Showing papers on "Collision avoidance published in 1989"

Aircraft instrument systems

Abstract: An aircraft collision avoidance instrument system has a display located in the aircraft glareshield in the peripheral field of view of the pilot when the pilot is looking forwardly through the aircraft window. The display has a matrix array of LCD elements which is controlled to provide a continually changing image that is visible in the peripheral field of view of the pilot when a possible collision with another aircraft is likely. The changing image may be arrows moving up or down the display to indicate climb or decend, or a flashing horizontal line to indicate that present height must be maintained. An alphanumeric legend indicative of the collision avoidance action to be taken is also provided by the display. When no collision is likely, the display is used to present other information to the pilot.

Knowledge-based collision avoidance

Abstract: This paper describes preliminary studies towards a navigational Knowledge-based System currently in progress within the School of Engineering and Technology Management at Liverpool Polytechnic

Ship collision-avoidance and pursuit-evasion differential games with speed-loss in a turn

Abstract: In this paper the problem is addressed of modelling the encounter of two ships in a seaway from the dual points of view of collision-avoidance and pursuit-evasion maneuvers. The pronounced effect of speed-loss experienced by ships during a (fixed throttle) turn ins incorporated into the model. In the first part of the paper due attention is given to modelling issues germane to ship performance. During a fixed rudder turn the turning radius of a ship remains constant. This, in turn, allows us to employ the classical “game of two cars” and “homicidal chauffeur” kinematic models (which have been modified to include the bleeding off of speed during the turn). The methods of the theory of differential games are then employed to yield a solution to the qualitative (preliminary) problems of establishing the safe zone or the capture zone in collision avoidance or pursuit-evasion, respectively. We mainly analyze the simpler “homicidal chauffeur” model, but it also becomes evident how specific instances of the more difficult but also more realistic variable speed “game of two cars” formulation should be treated.

Simulated Collision Avoidance Manoeuvres: a Parametric Study

Abstract: Research on collision avoidance during ships' meeting encounters has been carried out primarily through the analysis of shore-based radar ship track data or by using simulators to directly study watchkeeper behavior. It seemed useful to bring the two lines of inquiry closer together: to provide approaches to the modeling of ship encounters with a source of data obtained under experimental control to supplement the remote observations, and to apply theoretical model- fitting to the experimental data obtained in simulator studies. A study performed to fulfill this objective and so enable more detailed interpretation of behavioral differences between individual watchkeepers is described.

Collision avoidance between mobile robots

Abstract: This paper presents a local approach to real-time collision avoidance between mobile robots based on velocity vector modification method. In the approach, a risk evaluation function of neighbouring two mobile robots is introduced to detect their potential collision and to lead the velocity modification method. Simulation results show the validity of this method. In this paper, a local approach to real-time collision avoidance of two dimensional mobile robots is proposed being based on a velocity vector modification method. A distance function obtained from the state information of neighbouring mobile robots is introduced to evaluate the risk of collision. The desired velocity vector is determined in accordance with the encounter situation of robots resulting from a risk evaluation. This method is demonstrated by several cases of four mobile robots. Here we concentrate our attention to the velocity modification strategy which allows multiple mobile robots to avoid collision each other during their navigation. Little will be said about the motion control of mobile robots, except to show that our method is applicable to real time motion control of robots. of mobile robots includes following four stages: In the approach, the collision avoidance procedure

Tree LANs with collison avoidance: station and switch protocols

Abstract: Packet collisions and their resolution create a performance bottleneck in random access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the implementation of random access protocols without the penalty of collisions among packets. We describe some tree LANs that use collision avoidance switches. These LANs have the potential of combining the benefits of random access (low delay when traffic is light; simple, distributed, and therefore robust, protocols) with concurrency of transmission and excellent network utilization. The collision avoidance LANs we describe are broadcast star, CASB Tree (Collision Avoidance Single Broadcast Tree), CAMB Tree (Collision Avoidance Multiple Broadcast Tree), and Tinker Tree.

A tree LAN with collision avoidance: photonic switch design and simulated performance

Abstract: In order to solve a performance bottleneck due to collisions and their resolution in random access LANs, a new network architecture called CAMB (Collision Avoidance Multiple Broadcast) Tree Network is proposed in a companion paper. It is based on collision avoidance switches, which allow the implementation of random access protocols without the penalty of collisions among packets. After briefly describing the CAMB Tree, we discuss the suitability of this network for high-speed, lightwave communications, and we propose a possible implementation of a collision avoidance switch using current photonic technology. We then present simulation results and show how the CAMB Tree performance depends on network traffic conditions.

