Showing papers on "Collision avoidance published in 2000"

Implementing fast cloth simulation with collision response

Abstract: The article details and implements efficient techniques for cloth simulation, both in the area of numerical simulation and the area of collision detection and response. Emphasis is put on the efficient implementation of implicit numerical methods with many improvements toward better realism, as well as computation simplicity. A constraint based collision response scheme is adapted to this scheme in order to provide an accurate and stable collision response.

Nearness diagram navigation (ND): a new real time collision avoidance approach

Abstract: This paper presents a new real-time collision avoidance approach for mobile robots. The nearness diagram method (ND) performs a high level information extraction and interpretation of the environment. Subsequently, this information is used to generate the motion commands. The proposed approach is well-suited to deal with unknown, unstructured and dynamic environments, where problems of other approaches are avoided. Some experimental results are shown using an holonomic mobile base to demonstrate the usefulness of the method.

Mobility assist device

Abstract: The present invention is directed to a visual mobility assist device which provides a conformal, augmented display to assist a moving body. When the moving body is a motor vehicle, for instance (although it can be substantially any other body), the present invention assists the driver in either lane keeping or collision avoidance, or both. The system can display objects such as lane boundaries, targets, other navigational and guidance elements or objects, or a variety of other indicators, in proper perspective, to assist the driver.

High-level modeling and analysis of the traffic alert and collision avoidance system (TCAS)

Abstract: We demonstrate a high-level approach to modeling, analyzing, and verifying complex safety-critical systems through a case study on the traffic alert and collision avoidance system (TCAS); an avionics system that detects and resolves aircraft collision threats. Due to the complexity of the TCAS software and the hybrid nature of the closed-loop system, the traditional testing technique of exhaustive simulation does not constitute a viable verification approach. Moreover, the detailed specification of the system software employed to date as a means toward analysis and verification neither helps in intuitively understanding the behavior of the system nor enables the analysis of the closed-loop system behavior. We advocate defining high-level hybrid system models that capture the behavior not only of the software but also of the airplanes, sensors, pilots, etc. In particular, we show how the core components of TCAS can be captured by relatively simple hybrid I/O automata, which are amenable to format analysis. We then outline a methodology for establishing conditions under which TCAS guarantees sufficient separation in altitude for aircraft involved in collision threats. The contributions of the paper are the high-level models of the closed-loop TCAS system and the demonstration of the usefulness of high-level modeling, analysis, and verification techniques.

Collision avoidance and resolution multiple access for multichannel wireless networks

Abstract: We introduce and analyze CARMA-MC (for collision avoidance and resolution multiple access for multiple channels), a new stable channel access protocol for multihop wireless networks with multiple channels. CARMA-MC relies on the assignment of a unique channel and a unique identifier to each node to support correct deterministic collision resolution in the presence of hidden terminals. CARMA-MC dynamically divides the channel of each node into cycles of variable length; each cycle consists of one or more receiving periods and a transmission period. During the receiving period, stations with one or more packets to send compete for the right to acquire the floor of a particular receiver's channel using a deterministic tree-splitting algorithm. Each receiving period consists of collision resolution steps. A single round of collision resolution (i.e., a success, and idle or a collision of control packets) is allowed in each contention step. The receiving period is initiated by the receiver and takes place in the channel assigned to the receiver station. The channel utilization and packet delays are studied analytically and by simulation.

An algebraic solution to the problem of collision detection for rigid polyhedral objects

Abstract: This paper describes a new collision detection algorithm designed for interactive manipulation in virtual environments. Making some assumptions on object motion, the collision time between two objects can be computed by solving a polynomial equation whose degree is equal to or smaller than three.

Neural Nets Trained by Genetic Algorithms for Collision Avoidance

Abstract: As air traffic keeps increasing, many research programs focus on collision avoidance techniques. For short or medium term avoidance, new headings have to be computed almost on the spot, and feed forward neural nets are susceptible to find solutions in a much shorter amount of time than classical avoidance algorithms (i>Aa, stochastic optimization, etc.) In this article, we show that a neural network can be built with unsupervised learning to compute nearly optimal trajectories to solve two aircraft conflicts with the highest reliability, while computing headings in a few milliseconds.

