[ros-users] iRobot - Roomba vs Create

Sat Dec 4 20:46:08 UTC 2010

Using the brown-ros-pkg driver for the Creates we've found the odometry to
be good enough that gmapping/amcl can handle the error (with the shorter
range URG-04LX-UG01 lidar). However, I can't say we've gone more than maybe
an hour during any particular run. (also, just a note, I can't seem to find
the reference anywhere, but I seem to recall the Create encoders being 26
cpr of the drive wheel)

Mike Ferguson
ILS Social Robotics Lab
SUNY Albany

On Sat, Dec 4, 2010 at 3:18 PM, Ken Conley <kwc at willowgarage.com> wrote:

> 2010/12/4 Gonçalo Cabrita <goncabrita at gmail.com>:
> > out.  Also the Create can have that green block, the Command Module that
> I
> > believe can be used to connect a bunch of stuff that can be accessed over
> > the iRobot OI protocol.
>
> We ended up not using the Command Module.  To the best of my
> understanding, it's meant to be used as alternative to mounting your
> own laptop.  The OI protocol appears to be disabled whenever the
> Command Module is connected.
>
> > Still, bottom line, if the Roomba's odometry proves to be better I would
> go
> > for the Roomba. However that ROS vision odometry stack could solve the
> > odometry problem if one could use a cheap one camera system (at the
> expense
> > of extra computational power, which in our case is really bad since we
> have
> > tiny EeePCs!!!).
>
> We've thought about trying the Neato XV-11's instead -- they're more
> expensive, but you get LIDAR.  However, they don't sell stripped down
> units nor publish their documentation like iRobot does, so we're going
> with the Creates for now.
>
>  - Ken
>
> > Gonçalo Cabrita
> > ISR - University of Coimbra
> > Portugal
> > On Dec 4, 2010, at 7:22 PM, Ken Conley wrote:
> >
> > FYI: We're starting an effort here at WG to use Creates.  We didn't
> > benchmark against the Roombas, and perhaps some of those will end up
> > in our arsenal as well.  Also, we've noticed Gonçalo's great
> > documentation coming online, so we hope we can build on each other's
> > efforts.  We're using it to integrate some of our main libraries
> > (navigation, OpenCV, PCL) into a low-cost platform.  We've already
> > posted our Kinect + Create tutorial, which is part of this effort.
> >
> > One main difference between the Creates and the 500 series is (IIRC)
> > that you can't read the raw encoder counts off the Create. The Open
> > Interface for the Create only goes up to Packet 42. The 500 Open
> > Interface adds Packets 43-58, which include encoders, light bumper,
> > motor currents, and stasis caster. I assume this means the odometry
> > with the Create will be worse, but, like Gonçalo, I don't have
> > experience with both.
> >
> > Our driver right now is in Python and uses Damon Kohler's PyRobot,
> > plus bits and pieces for other ROS drivers.  The stack is still a work
> > in progress and will move soon, but for now you can find it here:
> >
> https://code.ros.org/svn/ros-pkg/branches/trunk_cturtle/stacks/create_robot/
> >
> > - Ken
> >
> > 2010/12/4 Gonçalo Cabrita <goncabrita at gmail.com>:
> >
> > 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
> >
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