Showing papers on "Collision avoidance published in 1994"

Time-to-collision and collision avoidance systems

Abstract: An important issue in developing Collision Avoidance Systems (CASs) is to define a proper warning strategy, that warns the driver only when he or she is really in danger and immediate action is required. The results of several studies point to the direct use of Time-To- Collision (TTC) as a cue for decision-making in traffic. Therefore, TTC could be an adequate criterion for activating a CAS. First tests indicate that drivers prefer TTC-based warning strategies. Recently, some studies on driver behaviour in fog enable a more precise definition of CAS-critical situations and relevant criterion values for TTC. TTC values in the range of 4.5 to 5 appear to be the most suitable. Special attention should be given to visibility conditions between 40 and 120 meter, since in that range driving speeds are found much too high to stop in time for an unexpected obstacle. (A) For the covering abstract of the report see IRRD 874607.

Development of a rear-end collision avoidance system with automatic brake control

Abstract: We have studied active safety technologies from the standpoint of “collision avoidance”. This paper describes a rear-end collision avoidance system with automatic brake control, which avoids a collision to the vehicle in front caused by inadvertent human errors using automatic emergency braking. The system is comprised of four key technological elements, headway distance measurement using scanning laser radar, path estimation algorithm with vehicle dynamics, collision prediction to the vehicle in front by a safe/danger decision algorithm, and longitudinal automatic brake control.

VITA II-active collision avoidance in real traffic

Abstract: An autonomous road vehicle is presented which will prevent collisions automatically. This safety relevant project is part of PROMETHEUS (program for a European traffic with highest efficiency and unprecedented safety). The vehicle demonstrator VITA II (vision technology application) consists of a passenger car which demonstrates its capabilities of collision avoidance on motorways. The video cameras installed in the vehicle acquire information about the environment. The hardware consists of two clusters of parallel processors. The application cluster hosts the computer vision, planning, decision and control modules to perform driving tasks such as: lane keeping with desired speed, reduction of the speed in narrow curves obeying the restrictions given by traffic signs, following the vehicles in front with adaptive distance control, computer vision based traffic sign recognition, object detection and recognition around the vehicle and autonomous immediate collision avoidance maneuvres including overtaking. The vehicle cluster provides the basic structure to control the vehicle by computer.

Collision avoidance of two general robot manipulators by minimum delay time

Abstract: A simple time delay method for avoiding collisions between two general robot arms is proposed. Links of the robots are approximated by polyhedra and the danger of collision between two robots is expressed by distance functions defined between the robots. The collision map scheme, which can describe collisions between two robots effectively, is adopted. The minimum delay time value needed for collision avoidance is obtained by a simple procedure of following the boundary contour of collision region on collision map. To demonstrate the effectiveness of the proposed time delay method, a computer simulation study is shown where a collision is likely to occur realistically. >

Collision-avoidance by fuzzy-logic control for automated guided vehicle navigation

Abstract: A fuzzy approach to collision avoidance for automated guided vehicle (AGV) navigation is proposed. Static obstacles with no a priori position information as well as moving obstacles with unknown trajectories are considered in this study. Intuitive and subjective human ideas of collision avoidance are modeled into fuzzy rules. Fuzzy logic is applied in the inference procedure for AGV navigation, such that the AGV is guided from the starting point toward the target without colliding with obstacles. Furthermore, the proposed method can also be used for the navigation of multiple AGVs, where each AGV must avoid other AGVs as well as obstacles in the environment. Simulation results are presented to show the feasibility of the proposed fuzzy approach. © 1994 John Wiley & Sons, Inc.

