Advanced UR

This section is for information. Please conduct your lecturer/lab assistant before applying anything yourself.

Theme

  1. URCap
  2. External Control
  3. Communicating with UR5e using Python

Equipment

  1. UR5 / UR5e robot with PolyScope (at least version 5.1).
  2. A pick and place setup (Lab-1 setup is suitable).

Procedure

  1. Make sure that the URCap External Control is installed on the robot.
  2. Make sure that RTDE Library is installed on your PC. This must be installed in the virtual machine which is given to you. The documentation of the ur_rtde package is attacheced to the link. The package is originally a C++ package but has full Python binding. Nonetheless, the package works best in Linux environment.
  3. Connect your PC and the robot to the same network. (Eduroam is problematic. Either use a local LAN or connect directly via ethernet cable.
  4. Check your robot’s IP from Network settings. 172.31.1.144 in Førde
  5. Ping your robot to make sure that the connection is successful: ping 172.31.1.144
  6. Check your PC’s IP with ifconfig (for Ubuntu) or ipconfig (for Windows).
  7. Make sure that the first 3 groups of the IP numbers matches (for example 172.31.1.XXX).
  8. Make a program on UR:
    • Add External Control element (from the installation tab). Use your PC’s IP number. 50002 is the external control port number.
    • Add a simple Move element.
  9. Make a program on your PC:
  import rtde_receive
  from rtde_control import RTDEControlInterface as RTDEControl

  from math import radians as d2r

  _ROBOT_IP = 172.31.1.144
  rtde_c = RTDEControl(_ROBOT_IP, RTDEControl.FLAG_USE_EXT_UR_CAP)
  rtde_r = rtde_receive.RTDEReceiveInterface(_ROBOT_IP)
  actual_q = rtde_r.getActualQ()  # read joint angles

  example_joints = [d2r(-175.82), d2r(-58.56), d2r(73.26), d2r(-11.08), d2r(19.57), d2r(-96.67)] ## Joint angles must be in radians
  rtde_c.moveJ(self.example_joints)

If you want to use MoveL, make sure that you don’t give the joint angles as input but (x,y,z, θ, ɸ, Ψ) TCP pose.

Report

There is no need to hand in a report after this lab.

Signed attendance will suffice as approved lab exercise.

Tasks

  1. Pick-and-place example as you did in Lab-1. You may want to check API.
  2. Move until contact example: 
     import rtde_control

 rtde_c = rtde_control.RTDEControlInterface("127.0.0.1")
 speed = [0, 0, -0.100, 0, 0, 0]
 rtde_c.moveUntilContact(speed)

 rtde_c.stopScript()

3.Force mode example:

  import rtde_control

  rtde_c = rtde_control.RTDEControlInterface("127.0.0.1")

  task_frame = [0, 0, 0, 0, 0, 0]
  selection_vector = [0, 0, 1, 0, 0, 0]
  wrench_down = [0, 0, -10, 0, 0, 0]
  wrench_up = [0, 0, 10, 0, 0, 0]
  force_type = 2
  limits = [2, 2, 1.5, 1, 1, 1]
  dt = 1.0/500  # 2ms
  joint_q = [-1.54, -1.83, -2.28, -0.59, 1.60, 0.023]

  # Move to initial joint position with a regular moveJ
  rtde_c.moveJ(joint_q)

  # Execute 500Hz control loop for 4 seconds, each cycle is 2ms
  for i in range(2000):
      t_start = rtde_c.initPeriod()
      # First move the robot down for 2 seconds, then up for 2 seconds
      if i > 1000:
          rtde_c.forceMode(task_frame, selection_vector, wrench_up, force_type, limits)
      else:
          rtde_c.forceMode(task_frame, selection_vector, wrench_down, force_type, limits)
      rtde_c.waitPeriod(t_start)

  rtde_c.forceModeStop()
  rtde_c.stopScript()

Intended movement:

image-center