Development of an Automatic Ground Collision Avoidance System Using a Digital Terrain Database

Abstract: : Several ground collision avoidance systems (GCAS) have been developed to warn the pilot of a potential collision with the terrain is some action is not taken. All current systems have shortcomings pertaining to the sensors that are used and the recovery maneuver that is flown. The USAF is evaluating the potential of digital terrain databases for onboard navigation and terrain avoidance in combat aircraft. The purpose of this thesis was to develop a control system for performing terrain avoidance using a simulated terrain database. This study was conducted for an F-16 aircraft in level flight at 0.6 Mach and sea level conditions. A state-space model of the aircraft and its flight control system was developed using aircraft control derivatives, an F-16 control law diagram, and traditional linearization techniques on the aircraft equations of motion. A control system for implementing terrain avoidance was derived based on the look-ahead capability of the terrain database. Control system response was evaluated using a simulated terrain obstacle and various look-ahead distances on the terrain database. Results indicated that a 1200 foot, or roughly 1.8 second, look-ahead distance provided good improvement in terrain avoidance capabilities for the F-16 compared to looking strictly downward from the aircraft for terrain information. Theses.

Robot path planning using a potential field representation.

Abstract: Finding a safe, smooth, and efficient path to move an object through obstacles is necessary for object manipulation in robotics and automation. This thesis presents an approach to the two-dimensional as well as three-dimensional findpath problems that divide the problem into two steps. First, rough paths are found based only on topological information. This is accomplished by assigning to each obstacle an artificial potential similar to the electrostatic potential to prevent the moving object from colliding with the obstacles, and then locating minimum potential valleys. Second, the paths defined by the minimum potential valleys are modified to obtain an optimal collision-free path and orientations of the moving object along the path. Three algorithms are given to accomplish this second step. The first algorithm simply minimizes a weighted sum of the path length and the total potential experienced by the moving object along the path. This algorithm solves only "easy" problems where the free space between the obstacles is wide. The other two algorithms are developed to handle the problems in which intelligent maneuvering of the moving object among tightly packed obstacles is necessary. These three algorithms based on potential fields are nearly complete in scope, and solve a large variety of problems.

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.

Frame collision avoidance control method

Abstract: PURPOSE:To prevent the occurrence of collision of frames due to simultaneous timeout of plural stations by setting a timer count of a controller of a data communication system so as to be deviated from that of other station automatically, thereby allowing the user to eliminate the consciousness to other station. CONSTITUTION:A host processor 20 of a frame collision avoidance control system processes a data and a communication control processing unit 21 controls the communication. Moreover, a program group operating the unit 21 is stored in a network control program 22. A multiple address control section 23 of the program 22 controls the multiple address communication. Furthermore, a timer value is set to a multiple address communication control table 14 to supply it to transmission acknowledgement waiting timer start of the control section 23. The timer is set so as to diviate the value from the other station automatically, thereby eliminating the need for the user to be aware of the other station and preventing the occurrence of collision of frames due to simultaneous timeout of plural stations.

Method for collision avoidance in systems with driverless vehicles and vehicle equipment for vehicles for carrying out the method

Abstract: In order to avoid collisions between vehicles in systems with driverless vehicles, transmitters and receivers, which can be used alternatively, for energy radiations are arranged on these vehicles. Measurements which are based on the respective time elapsing between transmission and reception supply a signal. In this case, two radiations are emitted at a different propagation rate, of which one radiation is emitted as activation radiation at a higher propagation rate than the other radiation. The received difference between the various radiations is measured as a parameter for a separation value.

An algorithm with real-time response for avoiding moving obstacles

Abstract: A method is presented for modeling the trajectories of a robot and obstacles in three spaces (x, y, and time) such that potential collisions can be detected in a direct manner; no a priori knowledge of the obstacle's trajectory is required. Having determined that a collision will occur, a method for avoiding such collisions by altering the time and space trajectory for the robot is presented. The modeling has been intentionally designed to be succinct enough that the collision avoidance algorithm can run in real-time, thus making it suitable for inclusion as part of a robot navigation system for a real mobile robot. Results of simulations are presented and discussed. >

Two-armed robot systems-a review of current theory and the development of algorithms for real-time collision avoidance

Abstract: The applications of two-armed robots is discussed and a review carried out of the main control methods. The teleoperation of robotic systems is then discussed and the need for good operator visualisation coupled with minimum work load was identified as the key to system efficiency. The collision problem is discussed and the method of detecting and avoiding collisions are presented. The authors also identify the need for a real-time collision avoidance system suitable for two co-operating teleoperated arms, and develop a kinematics based modelling scheme which could be used for collision detection and avoidance. >

