This is the firmware for the Oruga robot. It allows you to interact with the hardware through ROS topics. For example, you can move the robot by sending it /cmd_vel topics or read the generated odometry from the /odom topic.

This firmware is based on the micro_rosso_platformio library.

This software runs on the onboard ESP32 microcontroller. The associated ROS system intended to run on a computer / SBC is available here: oruga_ws. You can find the robot's URDF model and other high-level control tools there.

Oruga is a differential tracked robot for outdoor use. It is based on the Lynxmotion A4WD3 platform and has a custom-built ESP32-based control system.

The wiring schematics are in the docs directory. As always, the first movements must be done with the robot "in the air". If the motor's polarities or encoder directions are reversed, the robot can misbehave violently. It is recommended to run with rviz2 enabled to verify that all directions match: physical motors vs reported odometry and joint rotation in rviz2 (see oruga_ws for instructions).

//FIXME

The default node name for this firmware is oruga_rclc.

The robot subscribes to the following topics:

• geometry_msgs.msg.TwistStamped /cmd_vel.

The robot publishes the following topics to report on movement:

• sensor_msgs.msg.JointState /joint_states for each wheel. The joints are named fl_wheel_joint (forward-left), rr_wheel_joint (rear-right), and so on. Notice that there are 4 joints reported, but if you have tracks installed, the same-side pairs should move in sync.

• nav_msgs.msg.Odometry /odom (and the associated /tf transform)

The robot publishes the following topics from and onboard MPU6050 IMU:

• sensor_msgs.msg.Imu /imu/raw.

• sensor_msgs.msg.Temperature /imu/temperature.

The robot publishes the following topics from and onboard BME680 environmental sensor (installed inside the chassis):

• sensor_msgs.msg.Temperature /internal/temperature

• sensor_msgs.msg.RelativeHumidity /internal/humidity

• sensor_msgs.msg.FluidPressure /internal/pressure

• std_msgs.msg.Float32 /internal/gas_resistance

Some other interfaces associated with micro_rosso are available, such as the /rosout topic and time synchronization service.

//TODO

//TODO udev

Connect your PC to the USB cable, and on a console start the agent:

docker run -it --rm --device=/dev/ttyUSB0 --net=host microros/micro-ros-agent:jazzy serial --dev /dev/ttyUSB0 -b 115200

Do ros2 topic list to see the robot's topics.

At the default 115200 bauds serial setting the system handles topics at about 100Hz. If you go over this, the system might suffer random disconnects. If you need more than this you can increase the serial link speed with the#SERIAL_BAUD define in the main.cpp. You can try 230400, 460800, 921600, and 1500000. Remeber to also change the agent's -b parameter to match.

Some pending work:

• Add a kill switch: pull Sabertooth's S2 low. Also sense (through a divider or a 5 - 3.3 converter) on the ESP32, notify throug topic.

• Emergency stop on IMU limits

• Perhaps isolate 3.3 - 5 everything, S1 serial, and encoders.

• Sense battery voltage (with ADC?), report status

• Alternative ROS architecture, with ros2_control and only joint driver on micro-ros.

Problems with the firmware to be fixed:

• ...

jvisca@fing.edu.uy - Grupo MINA, Facultad de Ingeniería - Udelar, 2024

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