Automatic car wash wheel detector

xanadu

I went through this automatic car wash today and noticed it had a spinning brush to clean your rims.



The touch version of this car wash is like a giant paint scratching robot in somewhat harsh conditions. The guy in front of me opted for the non touch free wash, so I got to see it in action. It pinpointed the tire with ease.

Initially I thought wow the car wash has a machine vision camera that detects a circle like a car tire. But now that I'm trying not to think about anything for the rest of the day... I can't help but wonder how machine vision would see well with all the spraying water.

When I went through I didn't see anything that resembled a camera, lens or even a hole, not to mention there was constantly water flowing all over the place while the wheel cleaner was in action.

So that leaves the question, how does this giant paint scratching robot know where a tire is with speed and accuracy in these conditions?

RDL2004

One of their brochures for a similar system says:

...direct-wired photo cells.

Not sure how else you could wire them. Sounds like marketing speak to me.



http://www.istobalusa.com/uploads/M_SMART.pdf

Beau Schwabe

Photo cells would be "blind" in the water conditions .... an inductive sensor maybe?

Gadgetman

Pressure sensors in the floor?

bsnut

Beau Schwabe (Parallax) wrote: »

Photo cells would be "blind" in the water conditions .... an inductive sensor maybe?

The wash PLC (programmable logic controller) looks at the photoeye that is at the beginning of the car wash entrance to detect the entry and length. Once in the wash, there is a treadle switch to detect the car in the correct position within the wash. Now to detect the wheels is either done with an encoder in the washer itself (based on photo) or uses the photoeye that is at the beginning of the car wash that uses timing to time how long the car is.

SRLM

xanadu wrote: »

Initially I thought wow the car wash has a machine vision camera that detects a circle like a car tire. But now that I'm trying not to think about anything for the rest of the day... I can't help but wonder how machine vision would see well with all the spraying water.

When I went through I didn't see anything that resembled a camera, lens or even a hole, not to mention there was constantly water flowing all over the place while the wheel cleaner was in action.

Beau Schwabe (Parallax) wrote: »

Photo cells would be "blind" in the water conditions .... an inductive sensor maybe?

The wheel is stationary, right? So the system can detect the wheel positions before any washing is done and store that information for later.

xanadu

Good point SRLM, it could be finding the position before the spraying. I still did not see anything resembling a sensor that could detect a wheel though.

It cannot use the position of the car alone, there are too many different sized cars. If it does maybe there is some magic formula involved but that seems overly complex in comparison to a sensor.

I am going to walk down to that car wash this evening and go inside of it without a car and look for sensors and report back. It could be possible the sensor is on the passenger side where I didn't get a good look at it.

xanadu

RDL2004 wrote: »

One of their brochures for a similar system says:




Not sure how else you could wire them. Sounds like marketing speak to me.



http://www.istobalusa.com/uploads/M_SMART.pdf

They could be trying to protect IP. It is possible we'll never know without taking it apart.

Anyone know what the fine is for taking apart a car wash?

kwinn

I would be very surprised if the wheel detection was done with anything other than a simple switch that was opened or closed by the weight of the wheel. Simple, reliable, and cost effective.

xanadu

On the passenger side there are holes, mystery solved.

I think the two lower holes on either side of the black bolt are a distance sensor, possibly doubled up for redundancy. Since there are no holes on the other side I would guess it is measuring distance and not just a break beam. The brush also needs to know how far in to go. My camera didn't pickup what was in the holes at any angle.



If you ever walk into a car wash like this, it's slippery.

bsnut

I think the hole that you are talking about is for the through-beam photoeye (emiter is on one side and receiver on other side) since these work better wet conditions such a car wash.

BTW, when, I worked amusement park industry we use these types of photoeye on water rides, since they work better around water.

Lawson

I'd use an encoder on the drive chain. This combines with the drive-wheel chock gives us the front wheel location. To locate the back wheel, I'd use a tire activated switch at the entrance to measure the wheel-base of every car. (optical beam-brake, pressure switch, etc.)

Marty

knowclue4u

Narrow beam industrial photocells are the item of choice. I do maintenance at an auto-wash. The car position is logged by a PLC and is coded by these types of sensors through small holes in the machine's walls as show in one of the pictures here. The PLC remembers the on-off and logs the tires' and auto's position, some even profile a car or truck. Here is a photo of a sensor. They use a matching Transmit and Receive pair and generally run on 24vdc. They work similar to a garage door safety sensor but have high intensity IR beams which penetrate water well and some read up to 100'. They cost between $50 -$200 each depending upon distance needed and amplified or not. I hope this helps.

erco

knowclue4u swoops in and saves the day on his very first post! Well done I say. Nice to hear some real-world facts from someone who's actively in the game.

Welcome to the forums and keep on posting until you catch up to my post count. Of course, most of my posts (!) are pure drivel, wise cracks, rhyming code and cheap Ebay deals. I'm surprised that the good people of Parallax haven't banned me from the forums.

So please continue with helpful and meaningful posts. IOW, do as I say, not as I do...