Showing papers on "Collision avoidance published in 1995"

Visual collision avoidance system for unmanned aerial vehicles

Abstract: A collision avoidance ability for UAV (42) during its non-VFR pre-programmed autonomous flight is achieved by using a forward-looking TV camera (20) which senses visual obstacles in direction of flight. The UAV is equipped with an autopilot which is able of maneuvering and incorporated in a form of flight/mission computer's (10) program. Image processor (18) locks and tracks obstacles in the camera's field of view in real time. It provides the autopilot with information about level of threat and generates appropriate commands. Being warned by the TV camera (20), flight/mission computer (10) initiates appropriate maneuver, in order to avoid possible collision. After that, it returns to interrupted pre-programmed flight. Two forward-looking TV cameras are used to measure a distance between the UAV (42) and the obstacle considering that the level of threat is higher if this distance is less.

Highway traffic accident avoidance system

Abstract: An accident avoidance system in which a substantially continuous data stream consisting of multiple vehicle velocity and location information is processed by means that will generate advisories to vehicles that are approaching potentially hazardous situations. These advisories are in advance of the vehicles hazard encounter so that driver corrective action can be taken to avoid collision. For each vehicle along a monitored length of highway, means are provided for computing the vehicles actual acceleration or deceleration and for computing the deceleration required for the vehicle to avoid an accident. Collision avoidance advisories are generated whenever the vehicle's acceleration or deceleration deviates from the deceleration required to avoid a collision. Means are provided for detecting vehicles that may be operated by drivers whose performance is impaired.

Collision detection and avoidance during treatment planning

Abstract: Purpose: To develop computer software that assists the planner avoid potential gantry collisions with the patientor patient support assembly during the treatment planning process. Methods and Materials: The approach uses a simulation of the therapy room with a scale model of the treatment machine. Because the dimensions of the machine and patient are known, one can calculate a prim+ whether any desired therapy field is possible or will result in a collision. To assist the planner, we have developed a graphical interface enabling the accurate visualization of each treatment field configuration within a “room’s eye view” treatment planning window. This enables the planner to be aware of, and alleviate any potential collision hazards. To circumvent blind spots in the graphic representation, an analytical software module precomputes whether each update of the gantry or turntable position is safe. Results: If a collision is detected, the module alerts the planner and suggests collision evasive actions such -either an extended distance treatment or the gantry angle of closest approach. Conclusions: The model enables the planner to experiment with unconventional noncoplanar treatment fields, and immediately test their feasibility. Collision avoidance, Patient safety, Radiation therapy, Computer control.

Collision avoidance device with reduced energy balance for aircraft, notably for avoiding collisions with the ground

Abstract: Disclosed is a collision avoidance device with reduced energy balance for aircraft, in particular for avoiding collision with the ground. This device comprises means for the geographical localization of the aircraft, a database containing a description of safety altitudes, means for the construction of an air floor about the vertical passing through the aircraft, the altitude of the floor being greater than or equal to the safety altitudes about this vertical, means for predicting the air position of the aircraft, means to compare this position with the air floor, means for the computation of avoidance paths and means to determine the energy balance of each of the computed paths. Application to equipment for aircraft, notably for civilian airliners.

An acquisition of operator's rules for collision avoidance using fuzzy neural networks

Abstract: The procedure for acquiring control rules to improve the performance of control systems has received considerable attention previously. This paper deals with a collision avoidance problem in which the controlled object is a ship with inertia which must avoid collision with a moving object. It has proven to be difficult to obtain collision avoidance rules, i.e., steering rules and speed control rules, which coincide with the operator's knowledge. This paper shows that rules of this type can be acquired directly from observational data using fuzzy neural networks (FNNs). This paper also shows that the FNN can obtain portions of the fuzzy rules for the inferences of the static and dynamic degrees of danger and the decision table based on the degrees of danger to avoid the moving obstacle. >

Collision avoidance system for vehicles using digital logic circuitry and retro-fitting techniques

Abstract: A continuous exterior perimeter monitoring system for collision avoidance by vehicles with exterior objects is provided utilizing microelectronic digital logic circuits and techniques to produce a visual three-digit numerical display, a discrete multi-color display and a multi-level sound warning system, indicating precise and range of distances of exterior objects from vehicles which could collide therewith within pre-selected distances. The time-to-distance circuits of the system are an integral part of the digital logic circuits that are utilized to ascertain distances and such circuits are in a compact electronic package adapted to and is readily installed and integrated into existing vehicles utilizing the existing wiring electrical power systems primarily as a retro-fitting process for vehicles or as an original installation.

