collision detection


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collision detection

[kə′lizh·ən di‚tek·shən]
(computer science)
A procedure in which a computer network senses a situation where two computer devices attempt to access the network at the same time and blocks the messages, requiring each device to resubmit its message at a randomly selected time.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

collision detection

(networking)
A class of methods for sharing a data transmission medium in which hosts transmit as soon as they have data to send and then check to see whether their transmission has suffered a collision with another host's.

If a collision is detected then the data must be resent. The resending algorithm should try to minimise the chance that two hosts's data will repeatedly collide. For example, the CSMA/CD protocol used on Ethernet specifies that they should then wait for a random time before re-transmitting.

See also backoff.

This contrasts with slotted protocols and token passing.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

collision avoidance system

(1) See adaptive cruise control, semiautonomous vehicle and self-driving car.

(2) An in-vehicle safety system that applies the brakes when it detects a possible forward collision. Based on the current driving speed and the distance to the vehicle ahead (determined by radar), a collision avoidance system warns the driver first and intervenes if no human action is taken. Advanced systems can apply the brakes when heading into an oncoming car while turning the corner.

Cross Traffic Avoidance
A cross traffic system alerts the driver that a car or cyclist is about to cross in front. It may also stop the vehicle.

Collision Avoidance in Reverse
Safety devices when backing up a vehicle have matured. The most elementary "rear blind zone assist" is a set of sensors that cause audible beeps when getting close to an object. That evolved to a rear camera that enables drivers to see objects on screen that are directly behind the car. The camera was later augmented with a "cross traffic" or "cross path alert" system that warns the driver when a car is moving perpendicular to the rear. Advanced systems can also sense pedestrians and cyclists and may even be able to apply the brakes as in forward collision detection. See automotive safety systems.


Rear Cross Path Alert
When backing up in this 2017 Honda, cars coming into the driver's path are alerted by audio and visual alerts. In this example, beeps were heard along with flashing orange arrows (right side) as a car was approaching from behind on the passenger side.

CSMA/CD

(Carrier Sense Multiple Access/Collision Detection) The transmission method used in Ethernet networks. When Ethernet was designed in the 1970s, it was a shared medium. At any moment, only one frame from one station was transmitting in one direction (half duplex). See 10Base5 and 10Base2.

With CSMA/CD, if the network is busy when a station wants to transmit (carrier sense), the station waits a random number of microseconds before trying again. However, if two stations coincidentally transmit their frames at exactly the same time, their signals will collide. Both stations detect the collision and back off a random duration before retrying.

Today, collisions have been mostly eliminated, because shared Ethernet gave way to full-duplex, point-to-point channels between sender and receiver (see switched Ethernet). However, CSMA/CD provides compatibility for older shared Ethernet hubs that may still be in place. Ethernet is a data link protocol, and CSMA/CD is a MAC layer protocol (see MAC layer). See data link protocol, Ethernet and CSMA/CA.
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References in periodicals archive ?
In Section 5, we compare our collision detection method with other widely used detection techniques under different intensity of noise and analyze our model, and the experiments as well as the comparisons are also shown.
The collision detection method is largely classified into a method of detecting all nodes of an object and a boundary deteciton method of an object represented by a bounding volume.
These three new types of collision space use different collision detection algorithms and different data structures.
According to our literature review, although research to date has explored a number of aspects of rear-end collision detection, the assumptions and test data used for such collision detection are different.
The rest of this paper is arranged as follows: Section 2 introduces the mathematical basis of the optimal collision avoidance planning, including the evaluation function, the calculation of the parameters of the evaluation function, the TRAC-IK inverse kinematics solver, and the collision detection method; Section 3 presents an overall framework of optimal collision avoidance planning based on trajectory evaluation; in Section 4, we set different evaluation functions of collision avoidance trajectory and test the optimal collision avoidance trajectory planning method proposed in this paper; Section 5 discusses the influence of the replanning time on the optimal trajectory and the statistical law of the parameters of the collision avoidance trajectory; this paper concludes in Section 6.
Inspections of the subway projects are mainly divided into two aspects: one is the single professional of collision detection which are collision detections on construction model and integrated pipelines, the other is overall professional model collision detection.
A literature review of bounding volumes hierarchy focused on collision detection
Collision detection now works with all imported IFC MEP elements as well.
Silicon photonics could significantly increase the power and speed of machines such as supercomputers, data center servers and the specialized computers that direct autonomous cars and drones with collision detection. Eventually, the technology could reach home computers and mobile devices and improve applications from gaming to video streaming.
Nissan has said it hopes to introduce at least some autonomous driving technologies--such as self-parking cars and collision detection systems, to cars by 2016.

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