Differential drive node?

Question

I have a two-wheeled platform controlled by an Arduino that reports motor encoder counts. So I don't reinvent the wheel, I'm looking for a pre-existing ROS node that can convert those counts into standard odometry and tf messages. Is there a standard ROS package that implements this?

I found this differential_drive project, but it appears to be dead and doesn't have a Kinetic package available.

I also found this differential_drive_controller project, but it appears to be more high-level and doesn't support listening to motor encoders directly. I'd still need to implement a custom node to convert my motor encoder messages to joint messages, so if I need to overcome that overhead, it would make more sense to just implement the odometry reporting myself instead of running two separate nodes in memory.

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Originally posted by Cerin on ROS Answers with karma: 940 on 2017-04-09

Post score: 0

Answer 1

I've used differential_drive in Indigo and Jade. You cannot install via rpm but can get the source from GitHub and add to your catkin_src. The original code was for Groovy, but the author has incorporated some changes I supplied to make the package more ROS-up-to-date and remove compile warnings for Hydro and above. (https://github.com/jfstepha/differential-drive)

That said, I no longer use differential_drive for these reasons:

• I intended to use differential_drive together with rosserial_python to talk to an Arduino-based robot controller. However, rosserial proved unreliable on Arduino-class devices with only 2kb RAM, so I had to abandon that approach.

• I shifted to using ros_arduino_bridge, which incorporates the functionality that differential_drive supplies, so I no longer needed it.

If you decide to use differential_drive, a few observations:

• differential_drive incorporates a PID controller in Python to send motor controls via ROS messages. However, the author of differential_drive doesn't recommend that method any more. (From email communication.) He recommends instead putting the PID controller closer to the motor control hardware.

• differential_drive mixes units at times. For example, motor commands sent by the node are in m/s, while odometry returned from the motor control system is in encoder ticks per second.

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Originally posted by Mark Rose with karma: 1563 on 2017-04-10

This answer was ACCEPTED on the original site

Post score: 1