Showing papers on "Obstacle avoidance published in 1988"
01 Jan 1988
TL;DR: The obstacle avoidance strategy used for this robot is described, which depends heavily on the performance of the ultrasonic range finders, these sensors and the effect of their limitations on the obstacle avoidance algorithm are discussed in detail.
Abstract: A mobile robot system, capable of performing various tasks for the physically disabled, has been developed. To avoid collision with unexpected obstacles, the mobile robot uses ultrasonic range finders for detection and mapping. The obstacle avoidance strategy used for this robot is described. Since this strategy depends heavily on the performance of the ultrasonic range finders, these sensors and the effect of their limitations on the obstacle avoidance algorithm are discussed in detail. >
451 citations
01 Aug 1988
TL;DR: A path planning technique is presented which produces time-optimal manipulator motions in a workspace containing obstacles through the use of the full nonlinear equations of motion in conjunction with the actuator limitations.
Abstract: A path planning technique is presented which produces time-optimal manipulator motions in a workspace containing obstacles. The full nonlinear equations of motion are used in conjunction with the actuator limitations to produce optimal trajectories. The Cartesian path of the manipulator is represented with B-spline polynomials, and the shape of this path is varied in a manner that minimizes the traversal time. Obstacle avoidance constraints are included in the problem through the use of distance functions. In addition to computing the optimal path, the time-optimal open-loop joint forces and corresponding joint displacements are obtained as functions of time. The examples presented show a reduction in the time required for typical motions. >
282 citations
24 Apr 1988
TL;DR: An obstacle-avoidance potential based on superquadrics is discussed, a modified form of the superquadric potential that provides safe approach objects and an algorithm that eliminates collisions with obstacles by calculating the repulsive forces exerted on links based on the shortest distance to an object.
Abstract: An obstacle-avoidance potential based on superquadrics is discussed. The superquadric formulation is a generalization of the elliptical potential function method and therefore is viable for a much larger class of object shapes. As with elliptical potentials, a modified form of the superquadric potential provides safe approach objects. The avoidance and approach potentials are implemented in simulations and the results exhibit an improvement over existing potential schemes. The simulations also use an algorithm that eliminates collisions with obstacles by calculating the repulsive forces exerted on links, based on the shortest distance to an object. >
254 citations
TL;DR: The article presents a new topic in path planning for mobile robots, region filling, which involves a sweeping operation to fill a whole region with random obstacle avoidance.
Abstract: The article presents a new topic in path planning for mobile robots, region filling. which involves a sweeping operation to fill a whole region with random obstacle avoidance. The approaches for global strip filling and local path searching driven by sensory data procedures are developed. A computer graphic simulation is used to verify the filling strategy available. The research was developed from the program for the design of a robot lawn mower. However, the solution appears generic. The significance is that a problem of wide application and generic solutions for general autonomous mobile robots have been developed.
131 citations
24 Apr 1988
TL;DR: Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles that makes effective use of the complementarity between global trajectory planning and local obstacle avoidance.
Abstract: Global geometric algorithms for trajectory planning are used in conjunction with a local avoidance strategy. Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles. Essentially, the robot has a geometric planner that provides a coarse trajectory (the path and the velocity along it), which may be modified by a (low-level) local avoidance module if sensors detect obstacles in the vicinity of the robot. This hierarchy makes effective use of the complementarity between global trajectory planning and local obstacle avoidance. >
97 citations
24 Apr 1988
TL;DR: An iterative method of computing the solution of the inverse kinematic problem is developed for redundant systems using the transpose of the Jacobian matrix instead of the pseudoinverse to remain easily tractable close to the singular configurations of the manipulator.
Abstract: An iterative method of computing the solution of the inverse kinematic problem is developed for redundant systems using the transpose of the Jacobian matrix instead of the pseudoinverse. The solutions may be optimized on a criterion function or on physical constraints, such as obstacle avoidance. Stability and convergence of the method are shown. Although its convergence rate is only about half that of Newton's method, the advantage of the method is that it remains easily tractable close to the singular configurations of the manipulator. A hybrid method combining the Jacobian transpose and Newton's methods is proposed. Results of the application of the method on a 10-link manipulator in 2-D space are shown. >
83 citations
TL;DR: The paper describes an approach to the solution of the find path problem, including obstacle avoidance in multirobot systems, which is based on the nonlinear approach and employs the hierarchical coordinator for real-time collision avoidance.