Multifunction aircraft transponder

Abstract: A combined airborne Air Traffic Control Radar Beacon System/Mode-Select (ATCRBS/Mode-S) surveillance system and Traffic Alert and Collision Avoidance (TCAS) collision avoidance system device having common antennas and a switch coupling the common antennas to the relevant functions.

Cooperative Collision Avoidance between Multiple Mobile Robots

Abstract: This paper presents a new collision avoidance technique, called cooperative collision avoidance, for multiple mobile robots. The detection of the danger of collision between two mobile robots is discussed with respect to the geometric aspects of their paths as are cooperative collision avoidance behaviors. The direction control command and the velocity control command for the cooperative collision avoidance are then proposed. The avoidance technique is extended to cases in which the number of mobile robots is more than two. Furthermore, the conditions for collision avoidance are considered with respect to the navigation parameters and guidelines of designing the navigation parameters are obtained. The effectiveness of the proposed technique is demonstrated by means of numerical simulation and navigation experiments using two real mobile robots named Pioneer-1. Q 2000 John Wiley & Sons, Inc.

Preliminary studies in haptic displays for rear-end collision avoidance system and adaptive cruise control system applications

Abstract: In this report, the authors examine the applicability of haptic displays for rear-end collision avoidance warnings. Concepts and published research studies are reviewed in the report. This is followed by three small-scale studies of mono-pulse braking and active steering displays. Two parameter setting studies are first discussed. The first examined the display parameter settings of a mono-pulse braking display, while the second examined the effects of active steering vibration amplitude frequency, and duration on display detectability and appropriateness ratings. Based on the results obtained, the authors suggest that active steering displays be reserved for future collision avoidance system integration. In the third study, the authors examined the response of drivers in a car following situation to a mono-pulse braking display under two different simulated rear-end collision avoidance warning scenarios. Results suggest that mono-pulse braking displays might be of use in rear-end collision avoidance applications.

Detection and avoidance of simulated potholes in autonomous vehicle navigation in an unstructured environment

Abstract: In the navigation of an autonomous vehicle, tracking and avoidance of the obstacles presents an interesting problem as this involves the integration of the vision and the motion systems. In an unstructured environment, the problem becomes much more severe as the obstacles have to be clearly recognized for any decisive action to be taken. In this paper, we discuss a solution to detection and avoidance of simulated potholes in the path of an autonomous vehicle operating in an unstructured environment. Pothole avoidance may be considered similar to other obstacle avoidance except that the potholes are depressions rather than extrusions form a surface. A non-contact vision approach has been taken since potholes usually are significantly different visually from a background surface. Large potholes more than 2 feet in diameter will be detected. Furthermore, only white potholes will be detected on a background of grass, asphalt, sand or green painted bridges. The signals from the environment are captured by the vehicle's vision systems and pre-processed appropriately. A histogram is used to determine a brightness threshold to determine if a pothole is within the field of view. Then, a binary image is formed. Regions are then detected in the binary image. Regions that have a diameter close to 2 feet and a ratio of circumference to diameter close to pi are considered potholes. The neuro-fuzzy logic controller where navigational strategies are evaluated uses these signals to decide a final course of navigation. The primary significance of the solution is that it is interfaced seamlessly into the existing central logic controller. The solution can also be easily extended to detect and avoid any two dimensional shape.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Automobile radar antenna alignment system using transponder and lasers

Abstract: A transponder ( 200 ) is attached to a laser alignment fixture ( 210 ) and used to align an automobile collision avoidance radar antenna boresite with the thrust vector of the vehicle. The alignment fixture ( 210 ) has attached reflectors for alignment with two laser beams. To align the collision avoidance radar, the transponder ( 200 ) is positioned along the thrust vector of the automobile using a first laser beam ( 203 ) aligned perpendicular to a wheel axle. The first laser beam ( 203 ) is aligned when transmitted from the wheel axle onto a first piece of reflective material attached to the alignment fixture ( 210 ). A second laser ( 216 ) is provided parallel to the centerline of the collision avoidance radar antenna to remove azimuth and elevation translation errors between the transponder antenna centerline and the collision avoidance radar antenna centerline. The second laser beam ( 216 ) is aligned when transmitted from the automobile onto a second piece of reflective material attached to the alignment fixture ( 210 ). The transponder ( 200 ) is then used to zero an angle (α) between the electrical boresite of the collision avoidance radar antenna and the boresite of the transponder antenna. The angle (α) is set to zero by adjusting the automobile collision avoidance radar antenna until a processor in the collision avoidance radar indicates the angle a is zero.

