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Update Stretch Gazebo README.md
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Removing the setup instructions since Stretch Gazebo and its dependencies are installed by default. Adding a section to explain how to start the Gazebo simulation with a Dex Wrist.
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hello-binit authored Jan 17, 2024
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Expand Up @@ -19,28 +19,10 @@ The *config* directory contains rviz files and [ros_control](http://wiki.ros.org
The *launch* directory includes two files:

* gazebo.launch: Opens up an empty Gazebo world and spawns the robot loading all the controllers, including all the sensors except Cliff sensors and respeaker.
* teleop_keyboard.launch: Allows keyboard teleop in the terminal and remaps *cmd_vel* topics to */stretch_diff_drive_controller/cmd_vel*, which the robot is taking velocity commands from.
* teleop_joy.launch: Spawns a joy and teleop_twist_joy instance and remaps *cmd_vel* topics to */stretch_diff_drive_controller/cmd_vel*, which the robot is taking velocity commands from. Note that the *teleop_twist_joy* package has a deadman switch by default which disables the drive commands to be published unless it is being pressed. For an Logitech F310 joystick this button is A.

The *script* directory contains a single python file that publishes ground truth odometry of the robot from Gazebo.

## Setup

These set up instructions will not be required on newly shipped robots. Follow these instructions if *stretch_gazebo* is not present in your ROS workspace or you are simulating Stretch on external hardware. Clone stretch_ros and realsense_gazebo_plugin packages to your catkin workspace. Then install dependencies and build the packages, with the following set of commands:

```bash
mkdir -p ~/catkin_ws/src
cd ~/catkin_ws/src
git clone https://github.com/hello-robot/stretch_ros -b dev/noetic
git clone https://github.com/pal-robotics/realsense_gazebo_plugin
cd ~/catkin_ws
rosdep install --from-paths src --ignore-src -r -y
catkin_make
```

In order to use the built packages, make the packages discoverable by sourcing the ROS workspace: `source ~/catkin_ws/devel/setup.bash`. It is popular to add the sourcing command to your `~/.bashrc` file, so that the ROS packages are discoverable in every new terminal that is opened.

## Running Demo
## Running Gazebo

```bash
# Terminal 1:
Expand All @@ -53,7 +35,7 @@ This will launch an Rviz instance that visualizes the sensors and an empty world

![](../images/gazebo.png)

#### Running Demo with Keyboard Teleop node
### Running Gazebo with Keyboard Teleop node
*keyboard_teleop_gazebo* : node that provides a keyboard interface to control the robot's joints within the gazebo simulation.

```bash
Expand All @@ -63,29 +45,16 @@ roslaunch stretch_gazebo gazebo.launch rviz:=true
rosrun stretch_gazebo keyboard_teleop_gazebo
```

## Running Gazebo with MoveIt! and Stretch
### Running Gazebo with Dex Wrist

```bash
# Terminal 1:
roslaunch stretch_gazebo gazebo.launch
# Terminal 2:
roslaunch stretch_core teleop_twist.launch twist_topic:=/stretch_diff_drive_controller/cmd_vel linear:=1.0 angular:=2.0 teleop_type:=keyboard # or use teleop_type:=joystick if you have a controller
# Terminal 3
roslaunch stretch_moveit_config demo_gazebo.launch
roslaunch stretch_gazebo gazebo.launch dex_wrist:=true rviz:=true
```

This will launch an Rviz instance that visualizes the joints with markers and an empty world in Gazebo with Stretch and load all the controllers. There are pre-defined positions for each joint group for demonstration purposes. There are three joint groups, namely *stretch_arm*, *stretch_gripper* and *stretch_head* that can be controlled individually via Motion Planning Rviz plugin. Start and goal positions for joints can be selected similar to [this moveit tutorial](https://ros-planning.github.io/moveit_tutorials/doc/quickstart_in_rviz/quickstart_in_rviz_tutorial.html#choosing-specific-start-goal-states). A few notes to be kept in mind:

* Planning group can be changed via *Planning Group* drop down in Planning tab of Motion Planning Rviz plugin.
* Pre-defined start and goal states can be specified in *Start State* and *Goal State* drop downs in Planning tab of Motion Planning Rviz plugin.
* *stretch_gripper* group does not show markers, and is intended to be controlled via the joints tab that is located in the very right of Motion Planning Rviz plugin.
* When planning with *stretch_head* group make sure you select *Approx IK Solutions* in Planning tab of Motion Planning Rviz plugin.

![](../images/gazebo_moveit.gif)

## Differences in Gazebo vs Stretch

The simulated Stretch RE1 differs from the robot in the following ways.
The simulated Stretch differs from the robot in the following ways.

### Gazebo Sensors vs Stretch Sensors

Expand All @@ -100,13 +69,13 @@ The simulated Stretch RE1 differs from the robot in the following ways.

*Notes:* Although there is no microphone in Gazebo, Respeaker can be represented with a ROS node that accesses compputer's microphone. Cliff sensors are not modeled but they can also be represented as 1D LIDAR sensors. See LIDAR definition in *stretch_gazebo.urdf.xacro* file.

### MoveIt Controllers vs stretch_core
### ROS_Control Controllers vs stretch_core

Actuators are defined as *ros_control* transmission objects in Gazebo using [PositionJointInterfaces](http://docs.ros.org/en/melodic/api/hardware_interface/html/c++/classhardware__interface_1_1PositionJointInterface.html). MoveIt is configured to use three different action servers to control the body parts of stretch in Gazebo through the srdf file in *stretch_moveit_config* package. See the section above about MoveIt for details. Please note that this behavior is different than *stretch_core* as it works with a single Python interface to control all the joints.

### Uncalibrated XACRO vs Calibrated URDF

We provide [stretch_calibration](../stretch_calibration/README.md) to generate a calibrated URDF that is unique to each robot. The calibrated URDF is generated from the nominal description of Stretch RE1, the xacro files that live in [stretch_description](../stretch_description/README.md). The simulated Stretch RE1 is generated from the gazebo xacro description in the *urdf directory* and is not calibrated.
We provide [stretch_calibration](../stretch_calibration/README.md) to generate a calibrated URDF that is unique to each robot. The calibrated URDF is generated from the nominal description of Stretch, the xacro files that live in [stretch_description](../stretch_description/README.md). The simulated Stretch is generated from the gazebo xacro description in the *urdf directory* and is not calibrated.

## License

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