[ros-users] iRobot - Roomba vs Create

[Gonçalo Cabrita]

Hi Alex,

Hope you don't mind I started a new thread for this.

Buying the Roomba instead of the Create was not an option for us. At first we were aiming for the Create since it was designed having research in mind, but the Portuguese iRobot reseller told us we could only acquire the Create on the United States. So we got a sweet deal on a bunch of Roombas instead. Let it be clear that I never worked with a Create in my life, so I cannot make a comparison between both robots.

When we first got the Roombas we had some trouble with the odometry... ok a lot of trouble! The Roombas have very poor encoders, single channel, 4 pulses per motor shaft turn (I believe direction is determined from the motor speed, I don't think you can even call this an encoder). Also, initially we were getting distance travelled and amount turned from the robot, which resets after each read, so at the speed we were polling the Roomba (10Hz) and due to the low resolution on these values (1 degree for the angle for example), we were getting really bad odometry readings. Later we decided to poll the encoder counts instead, which greatly improved our odometry (this is how the roomba_500_series package works) however we bumped into another problem. Usually encoder counts increase as the wheel moves forward and decrease as the wheel moves backwards. However on some Roombas encoder counts only increase. You can still make a quick fix using the motor speeds as an indicator of the wheel direction, but the odometry on these robots is far worse. Now that i think of it, this should go into the roomba_500_series troubleshoot section! We recently got a batch of 555, non of them seem to have this problem. However some of the 530 and 560 we have suffer from the "crappy" encoder problem.

Globally the Roomba is a very robust platform, it can take a lot of beating. It also brings a nice package of sensors and actuators. iRobot 's documentation on the communication protocol is very good, you get access to pretty much everything the Roomba has. The docking station is very cool, we love it. The battery usually holds for 2-3 hours pumping juice to the Roomba and an Hokuyo laser. We run it with the ROS navigation_stack and it moves without problems

Finally I guess for the money we spent we couldn't expect better, the value for money is great, specially for us, we have a lot of Roombas for swarm and multi-robot experiments. You can't compare it to a robot designed specifically for research though.

Now I guess people who are using the Create could give their opinion on this matter :)

Hope this helps!

Gonçalo Cabrita
ISR - University of Coimbra
Portugal

On Dec 4, 2010, at 6:01 PM, Alex Bravo wrote:

> Goncalo,
>  
> I've been looking at the package you created for Roomba 560 http://www.ros.org/wiki/roomba_500_series
> and I just wanted to say thank you for such an excellent job!
>  
> We are considering purchase of iRobot and wondering if extra expense of Roomba 535/560/570 is worth it compared to iRobot Create. We also see that, say Brown University still uses iRobot Create.
>  
> Considering your experience (if I remeber correctly, you were mentioning those robots a year ago), what are you thoughts on the advantages/disadvantages between those models?
>  
> Thank you,
> Alex Bravo
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osuosl.org/pipermail/ros-users/attachments/20101204/2c321a84/attachment-0002.html>