dead reconing navigation with compass modual

Solo460

Is there any way and is it possible for a boe bot to use the compass sensor for navigation by degrees north or south and to help it go straight. Basicly jave it do dead reconing with a compass and a wheel distance sensor. Any help on this is appreciated.

Mike Green

Not really.

The problem is that the compass isn't that precise nor, for that matter, are the wheel encoders (wheels slip on the floor). You can demonstrate dead reckoning using a compass and wheel encoder and demonstrate how quickly the robot loses its way as errors accumulate.

Solo460

Ok so is it even possible to make a decient dead reconing bot? Maybe using a gyro and a mechanical or gps distance mesuring tool. Or do i need to look at a better micro controler
Any help is appreciated.

agfa

As Mike pointed out, errors do accumulate causing a robot to loose it's way, but I think the challenge for most is to demonstrate how accurately it can find it's way, not how quickly it looses it.

I think it's possible to make a decent dead reckoning robot with what you have. Some do it with just wheel encoders. The accuracy can be increased by adding additional sensors to help such as, bump sensors, compass, gps, IR, sonar and using techniques such as mapping or triangulation.

You could start by buying, or making some wheel encoders. You can get these at Parallax
http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/80/Default.aspx?txtSearch=wheel+encoders
Using the link on the product page, you can download a tutorial that is very helpful wheather you use the encoders or not.

Take a look in the robotics forum. You can find several threads discussing this.

agfa

erco

Compasses are too inaccurate, but I've been happily surprised at the accuracy that careful dead reckoning can yield. Low speeds, careful acceleration/deceleration, optical encoders, tight transmissions and dynamic braking are key. Check the long & winding thread at http://forums.parallax.com/showthread.php?t=118861 and a video at http://www.youtube.com/watch?v=PX0IhUqnwrk

Damo

I've used dead reconing on the boe bot with a HMC3652 compass. I swapped the basic stamp board for the MSRI propellor board. The basic stamp was not fast enough to make all the calulations.

I also used the ping sensor to make corrections as it travelled, this way there were no accumulated errors. The HMC6352 compass was able to give very accurate results once I adjusted to programme to use averaged values, to remove the jitter.

However, these compasses are affected greatly by their surroundings, so different results were given at different points in the room. (kinda ruined the whole project really.)

Good Luck.