Has anyone worked with this technology for automotive applications? This is in connection to using this technology to measure ground speed of vehicles. But it would have to be cost competitive with the other conventional methods...
Ideas? Thanks.
Measure speed of vehicle from side of road or onboard vehicle measure same vehicle speed accuractely?
There have been various optical and doppler techniques onboard vehicles for highly accurate dynamic speed measurements for many years. Especially used for measuring speeds on test vehicles, during logging of other attributes.
Long time since I had dealings with them (like 15-20 years) from my days of visiting research and engineer folks at some of the manufacturers.
Don't even get me on some of the test names.
Over here the speed cameras usually have a doppler trigger (or other trigger) but two photos have road markers, to back up the trigger.
Mind you the early bull-horn style of hand held 'radar' guns actually doppler could measure the speed of trees up to 80 mph.
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Yes.
It depends.
Are you trying to measure the vehicle speed from some other location or are trying to make the ground speed sensor to be located onboard the vehicle?
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
If the trees were going 80 mph I sure wouldn't want to be the one standing there with a radar gun taking the measurements.
(Sorry, it's late...)
you can use magnet and a hall effect sensor. put magnet on one of rims and put sensor onto the chasis. Of course they must see each other each wheel turn. Use timers to measure each pass of magnet. I think it is going to be very accurate.
I used SAM7 timer prescaled mck/1024. It was still to fast for my application.
What, exactly, do you want to do that isn't already being done cheaply and reliably by standard vehicle speedometers?
-- Guy Macon
What reasons could there be to use this method when the job is already performed quite adequately/reliably/accurately by:
1) sender on transmission output shaft (most vehicles) 2) wheel speed sensors (ABS/Traction control equipped cars) 3) GPS/Radio telemetry (High end race car telemetry systems)1 & 2 work perfectly well so long as wheels have traction, and 3 works so long as there is adequate signal sources.
And if you are thinking about doing this on road going vehicles how is your system going to cope with the multiple doppler returns you will get in traffic moving at different speeds?
Sorry, but this idea sounds like a non-starter to me unless it is being incorporated with a self-drive/collision avoidance radar/lidar/sonar system.
There are quite many practical cases when the standard speedometer/odometer can't be used.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
Use a laser Doppler velometer. You would have to develop the technique further for use slung underneath a vehicle measuring ground speed. I used the technique with great success in the early 80's as a non contact means of accurately measuring (i.e. without slippage) velocity of high speed strip products in manufacturing industry.
Alternatively develop a system based around high speed frame imaging and direction sensing as used in today's optical mice.
Icky
Any optics gets covered with the dust and dirt, especially in the vehicle environment. The optical sensors like you mentioned can hardly be used for anything other then R&D and testing. The microwave and the ultrasound speed pickups are much more robust.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
OBD-II has a code that gives you speed. That applies to a large enough market segment that it may be worthwhile to forgo the vehicles that don't have OBD-II.
-- David M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)
In article , ElderUberGeek writes
It's been done already.
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Not quite.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
Hi All, Out of curiosity asking this: How do they measure speed when you are flying in an aircraft?Guess its even more difficult then what we do in ground,believe we also need more accuracy incase of flying vehicle?Can anyone share their thoughts?
Regards, s.subbarayan
Radar, GPS, radio beacons, inertial nav systems.. take your pick.
El Chippy wrote in news:46889b1a$1 @news01.wxnz.net:
And Doppler :-))
Sam
Get a standard optical mouse and drag it behib=nd the car. As it travels over the road se=urface you can log how far it went.
I hope the helps...
How do you measure the speed of the elephant?
VLV
In article , ssubbarayan writes
You need two speeds. The distance flown in the air and ground distance covered.
-- \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ \/\/\/\/\ Chris Hills Staffs England /\/\/\/\/ /\/\/ chris@phaedsys.org www.phaedsys.org \/\/\ \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Aircraft measure airspeed, not ground speed. ie 90knts airspeed into a 30knts headwind, results in 60knts groundspeed.
The airspeed is derived by comparing the static airpreasure (air preasure outside the aircraft) against the preasure rushing into a sensor as a result of moving forward through the air.
For aircraft, airspeed is what is important, as too little airspeed, the plain will litterly fall out of the sky.
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