Purpose

The purpose of this repo is to control a 3D printed robot arm (with one ODrive actuator and one NEMA17 stepper motor). It uses ROS2 control hardware interfaces to send commands and recieve states from the actuators, and a ROS2 control controller interface to generate joint position commands from cartesian position commands published over a ROS topic. The transformation from end-effector cartesian space to joint-space is done with the help of the Drake library, and uses differential inverse kinematics.

Repo Summary

This repository consists of 3 ROS2 packages and code to run on the hardware to act as a CAN reciever and stepper motor controller. 2 of the ROS packages (odrive_base and odrive_ros2_control) are almost direct copies from the ODrive ROS2 Control github repo.

Setup on RPi 5

It took me a while to figure out how to get ROS2 running and Drake installed on an RPi 5 running Ubuntu 22.04.

Below are some noteable things that I got stuck on...

Installing Drake

I first tried building Drake via bazel build... after installing bazel with bazelisk. Even though the build was successful, I had a lot of trouble connecting the library up to my ROS2 project, which used CMake. It was recommended that since my ROS2 project is built with CMake, I should build Drake with CMake too.

Building Drake via CMake worked better...

First, I added build --jobs=1 to the text file $HOME/.bazelrc, as described in the Drake documentation. Without this, the build failed a few hours in with the error cc: fatal error: Killed signal terminated program cc1plus.

git clone --filter=blob:none https://github.com/RobotLocomotion/drake.git
mkdir drake-build
cd drake-build
cmake ../drake -DCMAKE_INSTALL_PREFIX=/the/destination/you/want
make install

Then, my launch files work as long as I add LD_PRELOAD.

LD_PRELOAD=/home/louis/Documents/drake-build/install/lib/libdrake.so ros2 launch base_packager master.launch.py

I have not yet figured out how to connect the Drake library within base_package's CMakeLists.txt file.

RPi RS485 CAN Setup

Waveshare has good install instructions, however I had to make one change since the RPi5 is running Ubuntu, not RPiOS.

Instead of sudo nano /boot/config.txt, I did sudo nano /boot/firmware/config.txt

Starting CAN on RPi5

Before launching the master.launch.py file, you also need to begin CAN. Make sure the bitrates match on the Arduino's MCP2515, the ODrive S1, and the RPi5 RS485.

sudo ip link set can0 up type can bitrate 250000

Publishing Commands to the ROS Topic

ros2 topic pub /my_ik_controller/commands std_msgs/msg/Float64MultiArray "data:
- 0.5
- 0.5"