Abstract: The paper describes an approach to the solution of the find path problem, including obstacle avoidance in multirobot systems. The design of multirobot systems requires an overall approach where not only parts of the structure, including the hierarchy are considered, but a complete concept, including the dynamics of the robots, has to be developed. In this paper the structure of these systems is based on the nonlinear con trol approach. The method for real-time pathfinding itself uses a systematic design procedure for multirobot systems, which includes the hierarchical coordinator. This hierarchical coordinator is designed for real-time collision avoidance, where the collision avoidance strategy is based on an analyti cally described avoidance trajectory that serves for collision detection as well as avoidance. The efficiency of the new approach for real-time pathfinding is demonstrated by several cases of practical interest, such as collision avoidance between three robots, interaction of three stationary...
82 citations
TL;DR: Fuzzy control rules which were derived on the basis of a human's driving actions were modified by computer simulation for obstacle avoidance of a mobile robot which has two independent driving wheels.
77 citations
24 Apr 1988
TL;DR: A description is given of an obstacle avoidance perception sensing system developed for use on Martin Marietta's autonomous land vehicle and techniques for fusing video/range sensor data, locating obstacle regions in range imagery, and mapping of the algorithm onto Warp machine.
Abstract: A description is given of an obstacle avoidance perception sensing system developed for use on Martin Marietta's autonomous land vehicle. The focus is on range-image-based methods developed to run on a high-speed systolic array processor called the Warp machine. Techniques are presented for fusing video/range sensor data, locating obstacle regions in range imagery, and mapping of the algorithm onto Warp machine. The results of applying the perception sensing system in an experimental test run are presented, and limitations of its use are discussed. >
69 citations
05 Dec 1988
TL;DR: It is shown that a quantity termed the directional divergence of the 2-D motion field can be used as a reliable indicator of the presence of obstacles in the visual field of an observer undergoing generalized rotational and translational motion.
Abstract: The use of certain measures of flow field divergenee is investigated as a qualitative cue for obstacle avoidance during visual navigation. It is shown that a quantity termed the directional divergence of the 2-D motion field can be used as a reliable indicator of the presence of obstacles in the visual field of an observer undergoing generalized rotational and translational motion. Moreover, the necessary measurements can be robustly obtained from real image sequences. A procedure for robustly extracting divergence information from image sequences which can be performed using a highly parallel architecture is described. Experimental results are presented showing that the system responds as expected to divergence in real world image sequences, and the use of the system to navigate between obstacles is demonstrated.
69 citations
15 Jun 1988
TL;DR: This paper identifies obstacle detection and obstacle avoidance as the two critical components requiring substantial advancement before an automatic guidance system can be realized, and discusses the major sources of difficulties in developing these two components.
Abstract: In this paper, we consider nap-of-the-earth (NOE) rotorcraft flight as one of the applications in which obstacle avoidance plays a key role, and investigate the prospects of automating the guidance functions of NOE flight. Based on a proposed structure for the guidance functions, we identify obstacle detection and obstacle avoidance as the two critical components requiring substantial advancement before an automatic guidance system can be realized. We discuss the major sources of difficulties in developing these two components, including sensor requirements for which we provide a systematic analysis.
Patent•
09 Feb 1988
TL;DR: In this paper, an improved wire detection and avoidance system for helicopters is characterized by the use of a solid state laser transmitter which emits radiation in the near infrared wavelength region, using either a beam dividing device or a plurality of laser diode arrays.
Abstract: An improved wire detection and avoidance system for helicopters is characterized by the use of a solid state laser transmitter which emits radiation in the near infrared wavelength region. Using either a beam dividing device or a plurality of laser diode arrays, separate laser beam lobes are generated which are passed through optical lenses for deflection in slightly different directions to define a field of coverage. A wire obstacle in the field of coverage intercepts one or more of the lobes and reflects return signals thereof to a receiver detector array. The return signals are compared with the transmitted laser lobes, with the difference therebetween being a function of the range between the obstacle and the helicopter. The range information is displayed to the pilot who then takes evasive action to avoid striking the obstacle.
03 Oct 1988
TL;DR: By allowing overlap situations and controlling them with appropriate cost function, the algorithm is capable of producing very good results with the advantage of decreased runtime from the parallelism.
Abstract: The algorithm begins with an initial placement of nets in the channel using the number of tracks equal to the density of the channel. Overlapping subnets are permitted at this stage as the annealing process will gradually work to remove the overlaps. Transformations are then repeatedly applied to the channel state by moving nets around the channel in a parallel fashion. By allowing overlap situations and controlling them with appropriate cost function, the algorithm is capable of producing very good results with the advantage of decreased runtime from the parallelism. and can also be applied to extensions of the channel routing problem, such as switchbox routine with obstacle avoidance. >
05 Jun 1988
TL;DR: The authors present an operational perception system for cross-country navigation which has been verified in both simulated and real-world environments and proposes enhancements to their current operational system.
