Showing papers on "Collision avoidance published in 1992"

Real time three dimensional geo-referenced digital orthophotograph-based positioning, navigation, collision avoidance and decision support system

Abstract: Herein is presented a positioning, navigation and collision avoidance system for ships, aircraft, land vehicles and the like, which utilizes a geo-referenced digital orthophotograph data-base and a positioning signal to display upon a computer stereo graphics device a high visibility dynamic photographic image of the user's immediate environment, including both moving and stationary obstacles. The position and temporal data along with the geo-referenced elevation data utilized to derive the digital orthophotograph(s) can serve to warn the user of nearby obstacles; and optionally, to implement semi-automatic avoidance. Substituting user generated x-y-z positions and times, the system may be used in a static mode as a flight simulator or a simulator for other modes of transportation. The system may also be used as a mobile Geographic Information Systems decision making tool with the addition of user supplied geo-referenced digital data layers.

A capacitance-based proximity sensor for whole arm obstacle avoidance

Abstract: The authors address the issue of collision avoidance in unknown or partially modeled environments using a capacitative sensor. An eight channel capacitance-based sensor system which can detect obstacles up to 400 mm away has been developed. This sensor can detect both conductive and nonconductive obstacles of arbitrary color and shape. The sensor hardware was reliable and inexpensive, and may be fabricated using flexible printed circuit boards to provide whole-arm and joint protection for any robot or manipulator. Simple collision avoidance control algorithms have been implemented on a two-link robot arm. The sensor and control system enable the robot arm to avoid a conductive post and a concrete block. >

Minimum-time collision-free trajectory planning for dual-robot systems

Abstract: Collision-free multirobot motion planning can be achieved in two steps: path planning and trajectory planning. Path planning finds for the robots geometric paths to avoid collision with static obstacles and trajectory planning determines how fast each robot must move along its geometric path to avoid collision with other moving robots. For a dual-robot system, a simple trajectory planning strategy is to let each robot move along its path as fast as possible and delay one robot at its initial position to avoid collision with the other robot. A sufficient condition under which this simple (thus easy to implement) strategy for dual-robot systems can achieve time optimality as well as collision avoidance, i.e., the two robots reach their final positions without colliding with each other in the minimum amount of time, is derived. A demonstrative example is presented, showing how this strategy can be used for loading and unloading applications. >

A new representation for collision avoidance and detection

Abstract: By combining the simplicity of the sphere and the power of the motion of hierarchy of detail, a novel model is proposed with applications to collision avoidance and detection in 3D. The model is based on a double spherical representation for solid bodies. First, each element making up the robot and the obstacles is approximated by a set of exterior spheres which are automatically defined. Second, another set composed of interior spheres is generated. These representations define a hierarchy, since they can be redefined as many times as necessary; starting with two spheres per element, the approximation may be improved until it contains hundreds of spheres. Moreover, they converge to a zero-error representation. The proposed models leads to a simple treatment for the problem of collision detection, and it is further applied to collision-free path planning for manipulators in 3D. >

Fast distance computation for on-line collision detection with multi-arm robots

Abstract: A fast method for computing the collision vector for online collision detection with a multi-arm robot is presented. Manipulators and obstacles are modeled by sets of convex polytopes. Known distance algorithms serve as a foundation. To speed up the collision detection dynamic obstacles are approximated by geometric primitives and organized in hierarchies. Online, the dynamic hierarchies are adjusted to the current arm configuration. A comparison with previous methods showed an increased acceleration of the computations. >

Sonar Based Outdoor Vehicle Navigation And Collision Avoidance

Abstract: Abstruct - Detecting unexpected obstacles and avoiding collisions is an important task for any autonomous mobile system. This paper describes an approach using a sonar system that we implemented for the autonomous land vehicle Navlab. The general hardware configuration of the system is shown, followed by a description of how the system builds a local grid map of its environment. The information collected in the map can then be used for a variety of applications in vehicle navigation like collision avoidance, feature tracking and parking. A simple algorithm was implemented that can track a static feature such as a rail, wall or an array of parked cars and use this information to drive the vehicle. Methods for filtering the raw data and generating the steering commands are discussed and the implementation for collision avoidance and its integration with other vehicle systems is described. I. INTRODUCTION The autonomous land vehicle Navlab has already successfully been driven on roads and cross country. Different sensors are used to perceive the structure of the environment and navigate the vehicle under a variety of conditions as described for example in [SI. The sensors mainly employed so far were colour video

Coordination and control of multiple autonomous vehicles

Abstract: The DARPA SIMNET project allows hundreds of soldiers to train together in a virtual air, land, and sea environment through a network of interactive simulators. In addition to the manned simulators, the virtual environment is also populated by a large number of autonomous vehicles called semi-automated forces, which are controlled by an operator at a single workstation. The authors address the issues of collision avoidance and formation keeping. The autonomous vehicles are responsible for the lower-level path planning, collision avoidance, and formation following. Routines are described for maneuvering among large obstacles, smaller objects, and moving vehicles. >

Design method for an automotive laser radar system and future prospects for laser radar