Visual collision avoidance by segmentation

Abstract: Visual collision avoidance involves two difficult subproblems: obstacle recognition and depth measurement. We present a class of algorithms that use particularly simple methods for each subproblem and derive a set of sufficient conditions for their proper functioning based on a set of idealizations. We then discuss and compare two different implementations of the approach on mobile robots and discuss their performance. Finally, we experimentally validate the idealizations. >

Trajectory planning and collision avoidance for underwater vehicles using optimal control

Abstract: Energy-optimal trajectories for underwater vehicles be computed using a numerical solution of the optimal control problem. A performance index consisting of a weighted combination of energy and time consumption is proposed. Collision avoidance is solved by including path constraints. Control vector parameterization with direct single shooting is used in this study. The vehicle is modeled with six-dimensional nonlinear and coupled equations of motion. Optimal trajectories are computed for a vehicle controlled in all six degrees of freedom by dc-motor-driven thrusters. Good numerical results are achieved. >

Active infrared sensors for mobile robots

Abstract: Sensors based on the ultrasonic, pulse-echo technique for measuring range have been the mainstay for robotic collision avoidance systems. Although these sensors have been successfully applied to both indoor and outdoor mobile robotic applications, certain disadvantages of these systems prompted our investigation of inexpensive sensors that use light to determine the range or presence of targets. A number of commercially available, light-based sensors are analyzed for application in a mobile robotic space application. The objective of the analysis is to develop a cost-effective, light-based ranging sensor for a collision avoidance system for an experimental Mars Rover. This paper presents some results from our investigation. >

Posture interpolation with collision avoidance

Abstract: While interpolating between successive postures of an articulated figure is not mathematically difficult, it is much more useful to provide postural transitions that are behaviorally reasonable and that avoid collisions with nearby objects. We describe such a posture interpolator which begins with a number of pre-defined static postures. A finite state machine controls the transitions from any posture to a goal posture by finding the shortest path of required motion sequences between the two. If the motion between any two postures is not collision free, a collision avoidance strategy is invoked and the posture is changed to one that satisfies the required goal while respecting object and agent integrity. >

Fuzzy logic based collision avoidance for a mobile robot

Abstract: Navigation and collision avoidance are major areas of research in mobile robotics that involve varying degrees of uncertainty. In general, the problem consists of achieving sensor based motion control of a mobile robot among obstacles in structured and/or unstructured environments with collision-free motion as the priority. A fuzzy logic based intelligent control strategy has been developed here to computationally implement the approximate reasoning necessary for handling the uncertainty inherent in the collision avoidance problem. The fuzzy controller was tested on a mobile robot system in an indoor environment and found to perform satisfactorily despite having crude sensors and minimal sensory feedback.

Collision avoidance planning of a robot manipulator by using genetic algorithm. A consideration for the problem in which moving obstacles and/or several robots are included in the workspace

Abstract: There have been proposed various approaches for solving the collision avoidance problem of a robot manipulator. However, unfortunately, almost all of the research in this area has so far only dealt with the collision avoidance problem in which moving obstacles are not included in the workspace of a robot manipulator. In this paper, it is shown that path planning and the collision avoidance planning problem of a robot manipulator whose workspace includes moving obstacles can be solved successfully by using a genetic algorithm. Following a brief explanation of Simple GA, the new concept of pseudo-potential is introduced in order to detect the possibility of collision with moving obstacles in the future steps. This concept is utilized in order to evaluate a fitness function of a chromosome which represents a path connecting the starting point with the goal in the workspace of a robot manipulator and construct an appropriate collision avoidance planning. A computer simulation dealing with the collision avoidance problem of two robot manipulators confirms the effectiveness of our approach. >

Real-time collision avoidance at road-crossings on board the Prometheus-ProLab 2 vehicle

Abstract: The control system presented in this paper is part of the European Prometheus-ProLab 2 test vehicle which proposes several new significant aids to the driver for an enhanced traffic safety. The goal of this system is to detect and to provide a low-level interpretation of the movements of side-obstacles (vehicles) occurring at crossings. The system is composed of two video cameras and a real-time vision machine (Transvision) on which a specific software performing the obstacle detection and interpretation task has been implemented. The proposed system provides reliable and robust (real-time) control of standard intersections up to a distance of about 150 m.

