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# Stretch RE1: Tool Change Tutorial
Many users will want to work with tools other than the default Stretch Gripper that ships with the robot. In this tutorial you will learn how to configure the Stretch software interfaces to support other tools.
## Changing Tool Interfaces in Stretch Body
Stretch Body v0.1.x and later supports a plug-in based architecture for tools. A tool interface is an extension of the [EndOfArm](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/end_of_arm.py) class that supports additional degrees of freedom.
### Standard Tools
Stretch Body supports two tool interfaces by default: The [ToolNone & ToolStretchGripper](https://github.com/hello-robot/stretch_body/tree/master/body/end_of_arm_tools.py). We will explore swapping between these default tools.
#### ToolStretchGripper
The RE1 is configured to load the ToolStretchGripper interface by default. This tool is loaded according to the `stretch_re1_user_params.yaml` field:
```yaml
robot:
tool: tool_stretch_gripper
```
We can interact with this tool from iPython
```python
In [1]: import stretch_body.robot as robot
In [2]: r=robot.Robot()
In [3]: r.startup()
In [4]: r.end_of_arm
Out[4]: <stretch_body.end_of_arm_tools.ToolStretchGripper instance at 0x7f99109155a0>
In [5]: r.end_of_arm.motors
Out[5]:
{'stretch_gripper': <stretch_body.stretch_gripper.StretchGripper instance at 0x7f99109159b0>,
'wrist_yaw': <stretch_body.wrist_yaw.WristYaw instance at 0x7f9910915820>}
In [6]: r.end_of_arm.stow()
--------- Stowing Wrist Yaw ----
--------- Stowing Gripper ----
In [7]: r.stop()
```
#### ToolNone
The ToolNone interface can be loaded when no tool is attached to the Wrist Yaw joint. To switch to this interface, simply update the field in your `stretch_re1_user_params.yaml` to:
```yaml
robot:
tool: tool_none
```
After updating the YAML we can interact with the ToolNone via iPython
```python
In [1]: import stretch_body.robot as robot
In [2]: r=robot.Robot()
In [3]: r.startup()
In [4]: r.end_of_arm
Out[4]: <stretch_body.end_of_arm_tools.ToolNone instance at 0x7f245f786fa0>
In [5]: r.end_of_arm.motors
Out[5]: {'wrist_yaw': <stretch_body.wrist_yaw.WristYaw instance at 0x7f245e69e410>}
In [6]: r.end_of_arm.stow()
--------- Stowing Wrist Yaw ----
In [7]: r.stop()
```
## Loading Tool Interfaces from the Stretch Tool Share
The [Stretch Tool Share](https://github.com/hello-robot/stretch_tool_share/) is an open Git repository for non-standard RE1 tools. It hosts the CAD, URDF, and Python files needed to integrate these tools onto your robot.
To use Stretch Tool Share tools, first update your installation:
```console
$ pip2 install hello-robot-stretch-tool-share
```
As an example, we see on the Tool Share that there is a tool, the [ToolDryEraseToolHolderV1](https://github.com/hello-robot/stretch_tool_share/blob/master/python/stretch_tool_share/dry_erase_holder_v1/tool.py) which [extends the EndOfArm](https://github.com/hello-robot/stretch_tool_share/blob/master/python/stretch_tool_share/usbcam_wrist_v1/tool.py) class. In order to load this tool interface , modify your `stretch_re1_user_params.yaml` to load the tool as before. We will also need to tell it where to find the tool's [parameter file](https://github.com/hello-robot/stretch_tool_share/blob/master/python/stretch_tool_share/dry_erase_holder_v1/params.py):
```yaml
robot:
tool: tool_dry_erase_holder_v1
params:
- stretch_tool_share.dry_erase_holder_v1.params
```
We can now interact with the tool in iPython:
```python
In [1]: import stretch_body.robot as robot
In [2]: r=robot.Robot()
In [3]: r.startup()
In [4]: r.end_of_arm
Out[4]: <stretch_tool_share.dry_erase_holder_v1.tool.ToolDryEraseHolderV1 instance at 0x7f3b61c17f00>
In [5]: r.end_of_arm.motors
Out[5]: {'wrist_yaw': <stretch_body.wrist_yaw.WristYaw instance at 0x7f3b61c59280>}
In [6]: r.end_of_arm.stow()
--------- Stowing Wrist Yaw ----
```
# Changing Tool Interfaces in Stretch ROS
Next we'll show how to change the ROS interface for a tool. Here we will continue with the [ToolDryEraseHolderV1](https://github.com/hello-robot/stretch_tool_share/blob/master/python/stretch_tool_share/dry_erase_holder_v1/tool.py#L3) example. First, configure Stretch Body to use the tool as in the previous exercise.
Next, ensure your ROS is up to date:
```console
$ cd ~/catkin_ws/src/stretch_ros/
$ git pull
```
To access the URDF data for the [ToolDryEraseHolderV1](https://github.com/hello-robot/stretch_tool_share/blob/master/python/stretch_tool_share/dry_erase_holder_v1/tool.py#L3) we'll need to clone the Tool Share repository:
```console
$ cd ~/repos
$ git clone https://github.com/hello-robot/stretch_tool_share
```
Copy in the tool's URDF data into the Stretch ROS repository:
```console
$ cd ~/repos/stretch_tool_share/tool_share/dry_erase_holder_v1
$ cp stretch_description/urdf/*.xacro ~/catkin_ws/src/stretch_ros/stretch_description/urdf/
$ cp stretch_description/meshes/*.STL ~/catkin_ws/src/stretch_ros/stretch_description/meshes/
```
Now we will update the tool Xacro for Stretch. Open the file `~/catkin_ws/src/stretch_ros/stretch_description/urdf/stretch_description.xacro` in an editor. Comment out the current tool Xacro and include the Xacro for the dry erase holder.