Cars that know where they're going

Abstract: The article describes new automobile electronic devices and navigation systems that will help drivers reach their destination faster, avoid traffic jams, and even find a parking space. Presently, on-board computer systems can control the engine, prevent the wheels from locking when braked, and adjust the suspenion when the car is carrying a heavy load or when the road is bad. The next major step will be the addition of navigation computers. Later generations of smart cars will integrate these systems with collision avoidance systems and automatic headway control. The use of proximity beacons and the Electronic Route Guidance System (ERGS) research by the U.S. government is described. Satellite approaches to automobile navigation, and General Motors and Chrysler research in this area are also discussed. Dead reckoning and map matching are described. Navigation systems near the market stage of development are reviewed and include Electro Multivision (Toyota); Etak Navigator used by General Motors; CARIN (developed in the Netherlands); ALI-SCOUT; and MAPIX-III. Government-industry cooperative programs will determine how fast these developments are available.

Improvements to aircraft collision avoidance

Abstract: A collision avoidance arrangement where aircraft transmits and receives radio signals modulated by a digital pulse sequence (34), if a potential collision is detected (35) the arrangement is adapted to transmit and receive interrogation radio signals and from these signals each aircraft estimates the closing speed of the aircraft (36) and then determines the range between the aircraft (37), and the arrangement also being adapted such that each aircraft transmits to the other the estimate of the closing speed calculated aboard the aircraft and then averages the estimates of the closing speed from each aircraft to obtain a more accurate value for the closing speed of the aircraft.

General Aviation Collision‐Avoidance Alternatives

Abstract: Midair collisions are often perceived as the number‐one safety issue in aviation. Though the actual incidence of such accidents is (thankfully) small, public perception of the problem, and the government's reaction to it, may threaten the very future of general aviation. Midair collisions are primarily a general aviation problem. Its solution starts with the review of accident statistics and nearmidair report data, an exploration of prior art, and an understanding of the capabilities and limitations of TCAS (Threat alert and Collision Avoidance System), the FAA's supplement to visual traffic avoidance. This paper contemplates the need for an “ideal” general aviation collision avoidance system—one which is selfcontained, noncooperative in nature (requiring no equipment in the “other” plane), transparent to the Air Traffic Control System, and fully compatible with TCAS and all other FAA proposals.

Collision avoidance in vehicular traffic

Abstract: Presents new and comprehensive strategies for on-line collision avoidance by an autonomously operating vehicle. In this system, when danger of collision suddenly occurs, the board acts independently and initiates maneuvers to avoid the collision. The vehicle is exclusively sensor guided. The collision avoidance strategy assumes that all other vehicles are non-cooperating obstacles. The collision avoidance strategy is based on a hierarchically structured concept of automated vehicle guidance.

A collision avoidance system for a spaceplane manipulator arm

Abstract: Part of the activity in the area of collision avoidance related to the Hermes spaceplane is reported. A collision avoidance software system which was defined, developed and implemented in this project is presented. It computes the intersection between the solids representing the arm, the payload, and the objects. It is feasible with respect to the resources available on board, considering its performance.

A Fast Method of Collision Avoidance for an Articulated Two Link Planar Robot using Distance Functions

Abstract: This paper presents a heuristic method of collision avoidance for robots with two degrees of freedom. The algorithm is simple, geometrically intuitive and strongly uses distance functions for its implementation. The method is applied to an articulated, two link planar arm and shown to generate good paths using only short computing times.

Taking the crush out of rush hour

Abstract: The article describes several conventional and innovative measures that will relieve highway congestion. Computerized traffic lights guided by magnetic sensors set in the pavement, and computerized dashboard navigation systems for drivers are described. The pilot program, Pathfinder, launched by the Federal Highway Adminstration, the California Department of Transportation and General Motors in the Santa Monica Freeway will relay traffic information to cars via radio or cellular phone, and navigational systems will display alternate routes. The $875 million Prometheus program (with its navigator called Autoguide) in Europe is also described. Other proposed electronic systems include devices that alleviate traffic by allowing 'safe' tailgating by cars with radar devices on car brakes and accelerators. Developments is this area are described. Collision avoidance systems, as well as car trains are described. Apart from the technical feasibility of these systems, other issues that would have to be resolved before these systems could be broadly used are noted.

Collision detection between the wrists of two robot arms in a common workspace

Abstract: Detecting collisions for planning collision-free motion of the wrists of two robot arms in a common workspace is discussed in this paper. A collision-free motion can be obtained by detecting collisions along the preplanned trajectories using a sphere model for the wrist of each robot and then modifying the paths and/or trajectories of one or both robots to avoid the collision. In this paper, a collision detection algorithm is described and its role in collision avoidance is discussed. Collision detection is based on the premise that (1) the wrists of robots move monotonically on their preplanned straight line trajectories and (2) collisions never occur between the two wrists at the beginning points or end points.