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 ?
For example, high-feed cutters have a cutting geometry that is easy to define using tool management: The program then uses the free geometries of the cutting tool edge for calculation, simulation and collision checking. openmind-tech.com
The Collision Compute Shader level includes a Compute Shader that performs object boundary collision checking, surface collision checking, and subsequent collision response computation.
However, building the RRT tree or connecting PRM edges require extensive collision checking. In our case, collision checking between triangle meshes will severely hurt the performance.
Recently, with the development of parallel computing technologies [32-34], some approaches use GPU technology to improve processing time of robot collision checking [35-37].
Version 10 of its Unibend package features a collision checking feature that enables users to program the machine for new parts.
* performing overall collision checking (automate collision detection between machine/robot/part's elements) in order to prevent such events during part machining/manipulation; performing first stage simulation for i type part's uploading from [C.sub.1i] conveyor on the machine-tool's table, second stage simulation for j type part's uploading from [C.sub.1j] conveyor on the machine-tool's table, third stage simulation for i type part's machining (Fig.
Nearly 7,500 solid models are arranged by machining area or product family and come in the 3D Step format so they can be incorporated into design packages for collision checking in tool path simulations.
When they were run by EEW, PowerMILL fully justified the confidence placed in the software's ability to calculate the residual material model and to undertake collision checking of the milling machine.
It also includes enhanced collision checking that monitors spindle states for milling and turning simulation, enabling Vericut to catch common programming errors with spindle and cutting tool usage.
Collision checking is integral, as is machining, which is tied to either step-over or constant scallop height.

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