Showing papers on "Collision avoidance published in 1990"
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01 Jul 1990
TL;DR: This paper reformulated the manipulator control problem as direct control of manipulator motion in operational space-the space in which the task is originally described-rather than as control of the task's corresponding joint space motion obtained only after geometric and kinematic transformation.
Abstract: This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an...
3,063 citations
01 Jan 1990
50 citations
01 Jan 1990
TL;DR: SAMUEL, a learning system based on genetic algorithms, is used to learn high-performance reactive strategies for navigation and collision avoidance that also achieve real-time performance.
Abstract: : Navigation through obstacles such as mine fields is an important capability for autonomous underwater vehicles. One way to produce robust behavior is to perform projective planning. However, real-time performance is a critical requirement in navigation. What is needed for a truly autonomous vehicle are robust reactive rules that perform well in a wide variety of situations, and that also achieve real-time performance. In this work, SAMUEL, a learning system based on genetic algorithms, is used to learn high-performance reactive strategies for navigation and collision avoidance. (AN)
41 citations
01 Jan 1990
TL;DR: This paper presents a local approach for real-time collision avoidance among autonomous mobile robots based on non-linear programming and considers multiple mobile robots travelling to their own destinations in a two-dimensional workspace, e.
Abstract: This paper presents a local approach for real-time collision avoidance among autonomous mobile robots based on non-linear programming. Here, we consider multiple mobile robots travelling to their own destinations in a two-dimensional workspace, e. g., automated guided vehicles in a factory shop. Each robot is assumed to have its identical area and limited sensing area represented by closed circles. In this approach, a distance function between neighbouring two robots is introduced to set up the velocity vector constraint for robots. The desired velocity vector, which enables a robot to navigate without collision by following it, is given as the optimal solution of the objective function under this velocity vector constraint. Our method is implemented using the computer simulated robots. The feasibility and effectiveness of our method are also discussed through the simulation results.
18 citations
05 Jun 1990
TL;DR: In this paper, a 3D collision avoidance controller for an autonomous underwater vehicle (AUV) that uses a forward-looking high-frequency active sonar is described, where multiple objects are differentiated by clustering sonar returns, and Kalman filters are then used to track both stationary and moving obstacles.
Abstract: A 3D collision avoidance controller for an autonomous underwater vehicle (AUV) that uses a forward-looking high-frequency active sonar is described. Multiple objects are differentiated by clustering sonar returns, and Kalman filters are then used to track both stationary and moving obstacles. A minimum safe distance must be maintained between the AUV and any obstacle, and a modified potential field is used to determine appropriate maneuvers. The merit function which defines this potential field is based on obstacle bearing, distance, and visit count, as well as the AUV heading, the depth, and the direction of the goal. >
17 citations
17 citations
TL;DR: In this article, a new threat detection criterion is described which provides a better match to the requirements than the well-known modified tau criterion for a civil air transport collision avoidance system.
Abstract: A new threat detection criterion is described which provides a better match to the requirements than the well-known modified tau criterion for a civil air transport collision avoidance system. Experimental evidence is given to show that it also reduces the number of undesirable alerts.
16 citations
TL;DR: In this paper, a model based on probability theory is used to analyze meeting encounters in which it is uncertain at what range the give-way ship will maneuver, and the course alteration ranges of both a giveway and (if necessary) stand-on ships are closely fitted by a simple mathematical model, which is also used to interpret the efficiency of the Collision Regulations.
Abstract: Meeting encounters, in which it is uncertain at what range the give-way ship will maneuver, are analyzed using a model based on probability theory. Course alteration ranges of both a give-way and (if necessary) stand-on ships are closely fitted by a simple mathematical model, which is also used to interpret the efficiency of the Collision Regulations.
16 citations
01 Jan 1990
TL;DR: In this paper, the decision process of navigators on collision avoidance manoeuvres under certain information using a ship handling simulator was analyzed and evaluated with four navigators using the Analytic Hierarchy Process.
Abstract: The authors analysed and evaluated the decision process of navigators on collision avoidance manoeuvres under certain information using a ship handling simulator. Factors concerned with the assessment of risk of collision were evaluated with four navigators using the Analytic Hierarchy Process. The results indicated that the intention of the target vessel was the most important factor for the assessment process. Two series of simulator studies were carried out to get the knowledge base of navigators on collision avoidance manoeuvres. The simulator was frozen at one minute intervals to get a subjective assessment on the process. Based on the results the authors expressed, each subjective assessment on the process at one minute intervals with fuzzy sets. In this way they made a simulation model for collision avoidance manoeuvres with fuzzy reasoning. The parameters of the model were tuned by repeating the simulation. Thereby the authors could find the usefulness of making use of the ship handling simulator for the knowledge acquisition of shiphandling and its evaluation.
