Soft Gripper controller: ROS2-Control Hardware Interface using GPIO interface

This package provides a ROS2 service to control the pneumatic pump actuating the soft gripper. The service call can be used to open (release), close (grip) or turn off (off) the pneumatic pump actuating the gripper. This hardware interface is meant to be a bridge between the ROS2-Control and the Arduino controller that actuates the pneumatic pump. The pneumatic pump is controlled by the Arduino, which receives the commands via a serial interface (UART). Arduino uses its digital pins to switch the relays, connected to the pneumatic pump digital pins, which in turn actuate the soft gripper.

Contributor: Simone Giampà

Project developed as part of a master’s degree thesis project.

• Master’s Thesis in Computer Science Engineering - Robotics and Artificial Intelligence
• Author: Simone Giampà – contact email
• Politecnico di Milano, Academic Year 2023/2024.

Developed at AIRLAB: Artificial Intelligence and Robotics Laboratory, website

Description

The pneumatic pump actuating the soft gripper is controlled by an Arduino, running the code inside the src/pump_control directory. In order to actuate the soft gripper it is sufficient to send the correct commands as string via serial interface, using the UART protocol. The commands will be received by the Arduino, which will then actuate the pneumatic pump accordingly.

The soft gripper can be operated via a ros2 service call. The service server listens for string commands that are then sent via a serial interface to the Arduino controller. The service call can be used to open, close or turn off the pneumatic pump actuating the gripper.

Package structure

igus_rebel_gripper_controller
├── include
│   ├── gripper_controller.hpp # Header file for the gripper controller service server and hardware interface
├── src
│   ├── gripper_controller.cpp # Service server and serial communication with ROS2 control hardware interface
├── srv
│   ├── GripperActuation.srv # Service definition for the gripper actuation service
├── pump_control
│   ├── pump_control.ino # Arduino code to control the pneumatic pump
├── CMakeLists.txt
├── package.xml
├── README.md

Establish serial communication

Before using the service call, it is necessary to establish serial communication between the Arduino and the computer. There are 2 ways to do this:

1. Using the Arduino IDE: launch the Arduino IDE and open and close the serial monitor
2. Use a sequence of commands in the terminal to create a serial connection between the Arduino and the computer.

The method 2 requires to run the following commands in the terminal:

stty -F /dev/ttyACM0 raw ispeed 115200 ospeed 115200 cs8 -ignpar -cstopb -echo
cat < /dev/ttyACM0 > /dev/null &

then test the connection with the following command:

echo -e "grip" > /dev/ttyACM0

Substitute /dev/ttyACM0 with the port at which the Arduino is connected. The port can be found by running the following command:

ls -l /dev/tty*

To make it more convenient to establish the serial connection, a series of bash aliases can be created to run the above commands as soon as the bash command line is launched. To do so, add the following lines to the .bashrc file:

# enable serial communication on port /ttyACM0 for arduino
alias enable_arduino='stty -F /dev/ttyACM0 raw ispeed 115200 ospeed 115200 cs8 -ignpar -cstopb -echo & cat < /dev/ttyACM0 > /dev/null &'
# pump control commands via bash: quick commands
alias pump_grip='echo -e "grip" > /dev/ttyACM0'
alias pump_off='echo -e "off" > /dev/ttyACM0'
alias pump_release='echo -e "release" > /dev/ttyACM0'

ROS2-Control Usage

To launch the service via CLI, you can type in a terminal the following command, where <command> can be either release, grip or off:

$ ros2 service call /gripper_actuate igus_rebel_gripper_controller/srv/GripperActuation "{command: '<command>'}"

It is also required that the main controllers are launched before using the gripper service. The main controllers can be launched using the following command:

$ ros2 launch igus_rebel_moveit_config demo.launch.py mount:=mount_v2 end_effector:=soft_gripper load_base:=true camera:=realsense

Port Configuration

The default port is set to /dev/ttyACM0, but it can be changed to any other port where the Arduino is connected. The port at which the Arduino is connected can be configured inside the soft_gripper.control.xacro file, in the folder igus_rebel_description_ros2/src/urdf/end_effectors/.