Abstract: The authors present an operational perception system for cross-country navigation which has been verified in both simulated and real-world environments. Range data from a laser range scanner is transformed into an alternate representation called the Cartesian elevation map (CEM). A detailed vehicle model operates on the CEM to produce traversability information along selected trajectories. This information supports a real-time reflexive planning system. The authors successfully demonstrated their obstacle detection and avoidance algorithms on board the autonomous land vehicle at Martin Marietta Aerospace Corporation in Denver. They also propose enhancements to their current operational system. >
24 Aug 1988
TL;DR: A real-time obstacle avoidance approach for mobile robots that permits the detection of unknown obstacles simultaneously with the steering of the mobile robot to avoid collisions and the advance of the robot toward the target.
Abstract: A real-time obstacle avoidance approach for mobile robots has been developed and implemented This approach permits the detection of unknown obstacles simultaneously with the steering of the mobile robot to avoid collisions and the advance of the robot toward the target The approach, called the virtual force field technique, integrates 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 (such as those produced by ultrasonic sensors) as well as for sensor fusion, and it allows continuous motion of the robot without stopping in front of obstacles Experimental results from a mobile robot running at a maximum speed of 078 m/s demonstrate the power of the proposed algorithm >
TL;DR: A two-level hierarchy for planning collision-free trajectories in time varying environments is proposed that makes effective use of the complementary aspects of the global trajectory planning approaches and the local obstacle avoidance approaches.
Abstract: We propose a two-level hierarchy for planning collision-free trajectories in time varying environments. Global geometric algorithms for trajectory planning are used in conjunction with a local avoidance strategy. Simulations have been developed for a mobile robot in the plane among stationary and moving obstacles. Essentially, the robot has a global geometric planner that provides a coarse global trajectory (the path and velocity along it), which may be locally modified by the low-level local avoidance module if local sensors detect any obstacles in the vicinity of the robot. This hierarchy makes effective use of the complementary aspects of the global trajectory planning approaches and the local obstacle avoidance approaches.
24 Apr 1988
TL;DR: A telerobotic control concept and its implementation using a PUMA-560 robot manipulator are reported, which provides a system which not only assists the operator in accomplishing tasks but modifies inappropriate operator commands which can result in safety hazards and/or equipment damage.
Abstract: A telerobotic control concept and its implementation using a PUMA-560 robot manipulator are reported The concept couples human supervisory commands with computer reasoning The control system is responsive and accomplishes an operator's commands while providing obstacle avoidance and controlled interactions with the environment where desired This provides a system which not only assists the operator in accomplishing tasks but modifies inappropriate operator commands which can result in safety hazards and/or equipment damage >
TL;DR: In this article, an autonomous mobile robot for obstacle avoidance based on finding permissible passageways using the edges between the floor and the wall or obstacles obtained by processing the image from a CCD camera in front of the robot is developed.
Abstract: Autonomous mobile robots should have the capability of recognizing their environments and manoeuvring through those environments on the basis of their own judgement. Fuzzy control is suitable for autonomous mobile robot control where the amount of information to be handled is limited as much as possible and the processing is simple. Autonomous mobile control of a robot is derived from two kinds of controls: for obstacle avoidance and for guidance following an appropriate path to a destination point. Fuzzy control of a robot for obstacle avoidance based on finding permissible passageways using the edges between the floor and the wall or obstacles obtained by processing the image from a CCD camera in front of the robot is developed. Furthermore, guidance control of the robot over paths that are specified in terms of maps may be developed by a process that treats a wrong path as a virtual obstacle on the screen, and the robot advances in the designated direction when it reaches intersections. An autonomous f...
24 Apr 1988
TL;DR: The author presents a method for building a 3D world model for a mobile robot from sensory data that consists of three kinds of maps: a sensor map, a local map, and a global map.