Collision avoidance among AGVs at junctions

Abstract: The movement of a vehicle in an automated guided vehicle system (AGVS) depends on the status of other vehicles present in the system. One of the objectives of automation is to have collision free movement to increase the safety. In this paper, two controllers are suggested that by design guarantee no collision between two vehicles at the junctions. The control laws obtained are used for finding out the initial conditions that will be safe under both of these laws, or at least under one law. Accordingly, the set of conditions for which collision can not be avoided is determined.

Close formation aircraft collision avoidance

Abstract: Collision avoidance systems are provided for groups of aircraft operating in close proximity, as during formation flights or cooperative missions. Fixed and rotary airfoil aircraft with separations of 30 feet to 5 miles, for example, participate in a local radio sub-net. An aircraft receiving CAS sub-net signals derives signal transit time values representing differences between send and receive times and which are used to derive data on inter-aircraft range and closing rate. With synchronized clocks, highly-accurate one-way ranging uses assigned time slots with predetermined sub-net time-of-day timing of transmissions. Round-trip ranging operates with less accurate time synchronization, and systems may operatively select between one-way and round-trip ranging. By exchange of range and closing rate data among aircraft, 3-D data for current three-dimensional location of aircraft enables evasive action determination. Data is thus made available for provision of audio and visual flight crew communications indicating alerts and warnings of impending collision danger and appropriate evasive action.

Inspection point placement and path planning algorithms for automatic CMM inspection

Abstract: This paper discusses development of automatic inspection point placement and path planning methods, for use in the integration of computer-aided design with coordinate measuring machine (CMM) inspection. The proposed system demonstrates that optimal collision-free inspection paths can be efficiently generated for geometrically complex parts consisting of multiple intersecting features. This is achieved by using iterative subdivision of surfaces for point placement coupled with, efficient 3D collision avoidance and path planning. This planning module is an integral part of an overall inspection planner to fully automate rapid and reliable inspection using computer-controlled CMMs. The paper discusses the structures and algorithms used, and presents experimental results.

Autonomous collision avoidance: the technical requirements

Abstract: Autonomous collision avoidance is necessary if Unmanned Aerial Vehicles (UAVs) are to "blacken the sky" in massed attacks, accompany manned fighters on combat missions, and transition civil airspace. These vehicles will, in some manner, have to "see and avoid" other aircraft. An automated air collision avoidance system will fulfill a part of this need. It will automatically maneuver an aircraft, at the last instant, to avoid an air-to-air collision. It will function in a manner similar to a pilot avoiding a collision. It is a system that must be reliable, verifiable, and partially redundant, forming the last line of defense against collisions. It must provide nuisance free operation and allow safe interoperability. The requirements for such a system will be discussed in detail. Of particular interest are criteria to enable a safe, nuisance free system that will have embedded rules of the road for all encounters. Autonomous control of unmanned aerial vehicles is a goal for the US Air Force in the future. However, flying multiple unmanned vehicles in the same tactical airspace with manned fighters presents very challenging problems. Autonomous collision avoidance is a necessary step in moving toward this goal.