Abstract: Presents a technical explanation of the specific procedure used in designing an automotive laser radar system. Laser radar represents an effective collision avoidance technology that can contribute to improved vehicle and traffic safety. An analysis is given of the problems involved in the practical application of laser radar and ways of overcoming them. The future prospects for automotive laser radar are also discussed. >

A Real-time Algorithm for Obstacle Avoidance of Autonomous Mobile Robots

Abstract: A real-time obstacle avoidance algorithm is proposed for autonomous mobile robots. The algorithm is sensor-based and consists of a H-mode and T-mode. The algorithm can deal with a complicated obstacle environment, such as multiple concave and convex obstacles. It will be shown that the algorithm is more efficient and more robust than other sensor-based algorithms. In addition, the algorithm will guarantee a solution for the obstacle avoidance problem. Since the algorithm only takes up a small computational time, it can be implemented in real time.

System aspects and design of an automotive collision warning PN code radar using wavefront reconstruction

Abstract: A collision avoidance system for automobiles to be used in freeways and similarly structured traffic environments is under study. The authors report on concepts, the state of realization and on first experimental results. A two-dimensional imaging problem has to be solved because the mere detection of objects in front of a vehicle is not sufficient; potential paths of collision can only be recognized by assigning objects to their surroundings. While digital wavefront reconstruction was used for angular discrimination, a high-resolution pseudonoise code radar applying a binary phase modulation to a continuous carrier has been implemented for longitudinal resolution. The laboratory evaluation has confirmed the specifications regarding essential system parameters such as radial resolution and sensitivity. >

Is visual reconstruction necessary? obstacle avoidance without passive ranging

Abstract: Is it possible to perform nontrivial visual tasks without using passive ranging? Is it necessary to create, using vision, an accurate 3-D description of the outside world to recognize, navigate, and manipulate? Could a visual system perform obstacle avoidance without reconstructing the depth of the scene in view, but through the recognition of a collision in some amount of time that is quite small and not far into the future? In this article, it is shown that it is possible to avoid obstacles without recovering depth and a detailed algorithm is provided for obstacle avoidance using the spatiotemporal derivatives of the image intensity function as input. © 1992 John Wiley & Sons, Inc.

A fast, on-line collision avoidance method for a kinematically redundant manipulator based on reflex control

Abstract: A computationally efficient method to achieve reflexive collision avoidance is described. The system consists of four parallel, asynchronous control layers: a conventional servo tracking controller, a reactive trapezoidal velocity profiler, a joint-by-joint reflexive collision avoidance layer, and a guiding potential-function layer. The lowest two layers guarantee that the robot will not overshoot any joint-space position setpoint. The higher two layers compute successive set points based on a continuous, online inspection of configuration space. The guiding potential-function layer incorporates task-space-based attraction to a hand goal, while the reflexes permit use of kinematic redundancy for obstacle avoidance. In many cases, no explicit path planning is required to achieve competent, collision-free motion to a task-space goal while moving in a cluttered environment. Experimental results are described for the physical implementation of the system on the first four joints of a kinematically redundant robot. >

Vehicle collision avoidance

Abstract: Vehicle collision avoidance apparatus for a motor vehicles measures the speed and distance of an approaching vehicle using a rearwardly directed laser measuring beam. A collision risk factor is computed and an appropriate display generated. The display may consist of the progressive activation of the vehicle's existing brake, rear fog and hazard warning lights. A dedicated display can be provided, visible to the driver of the rearwardly approaching vehicle.

Collision avoidance systems: effects of different levels of task allocation on driver behaviour

Abstract: The effects on driver behaviour, workload, and acceptance, of different levels of task allocation between a collision avoidance system (CAS) and the driver, were studied in an advanced driving simulator. Driving performance was described in terms of time headway, speed level, lateral position, and left lane driving (including overtaking behaviour). Workload was measured with the NASA-TLX questionnaire, acceptance with attitude questions. Forty subjects, between 23 and 58 years and experienced as drivers, were randomly assigned to four experimental conditions. It was found that a CAS system capable of taking over the control of the car produced the most favourable effects on drivers headway, and also reduced the number of overtakings. But, seen from the drivers point of view, that system was regarded as the most intrusive, and also most disturbing system. It was recommended that a GIDS, CAS system should either give a warning, or suggest an appropriate action. It was also found that the use of the intelligent gas pedal, as a link between driver and CAS, did not lead to an increase of the drivers' workload. Finally, some consequences of the time to collision criteria were discussed. This is a reprint from DRIVE project V1041 Generic Intelligent Driver Support Systems (GIDS), Sept 1991. (A)

An integrated collision prediction and avoidance scheme for mobile robots in non-stationary environments

Abstract: A formulation that makes possible the integration of collision prediction and avoidance stages for mobile robots moving in general terrains containing moving obstacles is presented. A dynamic model of the mobile robot and the dynamic constraints are derived. Collision avoidance is guaranteed if the distance between the robot and a moving obstacle is nonzero. A nominal trajectory is assumed to be known from off-line planning. The main idea is to change the velocity along the nominal trajectory so that collisions are avoided. A feedback control is developed and local asymptotic stability is proved if the velocity of the moving obstacle is bounded. Simulation results verify the value of the proposed strategy. >