Abstract: The author presents a method for building a 3D world model for a mobile robot from sensory data. The model consists of three kinds of maps: a sensor map, a local map, and a global map. A range image (sensor map) is transformed to a height map (local map) with respect to a mobile robot. The height map is segmented into four categories (unexplored, occluded, traversable, and obstacle regions) for obstacle detection and path planning. Obstacle regions are classified into artificial objects or natural objects using both the height image and video image. One drawback of height map-the recovery of vertical planes-is overcome by the utilization of multiple height maps which include the maximum and minimum heights of each point, and the number of points in the range image mapped into one point in the height map. The multiple height map is useful not only for finding vertical planes in the height map but also for segmentation of the video image. Height maps are integrated into a global map by matching geometrical properties and updating region labels. >
24 Apr 1988
TL;DR: The authors focus on collision detection for planning collision-free motion of two robot arms in a common workspace using a sphere model for the wrists and a novel approach to collision detection.
Abstract: The authors focus on collision detection for planning collision-free motion of two robot arms in a common workspace. A collision-free motion is obtained by detecting collisions along the straight-line trajectories of the robots using a sphere model for the wrists and then replanning the paths and/or trajectories of one or both of the robots to avoid collisions. A novel approach to collision detection is presented and a discussion on collision avoidance is given. >
15 Jun 1988
TL;DR: In this article, a case study for a snake-like robot operating in a constrained environment is developed and simulation results are included, where the augmented task space approach is adopted and a recently established computational method to solve the constrained inverse kinematic problem is proposed.
Abstract: Redundancy offers a potential over nonredundancy in robot design and control in terms of greater motion/force manipulability. The solution to the kinematic control problem is crucial for an effective use of redundancy. The redundant degree-of-freedom's (DOF's) can be exploited to meet additional motion/force constraints, such as dexterity, task compatibility, obstacle avoidance, and limited joint range. The augmented task space approach is adopted and a recently established computational method to solve the constrained inverse kinematic problem is proposed. Finally, a case study for a snake-like robot operating in a constrained environment is developed and simulation results are included.
TL;DR: An algorithm which will find suboptimal solutions for optimizing both path and velocity history of the trajectory by the use of piecewise joint-space polynomials is presented, which exploits the robot arm dynamics in realistic environments where obstacles are present and the minimization of task time is desired with smooth motion.
Abstract: The concept of a tube is introduced and is applied to the solving of the collision-avoidance, minimum-time trajectory planning problem. A collision-free space is represented by an articulated tube with parameters of reference points and path tolerances. For obstacle avoidance, the end effector is constrained to move inside of the tube. An algorithm which will find suboptimal solutions for optimizing both path and velocity history of the trajectory by the use of piecewise joint-space polynomials is presented. This algorithm exploits the robot arm dynamics in realistic environments where obstacles are present and the minimization of task time is desired with smooth motion. Experimental results show that as the path tolerance increases the new algorithm takes advantage of the spatial freedom to provide solutions superior to conventional approaches and to methods based on predefined paths.
19 Feb 1988
TL;DR: This paper concerned with the adaptive control of a robot manipulator with two degrees of freedom with the aim of generating the control signals for movement of the arm through the use of ANN.
Abstract: Fast real-time intelligent control of dynamic systems can be implemented with a combination of logic-based (higher level) strategies and automatic reflexive pattern driven responses generated with artificial neural-nets (ANN). In this paper we are concerned with the adaptive control of a robot manipulator with two degrees of freedom. The objective is to move the end effector of a two limbed manipulator towards a target point until the positions of two coincide. The task is to generate the control signals for movement of the arm through the use of ANN. Control algorithm is computationally simple and robust due to the exploitation of highly parallel information processing capabilities of multilayered neural-nets. Feasibility of obstacle avoidance is discussed also. The proposed approach was evaluated with a computer simulation. A feedforward neural-net was used for this purpose. The results are presented and discussed in this paper.
01 Dec 1988
TL;DR: In this paper, the authors proposed an obstacle avoidance strategy (OAS) which translates each state constraint (obstacle) into a state-dependent control constraint (SDCC), and then the intersection of the SDCC sets with the hard control bounds forms a polygon in the control space.
Abstract: A novel approach is suggested to the problem of obstacle avoidance for a point robot moving among circular or elliptical/spherical or ellipsoid obstacles. The obstacle avoidance strategy (OAS) translates each state constraint (obstacle) into a state-dependent control constraint (SDCC). Each SDCC defines a hyperplane in the control space u. The intersection of the SDCC sets with the hard control bounds forms a polygon in u. The optimal decision strategy (ODS) control algorithm is then used to find the control which lies in this polygon-assuring obstacle avoidance-and minimizes the deviation between the acceleration vector of the point robot and a desired acceleration field. Simulation results display the effectiveness of the algorithm for a workspace hosting multiple obstacles. The OAS algorithm has been implemented successfully on a small Cartesian-coordinate robot. >
01 Dec 1988
TL;DR: The development of automatic guidance is discussed for helicopter Nap-of-the-Earth (NOE) and near-NOE flight and the application of Defense Mapping Agency (DMA) digital terrain to both the mission planning workstation and toautomatic guidance is both discussed and illustrated.