Warp Speed: Path Planning for Star Trek®: Armada

Abstract: Star Trek®: Armada is a Real Time Strategy game (RTS) involving space combat between fleets of Federation, Romulan, Klingon, and Borg starships. Each side can have up to approximately 30 capital ships on its side, and maps can vary considerably in aspect ratio and size. Obstacles in space include moving asteroid belts (with gaps thr ough which ships can pass), nebulae which can slow ships down and cripple ships’ systems, starbases, black holes, ion storms, other ships, etc The nature of a 3D RTS is that it must be fast, and the path planning must be considerate with its CPU usage. Core algorithms such as the A* search algorithm are becoming widely accepted in the game industry. However, the key to efficient path planning is how the environment is spatially decomposed, what is left to search-based planning, what is avoided with reactive collision avoidance, and what is simply prevented with collision prevention. Star Trek®: Armada uses a quadtree decomposition of the playing field which greatly reduces the number of cells that A* needs to search. However, care must be taken to perform some kind of rubber-banding to make the paths look natural. We also use r eactive avoidance for most moving objects, and as a final safety measure we actually prevent ships from having overlapping shield ellipsoids in a post-simulation step. In this paper we shall describe the implementation of the path planning system in detail.

Intersection Collision Avoidance Using Its Countermeasures. Task 9: Final Report: Intersection Collision Avoidance System Performance Guidelines

Abstract: Phase III of the Intersection Collision Avoidance Using ITS Countermeasures program developed testbed systems, implemented the systems on a vehicle, and performed testing to determine the potential effectiveness of this system in preventing intersection crashes. The results are presented in this report in the following chapters: (1) Introduction; (2) Approach; (3) The Intersection Collision Problem; (4) Intersection Collision Avoidance System (ICAS) Testbed Design; (5) ICAS System Specifications; (6) ICAS System Analysis; and (7) Summary and Recommendations.

A multisensor-based collision avoidance system with application to a military HMMWV

Abstract: A multi-sensor collision avoidance system (GAS) presented in this paper is based on a fusion scheme that utilizes fuzzy clustering and estimation techniques. Measurements from radar, vision and sonar are discriminated, fused and used to estimate relative motion between the prime and front vehicles. The estimated motion is then used to predict possibility of collision with the vehicle in the headway. Fuzzy logic is employed to initiate an audio and visual warning system. It also deploys a throttle relaxer and brake actuator to slow down the prime vehicle. Simulation study was carried out to evaluate the CAS concept. An actual concept prototype was implemented on a military vehicle to validate the feasibility.

Independent validation and verification of the TCAS II collision avoidance subsystem

Abstract: This paper describes the specification-based testing, analysis tools, and associated processes used to independently validate, verify, and ultimately, provide for certifying safety-critical software developed for the Traffic Alert and Collision Avoidance System (TCAS II) program. These tools and processes comprise an effective and Independent Validation and Verification (IV and V) activity applied to the Collision Avoidance Subsystem (GAS) software development process. A requirements specification language called the Requirements State Machine Language (RSML), originally developed by the University of California, Irvine (UCI), was employed for the specification of GAS. The end result is the next generation of TCAS II collision avoidance logic, referred to as Version 7, that is of a higher quality than its predecessors, meets the certification requirements of DO-178B Level B (Ref. 1), and can be shown to satisfy the new operational requirements it was developed to address.

A cooperative collision avoidance and communication system for railway transports

Abstract: Automated people movers are employed or projected in some cities all over the world. To explore the possibility of new exploitation modes, a cooperative correlation based radar collision avoidance system is used to identify trains, detect their positions and compute the distance between them. A problem with such a sensor is that it uses pseudo random codes and that the codes currently employed (m.l.f.s.r.: maximum length feedback shift registers) are few in number, so only one can be used at a time in any place to avoid interference. This study looks for new codes available in a larger number, that deliver good performances in the radar system. Some families of codes used in CDMA or other mobile telecommunication systems have been tested. For these tests a radar detection parameter is defined.

Nhtsa light vehicle antilock brake systems research program task 5, part 1: examination of drivers' collision avoidance behavior using conventional and antilock brake systems on the iowa driving simulator

Abstract: The National Highway Traffic Safety Administration (NHTSA) has developed its Light Vehicle Antilock Brake Systems (ABS) Research Program in an effort to determine the cause(s) of the apparent increase in single-vehicle run-off-road crashes and decrease in multi-vehicle on-road crashes as vehicles transition from conventional brakes to ABS. As part of this program, NHTSA conducted research examining driver crash avoidance behavior and the effects of ABS on drivers' ability to avoid a collision in a crash-imminent situation. The study described here was conducted on the Iowa Driving Simulator and examined the effects of ABS versus conventional brakes, speed limit, ABS instruction, and time-to-intersection (TTI) on driver behavior and crash avoidance performance. This study found that drivers do tend to brake and steer in realistic crash avoidance situations and that excessive steering can occur. However, a significant number of road departures did not result from this behavior. Drivers in the ABS group showed significantly increased stability and control relative to conventional brakes.

