Showing papers on "Collision avoidance published in 1997"

The dynamic window approach to collision avoidance

Abstract: This approach, designed for mobile robots equipped with synchro-drives, is derived directly from the motion dynamics of the robot. In experiments, the dynamic window approach safely controlled the mobile robot RHINO at speeds of up to 95 cm/sec, in populated and dynamic environments.

The format and presentation of collision warnings

Abstract: This paper reports on two studies focusing on the design of collision avoidance headway displays. The first study aims at examining interface issues relating to the headway information to drivers. It investigates integrated visual and auditory warnings. The purpose of the second study is to examine two particular factors that may affect drivers' braking responses in their use of an experimental Collision Avoidance System. It looks at the effects of both the absolute speeds of the target and following vehicle and the relative speed differences between the two vehicles.

Collision-free tool path generation using 2-dimensional C-space for 5-axis control machining

Abstract: This study deals with the method of collision avoidance in the automatic tool path generation for 5-axis control machining. Five-axis NC machining offers the potential for efficient and accurate machining, but collisions between the tool and surrounding objects are still a severe problem. The method devised in this study avoids collision by producing the direction of collision avoidance, based on the 2-dimensional configuration space (C-space) defined by two parameters which determine the tool attitude. This method allows a test workpiece with overhanging parts to be milled without collisions. As a result, the validity of the method has been experimentally confirmed.

Fast swept-volume distance for robust collision detection

Abstract: The need for collision detection arises in several robotics areas, including motion-planning, online collision avoidance, and simulation. At the heart of most current methods are algorithms for interference detection and/or distance computation. A few recent algorithms and implementations are very fast, but to use them for accurate collision detection, very small step sizes can be necessary, reducing their effective efficiency. We present a fast, implemented technique for doing exact distance computation and interference detection for translationally-swept bodies. For rotationally swept bodies, we adapt this technique to improve accuracy, for any given step size, in distance computation and interference detection. We present preliminary experiments which show that the combination of basic and swept-body calculations holds much promise for faster accurate collision detection.

Validation and simulation of a decentralized intersection collision avoidance algorithm

Abstract: In this paper an approach to a decentralized intersection management is presented which does not require much additional infrastructure at the intersection and which can operate in today's traffic so as to increase safety and to avoid congestion. Collision avoidance is ensured by using semaphore-based algorithms which allow only one vehicle to stay in a critical intersection region. Verification of the collision avoidance algorithm is done by high level Petri net based analysis that shows the correctness and security of the algorithm. Simulation results will prove the effects of the strategy.

Experimental Studies Of Pilot Performance At Collision Avoidance During Closely Spaced Parallel Approaches

Abstract: Efforts to increase airport capacity include studies of aircraft systems that would enable simultaneous approaches to closely spaced parallel runway 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. Two part-task flight simulator studies have examined the procedural and display issues inherent in such a time-critical task, the interaction of the pilot with a collision avoidance system, and the alerting criteria and avoidance maneuvers preferred by subjects.

Collision avoidance as a differential game: real-time approximation of optimal strategies using higher derivatives of the value function

Abstract: Contemporary developments of on-board systems for automatic or semi-automatic driving include car collision avoidance. For this purpose a worst case approach based on pursuit-evasion differential games is investigated. On a freeway a correct driver (evader) is faced with a wrong driver (pursuer) ahead. The correct driver tries to avoid a collision against all possible wrong driver's maneuvers and additionally tries to stay on the freeway. The representation of an optimal collision avoidance strategy along a lot of optimal paths is used to synthesize a collision avoidance strategy globally by means of Taylor series expansions of the value function's gradient. Examples of simulations which proved satisfactory performance of the on-board collision avoidance system against various typical maneuvers of wrong drivers are presented.

Intersection collision avoidance by means of decentralized security and communication management of autonomous vehicles

Abstract: This paper presents an intersection management system which uses a token-based communication protocol among autonomous vehicles in a specified zone around the intersection. This allows for the exchange of information on current position, velocity, and acceleration, which would then factor into the decision on whether or not to enter the intersection. Semaphore-based algorithms are used to ensure collision avoidance. These algorithm allow only one vehicle at a time to stay in a critical segment of an intersection.

