willard-cui/python-urx

Python library to control a robot from 'Universal Robots' http://www.universal-robots.com/

urx is a python library to control the robots from Universal Robots. It is published under the LGPL license and comes with absolutely no guarantee.

It is meant as an easy to use module for pick and place operations, although it has been used for welding and other sensor based applications that do not require high control frequency.

Both the 'secondary port' interface and the real-time/matlab interface of the UR controller are used. urx can optionally use the python-math3d(GPL) library to receive and send transformation matrices to the robot urx is known to work with all release robots from Universal Robot.

urx was primarily developed by Olivier Roulet-Dubonnet for Sintef Raufoss Manufacturing.

Install

The easiest is probably to use pip:

pip install urx

Example use:

import urx

rob = urx.Robot("192.168.0.100")
rob.set_tcp((0, 0, 0.1, 0, 0, 0))
rob.set_payload(2, (0, 0, 0.1))
sleep(0.2)  #leave some time to robot to process the setup commands
rob.movej((1, 2, 3, 4, 5, 6), a, v)
rob.movel((x, y, z, rx, ry, rz), a, v)
print "Current tool pose is: ",  rob.getl()
rob.movel((0.1, 0, 0, 0, 0, 0), a, v, relative=true)  # move relative to current pose
rob.translate((0.1, 0, 0), a, v)  #move tool and keep orientation
rob.stopj(a)

robot.movel(x, y, z, rx, ry, rz), wait=False)
while True :
    sleep(0.1)  #sleep first since the robot may not have processed the command yet
    if robot.is_program_running():
        break

robot.movel(x, y, z, rx, ry, rz), wait=False)
while.robot.getForce() < 50:
    sleep(0.01)
    if not robot.is_program_running():
        break
robot.stopl()

try:
    robot.movel((0,0,0.1,0,0,0), relative=True)
except RobotError, ex:
    print("Robot could not execute move (emergency stop for example), do something", ex)

Development using Transform objects from math3d library:

from urx import Robot
import math3d as m3d

robot = Robot("192.168.1.1")
mytcp = m3d.Transform()  # create a matrix for our tool tcp
mytcp.pos.z = 0.18
mytcp.orient.rotate_zb(pi/3)
robot.set_tcp(mytcp)
time.sleep(0.2)

# get current pose, transform it and move robot to new pose
trans = robot.get_pose()  # get current transformation matrix (tool to base)
trans.pos.z += 0.3
trans.orient.rotate_yb(pi/2)
robot.set_pose(trans, acc=0.5, vel=0.2)  # apply the new pose


#or only work with orientation part
o = robot.get_orientation()
o.rotate_yb(pi)
robot.set_orientation(o)

Other interactive methods/properties

from urx import Robot
rob = Robot("192.168.1.1")
rob.x  # returns current x
rob.rx  # returns 0 (could return x component of axis vector, but it is not very usefull
rob.rx -= 0.1  # rotate tool around X axis
rob.z_t += 0.01  # move robot in tool z axis for +1cm

csys = rob.new_csys_from_xpy() #  generate a new csys from 3 points: X, origin, Y
rob.set_csys(csys)

Supported Grippers

Robotiq Gripper

urx can also control a Robotiq gripper attached to the UR robot. The robotiq class was primarily developed by Mark Silliman.

Example use:

import sys
import urx
from urx.gripper import Robotiq_Two_Finger_Gripper

if __name__ == '__main__':
    rob = urx.Robot("192.168.0.100")
    robotiqgrip = Robotiq_Two_Finger_Gripper()

    if len(sys.argv) != 2:
        print "false"
        sys.exit()

    if sys.argv[1] == "close":
        robotiqgrip.close_gripper()
    if sys.argv[1] == "open":
        robotiqgrip.open_gripper()

    rob.send_program(robotiqgrip.ret_program_to_run())

    rob.close()
    print "true"
    sys.exit()

OnRobot RG2 Gripper

urx can control an RG2 gripper as well. The class was primarily developed by Moritz Fey.

Example use:

import sys
import urx
from urx.gripper import OnRobotGripperRG2

if __name__ == '__main__':
    rob = urx.Robot("192.168.0.100")
    gripper = OnRobotGripperRG2(rob)

    if len(sys.argv) != 2:
        print "false"
        sys.exit()

    if sys.argv[1] == "close":
        gripper.close_gripper()
    if sys.argv[1] == "open":
        gripper.open_gripper()

    rob.close()
    print "true"
    sys.exit()

Various parameters can be controlled in the open and close functions. The parameters that can be set are:

    gripper.open_gripper(
        target_width=110,  # Width in mm, 110 is fully open
        target_force=40,  # Maximum force applied in N, 40 is maximum
        payload=0.5,  # Payload in kg
        set_payload=False,  # If any payload is attached
        depth_compensation=False,  # Whether to compensate for finger depth
        slave=False,  # Is this gripper the master or slave gripper?
        wait=2  # Wait up to 2s for movement
    )

The parameters are the same for opening and closing the gripper.