key_teleop

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Description

The key_teleop node provides a terminal-based keyboard teleoperation interface for controlling robot velocity using arrow keys. It uses curses to create a text-based interface in the terminal, allowing users to control linear and angular velocities with simple key presses.

Publishers

Topic	Type	Description
`key_vel`	`geometry_msgs/msg/TwistStamped` or `geometry_msgs/msg/Twist`	Publishes velocity commands based on arrow key inputs. Type depends on `twist_stamped_enabled` parameter

Parameters

Parameter	Type	Default	Description
`twist_stamped_enabled`	bool	true	If true, publishes `TwistStamped` messages; if false, publishes `Twist` messages
`hz`	int	10	Publishing rate in Hz
`forward_rate`	double	0.8	Linear velocity scale factor for forward movement (m/s)
`backward_rate`	double	0.5	Linear velocity scale factor for backward movement (m/s)
`rotation_rate`	double	1.0	Angular velocity scale factor for rotation (rad/s)

Example Usage

Basic Launch

ros2 run key_teleop key_teleop

Launch with Parameters

ros2 run key_teleop key_teleop --ros-args \
  -p hz:=20 \
  -p forward_rate:=1.0 \
  -p backward_rate:=0.5 \
  -p rotation_rate:=2.0 \
  -p twist_stamped_enabled:=false

Launch with Configuration File

ros2 run key_teleop key_teleop --ros-args --params-file /path/to/config.yaml

Example Configuration File

key_teleop:
  ros__parameters:
    hz: 10
    forward_rate: 0.8
    backward_rate: 0.5
    rotation_rate: 1.0
    twist_stamped_enabled: true

Example Launch File

from launch import LaunchDescription
from launch_ros.actions import Node
from ament_index_python.packages import get_package_share_directory
import os

def generate_launch_description():
    config_file = os.path.join(
        get_package_share_directory('key_teleop'),
        'config', 'key_teleop.yaml'
    )
    
    return LaunchDescription([
        Node(
            package='key_teleop',
            executable='key_teleop',
            parameters=[config_file],
            output='screen',
            emulate_tty=True  # Important for curses to work properly
        )
    ])

Remap Output Topic

ros2 run key_teleop key_teleop --ros-args -r key_vel:=cmd_vel

Operation

Keyboard Controls

Key	Action
↑ (Up Arrow)	Move forward
↓ (Down Arrow)	Move backward
← (Left Arrow)	Rotate left (counterclockwise)
→ (Right Arrow)	Rotate right (clockwise)
q	Quit the node

Behavior

Multiple arrow keys can be pressed simultaneously for combined motion
Key presses are effective for 0.5 seconds; hold the key to maintain velocity
Linear velocity is multiplied by forward_rate when moving forward, backward_rate when moving backward
Angular velocity is multiplied by rotation_rate
The terminal displays current linear and angular velocities in real-time

Notes

The node requires a terminal that supports curses (most Linux/Unix terminals)
The node uses a text-based interface, so it runs directly in the terminal without a separate window
Velocity commands are published at the rate specified by the hz parameter
Keys have a 0.5-second timeout; if not pressed again within that time, the velocity component becomes zero
The frame_id in published TwistStamped messages is set to “key_teleop”
Linear velocities are in m/s, angular velocities are in rad/s
For proper operation in launch files, use emulate_tty=True and output='screen'