Python GetCurrentTcpPosition UR5E

RobTop 2020-02-16

Hi,

I am working with the ur5e and want to control

Script:
I open the socket connection with python.

I receive the 1108 Bytes and I parse the actual position. I do this in a loop, 1000 times.
But the received position is every time the same.
But the robot is moving.

Now I close the socket

Question:
Why is the sent actual TCP position everytime the same?

Do I have to sent an URScript to the UR5e which is calling the get_actual_tcp_position() and is sending it to a digital out?

matthewd92 2020-02-17

Which port are you connecting to?

RobTop 2020-02-17

30003

RobTop 2020-02-17

It is only working if I call connect and close within the loop for receiving the full 1108 bytes.
But why do I need to reconnect to the UR5E to get the current position?
Why doesnt the UR5E send the actual tcp position without reconnecting to him?

I am confused

matthewd92 2020-02-17

I've never experienced that situation, we listen to port 30003 on all of the robots and they are streaming real time data. We use nodejs as our backend language, maybe there is something in the python code that is not allowing you to receive new data packets and you are just looping through the same packet each time.

I am not a python programmer but if you wanted to post the code I would be happy to look at it best I can, maybe others on here could help as well.

I know with nodejs once we establish the socket connection we have to add a listener to the socket that actually listens for the incoming data stream and then passes off each new packet to the code that breaks it down and stores it into the state tree.

RobTop 2020-02-17

Ok I deliver now detailled information
my python code:

# Echo client program
import socket
import time
import struct

HOST = "192.168.80.128" # The remote host
PORT_30003 = 30003

print "Starting Program"

count = 0
home_status = 0
program_run = 0

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(10)
s.connect((HOST, PORT_30003))
s.setblocking(0)

while (True):
    if program_run == 0:
        try:
            get_active_tcp(s)
            get_active_tcp(s)
            get_active_tcp(s)
            get_active_tcp(s)
            get_active_tcp(s)
            get_active_tcp(s)

        except socket.error as socketerror:
            print("Error: ", socketerror)

home_status = 1
program_run = 0
s.close()
print "Program finish"

//And the get_active_tcp:

def get_active_tcp(s):
    time.sleep(1.00)
    print ""
    packet_1 = s.recv(4)
    packet_2 = s.recv(8)
    packet_3 = s.recv(48)
    packet_4 = s.recv(48)
    packet_5 = s.recv(48)
    packet_6 = s.recv(48)
    packet_7 = s.recv(48)
    packet_8 = s.recv(48)
    packet_9 = s.recv(48)
    packet_10 = s.recv(48)
    packet_11 = s.recv(48)

    packet_12 = s.recv(8)
    packet_12 = packet_12.encode("hex") #convert the data from \x hex notation to plain hex
    x = str(packet_12)
    x = struct.unpack('!d', packet_12.decode('hex'))[0]
    print "X = ", x * 1000

    packet_13 = s.recv(8)
    packet_13 = packet_13.encode("hex") #convert the data from \x hex notation to plain hex
    y = str(packet_13)
    y = struct.unpack('!d', packet_13.decode('hex'))[0]
    print "Y = ", y * 1000

    packet_14 = s.recv(8)
    packet_14 = packet_14.encode("hex") #convert the data from \x hex notation to plain hex
    z = str(packet_14)
    z = struct.unpack('!d', packet_14.decode('hex'))[0]
    print "Z = ", z * 1000

    packet_15 = s.recv(8)
    packet_15 = packet_15.encode("hex") #convert the data from \x hex notation to plain hex
    Rx = str(packet_15)
    Rx = struct.unpack('!d', packet_15.decode('hex'))[0]
    print "Rx = ", Rx

    packet_16 = s.recv(8)
    packet_16 = packet_16.encode("hex") #convert the data from \x hex notation to plain hex
    Ry = str(packet_16)
    Ry = struct.unpack('!d', packet_16.decode('hex'))[0]
    print "Ry = ", Ry

    packet_17 = s.recv(8)
    packet_17 = packet_17.encode("hex") #convert the data from \x hex notation to plain hex
    Rz = str(packet_17)
    Rz = struct.unpack('!d', packet_17.decode('hex'))[0]
    print "Rz = ", Rz

packet_18 = s.recv(624)

// UR5-Simulator is running in the VMWare and is in the remote running.

// If I move the Roboter with another script, the Roboter is moving, but no change in the received message.
// But it is a different message because the timestamp in the received message is changing!

// So what is my mistake? Do I have to execute a URScript in the Roboter to get the current tcp?

matthewd92 2020-02-17

I had to make some changes to the program to get it to run as I am on Python 3.7 but I am seeing the same behavior you are. What is weird though is with the robot sitting still you will see slight variations in the data, I am seeing changes of around 0.05 mm in the data stream which corresponds nicely with what I am actually seeing on the screen of the pendant. But as soon as I move the robot, even manually, the data does not change but I am still seeing slight variations in the streaming data, so its not like it has a constant that it is stuck with.

Like I said, I am not a python programmer so I will have to dig a little deeper. I will try to do a simple nodejs program as well to see if I am seeing similar issues. We do not decode RTE for position data, we use RTDE for all of that now as RTE was deprecated a while ago and they are pushing everyone to RTDE which is a more robust data tool. I would recommend if you are building something new that you take a look at the RTDE documentation. I know there are some sample Python programs on the UR website as well as its a little more complex to set-up and get running.

RobTop 2020-02-17

Ok, can I have an working example for the RTDE Port? I will test immidiatly

I need an example with showing the current Position :-)

matthewd92 2020-02-17

You can find the RTDE documentation as well as sample programs here

RobTop 2020-02-17

I try it today

RobTop 2020-02-18

It is working with RTDE

Hints: starting the record.py with --samples 2500 works
starting without --samples 2500 leads to a corrupt csv file.

For plotting I started example_plot.py

Is RTDE the future?
Is there a sample code for parsing the RTDE Protocol in MATLAB?

matthewd92 2020-02-18

RTDE is the recommended port for gathering real time data. It’s also a 2-way channel meaning you can inject data back into the robot on that channel whereas 30003 RTE was only a streaming channel for data that you could send script over.

I’ve never used matlab but all of the packet types are there in the RTDE information so I’m sure you could use that to decode it in Matlab if you can make the connection.