GPS Questions?

Lynxmotion
1

Hey everyone,

I have a couple of questions to ask about some electronic stuff.
1)I know some people use a GPS thing to control where there robots move. I was wondering how these worked and if you can only send them to one destination before having to reprogram the robot.
2) what kind of board would i need to control this
3) how would I go about programming this board

Just to let you know my next project will hopefully be a GPS controlled wheelchair for a handicapped person

thanks

2

We could have used a better topic title!

First, I don’t know how many here use GPS for indoor robots, or even small scall outside robots. Perhaps a few. GPS has accuracy limitations, and normally doesn’t work indoors without a repeater of some sort. I understand the Robo-Magellan 'bots use GPS in addition to other sensors.

David P. Anderson and Mike Hamilton’s Journey Robot is an example of the size of robot that would use GPS.

geology.smu.edu/~dpa-www/robo/jbot/index.html

I’ve played with GPS. I’ve written code for programs that use GPS and plot positions, and do triangulation to targets (RDF).

I believe in a robot, GPS is used to “locate” the robot. It doesn’t directly “control” the robot. I suppose one COULD use waypoints programmed into the GPS, and use the heading corrections to control the path of the 'bot. Much the same as in ship navigation (auto helm).

With GPS and usually a compass, one could plan a course heading to a goal, and monitor the progress to that goal.

Study the GPS sentences, and you’ll find the ones that give you the information you need.

aprs.gids.nl/nmea/

You could have your 'bot controller set new waypoints. If you have the Lat/Lon location of your destination, you can also calculate the heading and range yourself. Although you’re more likely (more interesting) to want to plan a course around obstacles, and use the GPS “fixes” and headings to tell where you are.

Most any controller board with an RS-232 interface can read the messages from a GPS, and program waypoints as well.

How to program all this? Have you done any map work? Get familiar with the GPS sentences, compass output (I2C?) Robot control (you haven’t told us if you’re planning a walker or a wheeled 'bot). The course planning and mapping would probably be another “layer” on top of most any 'bot controller. You need to pass the 'bot controller a direction as a goal, and no doubt speed. That’s for starters. Are you ready for DARPA?

Alan KM6VV

3

You probably need to do a good bit of up front reading and research on what others have done. A google search for “GPS robot” is a good start. Bare in mind that a GPS “controlled” wheel chair will carry a significant amout of legal libility that should be checked into.

4

I want to eventually put GPS on W.A.L.T.E.R. I think he’s large enough now to go outside too. I don’t see it being of any use indoors though.

How do you do the triangulation? How do you know how to get from where you are to where you want to be? This has to be very useful for a RoboMagellan robot. I’m interested in this also.

This is pretty much what the RoboMagellan robots do, but jBot has superior navigation abilities without GPS.

This is apparently how the RoboMagellan robots do it, or at least try to do it. I want a chance to write some software for GPS and see what I can do with it.

This is what I have thought, but maybe out in the great outside it doesn’t work well. It seems like more robots that use GPS should be successful, but look at jBot with no GPS.

8-Dale

5

The GPRMB and GPRMC GPS messages are possible sources of range and bearing to destination. Other information as well.

There is even a project for an R/C auto pilot using a PIC. There is BASIC code for reading the GPS messages, and computing a heading correction. I haven’t studied the code yet. But if you want to work with way points and a GPS, this could probably do it.

rcpilot.sourceforge.net/modules/rcap/index.php

rcpilot.sourceforge.net/docs/nmea.html

$GPRMB,A,0.66,L,003,004,4917.24,N,12309.57,W,001.3,052.5,000.5,V*0B

A Data status A = OK, V = warning 0.66,L Cross-track error (nautical miles, 9.9 max.), steer Left to correct (or R = right) 003 Origin way point ID 004 Destination way point ID 4917.24,N Dest way point latitude 49 deg. 17.24 min. N 12309.57,W Dest way point longitude 123 deg. 09.57 min. W 001.3 Range to destination, nautical miles 052.5 True bearing to destination 000.5 Velocity towards destination, knots V Arrival alarm A = arrived, V = not arrived *0B mandatory checksum

$GPRMC,220516,A,5133.82,N,00042.24,W,173.8,231.8,130694,004.2,W*70

      1   220516     Time Stamp
      2   A          validity - A-ok, V-invalid
      3   5133.82    current Latitude
      4   N          North/South
      5   00042.24   current Longitude
      6   W          East/West
      7   173.8      Speed in knots
      8   231.8      True course
      9   130694     Date Stamp
      10  004.2      Variation
      11  W          East/West
      12  *70        checksum

HTH

Alan KM6VV

EDIT: And another one in C.

longtail.com/UAV2.c

6

Fixed…

7

Thanks for fixing the topic name.

After seeing the two GPS examples I’ve mentioned, I’m beginning to think that GPS in an “outside” 'bot may be useful.

Alan KM6VV