Hey! This is an issue I’m well aware of (just this week someone flagged it on GitHub too), but have not put any energy into resolving yet.
As I understand it the fix is a bit more involved than just the dependence on that file, and that it was a more substantial change to the API.
My current plan is that at the end of the build series (which is drawing near!) I will do a video specifically on how to write a hardware interface for humble, and as a demo I will take my foxy one and upgrade it.
In the meantime I’m not sure if anyone else has forked /updated it (I think someone might have but
I can’t remember). If I do find out I’ll post here. As @BigShark3000 helpfully noted, you could have a go at porting it yourself using the ros2_control_demos - if you do then let us know! That’s also a helpful note about the requirement to swap the interface order.
Thanks for the responses BigShark3000 and Josh. I figured it wasn’t going to be a simple fix but thought I would ask to be sure! I’ve been looking through the ros2_control_demos and diffdrive_arduino code to try and understand how it all works… definitely have a ways to go there. If I do manage to get something working, I’ll be sure to share.
ubuntu@ubuntu:~/robot_ws$ colcon build --symlink-install
Starting >>> serial_motor_demo_msgs
— stderr: serial_motor_demo_msgs
CMake Error at CMakeLists.txt:19 (find_package):
By not providing “Findament_cmake.cmake” in CMAKE_MODULE_PATH this project
has asked CMake to find a package configuration file provided by
“ament_cmake”, but CMake did not find one.
Could not find a package configuration file provided by “ament_cmake” with
any of the following names:
ament_cmakeConfig.cmake
ament_cmake-config.cmake
Add the installation prefix of “ament_cmake” to CMAKE_PREFIX_PATH or set
“ament_cmake_DIR” to a directory containing one of the above files. If
“ament_cmake” provides a separate development package or SDK, be sure it
has been installed.
Failed <<< serial_motor_demo_msgs [0.38s, exited with code 1]
Summary: 0 packages finished [0.87s]
1 package failed: serial_motor_demo_msgs
1 package had stderr output: serial_motor_demo_msgs
1 package not processed
ubuntu@ubuntu:~/robot_ws$
Hi Josh, Thanks for a great series. I got pretty much stuck on getting it all to work on a real robot. I’m running Humble on Ubuntu 22.04. Since ROS-Serial has been replaced by MicroRos I went that route.
Here’s my setup:
Ubuntu 22.04 on a virtual machine (some issues along the way as you mentioned but all sorted)
Completed diff drive robot with RPi4 (Ubuntu 22.04), Arduino Due (MicroRos), L298N motor driver.
I can control the robot with Twist messages and I can publish odometry from the Arduino. The problem is getting it to work with ros2_control and specifically implementing a hardware interface.
The way I understand it is that diffdrive_arduino won’t work in this scenario because it relies on ROS-Serial. I did try to use ros2_control_demos to solve the problem but did not succeed.
So my question is:
Can diffdrive_arduino work in this setup?
If so, how do I get that to work?
If diffdrive_arduino can’t work, what are my options?
The MicroRos and ros2_control combo seems pretty new and I can find very little about it. I’ve been working on this for a few weeks now but I’m not getting any further.
Yeah so the confusion here (and it’s not just you, others have had the same issue) is that diffdrive_arduino does NOT use rosserial (or micro-ROS for that matter).
rosserial is a method for sending ROS messages over a serial line (to an Arduino or similar). And now with micro-ROS those kinds of problems can be solved differently.
Whereas diffdrive_arduino isn’t sending ROS messages at all, it is making a pure serial connection to software on the other end, speaking a (very simple) custom protocol. So you shouldn’t have rosserial or micro-ROS running on the Arduino, it doesn’t know anything about ROS, just some simple motor control serial commands. diffdrive_arduino is doing all the translation from ROS to serial.
If you really want to use micro-ROS on the Arduino, it probably makes sense to skip ros2_control completely. And that is a perfectly acceptable setup - just not what I’ve done in my tutorials. In that case you’ll probably want to have the Arduino receiving a Twist and handling all the diff-drive calculations (which it seems you are doing), rather than implenting it on the ROS side.
I hope that clears things up, if not please ask further questions!
Thanks for the super quick reply Josh, that clears it all up. I’m going to stick with your route so that I can follow your track in coming videos. I’m going back to the motor control video to implement RosArduinoBridge and then implement diffdrive_arduino. Plenty of time to play around with MicroRos etc later.