Abstract: The development of automatic guidance is discussed for helicopter Nap-of-the-Earth (NOE) and near-NOE flight. It deals with algorithm refinements relating to automated real-time flight path planning and to mission planning. With regard to path planning, it relates rotorcraft trajectory characteristics to the NOE computation scheme and addresses real-time computing issues and both ride quality issues and pilot-vehicle interfaces. The automated mission planning algorithm refinements include route optimization, automatic waypoint generation, interactive applications, and provisions for integrating the results into the real-time path planning software. A microcomputer based mission planning workstation was developed and is described. Further, the application of Defense Mapping Agency (DMA) digital terrain to both the mission planning workstation and to automatic guidance is both discussed and illustrated.
TL;DR: A distributed hierarchical planning and execution monitoring system and its implementation on an actual mobile robot and a planning solution to the ‘Boxes and Wedge’ Problem is presented.
07 Dec 1988
TL;DR: In this article, the authors deal with an online planning algorithm for robot navigation and manipulation tasks in unstructured, dynamic environments, where sensory information is incomplete and must be expanded and/or redefined by active sensing during an exploratory motion phase.
Abstract: The authors deal with an online planning algorithm. The work is motivated by robot navigation and manipulation tasks in unstructured, dynamic environments. It is assumed that sensory information is incomplete and must be expanded and/or redefined by active sensing during an exploratory motion phase. Candidate targets are modeled as attractors, while obstacles are modeled as repellers. Path planning is reduced to an iterative Newton scheme that can readily adapt to changes in the environment and to new sensory information. Julia sets are used to detect and avoid chaotic convergence. >
01 Jan 1988
TL;DR: An effort in developing automatic guidance algorithms to meet the functional requirements of obstacle-avoidance guidance is presented, along with the necesssary simulation tools for evaluation of these algorithms.
Abstract: This paper studies the notion of obstacle-avoidance guidance, and investigates the issues in automating this function by considering helicopter nap-of-the-earth (NOE) flight as an example. In particular, it considers a hierarchy of guidance components, including mission planning and obstacle avoidance. Based on this hierarchical breakdown, the functional requirements of obstacle-avoidance guidance are identified. An effort in developing automatic guidance algorithms to meet these requirements is presented, along with the necesssary simulation tools for evaluation of these algorithms.
TL;DR: A description is given of research that applies techniques from computer vision to automation of rotorcraft navigation, especially when flying low to avoid detection by an enemy, based on a methodology for detecting the ranges to obstacles in the region of interest based on the maximum utilization of passive sensors.
Abstract: A description is given of research that applies techniques from computer vision to automation of rotorcraft navigation, especially when flying low to avoid detection by an enemy. The effort emphasizes the development of a methodology for detecting the ranges to obstacles in the region of interest based on the maximum utilization of passive sensors. The range map derived from the obstacle detection approach can be used as obstacle data for the obstacle avoidance in an automatic guidance system and as advisory display to the pilot. The lack of suitable flight imagery data, however, presents a problem in the verification of concepts for obstacle detection. This problem is being addressed by the development of an adequate, flight database and by preprocessing of currently available flight imagery. Some comments are made on future work and how research in this area relates to the guidance of other autonomous vehicles. >
16 Dec 1988
TL;DR: A model of the motion analysis subnetwork in the vertebrate retina to visual navigation in the AUV is applied and is appropriate for implementation in VLSI optoelectronics.
Abstract: Real-time motion analysis would be very useful for autonomous undersea vehicle (AUV) navigation, target tracking, homing, and obstacle avoidance. The perception of motion is well developed in animals from insects to man, providing solutions to similar problems. We have therefore applied a model of the motion analysis subnetwork in the vertebrate retina to visual navigation in the AUV. The model is currently implemented in the C programming language as a discrete- time serial approximation of a continuous-time parallel process. Running on an IBM-PC/AT with digitized video camera images, the system can detect and describe motion in a 16 by 16 receptor field at the rate of 4 updates per second. The system responds accurately with direction and speed information to images moving across the visual field at velocities less than 8 degrees of visual angle per second at signal-to-noise ratios greater than 3. The architecture is parallel and its sparse connections do not require long-term modifications. The model is thus appropriate for implementation in VLSI optoelectronics.