[ros-users] [Discourse.ros.org] [ROS Projects] Project Wayfarer

[Chris Albertson]

I don't mind here but this forum I thought was for announcements about ROS
itself.  Not for people who use ROS.    Eventually whoever manages this
list will jump in and tell us.

As for how to obtain a Wild Thumper with encoders there are several options

The 'Thumper is made in China by a company called "Dagu Robots"  Dagu has a
lot of interesting products  One is this motor.
http://www.dagurobot.com/goods.php?id=87
It is a Wild Thumper motor with encoder.

Also if you email Dagu Customer service and ask.  They will sell you a wild
thumper with this motor replacing the standard motor.   They charge not
much more than the cost of the motors and BELEIVE ME it is worth it to have
then do the work

Those are two ways where you have to deal with the Chinese factory.

The other way is to notice that the motors Dagu is selling are just normal
25D gear motors.   You can buy these from many different vendors.  One is
Pololu.
https://www.pololu.com/search?query=25d+motor&x=0&y=0

You can buy the samemorte and the same encoder from Pololu.    But Pololu
has something else:  They sell motors with no gearboxes.  These come with
and without encoders.   I bought a 25D, 6 volt motor with encoder and not
gearbox and swapped two of these into my stock wild thumper.    Logically
it should have been a screwdriver job and take about 15 minutes   But the
motors in the wild thumper are press fit into this black plastic holders
another is no room for the encoder leads.

One last comment.   You can NOT simple add encoders to the stock Wild
Thumper.  Encoders require the motor to have a "back shaft".  This back
shaft is an extension of the motor shaft out the rear of the motor.   Wild
thumper meters lack this so you have to replace the motor.      When I
found you can buy the motor with no gearbox, that is what I got.

Doing it all over again, I would simply buy the wild thumper from Dagu
directly and save a ton of work.  But if yu already own a wild thumper then
you have to swap the motor on the center  on each side.

Back to ROS....

You are going to need a source of odometry.  So people are using "virtual
odometry" by computing optical flow from video cameras but I think you need
real ground truth to calibrate everything else.   BTW I just discovered 360
degree cameras.  These have a true SPHERICAL field of view.  Yes they see
EVERYTHING.   I want to place one of these on this robot.  I am working on
software right now to computer optical flow.  With a spherical camera, I
think(?) vehicle heading is simply the average optical flow times -1.
These camera cost under $100.    So far i have a helmet mounted camera and
I'm walking, collecting test data.





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