WDM passive star networks: receiver collisions avoidance algorithms using multifeedback learning automata

Abstract: A receiver collision avoidance algorithm for WDM broadcast-and-select star networks is introduced. It is based on the use of learning automata to reduce the number of receiver collisions and, consequently, to improve the performance of the network. Each station has a learning automaton that decides which of the packets waiting for transmission will be transmitted at the beginning of the next time slot. The learning automaton used is a multifeedback automaton, specially designed for the receiver collision avoidance problem of WDM broadcast-and-select star networks. The asymptotic behavior of the system, which consists of the automata and the network, is analyzed. The probability of choosing each packet asymptotically tends to be proportional to the probability that no receiver collision will appear at the destination node of this packet. Extensive simulation results indicate that a significant performance improvement can be achieved when the algorithm is applied on the basic DT-WDMA protocol. >

The Development of Ship Collision Avoidance Automation

Abstract: This paper reviews the history and the evolution of international ship collision avoidance research. The direction which research should take in the Chinese People's Republic is discussed and the authors recognize that new ideas may be needed to take account of the conditions in their country.

Aircraft collision avoidance using statistical decision theory

Abstract: Collision avoidance involves the detection of impending collisions of an aircraft with either another aircraft or the ground from radar data and the timely alert of the danger to the pilot or air-traffic controller. The challenge is to provide sufficient warning (timely detections) with minimal false alarms. Radar measurement uncertainties degrade collision detection performance and must be accounted for in the algorithm design. This paper describes a method which uses statistical decision theory to control both missed or late detections and false alarms. The key to the technique is the mathematical description of the aircraft corridor uncertainty region. The corridor uncertainty region is derived from the position and velocity confidence ellipsoid associated with the aircraft radar track via a mapping from six dimensional space to three. By careful choice of the mapping, the minimum volume corridor uncertainty region is derived. This allows for the definition of the optimal collision avoidance decision rule. Since the method is based solely on the statistical properties of an aircraft's position and velocity track, it may be adapted to a variety of collision avoidance or guidance problems involving a radar or beacon-type sensors such as Mode C or Mode S.

An experimental evaluation of in-vehicle collision avoidance systems

Abstract: This report describes a simulator study in which seven candidate in- vehicle CAS (collision avoidance systems) were compared as to their effects on driving behavior in car-following situations. The use of the CAS systems studied is accompanied by behavioral changes affecting the way in which the driving task is performed. In general, the following effects seem to be associated with the availability of a CAS: 1) a change in the distribution of time headways, in particular a reduction in the occurrence of very short headways, 2) an increase in driving speed, 3) an increase in acceleration and deceleration levels and 4) an increase in time spend driving in the left land of the road.

Network management in short-range mobile radio networks: Performance tuning optimizes collision behaviour

Abstract: The authors evaluate several network management algorithms to increase the performance of short-range mobile radio networks concerning collision avoidance and reduction of collision duration measured in frames. It is shown that suitable choice of transmission power with independent antenna systems fulfils requirements of applications while increasing the communication performance. The evaluations are made by simulations of a three-lane unidirectional highway. It is shown that earlier investigations of optimal transmission ranges are not satisfactory compared to the requirements of applications. >

All terrain ground collision avoidance and maneuvering terrain following for automated low level night attack

Abstract: The development of an all-terrain ground collision avoidance system (GCAS) in conjunction with a maneuvering terrain following (TF) system is discussed. Both systems use a digital terrain database. The unprecedented pilot interaction available with the automatic systems provides a means to significantly improve combat survivability. The pilot is able to execute high rate turns, evasive maneuvers, and inverted ridge crossings while following the terrain contour. Safety is maintained in day, night, and weather by the ground collision avoidance system. The combination of these systems with an automated attack system, an automatic target handoff system, a night vision system, and a route planner to provide a lethal night attack capability is discussed. Piloted simulation and preliminary flight test results are presented. It is concluded that the GCAS is sufficiently mature to make the transition to operational use. The TF algorithm works well, but flight testing is incomplete. >

Survey of Collision Avoidance and Ranging Sensors for Mobile Robots. Revision 1

Abstract: : The past few years have brought about a tremendous rise in the envisioned potential of robotic systems and a significant increase in the number of proposed applications In the nonindustrial arena, numerous programs have evolved, each intending to harness some of this promise in hopes of solving some particular application need Many of these efforts are government sponsored, aimed at the development of systems for fighting fires, handling ammunition, transporting materials, conducting underwater search and inspection operations, and patrolling warehouses and storage areas, etc Many of the resulting prototypes, which were initially perceived as logical extensions of the traditional industrial robotic scenarios, have met with unexpected difficulty due to an insufficient supporting technology base This document provides some basic background on the various noncontact distance measurement techniques available, with related discussion of implementation in the acoustical, optical, and electromagnetic portions of the energy spectrum An overview of candidate systems, both commercially available and under development, is provided; followed by a brief summary of research currently underway in support of the collision avoidance and noncontact ranging needs of a mobile robot Robotics, Sensors, Artificial intelligence, Security