Wireless packet priority control method

Abstract: PROBLEM TO BE SOLVED: To solve a problem of a conventional wireless packet priority control method adopting a method for deciding transmission priority with a random number in the case of setting a collision avoidance period has had a deteriorated frequency utilizing efficiency because a data packet with low priority has a wait time without fail even when a data packet with high priority is not in existence. SOLUTION: This invention provides a wireless packet priority control method that realizes priority control of a data packet of an 'excellent effort type' by adopting a method where a collision avoidance period Tcw consisting of a multiple of basic unit times (slot times) is obtained by multiplying the slot times selected sequentially shorter for data packets with high priority ranking information with a random number without changing a distribution range of the random number, or a method where some waiting slots are inserted to a set collision avoidance period, or a method where the distribution range of the random number is changed to insert a fixed wait slot to a head of the collision avoidance period so as to set the length of the collision avoidance and a carrier sense method in response to the priority of transmission data.

Real-Time Collision Avoidance: Differential Game, Numerical Solution, and Synthesis of Strategies

Abstract: Contemporary developments of on-board systems for automatic or semiautomatic driving include car collision avoidance systems. For this purpose two approaches based on pursuit-evasion differential games are compared. On a freeway a correct driver (evader) is faced with a wrong-way driver (pursuer), i.e., a person driving on the wrong side of the road. The correct driver tries to avoid collision against all possible maneuvers of the wrong-way driver and additionally tries to stay on the freeway. The representation of the optimal collision avoidance behavior along many optimal paths is used to synthesize an optimal collision avoidance strategy by means of neural networks. Examples of simulations that prove a satisfactory performance of the real-time collision avoidance scheme are presented.

Prior Exposure, Warning Algorithm Parameters and Driver Response to Imminent Rear-End Collisions on a High-Sfideltiy Simulator:

Abstract: Rear-end collisions account for over 25% of crashes. Because driver inattention is a contributing factor in more than 60% of these collisions, rear-end collision avoidance systems (RECAS) offer a promising approach to reduce crashes and save lives. This study uses a high-fidelity driving simulator to examine driver response to imminent rear-end collision situations and address two issues. First, the study examines how variations in algorithm parameters affect RECAS effectiveness. The results show an early warning helps drivers react more quickly and avoid more collisions, providing critical data for tradeoff studies of RECAS parameters and nuisance alarm rates. Second, the study investigates how drivers respond to a second collision scenario shortly after their first exposure. The results show drivers react more quickly to the second exposure and avoid more collisions, but that the effect of the second exposure does not interact with other experimental variables or change the fundamental response dynamics...

Collision avoidance of moving obstacles for ship with genetic algorithm

Abstract: By use of a path planning method-genetic algorithms (GA), collisions with navigation obstacles and other moving ships can be avoided according to navigation traffic rule (the ship must pass on the right). Navigation obstacles and moving ships are identified by automatic radar plotting aids (ARPA), and then the future danger which is generated by the obstacles is predicted using a stochastic predictor. The stochastic predictor is designed such that the probability density map of the obstacle existence is predicted based on a Markov process model in enough future time. Evaluation of collision danger and efficiency of a path is taken in a cost function of GA. A safe and optimal path is given by this method. In heavy navigation traffic areas, correct selection of ship's speed, when accompanied by necessary path changes, is a crucial element in the safe navigation too. So the speed of own ship is introduced to the cost function of GA, and is modified along environment of navigation and the value of the cost function. The control method is confirmed by an experimental system that is the "Shioji Maru", which is the training ship of Tokyo University of Mercantile Marine. The experimental results are presented.