Motors and Gripper

The motor controllers are connected to the Raspberry Pi 4 (4GB RAM), which has Ubuntu 20.04 installed. The motor controllers are controlled using the ROS2 Foxy framework. Optionally one can enable the servo-driven gripper as well.

Usage

In the first terminal, run:

cd motors/
sudo ./scripts/canableStart.sh  # start the CANable interface
source install/setup.bash
ros2 launch ros_phoenix trunk.launch.py

In the second terminal, run:

cd motors/
source install/setup.bash
ros2 run converter converter_node  # optionally add --ros-args -p debug:=true

Last, in a third terminal, run:

cd gripper/
source install/setup.bash
ros2 run servo_control servo_control_node

Now that the motors are set up, in the main/ folder one can launch a slider interface to control each motor and the grippper:

cd main/
source install/setup.bash
ros2 run executor slider_node

Motor control modes

The motor control modes are as follows:

Mode	Value
`PERCENT_OUTPUT`	0
`POSITION`	1
`VELOCITY`	2
`CURRENT`	3
`FOLLOWER`	5
`MOTION_PROFILE`	6
`MOTION_MAGIC`	7
`MOTION_PROFILE_ARC`	10

To simply run a command once to test the motor control, the following command can be used:

ros2 topic pub --once /all_motors_control interfaces/msg/AllMotorsControl "{motors_control: [{mode: 0, value: 0.25},{mode: 0, value: 0},{mode: 0, value: 0},{mode: 0, value: 0},{mode: 0, value: 0},{mode: 0, value: 0}]}"

Motor control limits

The motor control limits are empirically established as follows:

\[ \operatorname{norm}\left(0.75\left(\vec{u}_3+\vec{u}_4\right)+1.0\left(\vec{u}_2+\vec{u}_5\right)+1.4\left(\vec{u}_1+\vec{u}_6\right)\right) \leq 0.6 \]

Going beyond this limit can result in the robot going outside of the workspace, which can be dangerous. Therefore, we enforce this limit in our controllers.