Interactive body awareness

Abstract: An important problem in the animation of human-like agents is self collision . While the problem of adjacent segment intersection can often be eliminated by explicitly limiting joint angles, avoiding collisions of nonadjacent segments is much more difficult when the response time is constrained in an interactive environment. Instead of using the traditional motion planning approach, an efficient way to handle obstacle avoidance through Collision response is proposed. This reactive behaviour is driven by inputs from the agent's simulated sensors which detect obstacles. A self-collision response system has been implemented following this approach. Its performance demonstrates that collision avoidance can be performed automatically in an interactive computer animation environment. This approach has also been successfully extended to handle collisions of agents with environment obstacles.

Using the reamacs model to compare the effectiveness of alternative rear end collision warning algorithms

Abstract: This paper presents the results of an analytical study of alternative rear end collision-avoidance algorithms using the Ford REAMACS simulation. REAMACS (Rear End Accident Model And Countermeasure Simulation) models rear end collision situations in freeway traffic and estimates the benefits of collision avoidance systems. Previously reported applications of the model indicate that the end crash warning system has the potential for a 60 percent reduction of the number of serious rear end crashes in freeway traffic. The present study confirmed and extended those findings to a broader range of conditions. Two different collision warning algorithms were analyzed: (1) a Closing Rate algorithm (CRA) which provides a warning only if the following vehicle has a positive closing rate with the lead vehicle, and (2) a Stopping Distance algorithm (SDA) which provides advanced warning of a potential hazard. The Stopping Distance Algorithm was more effective than the Closing Rate algorithm, with effectiveness rates approaching 100 percent, but gave 440 to 1,100 times more warnings than the Closing Rate Algorithm. Whether or not drivers would comply with such warnings is an issue.

DCPA simulation model for automatic collision avoidance decision making systems using fuzzy sets

Abstract: Decision making in collision avoidance is one of the major problems in ship manoeuvring. The basis of ships collision avoidance decision making at sea is the Collision Regulations which prescribe that two encountered vessels should pass at a safe distance. In this paper, several fuzzy sets are introduced to simulate the mariners' collision avoidance decision making behaviour and their psychology. Simulation models are established on an action to avoid collision in head-on, creasing and overtaking situations, in restricted waters in traffic separation schemes, in restricted visibility and with obstacles. This work lays a theoretical foundation on for the development of marine traffic simulation and automatic collision avoidance systems. Finally, an investigation on the mariners' behaviour is reviewed, and a simulation conducted to compare with other studies. >

Collision avoidance technologies

Abstract: This paper provides an overview of the status quo of vehicle collision avoidance technologies, and discusses the technological and social issues for the practical applications of such technologies. Efforts are discussed to develop technologies to support the driver's recognition, judgment, and operation in a more positive manner.

Using the REAMACS model to compare the effectiveness of alternative rear end collision warning algorithms

Abstract: This paper presents the results of an analytical study of alternative rear end collision-avoidance algorithms using the Ford REAMACS simulation. REAMACS (Rear End Accident Model And Countermeasure Simulation) models rear end collision situations in freeway traffic and estimates the benefits of collision avoidance systems. Previously reported applications of the model indicate that the end crash warning system has the potential for a 60 percent reduction of the number of serious rear end crashes in freeway traffic. The present study confirmed and extended those findings to a broader range of conditions. Two different collision warning algorithms were analyzed: (1) a Closing Rate algorithm (CRA) which provides a warning only if the following vehicle has a positive closing rate with the lead vehicle, and (2) a Stopping Distance algorithm (SDA) which provides advanced warning of a potential hazard. The Stopping Distance Algorithm was more effective than the Closing Rate algorithm, with effectiveness rates approaching 100 percent, but gave 440 to 1,100 times more warnings than the Closing Rate Algorithm. Whether or not drivers would comply with such warnings is an issue.

