Showing papers on "Obstacle published in 2001"

Motion planning in dynamic environments: obstacles moving along arbitrary trajectories

Abstract: This paper generalizes the concept of velocity obstacles given by Fiorini et al. (1998) to obstacles moving along arbitrary trajectories. We introduce the nonlinear velocity obstacle, which takes into account the shape, velocity and path curvature of the moving obstacle. The nonlinear v-obstacle allows selecting a single avoidance maneuver (if one exists) that avoids any number of obstacles moving on any known trajectories. For unknown trajectories, the nonlinear v-obstacles can be used to generate local avoidance maneuvers based on the current velocity and path curvature of the moving obstacle. This elevates the planning strategy to a second order method, compared to the first order avoidance using the linear v-obstacle, and zero order avoidance using only position information. Analytic expressions for the nonlinear v-obstacle are derived for general trajectories in the plane. The nonlinear v-obstacles are demonstrated in a complex traffic example.

Mobile robot and course adjusting method thereof

Abstract: A mobile robot capable of recognizing its location and adjusting its direction in response to an obstacle in its way includes a running device, an obstacle detecting device for detecting the presence of an obstacle, a location recognizing device, a controlling portion, and a power supply. The location recognizing device includes a first vision camera directed toward the ceiling of a room and a first vision board. The first vision camera recognizes a base mark on the ceiling. The first vision board processes an image from the first vision camera and transmits the image data to the controlling portion. The obstacle detecting device includes a line laser for emitting a linear light beam toward the obstacle, a second vision camera for recognizing a reflective linear light beam from the obstacle, and a second vision board for processing image data captured by the second vision camera.

The effect of obstacle position on reach-to-grasp movements.

Abstract: Numerous everyday tasks require the nervous system to program a prehensile movement towards a target object positioned in a cluttered environment. Adult humans are extremely proficient in avoiding contact with any non-target objects (obstacles) whilst carrying out such movements. A number of recent studies have highlighted the importance of considering the control of reach-to-grasp (prehension) movements in the presence of such obstacles. The current study was constructed with the aim of beginning the task of studying the relative impact on prehension as the position of obstacles is varied within the workspace. The experimental design ensured that the obstacles were positioned within the workspace in locations where they did not interfere physically with the path taken by the hand when no obstacle was present. In all positions, the presence of an obstacle caused the hand to slow down and the maximum grip aperture to decrease. Nonetheless, the effect of the obstacle varied according to its position within the workspace. In the situation where an obstacle was located a small distance to the right of a target object, the obstacle showed a large effect on maximum grip aperture but a relatively small effect on movement time. In contrast, an object positioned in front and to the right of a target object had a large effect on movement speed but a relatively small effect on maximum grip aperture. It was found that the presence of two obstacles caused the system to decrease further the movement speed and maximum grip aperture. The position of the two obstacles dictated the extent to which their presence affected the movement parameters. These results show that the anticipated likelihood of a collision with potential obstacles affects the planning of movement duration and maximum grip aperture in prehension.

Rapid adjustment of trajectories for land vehicles

Abstract: A method for adjusting a desired trajectory of an automatically guided vehicle guidance system to match a physical constraint such as an obstacle or boundary. The method works around obstacles and boundaries as they occur, consistent with the original trajectory. The method is independent of the type of vehicle. The method may be used regardless of whether the vehicle is under automatic guidance, and the method has a low computational cost.

Mappings of grazing-impact oscillators

Abstract: Impacting systems are found in a great variety of mechanical constructions and they are intrinsically nonlinear. In this paper it is shown how near-grazing systems, i.e. systems in which the impacts take place at low speed, can be described by discrete mappings. The derivation of this mapping for a harmonic oscillator with a stop is dealt with in detail. It is found that the resulting mapping for rigid obstacles is somewhat different from those presented earlier in the literature. The derivations are extended to systems with a compliant obstacle. We find that the map for impacts with a compliant obstacle is very similar to the one describing collisions with a rigid obstacle. A notable difference is a change of scale of the bifurcation parameter. We illustrate our findings in the limit of large damping, where the mechanism of period adding can be analysed exactly. The relevance of our results to experiments on practical impact systems is indicated.

Obstacle detection using adaptive color segmentation and color stereo homography

Abstract: Obstacle detection is a key component of autonomous systems. In particular, when dealing with large robots in unstructured environments, robust obstacle detection is vital. In this paper, we describe an obstacle detection methodology which combines two complementary methods: adaptive color segmentation, and stereo-based color homography. This algorithm is particularly suited for environments in which the terrain is relatively flat and of roughly the same color. We will show results in applying this method to an autonomous outdoor robot.

