse is transmitted by two adjacent ultrasonic waves and also received again at the transmission sources. In a progression by one another sound source, after the first sound source has been switched off, the same procedure of transmitting a single pulse and, in the presence of an obstacle, the reception of a reflected ultrasonic echo is possible. The size and position of an obstacle in front of the vehicle can then be received interference-free.

Optimal Obstacle Avoidance Path Planning for Autonomous Underwater Vehicles

Abstract: A reliable obstacle avoidance capability is a critical link in the quest for true underwater vehicle autonomy. Investigations in this area have culminated in a three-dimensional obstacle avoidance algorithm for autonomous underwater vehicles (AUVs). Using this algorithm, an AUV outfitted with an obstacle avoidance sonar (OAS) and a precise navigation system can localize obstacle positions and safely navigate a dense, unknown obstacle field. The algorithm overcomes the physical constraints of the OAS such as narrow field of view, missed detections, false alarms and poor angular resolution. Furthermore, based on the algorithm's present knowledge of obstacle positions, dynamic programming techniques plan the optimum safe path through the obstacle field. Additional logic ensures that in spite of the AUV's restricted maneuverability and the OAS's limited coverage, the vehicle always maintains the minimum, safe standoff distance from all obstacles. Computer simulation has verified the obstacle avoidance algorithm's integrity in six dense, box canyon obstacle fields and two random obstacle fields. In all cases the algorithm safely guides the AUV through the obstacle field and localizes many of the obstacle positions.

Fundamental Studies of Collision Avoidance Problems Between a Robot and a Moving Obstacle. Part 1: Heuristic Collision Avoidance Techniques and Fundamental Experiments with a Real Robot

Abstract: In this paper, we propose a means for materializing the robot that is capable of avoiding collisions with any moving obstacle, and present our experimental findings by applying the means to an actual robot.

Distance discriminating apparatus for vehicle

Abstract: PURPOSE:To enable the discrimination of distances between a vehicle and an obstacle without causing an error, by a method wherein a light of a belt-shaped pattern slanting with respect to a vertical direction is directed toward the obstacle. CONSTITUTION:An irradiation means 2 equipped on the rear side of a vehicle 1 directs a light of a specific pattern P1 toward the rear of the vehicle 1. The specific pattern P1 is one belt-shaped pattern slanting from the upper left to the lower right of the direction of advance of the vehicle 1. The specific pattern P1 shifts in the horizontal direction in accordance with distances between the vehicle 1 and an obstacle. By storing the positional relations the specific pattern P1 in the visual field in the rear as the correlation of the distance between the vehicle 1 and the obstacle; accordingly, distances from the obstacle can be discriminated by observing the specific pattern P1 by eyes.

Guiding method and system for unmanned-carrying vehicle

Abstract: PURPOSE:To freely change a route to avoid an obstacle, etc., by storing the information of all guiding pathes, in which a traveling can be executed as the couple of a guiding path number and the train of branching points on the guiding path and retrieving the route to achieve a destination from this branching point train. CONSTITUTION:An unmanned-carrying vehicle, which loads an obstacle avoiding route retrieving mechanism is traveled on the lattice shaped guiding path by the couple of magnetic substance blocks. The lattice shaped guiding path uses a ferrite block, for example, as a marking body and the indicator body is detected by a trace sensor 7 of the carrying vehicle. Then, position information are obtained. A map to be formed by coupling the arrangement of the mark is stored in a memory area 6. An operation control part 4 retrieves the route to achieve the destination from the prepared map and route data are prepared from the map and sent to a traveling control part 3. When the obstacle on the guiding path is recognized by an obstacle searching means 9, new route retrieval is executed from the place of the obstacle and a new route is prepared and sent to the control part 3. Thus, the route change can be freely executed to avoid the obstacle, etc.

