Wheel Slip & Ground Sensors

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Post Sun Feb 19, 2012 10:26 pm

raymondu999 wrote:No no; the concept is sound. The doppler effect you mentioned is how speedguns work.

I just don't think this is what's happening in this example.

Yes, my post was "general".
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italian
 
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Post Sun Feb 19, 2012 10:32 pm

...like I said, it's an optical sensor. It looks down at the ground and sees it moving along. There ya go.

The technical specifics are just a BIT more special than that, but like I say - feel free to read it yourself.
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Jersey Tom
 
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Post Sun Feb 19, 2012 10:34 pm

Yeap that's what I thought too- as I said above. It tracks the distance moved like an optical mouse; then divides by time. Or did you have another purpose in mind JT?
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raymondu999
 
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Post Sun Feb 19, 2012 11:56 pm

No that's about it. It sees a longitudinal and transverse velocity, from which you can determine the sideslip angle of the sensor.

You CAN do some additional math to get ESTIMATES of tire slip angles. Not "perfect" though.
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Jersey Tom
 
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Location: Huntersville, NC

Post Mon Feb 20, 2012 1:08 am

Jersey Tom wrote:...like I said, it's an optical sensor. It looks down at the ground and sees it moving along. There ya go.

The technical specifics are just a BIT more special than that, but like I say - feel free to read it yourself.

Do you know how the optical sensor can detect speed's vector?
As Italian said i know the doppler effect and time of fly method to detect speed, but in this example it's different and i have no idea how sensor works
Squall
 
Joined: 17 Feb 2012

Post Mon Feb 20, 2012 1:11 am

Jersey Tom wrote:No that's about it. It sees a longitudinal and transverse velocity, from which you can determine the sideslip angle of the sensor.

You CAN do some additional math to get ESTIMATES of tire slip angles. Not "perfect" though.

I meant "perfect" as to say it gives you absolutely usable data and only requires a simple maths channel rather than a complex maths channel
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Pierce89
 
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Post Thu Mar 08, 2012 6:43 pm

http://www.corrsys-datron.com/optical_sensors.htm

As was said,Optical sensors are what the "blub" under the nose is used for. They use an optical sensor that looks at the contact patch and measures the ground velocity and the transverse movement of the ground.
By combining several other sensors (steering, ride height, speed, lateral-long G-front and rear separately, suspension movement, tire pressure) either graphically or mathmatically that can determine lateral vs long speed change of the ground. Tire squash and deflection can be calculated from this "added" sensor with more accuracy.
This data can also be used to compare to a rolling tire deflection machine (for the same tire type/compound).
Though I might mention that use of an optical sensor is not perfect and can be "fooled" by pavement changes (it is measuring velocity changes) and needs to be verified
Once the "tire model" is created it is plugged into a simulation program for use in weekend racing conditions.

The "height" of the "blub" is the indication that it isn't a laser ride height sensor as lasers are larger in size than their optical counter parts. Also in side view you will see a side port or lens for the optical to look through.
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Post Thu Mar 08, 2012 7:51 pm

My question is: how an optical sensor can measures the absolute speed vector?
Squall
 
Joined: 17 Feb 2012

Post Fri Mar 09, 2012 2:31 am

Squall wrote:My question is: how an optical sensor can measures the absolute speed vector?

Similar way an optical mouse would.

the mouse has a small, red light-emitting diode (LED) that bounces light off that surface onto a complimentary metal-oxide semiconductor (CMOS) sensor.
The CMOS sensor sends each image to a digital signal processor (DSP) for analysis. The DSP, operating at 18 MIPS (million instructions per second), is able to detect patterns in the images and see how those patterns have moved since the previous image.
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Caito
 
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Post Fri Mar 09, 2012 9:24 am

Squall wrote:My question is: how an optical sensor can measures the absolute speed vector?


The sensor is looking at Long "G" Velocity of the ground movement next to the tires sidewall/contact area. When the car enters a corner, it moves from long "g" (as a decrease in velocity due to lateral velocity). The reflection of the asphalt is the target.
As the tire is in deflection it is in a constant mechanical state of trying to return to it's static "moving" state of Long "G". IE it will resist the lateral movement and attempt to rebound back to 100% long "g" velocity. I hope I make sense to you. It's a very interesting topic...
"Driving a car as fast as possible (in a race) is all about maintaining the highest possible acceleration level in the appropriate direction." Peter Wright,Techical Director, Team Lotus
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