ROS2 creating a robot arm
Based on the previous work, it is also easily possible to create a robot arm. In this chapter, we discuss the example of a prbt robot which has six axis that are controlled via CANopen.
Bus configuration
The bus configuration needs to configure six drives of the same type. The bus looks like this:
id 1: master
id 3: joint_1
id 4: joint_2
id 5: joint_3
id 6: joint_4
id 7: joint_5
id 8: joint_6
The robot uses interpolated position mode for controlling the robot in position mode.
options:
dcf_path: "@BUS_CONFIG_PATH@"
master:
node_id: 1
driver: "ros2_canopen::MasterDriver"
package: "canopen_master_driver"
sync_period: 10000
defaults:
dcf: "prbt_0_1.dcf"
driver: "ros2_canopen::Cia402Driver"
package: "canopen_402_driver"
period: 10
enable_lazy_load: false
heartbeat_producer: 1000
switching_state: 2 # Switch in CiA402 State 2
position_mode: 7 # Use interpolated position mode
scale_pos_from_dev: 0.00001745329252
scale_pos_to_dev: 57295.7795131
sdo:
- {index: 0x6081, sub_index: 0, value: 1000}
- {index: 0x60C2, sub_index: 1, value: 15} # Interpolation time period at 10 ms matches the period.
- {index: 0x6060, sub_index: 0, value: 7} # Make default mode to interpolated position mode.
tpdo: # TPDO needed statusword, actual velocity, actual position, mode of operation
1:
enabled: true
cob_id: "auto"
transmission: 0x01
mapping:
- {index: 0x6041, sub_index: 0} # status word
- {index: 0x6061, sub_index: 0} # mode of operaiton display
2:
enabled: true
cob_id: "auto"
transmission: 0x01
mapping:
- {index: 0x6064, sub_index: 0} # position actual value
- {index: 0x606c, sub_index: 0} # velocity actual position
3:
enabled: false
4:
enabled: false
rpdo: # RPDO needed controlword, target position, target velocity, mode of operation
1:
enabled: true
cob_id: "auto"
mapping:
- {index: 0x6040, sub_index: 0} # controlword
- {index: 0x6060, sub_index: 0} # mode of operation
- {index: 0x60C1, sub_index: 1} # interpolated position data
2:
enabled: true
cob_id: "auto"
mapping:
- {index: 0x607A, sub_index: 0} # target position
nodes:
prbt_joint_1:
node_id: 3
prbt_joint_2:
node_id: 4
prbt_joint_3:
node_id: 5
prbt_joint_4:
node_id: 6
prbt_joint_5:
node_id: 7
prbt_joint_6:
node_id: 8
Control configuration
The ros2_rontol configuration requires the prbt.ros2_control.xacro.
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
<xacro:macro name="prbt_ros2_control" params="
name
prefix
bus_config
master_config
can_interface_name
master_bin">
<ros2_control name="${name}" type="system">
<hardware>
<plugin>canopen_ros2_control/RobotSystem</plugin>
<param name="bus_config">${bus_config}</param>
<param name="master_config">${master_config}</param>
<param name="can_interface_name">${can_interface_name}</param>
<param name="master_bin">"${master_bin}"</param>
</hardware>
<joint name="${prefix}joint_1">
<param name="device_name">prbt_joint_1</param>
</joint>
<joint name="${prefix}joint_2">
<param name="device_name">prbt_joint_2</param>
</joint>
<joint name="${prefix}joint_3">
<param name="device_name">prbt_joint_3</param>
</joint>
<joint name="${prefix}joint_4">
<param name="device_name">prbt_joint_4</param>
</joint>
<joint name="${prefix}joint_5">
<param name="device_name">prbt_joint_5</param>
</joint>
<joint name="${prefix}joint_6">
<param name="device_name">prbt_joint_6</param>
</joint>
</ros2_control>
</xacro:macro>
</robot>
In addition we need to define the ros2_controllers.
controller_manager:
ros__parameters:
update_rate: 100 # Hz
joint_state_broadcaster:
type: joint_state_broadcaster/JointStateBroadcaster
forward_position_controller:
type: forward_command_controller/ForwardCommandController
arm_controller:
type: joint_trajectory_controller/JointTrajectoryController
forward_position_controller:
ros__parameters:
joints:
- prbt_joint_1
- prbt_joint_2
- prbt_joint_3
- prbt_joint_4
- prbt_joint_5
- prbt_joint_6
interface_name: position
arm_controller:
ros__parameters:
joints:
- prbt_joint_1
- prbt_joint_2
- prbt_joint_3
- prbt_joint_4
- prbt_joint_5
- prbt_joint_6
command_interfaces:
- position
state_interfaces:
- position
- velocity
stop_trajectory_duration: 0.2
state_publish_rate: 100.0
action_monitor_rate: 50.0
goal_time: 0.6
constraints:
goal_time: 0.6
stopped_velocity_tolerance: 0.05
prbt_joint_1: {trajectory: 0.157, goal: 0.01}
prbt_joint_2: {trajectory: 0.157, goal: 0.01}
prbt_joint_3: {trajectory: 0.157, goal: 0.01}
prbt_joint_4: {trajectory: 0.157, goal: 0.01}
prbt_joint_5: {trajectory: 0.157, goal: 0.01}
prbt_joint_6: {trajectory: 0.157, goal: 0.01}
limits:
prbt_joint_1:
has_acceleration_limits: true
max_acceleration: 6.0
prbt_joint_2:
has_acceleration_limits: true
max_acceleration: 6.0
prbt_joint_3:
has_acceleration_limits: true
max_acceleration: 6.0
prbt_joint_4:
has_acceleration_limits: true
max_acceleration: 6.0
prbt_joint_5:
has_acceleration_limits: true
max_acceleration: 6.0
prbt_joint_6:
has_acceleration_limits: true
max_acceleration: 6.0
Launch files
We have already prepared the launch files for you. To run the robot you need to do the follwing:
Terminal 1
sudo modprobe vcan
sudo ip link add dev vcan0 type vcan
sudo ip link set vcan0 txqueuelen 1000
sudo ip link set up vcan0
. install/setup.bash
ros2 launch prbt_robot_support prbt_fake_slave.launch.py
Terminal 2
. install/setup.bash
ros2 launch prbt_robot_support robot.launch.py
Terminal 3
. install/setup.bash
ros2 launch prbt_robot_moveit_config vcan.launch.py
Terminal 4
. install/setup.bash
ros2 control switch_controllers --activate arm_controller --deactivate forward_position_controller
In case there is an error with the ros2 control command, install it using the following command:
sudo apt install ros-rolling-ros2controlcli
Once you ran the ros2 control switch_controllers command, you can use the ros2 control list_controllers command to see the current state of the controllers.
The arm controller should be active.
No you can use RVIZ (moveit) to move your robot arm. The robot arm is emulated on the vcan0 interface.
You can also use candump vcan0 to the the CAN communication with the fake drives.