```xml
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="stretch_description">
<!--<xacro:include filename="stretch_gripper.xacro" />-->
<xacro:include filename="stretch_dry_erase_marker.xacro" />
<xacro:include filename="stretch_main.xacro" />
<xacro:include filename="stretch_aruco.xacro" />
<xacro:include filename="stretch_d435i.xacro" />
<xacro:include filename="stretch_laser_range_finder.xacro" />
<xacro:include filename="stretch_respeaker.xacro" />
</robot>
```
Finally, we'll update our already calibrated URDF to use this new tool:
```console
$ cd ~/catkin_ws/src/stretch_ros/stretch_description/urdf
$ cp stretch.urdf stretch.urdf.bak
$ rosrun stretch_calibration update_urdf_after_xacro_change.sh
```
Ctrl-C when the `rosrun` command terminates and you're ready to visualize the tool in RViz:
```console
$ roslaunch stretch_calibration simple_test_head_calibration.launch
```
![](./images/dry_erase_rviz.png)
# Advanced Topics
## Understanding How the Tool Plug-In Works
For users looking to create their own custom tools it can be useful to understand how the tool plug-in architecture works. Here we will walk through the basics of the system for both Stretch Body and Stretch ROS
### Stretch Body
The [Robot](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/robot.py#L97) class expects an instance of EndOfArm tool to be present. The EndOfArm tool is an extension of the [DynamixelXChain](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/dynamixel_X_chain.py#L16) class, which manages a chain of Dynamixel servos.
A tool is defined via its parameters (either in user YAML or Python). For example, the ToolStretchGripper is defined in [robot_params.py](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/robot_params.py). These parameters tell the plug-in which [DynamixelHelloXL430](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/dynamixel_hello_XL430.py) instances to load and manage. Here we see:
```python
"tool_stretch_gripper": {
'use_group_sync_read': 1,
'retry_on_comm_failure': 1,
'baud':115200,
'verbose':0,
'py_class_name': 'ToolStretchGripper',
'py_module_name': 'stretch_body.end_of_arm_tools',
'stow': {'stretch_gripper': 0, 'wrist_yaw': 3.4},
'devices': {
'stretch_gripper': {
'py_class_name': 'StretchGripper',
'py_module_name': 'stretch_body.stretch_gripper'
},
'wrist_yaw': {
'py_class_name': 'WristYaw',
'py_module_name': 'stretch_body.wrist_yaw'
}
}
},
```
This dictionary defines a tool of class ToolStretchGripper with two [DynamixelHelloXL430](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/dynamixel_hello_XL430.py) devices on its bus (StretchGripper and WristYaw).
We see that the [ToolStretchGripper](https://github.com/hello-robot/stretch_body/blob/master/body/stretch_body/end_of_arm_tools.py#L7) class extends the EndOfArm class and provides its own stowing behavior:
```python
class ToolStretchGripper(EndOfArm):
def __init__(self, name='tool_stretch_gripper'):
EndOfArm.__init__(self,name)
def stow(self):
# Fold in wrist and gripper
print('--------- Stowing Wrist Yaw ----')
self.move_to('wrist_yaw', self.params['stow']['wrist_yaw'])
print('--------- Stowing Gripper ----')
self.move_to('stretch_gripper', self.params['stow']['stretch_gripper'])
```
For tools that are not a part of Stretch Body, such as from the Tool Share, you must include the tool parameters as well in your `stretch_re1_user_params.yaml`. A robot that must support many tools may have user YAML that looks like:
```yaml
params:
- stretch_tool_share.usbcam_wrist_v1.params
- stretch_tool_share.stretch_dex_wrist_beta.params
- stretch_tool_share.dry_erase_holder_v1.params
robot:
tool: tool_dry_erase_holder_v1
#tool: tool_none
#tool: tool_stretch_gripper
#tool: tool_usbcam_wrist_v1
#tool: tool_stretch_dex_wrist_beta
```
For a more complex implementation of a tool we recommend reviewing the Stretch Dex Wrist implementation on the Stretch Tool Share.
### Stretch ROS
Stretch ROS also supports the tool plug-in architecture. Under ROS this is managed by extending the [SimpleCommandGroup](https://github.com/hello-robot/stretch_ros/blob/master/hello_helpers/src/hello_helpers/simple_command_group.py).
More coming soon.
------
<div align="center"> All materials are Copyright 2020 by Hello Robot Inc. The Stretch RE1 robot has patents pending</div>

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@ -79,17 +79,17 @@ extra:
link: https://linkedin.com/company/hello-robot-inc
nav:
- Overview: README.md
- Getting Started:
- Quick Start: getting_started/quick_start_guide.md
- Robot Safety: getting_started/robot_safety_guide.md
- Best Practices: getting_started/best_practices.md
- Untethered Operation: getting_started/untethered_operation.md
- Updating Software: getting_started/updating_software.md
- Getting to Know Stretch:
- Quick Start: docs/getting_started/quick_start_guide.md
- Robot Safety: docs/getting_started/robot_safety_guide.md
- Best Practices: docs/getting_started/best_practices.md
- Untethered Operation: docs/getting_started/untethered_operation.md
- Updating Software: docs/getting_started/updating_software.md
- Stretch Body:
- Basics:
- Commanding Joint Motion: Foo.md
- ROS1:
- Overview: README.md
- Basics:
- Getting Started: getting_started.md
- Gazebo Basics: gazebo_basics.md

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