Planning reaching and grasping movements: the problem of obstacle avoidance.

Abstract: In this article, we review a model of the movement-planning processes that people use for direct reaching, reaching around obstacles, and grasping, and we present observations of subjects' repeated movements of the hand to touch 2 target locations, circumventing an intervening obstacle. The model defines an obstacle as a posture that, if adopted, would intersect with any part of the environment (including the actor himself or herself). The model finds a trajectory that is likely to bring the end-effector to the target by means of a one-or two- stage planning process. Each stage exploits the principles of instance retrieval and instance generation. In the first stage, a goal posture is identified, and the trajectory of a direct transition to that posture is tested for collision. If the direct movement has no collision, the movement to the target is immediately executed in joint space. If, however, the direct movement is foreseen to result in a collision, a second planning stage is invoked. The second planing stage identifies a via posture, movement through which will probably avoid the collision. Movement to and from the via posture is then superimposed on the main movement to the target so that the combined movement reaches the target without colliding with intervening obstacles. We describe the details of instance retrieval and instance generation for each of these planning stages and compare the model's performance with the observed kinematics of direct movements as well as movements around an obstacle. Then we suggest how the model might contribute to the study of movements in people with motor disorders such as spastic hemiparesis.

Tracking chemical plumes in constrained environments

Abstract: This paper describes an on-going project to develop robotic systems for locating chemical sources in constrained environments. There is increasing interest in applying chemical sensing to mobile robots. Locating the source of a chemical plume is seen as an important use for a chemical sensing robot. Current research tends to concentrate on source location in open and relatively obstacle free environments. Many of the applications for this technology will be areas where airflow is constrained and deflected by obstacles such as inside buildings, mines and subway tunnels. It is this kind of situation that this project aims to address.

Personal collision warning and protection system

Abstract: A sensor transmits a pulse in the direction of travel of a user and receives reflections from any obstacle in the path. The sensor provides two signals which indicate the relative range and the relative velocity between the user and the obstacle. A decision logic and control circuit processes the signals and determines whether the user and the obstacle are close enough and there is sufficient closing velocity to present a hazard to the user. When the circuit determines there is a hazard, the circuit activates a warning device. An activation signal is also generated when the circuit determines that the user cannot avoid the obstacle. This signal is supplied to an automatic protection system which includes an air bag located on the front portion of a jacket worn by the user. The air bag is inflated by the activation signal to protect the user when colliding with the obstacle.

Autonomous moving apparatus having obstacle avoidance function

Abstract: An autonomous moving apparatus moving to a destination while detecting and avoiding an obstacle includes a radar device for scanning a horizontal plane in its travelling direction to thereby detect a position of an obstacle and an obstacle sensor for detecting an obstacle in a space different from the scanning plane of the radar device. The apparatus moves to the destination under such control as to avoid the obstacle based on detection information from the radar device and the obstacle sensor from a detection output provided by a specific-configuration detecting element for detecting a present specific configuration from scanning information by the radar device. By providing such a specific-configuration detecting element that detects a specific configuration based on the scan information by the radar device that can accurately know about position information, it is possible to guess an obstacle having an upper structure, thus providing efficient avoidance.

Braking control device for vehicle

Abstract: PROBLEM TO BE SOLVED: To generate a braking force at an exact timing without unnecessarily generating it. SOLUTION: This braking control device calculates a relative distance d between an obstacle and an own vehicle, a relative speed Vr, a lateral moving distance Y necessary for avoiding a contact with the obstacle (step S1) and determines whether or not the vehicle can avoid the obstacle by the braking based on the relative distance d and the relative speed Vr and whether or not the vehicle can avoid it by the braking after a lapse of a prescribed time TcB (steps S2 and S3). The control device calculates a necessary time Ty for the vehicle laterally moving by the lateral moving distance Y and determines whether or not the vehicle can avoid the obstacle by steering based on it and the necessary time required for the own vehicle contacting with the obstacle and whether or not the vehicle can avoid it by steering after a lapse of a prescribed time TcS (steps S4 and S5). When it estimates impossible to avoid the obstacle by the braking and the steering after the lapse of the prescribed time, a gradually increasing braking force FL is generated (steps S6-S10), and when it becomes impossible to avoid the obstacle by both of the braking and the steering, a further larger braking force FH is generated (steps S6 and S7). COPYRIGHT: (C)2003,JPO

The use of the Pontryagin maximum principle in a furtivity problem in time-dependent acoustic obstacle scattering

