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About 10,000 papers for “Collision avoidance”

COLLISION AVOIDANCE

World Scientific series in robotics and intelligent systems · 1998

Cited by 0

Collision Avoidance

Ison, David · Scholarly Commons (Embry–Riddle Aeronautical University) · 2004

Cited by 0

Spacecraft Collision Avoidance

Charles Bussy-Virat · Deep Blue (University of Michigan) · 2017

The rapid increase of the number of objects in orbit around the Earth poses a serious threat to operational spacecraft and astronauts. In order to effectively avoid collisions, mission operators need to assess the risk of collision between the satellite and any other object whose orbit is likely to approach its trajectory. Several algorithms predict the probability of collision but have limitations that impair the accuracy of the prediction. An important limitation is that uncertainties in the atmospheric density are usually not taken into account in the propagation of the covariance matrix from current epoch to closest approach time. The Spacecraft Orbital Characterization Kit (SpOCK) was developed to accurately predict the positions and velocities of spacecraft. The central capability of SpOCK is a high accuracy numerical propagator of spacecraft orbits and computations of ancillary parameters. The numerical integration uses a comprehensive modeling of the dynamics of spacecraft in orbit that includes all the perturbing forces that a spacecraft is subject to in orbit. In particular, the atmospheric density is modeled by thermospheric models to allow for an accurate representation of the atmospheric drag. SpOCK predicts the probability of collision between two orbiting objects taking into account the uncertainties in the atmospheric density. Monte Carlo procedures are used to perturb the initial position and velocity of the primary and secondary spacecraft from their covariance matrices. Developed in C, SpOCK supports parallelism to quickly assess the risk of collision so it can be used operationally in real time. The upper atmosphere of the Earth is strongly driven by the solar activity. In particular, abrupt transitions from slow to fast solar wind cause important disturbances of the atmospheric density, hence of the drag acceleration that spacecraft are subject to. The Probability Distribution Function (PDF) model was developed to predict the solar wind speed five days in advance. In particular, the PDF model is able to predict rapid enhancements in the solar wind speed. It was found that 60% of the positive predictions were correct, while 91% of the negative predictions were correct, and 20% to 33% of the peaks in the speed were found by the model. En-semble forecasts provide the forecasters with an estimation of the uncertainty in the prediction, which can be used to derive uncertainties in the atmospheric density and in the drag acceleration. The dissertation then demonstrates that uncertainties in the atmospheric density result in large uncertainties in the prediction of the probability of collision. As an example, the effects of a geomagnetic storm on the probability of collision are illustrated. The research aims at providing tools and analyses that help understand and predict the effects of uncertainties in the atmospheric density on the probability of collision. The ultimate motivation is to support mission operators in making the correct decision with regard to a potential collision avoidance maneuver by providing an uncertainty on the prediction of the probability of collision instead of a single value. This approach can help avoid performing unnecessary costly maneuvers, while making sure that the risk of collision is fully evaluated.

Cited by 1Open access

Visual Collision Avoidance

Matthews, Neil David · ePrints Soton (University of Southampton) · 1994

<p>Collision avoidance systems offer the possibility of significantly reducing the costs of road and specifically motorway driving, in terms of both accidents <i>and </i>their associated effects. Additionally, similar schemes such as autonomous intelligent cruise control (AICC) also offer the possibility of increased road capacity.</p><p>Accidents at night are relatively more frequent and severe, and thus this work initially concentrates on the development of techniques and algorithms to automatically detect potential night-time collisions. Hence, this thesis considers the design and development of a complete processing chain, from initial image acquisition, through the recovery of trajectory measures describing the threat or otherwise posed by other road vehicles. </p><p>Since lights are the dominant features in night imagery, a feature extraction algorithm has been developed to locate and extract vehicle tail-lights from input imagery. Trajectories are extracted by tracking such vehicle cues temporally, which may then be passed to a set of trajectory analysis processes.</p><p>The trajectory analysis initially considers area-based recession rates recovered from single regions. However, due to the low signal to noise ratio in the recovered areas and recession areas, a novel pairing technique is developed enabling a subsequent pair-wise trajectory analysis to be performed, which allows significantly improved recession rates to be recovered. A additional clustering technique is also developed which allows pairings consistent with individual vehicles to be aggregated, substantially reducing the number of recovered targets.</p><p>These techniques developed for night driving are further developed and extended to daylight scenarios, by the application of a novel combined vehicle detection and classification system.</p>

