Autonomous Robotic Mapping

[mreda]

Does anyone know of any way to create an accurate mapping system for a small area outdoor autonomous robot? I was thinking GPS but they can be off by 3 meters. Then I was thinking some sort of triangulation localization technique but I figured Id put it out there to see if anyone has any ideas.

Thanks,
mreda

[jtrv]

Perhaps this might be of interest to you https://github.com/JacisNonsense/Pathfinder

[mreda]

Originally Posted by jtrv

Perhaps this might be of interest to you https://github.com/JacisNonsense/Pathfinder

This can be added to a robot? I didnt see anywhere where I could purchase one. But it does look promising.

[RyanCahoon]

Originally Posted by mreda

Does anyone know of any way to create an accurate mapping system for a small area outdoor autonomous robot? I was thinking GPS but they can be off by 3 meters. Then I was thinking some sort of triangulation localization technique but I figured Id put it out there to see if anyone has any ideas.

Are you asking about mapping (exploring an area and cataloging features and their positions) or are you talking about localization (finding the position of something within a known area)?

Some variables to consider:
- You said that 3m is too much error, but what sort of resolution are you looking for?
- How large of an area are you dealing with? 10s of meters, 100s of meters, 1000s of meters?
- Is it a fixed workspace (i.e. you can set up beacons) or are you moving into an unknown territory?
- What's the line-of-sight visibility like? Is it a fairly open space, or are there frequently objects which can occlude the robot's sensors? If there are occluders, are they large and metallic (i.e. would block radio frequencies)?
- How much money do you want to spend?


If it's an unknown space, you're going to need something like SLAM. There are many prebuilt libraries available for this (check out some of the ones that are available through ROS for example).

If you have a workspace that you control, here's a few solutions for several settings of the above parameters:
- Use a single camera and use the position and apparent size of a target(s) to determine 3d pose. This is how most FIRST vision systems work, and how the Oculus Rift tracking camera works. For a fairly out-of-the-box solution, take a look at some of the fiducial tracking libraries, such as AprilTags.
- Use several different cameras and track a target(s) and triangulate the pose. This is how motion capture cameras work.
- Use a Microsoft Kinect or other RGBD camera
- One of the magnetic position sensing systems from Sixense
- Use one of the UWB (Ultra-wideband radio-frequency) localization systems. I have one of the kits from Decawave sitting on my desk waiting for when I have enough time to play with it more.
- Use a differential GPS system.
- Place a whole bunch of RFID tags with unique IDs around the space and use an RFID reader to scan the nearest tag to determine your position.
- Mount several string pots to your robot and connect the ends to various points around the space and trilaterate your position. As long as your workspace is very open, you have an instant, high accuracy estimate of your robot's position with very little processing required.

[Jaci]

Originally Posted by mreda

This can be added to a robot? I didnt see anywhere where I could purchase one. But it does look promising.

It's a piece of code that runs on the robot so the robot can 'plan' its movements. Using encoders on the wheels and a gyroscope, you can plot a path using Pathfinder and the code will manipulate the motor outputs in an attempt to follow that path. With a bit of clever code, you could even use something like the NavX (or even still an encoder / gyro combination) to derive your position relative to the origin your robot started at.

[mreda]

Originally Posted by RyanCahoon

Are you asking about mapping (exploring an area and cataloging features and their positions) or are you talking about localization (finding the position of something within a known area)?

Some variables to consider:
- You said that 3m is too much error, but what sort of resolution are you looking for?
- How large of an area are you dealing with? 10s of meters, 100s of meters, 1000s of meters?
- Is it a fixed workspace (i.e. you can set up beacons) or are you moving into an unknown territory?
- What's the line-of-sight visibility like? Is it a fairly open space, or are there frequently objects which can occlude the robot's sensors? If there are occluders, are they large and metallic (i.e. would block radio frequencies)?
- How much money do you want to spend?


If it's an unknown space, you're going to need something like SLAM. There are many prebuilt libraries available for this (check out some of the ones that are available through ROS for example).

If you have a workspace that you control, here's a few solutions for several settings of the above parameters:
- Use a single camera and use the position and apparent size of a target(s) to determine 3d pose. This is how most FIRST vision systems work, and how the Oculus Rift tracking camera works. For a fairly out-of-the-box solution, take a look at some of the fiducial tracking libraries, such as AprilTags.
- Use several different cameras and track a target(s) and triangulate the pose. This is how motion capture cameras work.
- Use a Microsoft Kinect or other RGBD camera
- One of the magnetic position sensing systems from Sixense
- Use one of the UWB (Ultra-wideband radio-frequency) localization systems. I have one of the kits from Decawave sitting on desk waiting for when I have enough time to play with it more.
- Use a differential GPS system.
- Place a whole bunch of RFID tags with unique IDs around the space and use an RFID reader to scan the nearest tag to determine your position.
- Mount several string pots to your robot and connect the ends to various points around the space and trilaterate your position. As long as your workspace is very open, you have an instant, high accuracy estimate of your robot's position with very little processing required.