Abstract: In this paper we consider a furtivity problem in the context of time-dependent three-dimensional acoustic obstacle scattering. The scattering problem for a ‘passive’ obstacle is the following: an incoming acoustic wavepacket is scattered by a bounded simply connected obstacle with locally Lipschitz boundary having a known boundary acoustic impedance. The scattered wave is the solution of an exterior problem for the wave equation. To make the obstacle furtive we leave ‘passive’ obstacles and we consider ‘active’ obstacles, that is obstacles that, when hit by the incoming wavepacket, react with a pressure current circulating on their boundary. The furtivity problem consists of making the acoustic field scattered by the obstacle ‘as small as possible’ by choosing a control function, that is a pressure current on the boundary of the obstacle, in the function space of the admissible controls. It consists of finding the control function that minimizes a cost functional that will be made precise later. ...

Online navigation of mobile robot under the existence of dynamically moving multiple obstacles

Abstract: Proposes an online navigation method of mobile robots for collision avoidance with dynamically moving obstacles, where the multiple obstacles always change their velocities. For more applications of mobile robots in the real world, the robots are expected to work well in everyday space where people are walking around. The robot must reach the desired point even in a dynamic environment where many people (obstacles) are moving. In such a situation where the environmental objects are dynamically changing their position, it is not realistic to have all information of the dynamical environment such as trajectory of a human being's motion. To cope with the situation, the robots usually have a sensor system to obtain real time environmental information, and robots should have an ability of sensor-based online motion planning for the dynamical environment. The paper considers the online motion planning problem where the workspace has multiple moving obstacles. The proposed motion planner basically uses an idea of velocity obstacle. After discussing some problems when applying the idea of velocity obstacle to online motion planning problem for dynamical environment, a modified method using the idea is presented. The main point of the modification is for coping with velocity changes of moving obstacles during the sensor cycle. The paper also discusses the efficiency of the resultant trajectory produced by the motion planner. Some simulations of online motion planning problems where multiple obstacles are changing their velocities are shown.

Wave front-obstacle interactions in cardiac tissue: a computational study.

Abstract: An understanding of wave front-obstacle interactions will greatly enhance our knowledge of the mechanisms involved in cardiac arrhythmias and their therapy. The goal of this computational study is to examine the interactions between wave fronts and various obstacles in a two-dimensional sheet of myocardium. The myocardium is modeled as an isotropic sheet with Luo-Rudy I membrane kinetics. An examination is conducted of wave front interactions with nonconductive and passive-tissue obstacles. Simulations were performed either in environments of reduced myocardial excitability, or with rapid stimulation via a line electrode. The shape of the obstacles and their ability to withdraw current from the active tissue greatly influence wave front-obstacle interactions in each of these environments. The likelihood of wave front detachment from an obstacle corner increases as the curvature of the obstacle corner is increased. A passive-tissue obstacle promotes wave front-obstacle separation in regions of depressed excitability. Under rapid pacing, the presence of the passive obstacle results in wave fragmentation, while the insulator obstacle promotes wave front detachment. The results of this study reveal the importance of obstacle composition and geometry in wave front interactions with cardiac obstacles.

Information processor for vehicle

Abstract: PROBLEM TO BE SOLVED: To provide information about an object needing breaking such as an obstacle timely. SOLUTION: Acceleration quantity of information providing timing is calculated as reference information providing timing correction quantity Δt 0 while reducing a speed at set deceleration Gp after starting to see an obstacle in the case the obstacle is not seen because the obstacle exists ahead of a curve and reducing a speed at deceleration Gq lower than the set deceleration Gp before starting to see the obstacle. Furthermore, information providing timing correction quantity Δt is calculated by multiplying the reference information providing timing correction quantity Δt 0 by a road surface friction coefficient correction coefficient k 1 , a road curvature radial correction coefficient k 2 and a traffic volume correction coefficient k 3 , and the information of the obstacle is provided at the timing. A position at starting to see an obstacle is corrected in accordance with a visual field environment and the working conditions of headlamps. In the speed of the self-vehicle at the position at starting to see an obstacle, a value regulated by a road shape such as a curve is defined as an upper limit value. COPYRIGHT: (C)2003,JPO

Robust Obstacle Detection from Stereoscopic Image Sequences Using Kalman Filtering

Abstract: In this paper a new approach for video based obstacle detection for a mobile robot is proposed, based on probabilistic evaluation of image data. Apart from the measurement data, also their uncertainties are taken into account. Evaluation is achieved using Kalman filter technique combining the results of video data processing and robot motion data. Obstacle detection is realised by computing obstacle probability and subsequent application of a threshold operator. The first experiments show remarkably stable obstacle detection.