Adaptive behavior acquisition of collision avoidance among multiple autonomous mobile robots

Abstract: We discuss adaptive behavior acquisition for collision avoidance among multiple autonomous mobile robots which are equipped with the locally communicable infrared sensory system (LOCISS). The LOCISS is a local sensing device for collision avoidance by which robots can detect other robots and obstacles and discriminate them by exchanging relevant information. We (1996) reported previously a collision avoidance method between two robots based on the predetermined rules using LOCISS. It is, however, difficult to realize collision avoidance among three or more robots by the predetermined rules only because situations around the robots become more complicated as the number of robots increases. Thus, it is desirable for the robots to have an adaptive capability for acquisition of the behaviors to avoid collision with other robots and obstacles. To acquire the adaptive behavior, the reinforcement learning is introduced in this paper. It is shown that appropriate behaviors for collision avoidance can be successfully acquired through the proposed learning process.

Collision avoidance behavior of unalerted drivers using a front-to-rear-end collision warning display on the Iowa driving simulator

Abstract: This study investigated whether drivers who operate a vehicle equipped with a front-to-rear-end collision warning system can avoid crashing when a lead vehicle brakes at its maximum potential (e.g., -0.85 g). Drivers in the experimental condition drove a 1993 General Motors Saturn mounted on the Iowa Driving Simulator's six-degree-of-freedom motion base. The simulator cab was equipped with a collision warning display that provided a primary auditory warning and secondary visual warning based on a time-to-collision algorithm between the subject's vehicle and the lead vehicle. Two headway distances were tested (2.7 sec and 3.2 sec). The collision avoidance performance of subject drivers was compared to the behavior of drivers in a baseline condition where no collision warning display was present. Relative to the baseline condition, results indicate that drivers using the collision warning display (a) showed significantly fewer crashes in the shorter headway condition, (b) collided with the lead vehicle at s...

A crash avoidance system based upon the cockroach escape response circuit

Abstract: A crash avoidance system for automobiles is developed based upon a distributed network of artificial neurons that mimic the neural organization of the escape system in the American cockroach. The cockroach escape circuit is shown to be an excellent source of inspiration for the development of a collision avoidance system. The crash avoidance system is implemented in an artificial neural network which is trained off-line, but then is shown to produce real-time performance. A collision avoidance scheme which makes use of a crash alarm strategy is developed for training the neural network. A dynamic model of a four-wheeled vehicle with front wheel steering and realistic performance constraints is used to test the crash avoidance system. Simulation results show that the well-trained neural network causes successful, reflexive crash avoidance behaviors in a dynamic environment without a priori information.

Automotive radar for adaptive cruise control and collision warning/avoidance

Abstract: This paper discusses the application for autonomous intelligent cruise control (AICC), also called adaptive cruise control (ACC). Tests have however, also indicated the radar's capability for the much more demanding application: collision warning/avoidance (CW/A). CelsiusTech Electronics (CTE) has a long experience in millimetre wave radar, which was used for initial testing within the Swedish car industry of a fully automatic ACC. The results of the tests were very gratifying and CTE is now in the process of full scale development, engineering, and preparations for large scale production, e.g. the design of ASICs. As an interim, a number of "second generation prototypes" called "X-models", are now being manufactured.

Benefits estimation for selected collision avoidance systems

Abstract: This paper presents safety benefits of three collision avoidance systems in terms of the number of crashes that might be avoided. The results were estimated in a recent preliminary study conducted by the National Highway Traffic Safety Administration of the United States (U.S.) Department of Transportation. The three selected systems address rear-end, lane change, and single vehicle roadway departure crashes which accounted for about 3.14 million police-reported crashes in the U.S. in 1994. A basic methodology was developed and applied to each of the three systems, using experimental data from driving simulator studies and on-road tests where subjects drove with and without the assistance of a collision avoidance system in a variety of driving situations and surrounding conditions. Collectively, the three systems have the potential to reduce about 1.8 million police-reported crashes annually in the U.S. based on 1994 crash statistics. For the covering abstract, see IRRD 490001.

Longitudinal driver support systems

Abstract: Adaptive cruise control, a development of conventional cruise control is likely to be introduced into the marketplace before the end of the decade. The acceptance of ACC, with limited brake intervention, is the first step towards interventive collision avoidance systems such as those being developed in the EU funded AC-ASSIST project. The key technology for the development of adaptive cruise control and advanced collision warning is the development of low cost, high integrity, range and relative velocity sensing systems. The requirements for ACC systems and sensors will be considered in this paper. Control and sensor issues are discussed and a comparison between the competing sensor technologies is made. (A) For the covering abstract of the conference see IRRD 493111.