14 citations
TL;DR: A 3-dimensional collision avoidance algorithm for controlling complicated machine motions to dynamically compute interference-free zones using a moving frame of reference based on solid modeling.
10 citations
TL;DR: A control strategy for a mobile robot, which makes use of fuzzy reasoning to avoid moving obstacles, which can realize a heuristic avoidance among moving obstacles.
20 Aug 1990
TL;DR: A general and efficient method of using a configuration space for planning a collision-free path for a manipulator among known stationary obstacles is presented.
Abstract: This paper presents a general and efficient method of using a configuration space for planning a collision-free path for a manipulator among known stationary obstacles. The basic approach taken in ...
30 Sep 1990
TL;DR: Presents a design of a collision avoidance switch for the collision avoidance multiple broadcast (CAMB) tree using transistor-transistor logic (TTL) devices and results show that the slotted broadcast star achieves better performance than the unslotted Broadcast star, especially when the traffic load is heavy.
Abstract: Presents a design of a collision avoidance switch for the collision avoidance multiple broadcast (CAMB) tree using transistor-transistor logic (TTL) devices. A simulation study exploring the performance of the broadcast star network in both synchronous and asynchronous operations is also presented. Simulation results show that the slotted broadcast star achieves better performance than the unslotted broadcast star, especially when the traffic load is heavy. >
08 May 1990
TL;DR: A review of future requirements is given and is illustrated by presentation of some experimental systems in the frequency range 2.4-60 GHz which are being studied in Europe.
Abstract: Short-range microwave communication links in traffic and transport can be used for automatic debiting, navigational aid, collision avoidance, and traffic flow improvements. Some examples of existing systems are presented. A review of future requirements is given and is illustrated by presentation of some experimental systems in the frequency range 2.4-60 GHz which are being studied in Europe. >
04 Nov 1990
TL;DR: A model of the total vessel traffic control process that includes the functioning of the human operator (HO) and the vessel traffic services (VTSs) are modeled in their possible role of monitor, conflict detector, and advisor for the total boat traffic system.
Abstract: A model of the total vessel traffic control process that includes the functioning of the human operator (HO) is presented. The vessel traffic services (VTSs) are modeled in their possible role of monitor, conflict detector, and advisor for the total vessel traffic system. The model assumes a number of ships, with a given planned route, in a given confined area. The navigation of each ship is based on a planned route, which is updated by information about the visual scene, instruments, and the VTS. Both normal operation and collision avoidance are modeled. The model is implemented in a C program. Typical traffic situations have been simulated to showing the ability of the model to address realistic vessel traffic scenarios. The model can answer questions related to safety and efficiency, the effect of HO functioning, information necessary to perform tasks, communication between ships and VTS, the optimization of procedures, automation of the total vessel traffic process, etc. >
20 Mar 1990
TL;DR: In this article, the authors reviewed maritime accident statistics during the last two decades and their correlation with the use of collision avoidance equipment, which was mandated for ships larger than 10000 tons by the International Maritime Organization a decade ago.
Abstract: The author reviews maritime accident statistics during the last two decades and their correlation with the use of collision avoidance equipment, which was mandated for ships larger than 10000 tons by the International Maritime Organization a decade ago. The author assumed that there have been no ships totally lost as a result of a collision with automatic radar plotting assist (ARPA) equipment aboard, because he does not know of any. It is known that approximately 80000 ship years of experience with ARPA equipment have been logged. It is pointed out that, if even one ship were totally lost since 1980, the improvement would be a factor of 49:1 in comparison to the previous decade. This improvement becomes 21:1 with a 90% confidence level. Some of the data obtained are based on discussions between ship owners and equipment manufacturers, not information reported formally through official channels. Based upon this information, the improvement factor could be as high as 150:1 in comparison to 1980. The improvement becomes 95:1 with a 90% confidence level. >
01 Jan 1990
TL;DR: In this paper, the authors describe the development of such a system, supported by a simulation environment incorporating two ancillary computers to simulate own-ship and hazard vessel, and the possibility of creating an intelligent guidance system is considered, whose normal task is to lock a vessel onto a predefined track at a given speed and heading.