Image understanding based on edge histogram method for rear-end collision avoidance system

Abstract: To avoid rear-end collision with the preceding vehicles on the road, we need the information of collision potentiality. It is decided primarily by the relative locations and velocities between vehicles and their absolute locations on the road lanes. We classify the recognition objects in the road scene into road lanes and vehicles for the goal of collision avoidance. We propose the consistent road scene recognition method using edge histogram with model based vision. The edge histogram can detect line elements of the objects stably with low calculation cost. If the suitable region of interests for each objects in the model are established and their projected edge histograms are observed in time series order, we can derive each objects from the model. Furthermore, we apply Kalman filter to predict the object locations for time series detection. From the recognition results, we can calculate the collision time. It is one of the measures of collision potentiality. >

Collision avoidance tree networks

Abstract: The Collision Avoidance Tree is a local area network based on a hardware device called the collision avoidance switch. The collision avoidance switch arbitrates random access to a shared communication channel and avoids the penalty of collisions among packets. This network combines the benefits of random access (low delay when traffic is light; simple, distributed, and robust protocols) with concurrency of transmission, excellent network utilization and suitability for the domain of high-speed optical networking. The Collision Avoidance Tree is classified in two groups: the Collision Avoidance Single Broadcast (CASB) Tree and the Collision Avoidance Multiple Broadcast (CAMB) Tree. The CASB Tree allows only a single transmission on the network at a given time, while the CAMB Tree allows concurrent transmissions on the network. This paper describes network architectures (station and switch protocols) as well as designs and implementations. Performance results derived from analyses, simulations, and measurements of experimental networks are also presented.

Safety evaluation of collision avoidance systems

Abstract: This paper presents the first results of a comparative evaluation of the behavioural effects of Collision Avoidance or Warning Systems. Three different systems were evaluated which differed in terms of the criteria used and their man-machine interfacing. The systems were implemented in a driving simulator and tested using critical vehicle interactions. Preliminary analysis concentrated on (1) time headways, which increased while driving with CAS operated by an active gas pedal and decreased while driving with autonomous intelligent cruise control, (2) subjective workload, which increased while driving with CAS operated by an active gas pedal and decreased while driving with autonomous intelligent cruise control, and (3) driver acceptance of CAS, which decreased while driving with CAS operated by an active gas pedal and with autonomous intelligent cruise control. (A) For the covering abstract see IRRD 868006.

Collision avoiding method for part mounting head and part mounting device using this head

Abstract: PURPOSE:To avoid collision between part mounting heads by stopping temporarily moving any of beams or by moving any of the beams to a refuge position in order to hold a collision avoidance limit space. CONSTITUTION:A space between moving destinations of each beam 24, 25 is judged for whether exceeding or not a limit space between the beams where collision can be avoided between the fellow part mounting heads 50, 51 mounted on each beam 24, 25. Next in the case of judging the space to exceed the collision avoidance limit space, the part mounting head, whose moving locus is judged short, is moved to its target position. In the case of providing the other beam in a collision avoidance limit region of moving to the target position, the other beam, that is, a part mounting head side beam of long moving locus is once moved to a refuge position capable of holding a collision avoidance limit space and here placed on standby.

Method and device for preventing collision of robot

Abstract: PURPOSE: To facilitate the preparation of a working program by obtaining the movement speeds of respective robots during the movement, calculating a required time until they stop the moving speeds and a stop position, and when the collision avoidance allowable areas of the respective robots are interfered to each other at the stop position, by stopping the robot with lower priority. CONSTITUTION: A controller 7 calculates the movement speeds of the X-, Y-, and Z-axis arms of robots RA and RB based on the detected signals from X-to Z-axis encoders 4X to 4Z and 6X to 6Z for each specified time. Also it calculates a required time until they stop at the movement speeds and a movement distance at the stop. Then the existence of interference of collision avoidance allowable areas for the robots RA and RB at this stop position is judged. When the collision avoidance allowable areas are interfered to each other, the robot RA or RB with lower priority is stopped to avoid collision. COPYRIGHT: (C)1995,JPO