Carrier sense collision avoidance with auto abort

Abstract: A Carrier Sense Multiple Access with Automatic Abort collision avoidance (CSMA/AA) controller for application in a wireless local area network (LAN). The CSMA/AA controller reduces the number of invalid states arising from collision conditions on the communication channel. The controller features hardware logic control for time critical functions. The hardware logic circuit detects events and fault conditions under the CSMA reservation protocol which may otherwise be missed by the Medium Access Control software layer and aborts the transmit procedure. The off-loading of time critical functions also improves the performance of the system and reduces the variability arising from overhead execution times associated with the system CPU.

Collision avoidance for two robots sharing a common workspace

Abstract: Two second hand robots and an old PC were used to demonstrate co-operative working in the same space. The overall performance of the system, though slow, was considerably greater than could have been achieved without the synergy of all three control elements, obtained through simple serial communications.

Collision-avoidance control for redundant articulated robots

Abstract: A new mathematical formulation of robot and obstacles is presented such that for on-line collision recognition only robot joint positions in the workspace are required. This reduces calculation time essentially because joint positions in workspace can be computed every time from the joint variables through robot geometry. It is assumed that the obstacles in the workspace of the manipulator are represented by convex polygons. For every link of the redundant robot and every obstacle a boundary ellipse is defined in workspace such that there is no collision if the robot joints are outside this ellipsis.In addition to this, a collision avoidance method is presented which allows the use of redundant degrees of freedom such that a manipulator can avoid obstacles while tracking the desired end-effector trajectory. The method is based on the generalized inverse with boundary ellipse functions as optimization criteria. The method permits the tip of the hand to approach any arbitrary point in the free space while the kinematic control algorithm maximizes the boundary ellipse function of the critical link. The effectiveness of the proposed methods is discussed by theoretical considerations and illustrated by simulations of the motion of three- and four-link planar manipulators between obstacles.

Comparison of alternative crash avoidance sensor technologies

Abstract: Sensor technologies of collision avoidance systems are identified based on a literature search about available products, prototypes, and experimental systems. These sensors constitute the front-end functional element of potential countermeasure systems to rear-end, backing, lane change, roadway departure, opposite direction, intersection, and reduced visibility crashes. The characteristics and capabilities of alternative sensor technologies are described based on published literature. Crash avoidance sensor technologies encompass microwave, millimeter- wave, and near-infrared radars; ultrasonic transducers, charge-coupled device cameras operating in near-infrared and visible bands; uncooled, passive far-infrared detectors; millimeter-wave imaging radar; and near-infrared communications.

Fuzzy collision avoidance for industrial robots

Abstract: An advanced concept to solve the collision avoidance problem in multi-robot workcells is presented which holds realtime conditions for industrial robot controllers. The approach is based on a fuzzy set description of critical configurations between robots in a common workspace. The authors' strategy assumes a careful offline path planning to unburden the algorithm from online path planning but to handle extraordinary events, which can not be treated offline. Though the authors' collision avoidance strategy is local, in general it switches towards the preplanned trajectory with decreasing degree of conflict and finally reaches planned goal positions. To handle the collision avoidance problem in realtime, the complex kinematic chain of any industrial robot with six degrees of freedom is replaced by a drastically reduced actual robot (RAR). Fuzzification of the actual RAR position in a workspace provides a fuzzy membership vector to sectors, which subdivide the robots' cylindrical workspace. A practical fuzzy-rulebase is given to evaluate the degree of conflict between the actual fuzzy membership vectors of two RARs and to propose secure fuzzy-membership vectors. Defuzzification gives crisp locations of a collision-free trajectory which are restricted by the preplanned trajectory locations if the conflict is small. The efficiency of this strategy is illustrated by an example with two PUMA 562 robots in decoupled motion.

Issues in airborne systems for closely-spaced parallel runway operations

Abstract: Efforts to increase airport capacity include studies of aircraft systems that would enable simultaneous approaches to closely spaced parallel runways in Instrument Meteorological Conditions (IMC). The time-critical nature of a parallel approach results in key design issues for current and future collision avoidance systems. These issues are being studied in two ways. First, a part-task flight simulator study has examined the procedural and display issues inherent in such a time-critical task. Second, a prototype collision avoidance logic capable of generating this maneuver guidance has been designed using a recently developed methodology.

