Robot navigation.

[Rickz2020]

Hey all,

I have a bit of a problem.

I am building a robot and I need to configure the navigation system. I have a GPS device and can code the robot fine, the problem is the navigation.

How do I get my robot from A to B? What I mean is, what if the robot is at (A) and is facing the opposite direction to (B)? The robot would need to turn around and know when it is facing (B)... but how do I accomplish this? Do I need the heading or bearing?

I'm not really clued up on how GPS and navigation works so I would appreciate it if someone could point me in the right direction.

I want the robot to be able to turn and face the direction it needs to go to get to B, regardless of what direction it's facing.

Regards,

Rich.

[s.frings]

As you migth have noticed using a GPS Navigator (e.g. a TomTom) in your real car, those devices do not know the direction you are facing to. You have to drive a little, then you know the direction of movement. Since cars cannot drive sideways and you normally always drive forwards, the TomTom knows what is in front of you after driving a few hundred meters.

I think you need to do the same with your robor or use an additional compass sensor.

[Rickz2020]

Yeah, I thought about driving a bit in a single direction first and then deducing from the coordinates received whether the robot is moving towards or away from the destination, but it's not really ideal.

I thought about the compass sensor too, but how would I use that to determine which way to face my robot? What I mean is, say I'm facing West and my destination is East. How can I know that I must turn 180? With coordinates, how do I tell where the destination coordinates are in relation to where I am?

Do you think I need to use headings and/or bearings?

Rich.

[gloomyandy]

Hi,
Before you go too far down this road I would make sure that the GPS unit provides sufficient resolution for your needs. Normally GPS will not do this for small robots (which tend to operate in small indoor spaces). But if you are getting the needed resolution then I'd love to hear more about your setup.

As to working out the direction etc, then there are a few areas you should investigate. Firstly you probably need to take a look at the concept of a robots Pose, which basically combines both position and orientation information. You may also want to consider using some form of absolute alignment for your co-ordinate system (so maybe aligning one of the axis with magnetic, or true, north). Deciding whether to use an external frame of reference like a co-ordinate system or a more robotic centric one distance/baring), tends to be very application specific. If you want to use maps etc, then co-ordinates tend to be best,...

Good luck and be sure to update us on how the project goes...

[Rickz2020]

Hi,

Well, my robot is not intended for indoor use and with the GPS device, it gives me really good accuracy. Is accuracy what you mean by "resolution"? and if not please tell me what you mean.

I don't really get how to determine the direction of the destination coordinates in relation to the direction the robot is facing. I hope this is not going to be too tough!

As for the setup, well, there isn't really one as of yet, but I have an idea of what I want.

So far I have my GPS device, NXT brick and a remote control car. As you can imagine, the RC car will house the NXT brick and the GPS device. I plan to move to a different platform other than the RC car at a later stage and will reveal more details as I progress. The RC car is really just a testing platform for the navigation and sensors as I am new to this NXT and leJOS.

I also plan to develop an android application to feed data to the robot and update destination coordinates and possibly feed data to a website so that the robot can be tracked via web.

Rich.

[gloomyandy]

Hi,
Sorry I probably wasn't very clear, here's an explanation of how I see the two terms (others may and probably will disagree with my usage!)...

In this case resolution means the smallest distance that can be resolved by the device. So for most indoor robots you would really like to have a resolution of a few centimetres so that you can use it to track the position of the robot. In this context accuracy is more of an absolute term so does it provide totally accurate latitude and longitude figures. For many robots it is not really required to have high absolute accuracy because the important thing is the relative movement from an often know starting point.

Even with an outdoor robot I'm surprised that gps provides sufficient resolution. How are you planning on using the device, what sort of navigation do you plan to use it for?

Either way I'm sure you will have fun...

Andy

[Rickz2020]

Well, the coordinates I receive from the device are really good and more than sufficient. If I open the coordinates up in Google Maps then it shows my house .

Anyways, I am planing on using the device to receive coordinates and move from one way-point to another until the final way-point has been reached. The distance expected to be traveled is in the Km's. It's going to be a long trip for the robot and I will add all sorts of sensors and power sources to it.

I'm confident that I can program it to navigate, I am just not too sure about how to determine which direction to rotate in and face, should the robot be facing the wrong direction.

My final year project starts next year, so I figured this would be a great project and fun too!

[EDV]

I use "AVM Navigator" for autonomous robot navigation and this module needs only in motorized video camera and works pretty well



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