EZGripper

A ROS package that serves as a driver to the EZGripper module designed by SAKE Robotics. If you are not using ROS, use https://github.com/SAKErobotics/SAKErobotics

Tutorial

Installation

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• Install the python EZGripper library. For kinetic and melodic use this link and for noetic use the ubuntu 20.04 branch.

• Install the upatras_gazebo_plugins by cloning the packge to your catkin workspace in order to enable Gazebo to mimic the EZGripper joints:

  git clone https://github.com/roboticsgroup/roboticsgroup_upatras_gazebo_plugins.git
  

• Install all the remaining dependencies using rosdep, at the root of your ROS workspace:

  rosdep install --from-paths src --ignore-src -r -y
  

• Clone the ROS Driver at you src folder:

  For ROS kinetic

  git clone --branch=kinetic-devel https://github.com/SAKErobotics/EZGripper.git
  

  For ROS Melodic

  git clone --branch=melodic-devel https://github.com/SAKErobotics/EZGripper.git
  

  For ROS noetic

  git clone --branch=noetic-devel https://github.com/SAKErobotics/EZGripper.git
  

• Build your workspace and source it:

  catkin_make && source devel/setup.bash
  

• For quickly testing hardware connect your USB joystick to the system, and execute:

  roslaunch ezgripper_driver joy.launch
  

Simulation testing

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• Launch the gripper module in RViz :

  roslaunch ezgripper_description display_single_mount.launch
  

• Similarly to launch in Gazebo:

  roslaunch ezgripper_gazebo gazebo_single.launch
  

• To actuate the gripper into its respective open/close configurations in Gazebo, in a new terminal execute these commands:

  # Open Gripper
  rosrun ezgripper_control open_gripper
  
  # Close Gripper
  rosrun ezgripper_control close_gripper
  

• Result of actuation:

  

MoveIt!

---

• To launch the ezgripper in RViz only:

  roslaunch ezgripper_single_mount_moveit_config demo.launch
  

• To launch the ezgripper in Gazebo and RViz for control:

  roslaunch ezgripper_single_mount_moveit_config demo_gazebo.launch
  

• To control the ezgripper hardware through MoveIt!:

  roslaunch ezgripper_single_mount_moveit_config ezgripper_single_mount_moveit_planning_execution.launch
  

Additional Configurations

• Setup parameters in joy.yaml file

  • port -
            serial device (like /dev/ttyUSB0) or tcp endpoint (like 192.168.0.200:5000) to use.

  • baudrate -
            baud rate of the serial device, not used for tcp.

  • no_of_grippers -
            number of grippers to control.

  • Depending upon the number of grippers, gripper profiles can be created as shown:

    gripper_1:
    	action_name: gripper_cmd
    	servo_ids: [1]
    	robot_ns: main
    

    action_name -
            name of the action to be used.
    servo_ids -
            list of servo ids to control. (several ids if several grippers are to be used as one group). For example [9] and [10,11] for two grippers.
    By default, SAKE Robotics delivers its grippers with address 1 for Duals and 1 and 2 for Quads and 57kbps.
    

    robot_ns -
            namespace of the robot.

• Example launch files to support various EZGripper configurations.

  roslaunch ezgripper_driver joy.launch
  # joy.launch is configured for a single servo gripper (dual) and the USB interface
  
  roslaunch ezgripper_driver joy2.launch
  # joy2.launch is configured for two independent servos (quad independent) and the USB interface
  
  roslaunch ezgripper_driver joy2sync.launch
  # joy2sync.launch controls two servos as if it were a single servo (quad dependent) and the USB interface
  
  roslaunch ezgripper_driver joy_tcp.launch
  # joy_tcp.launch controls a single servo via TCP instead of USB
  

Action API

---

• The driver provides an implementation of the SimpleActionServer, that takes in control_msgs/GripperCommand actions.
  
• A sample client (scripts/client.py) is included that provides joystick control using the action API.

URDF Models

---

Access the URDF models for additional information.

TroubleShooting

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Serial connection issues:

• The following message indicates you have a new version of serial library that causes issues.

  Error message: 'Serial' object has no attribute 'setParity'  ---
  

  Do the following command to load an older serial library.

  sudo apt-get install python-serial==2.0.0
  

• This indicates the user does not have privileges to use the /dev/ttyUSBx:

  Error message: permission denied (get accurate error message).
  

  The solution is to add the <user> to the dialout group. After executing the following command, reboot.

  sudo adduser <user> dialout
  reboot
  

ROS Controller Issues:

• Check whether the joint_state_controller and the ezgripper_controller modules are loaded:

  rosservice call /ezgripper_single_mount/controller_manager/list_controllers
  

ROS Diagnostics

• View the diagnostics of the ezgripper_module:

  rosrun rqt_runtime_monitor rqt_runtime_monitor