Cited by 0

Collision Avoidance Systems

G. L. Perry · The Aeronautical Journal · 1970

The density of air traffic, particularly in the USA, is now X increasing at such a rate that the overloading of the Air Traffic Control system seems inevitable. Fig. 1 shows the expected increase in the size of the US civil air fleet and its operations over an eleven-year span, from 1966 to 1977. Since January 1st 1968, there have been 58 mid-air collisions in the USA, including 19 this year. The majority of these were under positive Air Traffic Control in the vicinity of airports. Some form of airborne system to prevent collisions seems essential for the safe operation of aircraft in the 1970s. A considerable amount of discussion and development has been carried out in the USA during the past 14 years, and some prototype equipments are now flying. The purpose of this paper is to describe the technique employed in these systems, and to suggest an original principle as a design basis for a collision avoidance system (CAS).

Cited by 1

Collision Avoidance Technologies

Raleigh, Lani Hummel · University of North Texas Digital Library (University of North Texas) · 1975

This report is about collision avoidance technologies.

Cited by 0Open access

Midair collision avoidance /

Buckley Air National Guard Base (Aurora, Colo.). Tactical Fighter Wing, 140th. Safety Office., Buckley Air National Guard Base (Aurora, Colo.). Tactical Fighter Wing, 140th. · The Journal of the Abraham Lincoln Association

Cited by 0Open access

Decentralized Collision Avoidance

Jayasri K Janardanan · Insecta mundi · 2013

Autonomous Robots must carry out their tasks as independently as possible and each robot may be assigned different tasks at different locations. As these tasks are being performed, the robots have to navigate correctly such that the assigned tasks are completed efficiently, while also avoiding each other and other obstacles. To accomplish effective navigation, we must ensure that the robots are calibrated to avoid colliding with any kind of object on its path. Each robot has to sense the obstacles on its path and take necessary corrective measure to avoid those obstacles. In a situation with multiple robots, robots may cross each other’s paths and thus algorithms have to be developed to ensure collision avoidance among them. Collision avoidance among multiple robots has been studied extensively over many years. In this thesis, we investigate the Reciprocal n-body Collision Avoidance Algorithm (RCAA) where collision avoidance among multiple robots is addressed. One advantage of RCAA over other techniques is the decentralized approach that allows robots to take collision- avoidance decisions by themselves using only velocity and position of the nearby robots that are along its trajectory. Though this method is widely used, a major limitation is the assumption of perfect sensing, which is not a guaranteed behavior in real environments. In real world scenarios, erroneous measurements may be obtained during which the RCAA is not capable of ensuring perfect collision avoidance. This limitation in the RCAA needs to be addressed and in this thesis, we have devised a method to address this using particle filters. A particle filter is appended to the RCAA to sample velocities and thereby provide the robots with more options to avoid coming in the path of each other. A simulation program has been developed to implement the entire system showcasing different scenarios where the introduction of particle filter has made the system more stable as it ensures a more streamlined and efficient collision avoidance among robots. Advisor: Carrick J. Detweiler

Cited by 1Open access

Collision Avoidance Smartphone

Columbres, Matt, Parisi, Aaron, Schnecker, Joey et al. · DigitalCommons@CalPoly · 2018

There are many instances in day-to-day life where people cannot or would rather not pay full attention to their surroundings. Walking while preoccupied with a smartphone or walking while blind are excellent examples where technology could be used to make the task of avoiding 2collisions reactive, instead of proactive. A device which monitors a user’s surroundings and notifies the user when a potential collision is detected (and, additionally, notifying them as to where the obstacle is with respect to them) could be used to make walking distracted less of a hazard for the user and those around the user and potentially improve navigation for the visually impaired. The device will connect with the smartphone via bluetooth and the information sent by the device will be displayed over a smartphone app, and haptic feedback for the visually impaired. The device should be rechargeable, self-contained, small enough to connect to a smartphone, and it should be able to communicate with any smartphone that has bluetooth capability making the device universal.