Thank you these look pretty good. To answer your questions, it will be a known area with little to no variation. I was thinking something with beacons sort of like the UWB setup you were talking about. I wasnt sure how cheap/readily available such a system is.

Thanks

[RyanCahoon]

Originally Posted by mreda

the UWB setup you were talking about. I wasnt sure how cheap/readily available such a system is.

There are definitely more expensive (and correspondingly better performing) systems out there, but the reason why I got the Decawave system was because it's available on Digikey for under $1000. The TREK1000 kit appears to do localization as one of its featured example use cases. (They only had the EVK1000 when I bought mine, so I have to get a couple of them to do full positioning.) The limited testing I've done so far suggests that they perform well within the advertised 10cm accuracy.

[mreda]

Originally Posted by RyanCahoon

There are definitely more expensive (and correspondingly better performing) systems out there, but the reason why I got the Decawave system was because it's available on Digikey for under $1000. The TREK1000 kit appears to do localization as one of its featured example use cases. (They only had the EVK1000 when I bought mine, so I have to get a couple of them to do full positioning.) The limited testing I've done so far suggests that they perform well within the advertised 10cm accuracy.

So if I wanted to record a course and play it back through any means, the only accurate way would be through extremely expensive localization sensors. I saw something out there about a gps + landmark system for working in a predetermined area. Would you happen to know anything about that?

[AustinSchuh]

Originally Posted by mreda

So if I wanted to record a course and play it back through any means, the only accurate way would be through extremely expensive localization sensors. I saw something out there about a gps + landmark system for working in a predetermined area. Would you happen to know anything about that?

You may be thinking about differential GPS. For that to work, you need to be in an environment with little multipath. That means outside with a good view of the sky. Good GPS receivers are even more expensive than what was listed already. (You'll want to look into DRTK, which probably means a $6k+ receiver, and you'll need one for the bot and one for the base station.) You should be able to make cheaper receivers work, but that'll require you to solve the GPS solution yourself from the raw pseudoranges, and spend a lot of work getting the accuracy up.

Another method I've heard used is to point a camera at the ceiling and use identifiable features on the ceiling to localize. QR codes on the ceiling would make that even easier.

[mreda]

Originally Posted by AustinSchuh

You may be thinking about differential GPS. For that to work, you need to be in an environment with little multipath. That means outside with a good view of the sky. Good GPS receivers are even more expensive than what was listed already. (You'll want to look into DRTK, which probably means a $6k+ receiver, and you'll need one for the bot and one for the base station.) You should be able to make cheaper receivers work, but that'll require you to solve the GPS solution yourself from the raw pseudoranges, and spend a lot of work getting the accuracy up.

Another method I've heard used is to point a camera at the ceiling and use identifiable features on the ceiling to localize. QR codes on the ceiling would make that even easier.

This is for outside. Is there a similar method for outdoor use? I know how it would/should work, but actually making this work is what is throwing me through a loop.

[AustinSchuh]

Originally Posted by mreda

This is for outside. Is there a similar method for outdoor use? I know how it would/should work, but actually making this work is what is throwing me through a loop.

DRTK works only outdoors. If you have $ to throw at the problem, contact Novatel and they can tell you all the parts to buy.

[mreda]

Originally Posted by AustinSchuh

DRTK works only outdoors. If you have $ to throw at the problem, contact Novatel and they can tell you all the parts to buy.

And there is the problem I don't have that much money to throw. My budget for this part of the project is rather small. If there is an outdoor version of the ceiling camera idea that might work.

[Alan Anderson]

Originally Posted by mreda

If there is an outdoor version of the ceiling camera idea that might work.

Does your outdoor location have a ceiling?

I think your best bet might be to place visible beacons in known locations around the area, with a 360 degree camera view tracking the direction to each beacon in order to do inverse triangulation.

[tr6scott]

http://www.seattlerobotics.org/encod...ing_a_pid.html

[mreda]

Originally Posted by Alan Anderson

Does your outdoor location have a ceiling?

I think your best bet might be to place visible beacons in known locations around the area, with a 360 degree camera view tracking the direction to each beacon in order to do inverse triangulation.

thats more along the lines of what i was thinking. Is there a system out there that has this already?