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    How ROS is used in mechArm 270?

    PRODUCTS
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    • ElephantRoboticsE
      ElephantRobotics
      last edited by

      As an open-source meta-operating system used for robots, ROS is widely used in many robotics products, also in mechArm 270-Pi. Through the ROS system, we can simulate the control of robotic arms in a virtual environment. We will visualize robot arms through rviz, operates our robot arms in a variety of ways, and also plan and execute the action path through Moveit to control the mechArm. Now we will talk about how to control mechArm 270-Pi in rviz and Moveit.

      rviz
      rviz is a 3D visualization platform in ROS. It can graphically display external information. Meanwhile, we can also get the controlling information to an object through rviz, and realize the monitoring and control of a robot, such as the control of slider, GUI and keyboard, and model following. Here we're going to demonstrate how to implement these functions.

      1.Slider Control
      Open a terminal or command line and run :

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      roslaunch mecharm_pi slider_control.launch port:=/dev/ttyAMA0 baud:=1000000
      

      rviz and a slider component will be opened, and we will see the following interface:
      0_1655802447038_2.6.4ROS.png
      Then we can control the model in rviz to make it move by dragging the slider. If we want the real mechArm to move with the model, we need to open another command line and run:

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      rosrun mecharm_pi slider_control.py _port:=/dev/ttyAMA0 _baud:=1000000
      

      Note: Since the robot arm will move to the current position of the model when the command is input, make sure that the model in rviz does not appear to be worn out before we use the command.

      Note: Do not drag the slider immediately and too quickly after connecting the mechArm to prevent damages to the robot arm.

      2.GUI control
      Based on the previous contents, this package also provides a simple GUI control interface. This method is used to control the real robot arms. We should connect to mecharm first.

      Open a command line:

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      roslaunch mecharm_pi simple_gui.launch port:=/dev/ttyAMA0 baud:=1000000
      

      Running effect:
      0_1655802328353_GUI.jpg

      3.Keyboard control
      Keyboard control is added in mecharm package, and real-time Synchronization is performed in rviz. This function depends on pythonApi, so be sure to connect with the real robot arm.

      Open a command line and run:

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      roslaunch mecharm_pi teleop_keyboard.launch port:=/dev/ttyAMA0 baud:=1000000
      

      Running effect is as follows:
      0_1655802404850_mecharm_teleop.png
      We can control the mechArm by keyboard as instructed in the command line, mechArm information will be output in the command line as follows:

      SUMMARY
      ========
      
      PARAMETERS
       * /mecharm_services/baud: 1000000
       * /mecharm_services/port: /dev/ttyAMA0
       * /robot_description: <?xml version="1....
       * /rosdistro: melodic
       * /rosversion: 1.14.11
      
      NODES
        /
          mecharm_services (mecharm_communication/mypal_services.py)
          real_listener (mecharm_pi/listen_real.py)
          robot_state_publisher (robot_state_publisher/robot_state_publisher)
          rviz (rviz/rviz)
      
      ROS_MASTER_URI=http://localhost:11311
      
      process[robot_state_publisher-1]: started with pid [14764]
      process[rviz-2]: started with pid [14765]
      process[mecharm_services-3]: started with pid [14766]
      process[real_listener-4]: started with pid [14782]
      [INFO] [1646649869.148017]: start ...
      [INFO] [1646649869.156531]: /dev/ttyAMA0,1000000
      
      Mycobot Status
      --------------------------------
      Joint Limit:
          joint 1: -160 ~ +160
          joint 2: -90 ~ +90
          joint 3: -180 ~ +45
          joint 4: -160 ~ +160
          joint 5: -100 ~ +100
          joint 6: -180 ~ +180
      
      Connect Status: True
      
      Servo Infomation: unknown
      
      Servo Temperature: unknown
      
      Atom Version: unknown
      
      [INFO] [1646649869.427899]: ready
      

      Then open another command line and run:

      rosrun mecharm_pi teleop_keyboard.py
      # or
      rosrun mecharm_pi teleop_keyboard.py _speed:=70
      

      We will see the following output in the command line:

      mecharm Teleop Keyboard Controller
      ---------------------------
      Movimg options(control coordinations [x,y,z,rx,ry,rz]):
                    w(x+)
      
          a(y-)     s(x-)     d(y+)
      
              z(z-)       x(z+)
      
      u(rx+)      i(ry+)      o(rz+)
      j(rx-)      k(ry-)      l(rz-)
      
      Gripper control:
          g - open
          h - close
      
      Other:
          1 - Go to init pose
          2 - Go to home pose
          3 - Resave home pose
          q - Quit
      
      currently:    speed: 40    change percent: 5
      

      Parameters supported by this script:

      _speed: the movement speed of the robot arm
      _change_percent: movement distance percentage

      4.Model Following
      In addition, we can also make the model follow the movement of the real robotic arm. Open a command line and run:

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      rosrun mecharm_pi follow_display.py _port:=/dev/ttyAMA0 _baud:=1000000
      

      Then open another command line and run:

      roslaunch mecharm_pi follow.launch
      

      It will open rviz to show the model following effect.

      5.Moveit
      As an integrated development platform in ROS, Moveit consists of a variety of functional packages for manipulating robot arms, including motion planning, operation, control, inverse kinematics, 3D perception, and collision detection.
      For mechArm 270-Pi, mycobot_ros has integrated the MoveIt section, so we need to open the command line and run:

      roslaunch mecharm_pi_moveit mecharm_moveit.launch
      

      The operation effect is as follows:
      0_1655802526495_mecharm_moveit.png
      If we want a real robot arm to execute a plan synchronously, we need to open another command line and run:

      # The default serial port name of the mechArm version is "/dev/ttyAMA0", and the baud rate is 1000000".
      rosrun mecharm_pi_moveit sync_plan.py _port:=/dev/ttyAMA0 _baud:=1000000
      

      With the support of the ROS system, we can control mechArm and conduct algorithm verification under a virtual environment, which reduces the requirements for the experimental environment and improves efficiency.

      Should you have any ideas about using ROS in the robotic arm for more functions, please share with us in the comment.

      1 Reply Last reply Reply Quote 0
      • K
        kkkkkk
        last edited by

        What is the auxiliary control of this mechArm?

        ElephantRoboticsE 1 Reply Last reply Reply Quote 0
        • ElephantRoboticsE
          ElephantRobotics @kkkkkk
          last edited by

          @kkkkkk It is esp32

          1 Reply Last reply Reply Quote 0
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