Collision avoidance by using space-time representations of motion processes

Abstract: This paper handles the problem of collision avoidance in a multi-robot environment. To solve this problem, the motion processes of the mobile robots are modelled in space-time. Since the robots are autonomous and communication is non-deterministic, there is temporal uncertainty in addition to spatial uncertainty. The paper presents a method to model both uncertainty components in a homogeneous way. It is shown, that it is not sufficient to guarantee a spatial security distance between the robots. Distances in space-time and space-time vectors must be considered. The main result of this paper is a straightforward and efficient solution to the problem of collision avoidance between up to three mobile robots by applying a space-time displacement vector. The solution is based on space-time, which is a helpful view onto our world in relativity theory and quantum physics. Space-time methods are also very valuable in Robotics, especially for problems in dynamic environments and for motion coordination of mobile robots. Practical experiments with up to two robots, and simulations of up to three robots have been performed and are reported.

Driver behavior under a collision warning system : a driving simulator study

Abstract: This paper describes driving simulator experiments in which the subjects' collision avoidance behavior was examined. Results show that the braking response time and the number of simulated collisions were noticeably decreased with collision warnings. Additionally, the potential reduction of rear-end collisions was estimated by modeling drivers' braking responses.

Evolution to an Automated Highway System

Abstract: In the Precursor Systems Analyses (PSA) sponsored by the Federal Highway Administration in 1993, several of the researchers addressed how AHS would be first introduced to the market. The researchers identified several problems to be overcome including driver acceptance and the ability of state and regional departments of transportation to operate and maintain an AHS.(1–3) The researchers concluded that one of the most serious issues is the “chicken-or-egg” problem—which comes first, the AHS highway lanes or the AHS-equipped vehicles? Minimum AHS vehicle penetration for a particular corridor or highway segment is reached when, after conversion of one of the existing highway lanes to AHS, the number of AHS lane users equals the number of manual users of the lane before conversion. It was estimated that this minimum AHS vehicle penetration ranged from 5 to 30% of the total vehicle population depending on many factors such as number of lanes already existing in the corridor, frequency of entry and exit lanes, and average trip distance.

In-vehicle collision avoidance support under adverse visibility conditions

Abstract: This paper deals with longitudinal collision avoidance systems (CAS) where the target is a preceding vehicle in the same lane. It examines, in behavioral terms, the best way of giving CAS support in conditions that confront drivers with problems of reduced visibility while car following. It elaborates on earlier work on CAS support by asking whether the design of a CAS should be indifferent to varying external conditions, or whether it should be adapted to those conditions by introducing new parameter settings. The logic of the experiment rests on some assumptions that are presented before describing the experiment itself.

Affordable MMW aircraft collision avoidance system

Abstract: Collision avoidance is of concern to all aircraft, requiring the detection and identification of hazardous terrain or obstacles in sufficient time for clearance maneuvers. The collision avoidance requirement is even more demanding for helicopters, as their unique capabilities result in extensive operations at low-altitude, near to terrain and other hazardous obstacles. TO augment the pilot's visual collision avoidance abilities, some aircraft are equipped with 'enhanced-vision' systems or terrain collision warning systems. Enhanced-vision systems are typically very large and costly systems that are not very covert and are also difficult to install in a helicopter. The display is typically raw images from infrared or radar sensors, and can require a high degree of pilot interpretation and attention. Terrain collision warning system that rely on stored terrain maps are often of low resolution and accuracy and do not represent hazards to the aircraft placed after map sampling. Such hazards could include aircraft parked on runway, man- made towers or buildings and hills. In this paper, a low cost dual-function scanning pencil-beam, millimeter-wave radar forward sensor is used to determine whether an aircraft's flight path is clear of obstructions. Due to the limited space and weight budget in helicopters, the system is a dual function system that is substituted in place of the existing radar altimeter. The system combines a 35 GHz forward looking obstacle avoidance radar and a 4.3 GHz radar altimeter. The forward looking 35 GHz 3D radar's returns are used to construct a terrain and obstruction database surrounding an aircraft, which is presented to the pilot as a synthetic perspective display. The 35 GHz forward looking radar and the associated display was evaluated in a joint NASA Honeywell flight test program in 1996. The tests were conducted on a NASA/Army test helicopter. The test program clearly demonstrated the systems potential usefulness for collision avoidance.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Pilot non-conformance to alerting system commands

Abstract: Instances of pilot non-conformance to alerting system commands have been identified in previous studies. Pilot non-conformance changes the final behavior of the system, and therefore may reduce actual performance from that anticipated. Two simulator studies have examined pilot non-conformance, using the task of collision avoidance during closely spaced parallel approaches as a case study. The first study discovered subjects' decisions to alert, and their selected avoidance manoeuvre, differed from those typically commanded by collision avoidance systems. The second study found consonance between the display and the alerting system improved subject agreement with automatic alerts. Based on these results, a general discussion of the factors involved in pilot conformance is given, and design guidelines for alerting systems are suggested.