Autonomous Driving with Concurrent Goals and Multiple Vehicles: Mission Planning and Architecture

Abstract: We introduce a new distributed planning paradigm, which permits optimal execution and dynamic replanning of complex multi-goal missions. In particular, the approach permits dynamic allocation of goals to vehicles based on the current environment model while maintaining information-optimal route planning for each individual vehicle to individual goals. Complex missions can be specified by using a grammar in which ordering of goals, priorities, and multiple alternatives can be described. We show that the system is able to plan local paths in obstacle fields based on sensor data, to plan and update global paths to goals based on frequent obstacle map updates, and to modify mission execution, e.g., the assignment and ordering of the goals, based on the updated paths to the goals. The multi-vehicle planning system is based on the GRAMMPS planners the on-board dynamic route planner is based on the i>Da planner. Experiments were conducted with stereo and high-speed ladar as the to sensors used for obstacle detection. This paper focuses on the multi-vehicle planner and the systems architecture. A companion paper (Brumitt et al., 2001) analyzes experiments with the multi-vehicle system and describes in details the other components of the system.

Obstacle information display device

Abstract: PROBLEM TO BE SOLVED: To provide an obstacle information display device which always performs an appropriate display processing on an object and allows a driver to perform an avoiding operation on the safe side. SOLUTION: When a preceding vehicle exists between a present vehicle and the obstacle and it is judged that there is danger that the present vehicle hits the preceding vehicle (Yes in step S24) while display on the front obstacle is performed (step S16 and 26), display on the preceding vehicle important for the present vehicle is performed instead of display on the obstacle (step S28). The driver is urged to perform a brake operation. COPYRIGHT: (C)2003,JPO

Kinematic Control and Obstacle Avoidance for Redundant Manipulators Using a Recurrent Neural Network

Abstract: In this paper, a recurrent neural network called the Lagrangian network is applied for obstacle avoidance in kinematically redundant manipulators. Conventional numerical methods implemented in digital computers for obstacle avoidance redundancy resolution calculation could only compute the solution in milliseconds while neural network realized by hardware could complete the computation in microseconds, which is more desirable in real-time control of manipulators. By giving the desired end-effector velocities and the obstacle location, the neural network could generate the joint velocity vector which drives the manipulator to avoid obstacles and tracks the desired end-effector trajectory simultaneously. Simulation results show that the neural network is capable of computing the redundancy resolution for obstacle avoidance.

Multiobjective Navigation of a Guide Mobile Robot for the Visually Impaired Based on Intention Inference of Obstacles

Abstract: Different from ordinary mobile robots used in a well-structured industrial workspace, a guide mobile robot for the visually impaired should be designed in consideration of multiple moving obstacles of various types and with different speeds while it adaptively maintains a certain distance from the user. Here, the moving obstacles mostly refer to pedestrians in intentional motions. Thus, navigation of the guide robot can be facilitated if the intention of each obstacle detected can be known in advance. In the paper, we propose to use a fuzzy grid-type local map in order to infer the intention of a moving obstacle. And, then, we determine the motion control of the robot by adopting a multiobjective decision making method in order to take into consideration various requirements including goal-seeking, multiple obstacle avoidance and maintenance of a certain distance from the user. To show the effectiveness of the proposed method, some experimental results are provided.

Separating shear flow past a surface-mounted blunt obstacle

Abstract: The planar flow of incompressible fluid past a blunt obstacle mounted on a flat (horizontal) fixed solid surface of infinite extent is examined in the presence of an incident linear velocity profile, modelling the fluid behaviour close to a small surface roughness for instance. The motion is taken to be steady and laminar. The obstacle is blunt in the sense that its typical surface slopes are not small, a feature which here always induces flow separation both upstream and downstream of the obstacle. Computations and nonlinear theory are applied, together with comparisons. The direct computations of the Navier-Stokes equations, using for example a higher order upwind-difference scheme, deal with a moderate range of Reynolds numbers up to 200, based on the obstacle height and the incident uniform shear. In addition the accuracy is necessarily limited as the Reynolds number increases. The theory is for large Reynolds numbers and is based on viscous-inviscid reasoning, backpressure effects from the obstacle and slender-layer separation locally, among other influences. The comparisons nevertheless yield encouragingly close agreement, for the present computed cases of a vertical flap or a rectangular block. This is both quantitatively, in terms of the upstream separation and downstream reattachment positions in particular, and generally, in terms of the separating flow structure, even at the notably moderate Reynolds numbers covered accurately by the computations.

