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Speedometers and Collision Reconstruction
ISSN: 0148-7191, e-ISSN: 2688-3627
Published March 28, 2017 by SAE International in United States
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Various mechanisms have been used to drive speedometers and other instrument gauges. This paper reviews the mechanisms used; in particular investigates the ability of stepper motors which have become the most common instrument motor in the last decade to freeze at the apparent reading prior to impact. Stepper motors require power to drive the needle to any indicated position, including having to return it to zero. Hence if power to the instrument is lost as a result of a collision, there is no power to move the needle and it should be left at the reading shown at the moment the power was lost. However, not all stepper motor instruments are the same and before accepting the reading, a number of criteria need to be considered to give a level of confidence in the result. As part of recent ITAI (Institute of Traffic Accident Investigators) crash test events in the UK, a number of instrument clusters were installed in vehicles to simulate both frontal and side impacts. Impact speeds were recorded up to 75mph (120Kph). The results show that some instrument types will hold their pre-impact position even during high speed side impacts while others produce erratic readings.
CitationGoddard, C. and Price, D., "Speedometers and Collision Reconstruction," SAE Technical Paper 2017-01-1412, 2017, https://doi.org/10.4271/2017-01-1412.
Data Sets - Support Documents
|Unnamed Dataset 1|
- ISO 7637-2: 2004(E) Road Vehicles – Electrical disturbances from conduction and coupling
- David Price
- ITAI Contact 77 April 2004
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