Run-off-road collision avoidance countermeasures using ivhs countermeasures, task 3. volume 2

Abstract: The Run-Off-Road Collision Avoidance Using IVHS Countermeasures program is to address the single vehicle crash problem through application of technology to prevent and/or reduce the severity of these crashes. This report describes the findings of the Task 3 effort. Task 3 focused on testing of existing technology to meet the functional goals for run-off-road countermeasures identified in Task 2. These tests included all aspects of countermeasure performance, including sensing functions, algorithm or decision making functions and driver interface functions. Tests of existing technology were performed using a range of techniques and facilities, including laboratory experiments, in-vehicle tests and driving simulator tests. Two primary categories of run-off-road countermeasure technologies were tested in this effort - lateral countermeasures and longitudinal countermeasures. Lateral countermeasures are designed to prevent run-off-road crashes in which the vehicle drifts from its lane because of driver inattention or because the driver relinquishes steering control due to drowsiness, intoxication or some other medical condition. Technology tested in this category included forward and downward looking vision systems for sensing the vehicle's lateral position on the roadway. Longitudinal countermeasures are designed to prevent run-off-road crashes in which the vehicle departs the road due to excessive speed for the roadway geometry or pavement conditions. Technology tested in this category included a combination of Global Positioning System (GPS) and digital maps for sensing the distance to, and the severity of, upcoming curves.

Aircraft collision avoidance with potential gradient—ground-based avoidance for horizontal maneuvers

Abstract: This paper describes ground-based avoidance for horizontal maneuvers using a concept of potential as a collision avoidance aircraft procedure. First, mathematical formulation is introduced by using potential as a way to systematically represent the conditions contributing to collision avoidance such as a threat of collision with other aircraft and degrees of deviation from the original course. The flight course with a lower potential is considered safer. In the choice of a specific avoidance course, an avoidance pattern generation method by means of potential gradient is shown. the future location of the aircraft is sampled at a certain time interval. the shift of the sampling point corresponding to the potential gradient at each sampling point or the force applied to each sampling point (attractive or repulsive) is repeated. It was confirmed that by means of this method, avoidance patterns without danger of collision can be obtained with only horizontal avoidance except for special cases. However, when the sampling points are symmetric or when more than three aircraft are involved, the procedure is not adequate and some provisions are needed. to this end, the sampling point arrangement in the initial stage before the avoidance pattern is formed and the three-dimensional avoidance including vertical avoidance can be considered.

Obstacle avoidance and motion-induced navigation

Abstract: In nature, the visual detection of motion appears to be used in a variety of tasks, ranging from collision avoidance to posture maintenance. Many insects seem to rely primarily on information provided by an array of elementary movement detectors in order to navigate. Moreover, experimental evidence suggests that motion information is interpreted at an early stage of the insect visual system, and may be closely linked to motor control. A motion detector, whose design is based on some of the characteristics of the insect visual system, has been implemented on a single VLSI chip. This paper shows the manner in which motion information, provided by the chip in real-time, may be utilised by the control system of an autonomous vehicle in low-level perceptual tasks.

Distributed system-level control of vehicles in a high-performance material transfer system

Abstract: In this paper, a fully-distributed system-level control architecture is described for dispatching, routing, and collision avoidance of multiple passive vehicles moving in a guideway network formed by a multitude of propulsion units. Propulsion units cooperate using a communication network with a topology identical to that of the guideway network, eliminating the need for explicit knowledge of global topography and enabling rapid real-time response to service requests using a parallel, shortest-route algorithm. The concepts developed are applied to a high-performance system in which vehicles respond to spontaneous requests to transfer material from point to point in manufacturing facilities in seconds rather than the minutes required in conventional AGV and conveyor systems. In this application, the vehicle and propulsion-unit lengths are on the same order of magnitude, the propulsion-unit-length/maximum-vehicle-velocity time characteristic is small, and the ratio of the number of propulsion units to the number of vehicles is large. >

Potential fields for nonholonomic vehicles

Abstract: The problem of motion planing of a wheeled nonholonic vehicle is treated by decomposing the problem to the subproblems: 1) find a collision free path; and 2) approximate this path with a nonholonomic collision free path. This is treated, in real time, by solving the first subproblem using a potential fields strategy and the second one with nonholonomic tracking. Thus, collision avoidance of a nonholonomic wheeled vehicle in a feedback formulation is achieved.

Range sensor based outdoor vehicle Navigation, collision avoidance and parallel parking

Abstract: Detecting unexpected obstacles and avoiding collisions is an important task for any autonomous mobile system. This article describes GANESHA (Grid based Approach for Navigation by Evidence Storage and Histogram Analysis), a system using sonar 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. An 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, parallel parking and its integration with other vehicle systems is described.