Visual Feedback To Predict Obstacle Motion For On-line Collision-free Trajectory Planning Of Cylindrical Robots

Abstract: ABSmACT When a robot moves in a partially known environment, the desired trajectory generated in advance (off-line) may lead to collisions with nonstationary obstacles. Therefore, the on-line detection of obstacles in the workspace from sensor information, testing for potential collisions of the robot with obstacles, and possible on-line modifications of the planned trajectory are necessary. This paper describes a method that uses computer vision to detect a moving obstacle in the three-dimensional robot workspace. The movements of the obstacle of unknown dynamics are predicted by means of a recursive autoregressive (AR) time series model, in which the parameters are estimated by the least mean squared error method. This algorithm is combined with an on-line robot trajectory planning algorithm to generate a collision-free trajectory for the cylindrical robot. The approach is demonstrated by laboratory

Device for guiding the movement on the ground of a self-driven machine

Abstract: A method and device are disclosed for controlling the movement of a machine on a surface. The device comprises an obstacle disposed along at least part of an area to be traversed by the machine, a winder-unwinder device connected to the machine, and an anchor which is located remote from the machine and which is stationary with respect to the surface. A flexible connection is attached at one end to the machine at another end to the anchor. An obstacle detector, carried by the machine, detects the presence of the obstacle. A device successively frees a given length of the connection when the obstacle is detected. A propulsive device causes the machine to travel in a direction in which the connection is stretched again after the length of the connection is freed, and then causes the machine to travel in a direction which is opposite to a direction in which the machine was travelling before the obstacle was detected.

A laser obstacle avoidance and display system

Abstract: The authors describe an airborne laser system that provides a pilot with a display of obstacles such as power cables ahead of his aircraft. This system, LOCUS (Laser Obstacle and Cable Unmasking System), was flight-tested by the Naval Air Test Center at Patuxent River, where cable detection ranges of over 2 km were measured. It is found that real-time processing of the laser returns can achieve a real-time display of obstacles in the flight path sufficiently early to enable safe evasive action. In addition, real-time processing of the laser returns can provide unmapped obstacle data to enhance a digital terrain system in low-level covert terrain-following mode. >

Autonomous Knowledge-Based Navigation in an Unknown Two-Dimensional Environment with Convex Polygon Obstacles

Abstract: Navigation of autonomous vehicles in environments where the exact locations of obstacles are initially know has been the focus of research for two decades. More recently, algorithms for controlling progress through unknown environments have been proposed. The utilization of knowledge-based systems for studying the behavior of an autonomous vehicles presents new challenges for research. A knowledge-driven autonomous system simulation was developed which enabled an autonomous mobile system to move in a two-dimensional, obstacle strewn, environment and to use a simulated ranging/vision sensor to test whether a selected goal position was visible or whether the goal was obscured by one or more of the polygon obstacles. As the mobile system gained information about the location of obstacles, that knowledge is added to the system's knowledge-base. High-level navigation rules were fired when necessary conditions in the knowledge base existed. The necessary low-level computations (eg., vertex visibilities, etc) were, when required within the context of a selected rule, carried or' through appropriate Lisp functions. The knowledge-based program was implemented in the generalized decision-making paradigm, OPS5.

Realization Of Obstacle Avoidance By Biped Walking Robot Equipped With Vision System

Abstract: A couple of eyes composed of two CCD cameras is installed on the biped walking robot WL-IZRII-V (Waseda Leg-12 Refined IT with Vision). It is possible for a biped walking robot to "avoid" an obstacle by stepping over it instead of detouring around it, if it is low enough for it to do so. In this paper, this type of obstacle avoidance is described with experimental results. The stepping-over experiments have been successful in almost all processes. The robot succeeds in walking on a flat floor at given velocity when it finds an obstacle (for example, a long 3Ox30Lmml cross section square timber can be used) in its way, the robot measures accurately its position and height while walking and then steps over it. Furthermore, not only the bending waist pattern for short-range-measurement but also the approach walking and cr6ss walking patterns for the execution of "stepping-over" are automatically designed by the robot. Thus, the WL-1ZRII-V autonomously has realized biped walking for avoiding an obstacle.

