# joint_state_publisher

*This file is ai generated. Do not edit this file directly. Instead, edit the node source code and run the generate-node-docs command to update this file.*

## Description

The `joint_state_publisher` node publishes `sensor_msgs/JointState` messages for a robot described with URDF, SDF, or COLLADA formats. It reads the robot description from the `robot_description` topic or a file and publishes joint states for all non-fixed joints. The node can operate in several modes: publishing default/zero positions, subscribing to external joint state sources, or automatically updating joint positions with a configurable delta for animation.

## Publishers

- **joint_states** (`sensor_msgs/msg/JointState`)
  - Publishes the current state of all robot joints including positions, velocities, and efforts depending on configuration

## Subscribers

- **robot_description** (`std_msgs/msg/String`)
  - Receives robot description in URDF, SDF, or COLLADA format
  - QoS: Depth 1, Transient Local durability

- **{source_topics}** (`sensor_msgs/msg/JointState`)
  - Dynamically subscribes to topics specified in the `source_list` parameter
  - Updates joint states from external sources

## Parameters

- **publish_default_efforts** (bool, default: `false`)
  - Whether to publish default effort values (0.0) for all joints

- **publish_default_positions** (bool, default: `true`)
  - Whether to publish default position values (zero position) for all joints

- **publish_default_velocities** (bool, default: `false`)
  - Whether to publish default velocity values (0.0) for all joints

- **rate** (int, default: `10`)
  - Publishing rate in Hz for joint state messages

- **source_list** (string[], default: `[]`)
  - List of topics to subscribe to for joint state updates
  - Joint states from these sources override default values

- **use_mimic_tags** (bool, default: `true`)
  - Whether to process and use mimic joint tags from the robot description

- **use_smallest_joint_limits** (bool, default: `true`)
  - Whether to use safety controller soft limits when available (reduces joint range)

- **delta** (double, default: `0.0`)
  - Amount to increment joint positions each publish cycle
  - When > 0, joints automatically move within their limits for animation
  - Joints reverse direction at limits (continuous joints wrap around)

- **zeros.{joint_name}** (double)
  - Set the zero/center position for a specific joint
  - Example: `zeros.joint1:=0.5` sets joint1's zero position to 0.5 radians

- **dependent_joints.{joint_name}.parent** (string)
  - Specifies the parent joint for a dependent/mimic joint relationship
  - Required for each dependent joint

- **dependent_joints.{joint_name}.factor** (double, default: `1.0`)
  - Multiplier for the dependent joint position relative to parent

- **dependent_joints.{joint_name}.offset** (double, default: `0.0`)
  - Offset added to the dependent joint position

## Example Usage

### Basic usage with URDF file

```bash
ros2 run joint_state_publisher joint_state_publisher /path/to/robot.urdf
```

### Using robot_description topic

```bash
ros2 run joint_state_publisher joint_state_publisher
```

### With custom parameters

```bash
ros2 run joint_state_publisher joint_state_publisher \
  --ros-args \
  -p rate:=50 \
  -p publish_default_velocities:=true \
  -p use_mimic_tags:=false
```

### With animation (auto-moving joints)

```bash
ros2 run joint_state_publisher joint_state_publisher \
  --ros-args \
  -p delta:=0.01
```

### With custom zero positions

```bash
ros2 run joint_state_publisher joint_state_publisher \
  --ros-args \
  -p zeros.shoulder_pan_joint:=1.57 \
  -p zeros.elbow_joint:=0.785
```

### Subscribing to external joint sources

```bash
ros2 run joint_state_publisher joint_state_publisher \
  --ros-args \
  -p source_list:=['arm_controller/joint_states','gripper_controller/joint_states']
```

### Launch file example

```python
from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    return LaunchDescription([
        Node(
            package='joint_state_publisher',
            executable='joint_state_publisher',
            name='joint_state_publisher',
            parameters=[{
                'rate': 50,
                'publish_default_positions': True,
                'use_mimic_tags': True,
                'source_list': ['controller/joint_states']
            }]
        )
    ])
```