Industrial counter on incremental encoder position drift

[Komet]

Hello everybody,

 

I'm working on an industrial special machine and i want to control some part of it with bricklet. My machine can do round trip on a rail with a motor and its coder. the PLC keep the control of all the power, I just send him order with a RS232 bricklet.

For a first test i want to go to 30 000 counts, wait 2 seconds and then go back to my initial position ( 0 ) and repeat forever. Here is the issue : my machine drift in a single direction about some centimeters each time. When I control it directly by the PLC i haven't that and I don't understand why it does it with the counter bricklet.

the coder is a sew eurodriver EH1C, I connect CH0- and CH2- to GND and CH0+ and CH2+ to A & B

Here is my code :

 

from tinkerforge.ip_connection import IPConnection

from tinkerforge.bricklet_rs232_v2 import BrickletRS232V2

from tinkerforge.brick_master import BrickMaster

from tinkerforge.bricklet_industrial_counter import BrickletIndustrialCounter

import time

 

HOST = "localhost"

PORT = 4223

UID = "6eSrKP" # Change XXYYZZ to the UID of your Master Brick

UID_RS = "W9P"

UID_COUNTER = "QV8"

 

ipcon = IPConnection() # Create IP connection

rs232 = BrickletRS232V2(UID_RS, ipcon) # Create device object

counter = BrickletIndustrialCounter(UID_COUNTER, ipcon) # Create device object

ipcon.connect(HOST,PORT)

 

counter.set_counter_configuration(counter.CHANNEL_0,

                                      counter.COUNT_EDGE_RISING,

                                      counter.COUNT_DIRECTION_EXTERNAL_DOWN,

                                      counter.DUTY_CYCLE_PRESCALER_1,

                                      counter.FREQUENCY_INTEGRATION_TIME_1024_MS)

counter.set_all_counter_active([True, False, False, False])

counter.set_counter(0, 0)

 

i = 0

speed = 40

 

while True :

   

    message = [chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(speed),chr(2)] # the first 7 control IR power the 8th the speed and the 9th the direction

    rs232.write(message)

    time.sleep(2)

 

    message = [chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(speed),chr(1)]

    rs232.write(message)

    while counter.get_counter(0)<75000:

        print(counter.get_counter(0))

 

    message = [chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(speed),chr(2)]

    rs232.write(message)

    time.sleep(2)

 

    message = [chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(i),chr(speed),chr(0)]

    rs232.write(message)

    while counter.get_counter(0)>0:

        print(counter.get_counter(0))