Cited by 0Open access

Collision Avoidance Systems

John H. Watt · Journal of Navigation · 1973

I was sorry to have missed the two papers by Captain K. D. Jones and Mr P. J. Houseley on the above subject, presented at a recent meeting of the Institute, and the subsequent discussion. Fortunately both Captain Jones and Mr. Houseley have been kind enough to let me see copies of their papers and I would like to add two pieces of information which may be of interest with reference to Captain Jones's paper. The first is in regard to the making of ‘the first decision’ in clear weather. Captain Jones says that most mariners on sighting a target decide on the risk, or the probable miss distance, by an accurate even if intuitive evaluation of aspect and range. (They must also take into account the relative bearing of the target and its speed relative to that of own ship.) For the purposes of his argument Captain Jones omits from the clear weather case the alternative method of using radar in assessing the risk or probable miss distance. Evidence on the comparative accuracies of these two methods may be of interest; a series of demonstration runs on the Predictor automatic plotting radar in Elettra lll in the English Channel provided an opportunity to obtain some such evidence. On one occasion which I have in mind, under conditions of clear visibility in daylight, a ship estimated at about 2000 tons was seen about 45° off the port bow at a (radar) range of 7 miles in a crossing situation.

Cited by 1Open access

Differentiable Collision Avoidance Using Collision Primitives

Simon Zimmermann, Matthias Busenhart, Simon Huber et al. · 2022 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) · 2022

A central aspect of robotic motion planning is collision avoidance, where a multitude of different approaches are currently in use. Optimization-based motion planning is one method, that often heavily relies on distance computations between robots and obstacles. These computations can easily become a bottleneck, as they do not scale well with the complexity of the robots or the environment. To improve performance, many different methods suggested to use collision primitives, i.e. simple shapes that approximate the more complex rigid bodies, and that are simpler to compute distances to and from. However, each pair of primitives requires its own specialized code, and certain pairs are known to suffer from numerical issues. In this paper, we propose an easy-to-use, unified treatment of a wide variety of primitives. We formulate distance computation as a minimization problem, which we solve iteratively. We show how to take derivatives of this minimization problem, allowing it to be seamlessly integrated into a trajectory optimization method. We demonstrate that the resulting method can be used to plan smooth and collision-free paths based on a variety of single- and multi-robot scenarios with different obstacles.

Cited by 18

Reactive Collision Avoidance Algorithm

Acikmese, Behcet, Scharf, Daniel, Hadaegh, Fred et al. · NASA STI Repository (National Aeronautics and Space Administration)

The reactive collision avoidance (RCA) algorithm allows a spacecraft to find a fuel-optimal trajectory for avoiding an arbitrary number of colliding spacecraft in real time while accounting for acceleration limits. In addition to spacecraft, the technology can be used for vehicles that can accelerate in any direction, such as helicopters and submersibles. In contrast to existing, passive algorithms that simultaneously design trajectories for a cluster of vehicles working to achieve a common goal, RCA is implemented onboard spacecraft only when an imminent collision is detected, and then plans a collision avoidance maneuver for only that host vehicle, thus preventing a collision in an off-nominal situation for which passive algorithms cannot. An example scenario for such a situation might be when a spacecraft in the cluster is approaching another one, but enters safe mode and begins to drift. Functionally, the RCA detects colliding spacecraft, plans an evasion trajectory by solving the Evasion Trajectory Problem (ETP), and then recovers after the collision is avoided. A direct optimization approach was used to develop the algorithm so it can run in real time. In this innovation, a parameterized class of avoidance trajectories is specified, and then the optimal trajectory is found by searching over the parameters. The class of trajectories is selected as bang-off-bang as motivated by optimal control theory. That is, an avoiding spacecraft first applies full acceleration in a constant direction, then coasts, and finally applies full acceleration to stop. The parameter optimization problem can be solved offline and stored as a look-up table of values. Using a look-up table allows the algorithm to run in real time. Given a colliding spacecraft, the properties of the collision geometry serve as indices of the look-up table that gives the optimal trajectory. For multiple colliding spacecraft, the set of trajectories that avoid all spacecraft is rapidly searched on-line. The optimal avoidance trajectory is implemented as a receding-horizon model predictive control law. Therefore, at each time step, the optimal avoidance trajectory is found and the first time step of its acceleration is applied. At the next time step of the control computer, the problem is re-solved and the new first time step is again applied. This continual updating allows the RCA algorithm to adapt to a colliding spacecraft that is making erratic course changes.

Cited by 0Open access

Automobile collision-avoidance radar

Kiyoto, M., Tachibana, A, Motor Industry Research Association (MIRA), Nuneaton (United Kingdom) · OpenGrey (Institut de l'Information Scientifique et Technique) · 1988

Cited by 0