Stochastic Optimal Control of Moving Vehicles in a Dynamic Environment

Abstract: This article develops a fairly general framework for derivation of control strategies applying to moving objects, such as mobile robots or robot arms, in a dynamically changing environment. The basic idea is to consider stochastic terms for any uncertain future environment change and to apply stochastic dynamic programming for control strategy development. The method permits consideration of a number of possible missions such as collision avoidance or collision hitting and/or moving forward or following a trajectory. A number of examples demonstrate that the control strategies developed are capable of making efficient, human intelligence—like decisions in quite complicated conflict situations.

Cooperation of mobile robots by event transforms into local space-time

Abstract: Crossings represent a classical example for the conflict regions of mobile robot systems. Two robots in a crossing situation are considered where the priorities and sequences of passing have been determined beforehand. Communication and sensing are regarded as an ideal combination of data sources for the collision avoidance control process. Nevertheless, in this case, temporal uncertainties have to be considered in parallel to the spatial uncertainty of sensing and localisation. The event transformation into the local space-time coordinate frame of a robot is introduced as a major element of the iterative process to reduce the sources of uncertainty. This transform is the basic part of the collision avoidance control procedure. >

A sonar based obstacle avoidance system for AUVs

Abstract: In this paper we describe a sonar based, collision avoidance module for autonomous underwater vehicle, developed as part of a more complex navigation and guidance system. Its main features are the use of Kalman filters in evaluating both the motion of the detected obstacles and the risk of collision, and the possibility of working at two different levels of abstraction, according to the characteristics of the situation.

Radar based vehicle collision warning system

Abstract: This paper examines radar based automotive collision avoidance systems. It describes the system operation, variables that affect radar system performance, and the selection of radar frequency to be used. The paper concludes with a brief description of the Eaton VORAD collision warning system, considered to be the only radar collision warning system currently in use.

IVHS Countermeasures for Rear-End Collision, Task 1 Vol. VI: Human Factors Studies

Abstract: The media of specific interest to this study is that of microwave radar. Acoustic radar has been rejected due to its limitations in adverse weather conditions. Frequency range is between 22 and 94 GHz with the range around 60 GHz having possible advantages due to atmospheric attenuation in this bandwidth. However, increase frequency corresponds to higher cost. The modulation is most often in one of the following forms: pulsed (well suited for multiple targets but expensive), frequency modulation in continuous wave or FM/CW (cheaper with increased cost in signal processing), and bi-frequency or diplex Doppler (simplest but not effective in for multiple targets and rain clutter). Braking systems have been approached differently. In the US the approach has been to reduce the range of the radar to 50m on freeways (35m on curves) and incorporate automatic braking to improve efficiency. This is effective in reducing the number of false alarms. Due to the higher speeds in Europe, the approach there has been to focus on prevention through Previous work done about anti-collision (ac) radar is reviewed with requirements for the components of the systems given. The main requirements of ac radar are: physical media for target detection, automatic or manual braking, autonomous or cooperative systems, and antenna diagram warnings. Ranges in excess of 1OOm are necessary which results in an increase in false alarms. Autonomous systems are independent of other vehicles. Cooperative systems require reflectors on targets. The advantage of the latter being the possibility of vehicle information exchange. However, the danger of not detecting an unmarked target may be great enough to eliminate this option. The antenna diagram must be such to minimize false alarms while maximizing hazard detection. This is accomplished by confining the horizontal range to one lane. Vertically, the radar must not pick up overpasses or tops of tunnels whose height is generally around 6m. As such, the effective beam size is 2.5 degrees horizontally and 3.5 to 5 degrees in elevation,