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High Accuracy Indoor Location Tracking?
aletterman asks: "I am looking for technology that can allow my company to track the position of a fork lift as it moves around a warehouse. This would allow us to factor out one problem situation - where the lift was when the driver dropped off the product. Based on the width of our warehouse locations, we need a resolution of about +-1ft. Standard GPS can't get that accurate or work well indoors. The fork lifts already have a VT220 terminal running 802.11b, so adding another device would not be difficult. I am currently looking at a product that can triangulate via the RSSI of the 802.11b network, but I am concerned the changes in the product mix and density of the corrugated boxes will change the RSSI and introduce a mis-positioning of the locations. I would prefer that the device transmit a position either serially or via our 802.11b network. Our warehouses are fairly large (300,000+ sqft) and have a large of amount of corrugated boxes. Any suggestions are greatly appreciated!"
Paint a grid on the floor, with squares of 1 sq. ft., possibly with magnetic paint, and install cameras or magnetic sensors to sense the lines passing underneath. Add a compass or rotational sensor to help determine the orientation. Add some maths, stir, and you might just have something that might work. (Or not...)
I suffer from attention surplus disorder.
I dunno if the product you're looking at can handle this, but in principle, just because three points of reference theoretically allows a perfect calculation doesn't mean you can't add more to provide greater resolution in an error-prone environment.
Look into the technology used by the NHL on Fox for making the hockey puck more visible to the home viewers.
Here is an oversimplified diagram, but enough to get you pointed in the right direction.
Glonoinha the MebiByte Slayer
It's a bit more labor intensive, but i think it's the more sensible solution.
Each location (shelf/floor area) has a tag, RFID or iButton would both work i think. Each item/pallette has a similar tag. When dropping an item off he scans them both in with a mobile reader, uploaded to central, linking the two in a database.
Are you looking for the sexiest solution, or one that works?
Remember, it takes 42 muscles to frown and only 4 to pull the trigger of a sniper rifle.
Money is stored in cassettes in a fully automatic warehouse. The actual warehouse uses an automatic system, (if you have seen a storage robot, it isn't a whole lot different). However money is shipped from the loading/unloading dock to the procssing stations and then from the processing stations to the warehouse loading/unloading station using robot forklifts.
The forklift control system was German, but I can't remember whose. They used a pulsed transmission system and used the arrival time for navigation. The main control computer knew where the forklifts were to the centimetre and gave them orders.
See my journal, I write things there
I know a lot of forklifts or other equipment sometimes have a flashing light on top. Could you do something similar, like have a bright light on top of the forklift (and if you have multiple forklifts, each could have a different color light), and have a few video cameras mounted on the ceiling. Every second or so a screencapture program could read a frame from each camera and scan it for the color of the light.
That might cause a problem with employees and their clothing, so you could even use two lights on a forklift, each a different color, so one lift is identified by red and green, or maybe several lights so it shows up as a large blob, bigger than any employee. You won't have to worry about echo or other problems that come from a radio signal in a large warehouse (which is probably made of metal).
A little robotics might get you there. This may or may not be the best way, but it would work:
Careful odometry should get you within a foot or so, assuming you start from a known point. Yet, odometry coordinates inevitably degrade with time as errors build upon themselves.
There exists an algorithm, however, called the Extended Kalman Filter, that can help correct this. Using just a few sonar/iR sensors, corrections can be made to the coordinates.
Basically, as you move your forklift, its margin of error in position keeps increasing. Every once and awhile you fire off a handful of distance measurements from your sensors. Using the EKF, you can use this data along with a map of your warehouse to reduce your margin of error. The more measurements and the more accurate the readings, the closer you can properly position your forklift.
-dave
http://millionnumbers.com/ - own the number of your dreams
This is what you need: the "Bat Ultrasonic Location System", developed at ATT Cambridge labs (former).
From this page:
Encoders are the way to go, but a slightly different way.
YOu need to measure wheel rotation with these encoders. This will give you distance traveled. And mount a gyroscope and integrate to give you absolute angle.
This method will work. Only one thing is, at certain positions, the thing will have to reset. For example, if the fork lift has a specific parking spot, have a reset button set the co-ordinates at that location to (0,0) or whatever.
in most warehouses i've walked through there's often time product, grease, water, or any number of things on the floors. At times, the fork lift will slid through them in full brake. I've seen people play games with it it can become so slick (especially on polished concrete floors).
-Malakai
A Dragon Lives in my Garage
These are two companies I've heard of from Idealab where I used to work:
Newbury Network's Location Server products uses 802.11b signal monitoring to do location detection. They offer a virtual docent system that uses the technology to allow the virtual docents to provide location-appropriate information.
Evolution Robotic's VSLAM lets robots use odometry AND visual data to update its position information.
Depending on the size of the warehouse and the manner of "occlusion" that occurs, I'd say wiring up the warehouse with lots of cameras and triangulating to a beacon would be a pretty straightforward method... The hockey puck, indeed!
Check out the MIT Cricket Indoor Location System. http://cricket.csail.mit.edu/.
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It is commercially available from Crossbox Technologies http://www.xbow.com/Products/productsdetails.aspx