The driver's role in collision avoidance systems

Abstract: The application of advanced technology sensors, processors and software will have significant influence on highway vehicle safety in the coming decade. Advanced vehicle sensors and processing already play a significant role in AVCS (automatic vehicle control systems), so the application to collision avoidance systems will amount to an extension of current on-board sensing, processing and control systems. The main issues to be resolved will be the driver/system interface and the driver's reaction to and effective integration within the CAS. Because of the diverse nature of the driving population, and inability to provide consistent orientation or training, the CAS will have to be designed as a natural extension of the driver's current role in driving. Also, several types of CASs are envisioned to address different accident categories, so some form of integration must be provided to make the various systems compatible. There also must be some commonality of operation between different vehicle models so that drivers can easily and safely transition to different systems.

Vehicle-to-vehicle communication for collision avoidance and improved traffic flow

Abstract: The purpose of this Innovations Deserving Exploratory Analysis (IDEA) project was to determine the performance requirements of a vehicle-to-vehicle communication and on-board processing system which would provide prediction and driver warning of potential inter-vehicular collisions, thus improving collision avoidance. The approach taken was unique in that the warning system developed allows vehicles to operate independently and without the control problems associated with platooning, but with the ability to utilize data from several vehicles ahead, unlike two-vehicle interaction systems. The impact of the developed advisory system is potentially large, since some 20% of all accidents are of the rear-end collision type and such accidents result in substantial loss of life and substantial cost in the form of delay and property loss. Researchers have stated that 60% of all rear-end collisions could be avoided if the driver were given an additional one-half second of warning prior to an incident.

Dynamic obstacle avoidance

Abstract: Techniques to allow simulated entities to avoid static terrain, such as trees, buildings, rivers, etc., have been in use in Distributed Interactive Simulation (DlS) environments for many years. Avoidance of objects in motion, “dynamic obstacles”, is much more complex. Although simple dynamic obstacle collision avoidance has been implemented in other systems, the resulting behavior is usually less than realistic. The Institute for Simulation and Training (1ST) has investigated techniques to allow simulated entities to make reasonably intelligent and realistic maneuvers intended to avoid dynamic (and static) objects. The goal has been to find new methods which will yield improved collision avoidance behavior without excessive computational cost. As a result of this work, 1ST has developed a novel approach to attack the DIS dynamic obstacle avoidance (DOA) problem by combining two disparate motion planning approaches: potential fields and grid based route planning.

Collision avoidance for a two-arm robot by reflex actions: Simulations and experimentations

Abstract: This paper addresses the problem of collision avoidance between the two arms of a two-arm robot. In our case, the problem is solved through the reflex action theory. In fact, one arm is protected by virtual protection zones. When an unscheduled event occurs, in other words when the second arm is going to collide with the first one, the shape of the protection zones is modified. Then, a motion is computed for the first arm to rebuild the initial shape of the protection zones. The use of different shapes for the protection zones is explained and justified. Several strategies to compute the motion are proposed and discussed. Finally, this method is tested in simulation and on real experiments for different kinds of two-arm robots: planar manipulators, PUMA 560 robots and parallelogram robots.

A fuzzy logic approach for safety and collision avoidance in robotic systems

Abstract: A major factor that has limited the application of robots in industrial and human service applications has been the lack of robust sensing and control algorithms for detection and prevention of collision conditions. This paper discusses an approach to the collision avoidance control of robots using a fuzzy logic methodology for the integration of sensory input data from the robot's environment. The paper presents a formulation of the collision avoidance problem using the occupancy grid formulation, and discusses the use of a combination of Dempster-Shafer inference and fuzzy logic in fusing the sensory information and making robot movement decisions. This hybrid approach utilizes the strengths of both systems to provide an effective and computationally tractable result. @ 1995 John Wiley & Sons, Inc.

Dynamic Simulation, Nonlinear Control and Collision Avoidance of Hydraulically Driven Large Redundant Manipulators

Abstract: A detailed dynamic model of hydraulically driven mobile large-scale manipulators is presented. The model can be used as simulation model, for the calculation of the forces in the design process and for the development of the controllers, which are required for tracking given trajectories, but also to avoid vibrations. It takes into account all relevant coupling effects between hydraulic drives and arm elements as well as between flexible deformations and large nonlinear rigid body motion. The control concept makes use of the redundancy of the system in order to avoid collisions.