Hi, I’m having a problem getting my pi to locate the ros2 control package using ‘sudo apt install’. It just cannot find it. I’ve updated and upgraded, following the instructions here: Ubuntu (binary) — ROS 2 Documentation: Humble documentation
Any idea what’s going wrong? I’m surprised I can’t get the system to locate it. Is there a workaround? Thanks for any help!
@JoshNewans sir . I was able to run the robot in real time but unable to run in the rviz i.e the robot was not moving in the rviz
I have tried to change frames but no result , is there any solution I was using ros2 humble and 22.04
Hey Jon, this should be fixed with the latest humble update, so if you try an apt update and then go again hopefully it will be there. Let me know if you have further troubles.
Thanks for the great tutorial. I followed everything correctly till Ros2 Controller. My setup is a 4 wheel robot instead of 2 wheels. I have used differential drive and setup wheel count as 2. Everything worked perfectly until I added diffdrive_arduino package. I have modified the package to take in four wheels as input. However the issues are:
When I try driving, all the wheels are reversed. I modified the diffdrive package to take inverted inputs (- for all vel1, vel2, vel3 and vel4). This seems to fix and motors driving correctly
Teleop twist keyboard can be used to control the robot only if linear and angular velocity is set to 0.4xxx. Anything more than 5 or less than 3 does not move the wheels at all.
Not all motors rotate at the same speed.
So, my questions are:
Can I use the previous serial_motor_demo library to complete SLAM setup?
Any ideas why the robot is not responding to twist correctly?
There are a bunch of places that wheel reversing can occur, depending on your hardware. Getting the wrong pins on the driver in, the driver out, the controller, the wrong axis direction in URDF, etc. It sounds like what you’ve done there is probably not the “correct” solution, but if it works, it works
That’s very odd. To start with diagnosing I’ll need more detail on your motors/controllers/drivers etc. (which might also help us with problem 1). Depending on how things are being mapped it’s not unusual for there to be a lower limit that it won’t turn below, but an upper limit is strange.
This is unfortunate, but not too surprising. Again, we’ll need more details on how you have things hooked up but this is where the PID controller comes into play (which if you’re following the tutorials will be external to ROS/Pi stuff, in an Arduino or some other dedicated controller). The quality control of the motors will be a factor, but the PID controller should be able to be tuned to get the motors performing fairly similarly. If you don’t have a PID controller and are running in open loop, that might also be the cause of problem 2.
Sort of. You could modify it to accept a Twist and have differential drive control, but you’d be better off fixing the other issues instead and things should just work.
Yeah, by the sound of things it’s worth stepping through the details of your setup and making sure the low-level motor control is working before touching the ROS-level stuff. If it’s broken then no amount of ROS tweaking will fix things!
So please post some more details about your hardware and how it’s wired up (you can upload pictures to imgur and embed them here) and we’ll see what we can figure out
[INFO] [launch]: All log files can be found below /home/system/.ros/log/2023-03-21-14-56-32-932971-mapperbot-5148
[INFO] [launch]: Default logging verbosity is set to INFO
[ERROR] [launch]: Caught exception in launch (see debug for traceback): Caught exception when trying to load file of format [py]: name ‘Command’ is not defined
Is it possible to set a parameter for defining the Serial Port of arduino in the launch file. I can scan the ports automatically and say on which port is my Lidar and on which is the Arduino Motor Control but I do not know how to set it dynamically in the diffdrive_arduino.
I have lidar and arduino motor control on srial ports of my robot (on usbs of my raspberry pi). Sometimes lidar and arduino changes serial ports (lidar is on 1 instead of 0 and arduino on 0 instead of 1)and i have to change the configuration of both of them and recompile and start again. Is there an way to make it automatically on the start.
Hi Josh, do you know if it is possible to implement a real controller of a robot (reality) and in parallel a Gazebo simulation so that ros2_control controls both the hardware and the behavior in Gazebo like a digital twin? In your article i understood that its either the real robot or gazebo simulation.
Hello
All the hardware and software I use are the same as the one you use. The router is the same. When I connect the router to the development machine with ethernet as you do, and when I connect it to the raspberry pi 4, when I want to control the robot as in the 13th video, it gives a biiiip sound and cuts the internet for a short time. It gives buffer.cpp error, where could I have made a mistake?