Obstacle detecting device for running vehicle

Abstract: PURPOSE:To prevent erroneous detection of an obstacle by anticipating a running path of a vehicle running a narrow place in a plant in accordance with a steering angle, and by removing obstacle detecting sensors in detection areas out of the advancing direction of the vehicle, from those for obstacle detection CONSTITUTION:Obstacle sensors 4-8 set for detection areas 14-18 are attached on the front section of a vehicle self-traveling on a predetermined running path such as a floor 10 or the like in accordance with a program There are provided limit switches LS1-LS5 actuated by a striker 20 associated with a steering wheel 3, whose output signals are delivered to a selected circuit together with output signals from the obstacle detecting sensors 4-8 The sensors 4-8 are selectively actuated as follows For example, if an LS3 is turned on during advance of the vehicle 1, sensors 5-7 are turned on excepting both end sensors 4, 8, and further if an LS5 is turned on during right turn, right side sensors 7, 8 are turned on

Obstacle indicator device for vehicle

Abstract: PURPOSE:To give the driver an alarm in advance about possible hazard of collision or contact with any obstacle ahead the car for ex. an approaching car by displaying the image of obstacle on an image display means by the use of an image pickup means and also the configurational image of the own car in the obstacle position. CONSTITUTION:The image of any obstacle ahead and the car such as an approaching car is picked up by a video camera V, and the output image is passed to an edge processing circuit 4, and the edge is emphasized and forwarded to an image synthesizer circuit 5 as the next process. Into this the image of obstacle and the configurational image of own car from memory are fed and synthesized on one screen, and these image are sent to an overlap sensor circuit 8 and a CRT 7 as an image display means on the next step. When this overlap sensor circuit 8 senses the portion of overlapping W, the indication color of the overlapped portion W is varied on the CRT, and also an alarm circuit 9 is actuated to give alarming tone to the driver. This prevents collision or contact with the obstacle a head the car.

Limits of Obstacle Problems for the Area Functional

Abstract: We study the general form of the limit, in the sense of Γ-convergence, of a sequence of variational problems for the area functional with one-side obstacles.

Motion Analysis of Obstacle Striding for the Multifunctional Robot Vehicle

Abstract: 車輪とクローラ脚を複合した多機能移動ロボットMRV-3を開発した.このロボットは車輪, クローラ, 脚の3つの移動モードをもっている.車輪モードでは, 前後進, 横進, その場回転が可能である.クローラモードでは, 階段昇降, 不整地走行, 溝越えなどができる.さらに脚モードでは, 立脚したのち障害物またぎ越えが可能である.これらの移動モードは4つのモータと12個の電磁クラッチからなる駆動メカニズムにより実現される.MRV-3の重量はバッテリー搭載時で約150kg, 車輪モードのときの本体寸法は, 770W×650L×810Hmmである.本論文では, まずパイプなどの障害物を非接触でまたぎ越えるときの動作シーケンスについて考察する.さらにこのとき静的安定性とまたぎ越え可能な障害物の形状寸法について解析を行う.最後にこれらの解析に基づいて行なった障害物またぎ越え動作実験の結果についても報告する.

Traveling controller for remote control working vehicle

Abstract: PURPOSE:To accurately confirm the access degree of a working vehicle against an obstacle at a remote point from the vehicle which is remote-controlled based on the transmission instructing information, by displaying the access state of the vehicle via a non-contact type obstacle detecting means. CONSTITUTION:A working vehicle receives the instructing information from a transmitter and is remote-controlled. An ultrasonic wave sensor S1 is provided on the vehicle to detect the access to an obstacle with no contact. The result of this detection is supplied to a controller 15 and the access state of the vehicle is displayed by an access state display means incorporated into the controller 15. Thus it is possible to confirm accurately the access degree of the vehicle against an obstacle at a remote point from the vehicle.

A 3d closest pair algorithm and its applications to robot motion planning

Abstract: A pair of the closest points, the one lying on a robot and the other on its obstacles, yields the most important information for generation of obstacle avoiding robot motions. Almost all algorithms previously presented for determination of the closest points cannot work well in three-dimensional cluttered space which has many obstacles with complicated shape since their computational times are at least linear in the total number of vertices of polyhedra representing the robot and obstacles. In view of this, a feasible algorithm that runs on the octree representation integrating all obstacles is proposed in this paper. Due to a hierarchical structure of the octree, the algorithm can investigate a part of the obstacles in order of the distance from the robot and consequently its computational time does not directly depend on the shape complexities of the robot and obstacles, that is, the number of obstacles in the environment and the number of surfaces on each obstacle. It is shown from experimental results that the proposed algorithm fulfill its function even though the environment is cluttered and shape of the obstacles is complicated.