Variable dynamic testbed vehicle : dynamics analysis

Abstract: The Variable Dynamic Testbed Vehicle (VDTV) concept has been proposed as a tool to evaluate collision avoidance systems and to perform driving-related human factors research. The goal of this study is to analytically investigate to what extent a VDTV with adjustable front and rear anti-roll bar stiffnesses, programmable damping rates, and four-wheel-steering can emulate the lateral dynamics of a broad range of passenger vehicles.

Development of rear-end collision avoidance system

Abstract: RCAS (rear-end collision avoidance system) has been developed as a system of ASV (advanced safety vehicle). It is a driver assist system to avoid the rear-end collision by informing the distance headway. It also has automatic braking function in case of emergency and distance warning function to the trailing vehicle. This paper describes the outline of RCAS, techniques about the preceding vehicle recognition and collision potential hazard evaluation. And experimental results about distance headway warning and collision avoidance by automatic braking are reported.

Performance specification development for roadway departure collision avoidance systems

Abstract: The Run-Off-Road Collision Avoidance using IVHS countermeasures program is a four year program sponsored by the US National Highway Traffic Safety Administration (NHTSA). The primary goal of the program is to develop practical performance specifications for roadway departure collision avoidance systems. This paper describes the results to date of the efforts to: (1) characterize the problem of roadway departure crashes; (2) develop and test technology for preventing these crashes; (3) model countermeasure system performance; and (4) develop preliminary performance specifications. For the covering abstract, see IRRD 490001.

Future directions for motion detection based on the parallel computational intelligence of insects

Abstract: The visual system of insects consists of distributed neural processing, inherent parallelism and fuzzy collision avoidance algorithms. This forms the basis for artificial vision systems that exploit these computational intelligence schemes for anti collision tasks. Insects tend to detect motion rather than images and this, together with the parallelism in their visual architecture leads to an efficient and compact means of collision avoidance. A family of VLSI smart microsensors that mimic the early visual processing stage in insects has been developed. The system employs the 'smart sensor' paradigm in that the detectors and processing circuitry are integrated on one chip. The IC is ideal for motion detection, particularly collision avoidance tasks, as it essentially detects the speed bearing and time to impact of a moving object. Fuzzy algorithms may then be employed for decision making. The Horridge model for insect vision has been directly mapped into VLSI and therefore the IC truly exploits the beauty of nature in that the insect eye is so compact with parallel processing, enabling compact motion detection without the computational overhead of intensive imaging, full image extraction and interpretation. This world first has exciting applications in areas such as anti collision for automobiles and autonomous robots. The status and future directions of this work are outlined.

Expected impacts of anti-collision assist applications

Abstract: The scope of Anti-Collision Assist (ACA) is wide, covering a wide range of technologies and strategies which strongly influence the possible effects of the newly equipped vehicles. The paper describes the expected impacts of ACA applications from a European point of view. Starting from activities of EC DG XIII AC-Assist (Anti-Collision Assist) project an overview of actual research policies on "telematic" collision avoidance and of architectural design is provided here. Traffic efficiency and traffic safety are considered in this analysis together with a description of tools used to achieve a successful impact evaluation. Preliminary results based on a theoretical system are included. (A) For the covering abstract, see IRRD 490001.

Collision avoidance and resolution multiple access: first-success protocols

Abstract: Collision avoidance and resolution multiple access (CARMA) protocols establish a three-way handshake between sender and receiver to attempt to avoid collisions, and resolve those collisions that occur. This paper describes and analyzes CARMA protocols that resolve collisions up to the first success obtained by running a tree-splitting algorithm for collision resolution. An upper bound is derived for the average costs of resolving collisions of floor requests using the tree-splitting algorithm is obtained and applied to the computation of the average channel utilization in a fully connected network with a large number of stations. Our analysis indicates that, because CARMA protocols guarantee a successful transmission for every busy period of the channel, it achieves higher throughput than other contention-based MAC protocols based on collision-avoidance handshakes.

Rendezvous spacecraft collision avoidance device

Abstract: In the present invention four thrusters are provided as a group of thrusters for collision avoidance These thrusters contain a component of translational thrust for collision avoidance injection in their respective outputs, and are capable of simultaneously generating posture control torque around two coordinate axes, which are orthogonal to a thrust axis, in order to maintain the directional stability of the thrust axis during the injection When abnormality arises in a group of thrusters for ordinary use, collision avoidance is executed by replacing all the thrusters for ordinary use by these thrusters for collision avoidance