Application of a blind person strategy for obstacle avoidance with the use of potential fields

Abstract: This paper proposes a new obstacle avoidance algorithm for the CONTROLAB AGV which uses a similar strategy adopted by a blind person to avoid obstacles while walking. The AGV moves within an office environment with a known floorplan and uses an "electronic stick" consisting of infrared sensors to detect unknown obstacles. Initially, a global potential field function is defined for each floorplan room. While the AGV is moving the original potential function is modified each time an obstacle is detected by the infrared sensors. This modification is simply performed by the addition of previously calculated potential field values on a grid which represents the room working area. The interesting aspects of the proposed approach are that the potential function adaptation involves very low computational burden, the algorithm is free from local minima, the obstacles can have any shape and low cost sensors can be used to detect obstacles.

Recording medium, program executing system, and program executing device

Abstract: When obstacles inhibiting the progression of a character being operated on a screen with a controller are encountered, obstacle overcoming actions corresponding to the state of the character may be performed with a simple operation. An obstacle overcoming button is determined beforehand in the program. The character has perimeter ranges corresponding to its own speed. In the event that the obstacle object is a building, a perimeter range is also provided to a wall of the obstacle object, for example, and an obstacle overcoming table corresponding to the overlapping relations of the mutual perimeter ranges is created beforehand. In the event the obstacle overcoming button is operated and the perimeter range of the character and the perimeter range of the wall overlap, an action of jumping over the obstacle object, for example, is automatically invoked.

Combining EMS-Vision and Horopter Stereo for Obstacle Avoidance of Autonomous Vehicles

Abstract: A novel perception system for autonomous navigation on low level roads and open terrain is presented Built within the framework of the US-German AutoNav project, it combines UBM's object oriented techniques, known as the 4D approach to machine perception (EMS-Vision), with Sarnoff's hierarchical stereo processingThe Vision Front End 200, a specially designed hardware device for real-time image processing, computes and evaluates 320×240 pixel disparity maps at 25 frames per second A key element for this step is the calculation of the horopter, a virtual plane that is automatically locked to the ground plane For improved reliability, the VFE 200 results are integrated over time in a grid-based terrain representation Obstacle information can then be extracted The system's situation assessment generates a situation representation that consists of so-called situation aspects assigning symbolic attributes to scene objects The behavior decision module combines this information with knowledge about its own body and behavioral capabilities to autonomously control the vehicleThe system has been integrated into the experimental vehicle VaMoRs for autonomous mobility through machine perception In a series of experiments, both positive and negative obstacles could be avoided at speeds of up to 16km/h (10mph)

Method for generating route of mobile object

Abstract: PROBLEM TO BE SOLVED: To provide a mobile object route generating method for finding out the shortest route out of plural routes on which a mobile object such as a mobile robot moves up to a goal point while evading obstacles as to a motion plan for allowing the mobile object to autonomously travel in an environment having the obstacles. SOLUTION: An environment temperature map is prepared by substituting a two-point boundary value problem for solving a heat conduction phenomenon for a motion plan problem for autonomously guiding the mobile object from an initial position to a goal position in a two-dimensional environment including obstacles and an obstacle evading model for the mobile object expressed as a rectangular parallelepiped in the map is prepared. The shortest route connecting the start point to the final goal point is prepared while searching the route in eight directions on respective grating points of the obstacles constructed in the environment temperature map on the basis of the potential (temperature field) information of respective grating points and the obstacle evading model is moved up to the final goal point along the shortest route.

A destination driven navigator with dynamic obstacle motion prediction

Abstract: A real time navigating system, called destination driven navigator, is developed. The paper presents an obstacle representation method named cross-line, the concept "work space" to reduce the robot's search space and the environment storage cost, an adapted regression model to predict the dynamic obstacles' motion, and the multi-state path repair rules to quickly translate an infeasible path into feasible one, the path-planning algorithm and destination driven navigator to guide a mobile robot traveling in dynamic environments and reach a destination safely. A group of experimental results is conducted that exhibit that the destination driven navigator is a powerful and effective paradigm for robot motion planning and obstacle avoidance.

Open-end spinning machine robotic maintenance unit has obstacle detectors linked to control system

Abstract: An open-end spinning machine (10) has a rail (15, 16) mounted maintenance unit (14a, 14b) which passes a series of work stations. The first maintenance unit has a detector (23) which locates an obstruction (14a. 14b, 26) in one direction of its path. The detector esp. emits a signal specifying the distance remaining to the obstruction. A second detector (24) operating in a single direction identifies the distance remaining to a further obstruction (14a. 14b, 26). Also claimed is an associated operating control process in which at least one of the two obstacle signals identifies the presence of and distance to an obstacle. In a preferred embodiment the system has a third obstacle detector. The non-contact obstacle detectors are linked to an emergency stop system.