Abstract: A potential encounter situation between two or more vessels requires an intelligent, reasoned response from the master of each of those vessels. A computer-based expert system for marine collision avoidance should also be capable of emulating all of these functions. Notably, the decision-taking function requires considerably more than a simple mechanistic application of the anti-collision regulations. This paper describes the development of such a system, supported by a simulation environment incorporating two ancillary computers to simulate own-ship and hazard vessel. To date, a very simplistic ship model has been used, comprising simple constant velocity motion plus arcs of circles at constant speed for turning curves. Multivariable system theory is employed to describe the dynamic characteristics of surface vessels to provide a more elegant, and accurate ship model. Optimal control theory is employed to provide a completely automatic guidance system. The possibility of creating an intelligent guidance system is considered, whose normal task is to lock a vessel onto a predefined track at a given speed and heading. If an encounter situation with another vessel onto a predefined track at a given speed and heading. If an encounter situation with another vessel arises, the collision avoidance module will flag the control system as to the necessary course of action to take so that the international regulations are not breached.
23 May 1990
TL;DR: In this paper, the measurement capabilities and limitations of millimetre wave radars for collision avoidance sensors are reviewed, and a system design for a railway collision avoidance system capable of fully automatic control of a train under simple and low speed conditions, and providing useful extra information to the driver of a high speed train or in a complex situation under all weather conditions and at night.
Abstract: The author reviews the measurement capabilities and limitations of millimetre wave radars for collision avoidance sensors. Possible applications include aircraft landing aids, and collision avoidance systems for motorway and railway use. Examples of relevant radar signatures are shown, and the problems of false alarms discussed. A system design is presented for a railway collision avoidance systems capable of fully automatic control of a train under simple and low speed conditions, and providing useful extra information to the driver of a high speed train or in a complex situation under all weather conditions and at night.
TL;DR: In this article, the critical range at which collision is unavoidable by course changing manoeuvre is estimated. But the authors used a new analytical technique, using an area of collision target's position.
Abstract: It is very important and necessary to know the critical range at which collision is unavoidable by course changing manoeuvre. To obtain this it has been necessary to develop a mathematical model of collision avoidance and occurrence. The authors have used a new analytical technique,using an area of collision target's position. Different versions of the critical range by course changing are obtained under assumptions such as a) one ship evades while the other stand on b) one ship evades while being pursued by the other. The study shows that the critical range by course changing depends strongly on the two ship's speed difference and on the permissible manoeuvre.
16 Jul 1990
01 Jan 1990
TL;DR: An algorithm will be presented that ensures safe navigation in an environment in which other vehicles are present and special attention is paid to the problem of navigating in a corridor and how to decide whether to overtake a slower vehicle ahead or not.
Abstract: An algorithm will be presented that ensures safe navigation in an environment in which other vehicles are present. Each vehicle knows its own position and speed and the position and speed of the other vehicles within a certain distance. Each vehicle can assume that the other vehicles try to avoid collision in the same way as own vehicle. It does not know the destination of other vehicles. The space in which a collision manoeuvre takes place is classified in five categories. For each category a collision avoidance strategy is specified, which determines how vehicles pass each other and gives a control law which specifies the actual speed and course alterations during the manoeuvre. Special attention is paid to the problem of navigating in a corridor and how to decide whether to overtake a slower vehicle ahead or not.
30 Sep 1990
TL;DR: Collision, avoidance mechanisms make it feasible to use Ethernet efficiently for voice transmission, and this result is significant in the light of earlier pessimism regarding the suitability of CSMA/CD as voice/data protocol.
Abstract: Ethernet with standard CSMA/CD (carrier sense multiple access with collision detection) is not suitable for voice due to its high bandwidth requirements and low tolerance to network delays. Collision avoidance approaches offer attractive pay-offs in terms of deterministic delays and increased throughputs. Two such mechanisms, virtual slotting and pseudo-token-pass were previously proposed. A collision avoidance technique, frame sensing, is proposed to improve throughput performance of Ethernet for voice transmission. While virtual slotting and pseudo-token-pass form part of the client layer in the OSI model, additional hardware is required for the frame sensing technique. The performance of the three techniques is compared in terms of access delays and the number of voice channels on the network. All the methods provide a substantial improvement over CSMA/CD. Therefore, collision, avoidance mechanisms make it feasible to use Ethernet efficiently for voice transmission. The result is significant in the light of earlier pessimism regarding the suitability of CSMA/CD as voice/data protocol. >