What is the accuracy on the UNITS / REP_DIST?

What is the accuracy on the UNITS / REP_DIST?

Q: What is the accuracy on the UNITS / REP_DIST?

  UNITS = 2^23*3/360 '    Counts/deg
  REP_DIST = 180 '   deg

  REP_OPTION = 0 '            [-REP_DIST..REP_DIST]

As UNITS is approx. 69905.0667 then what will happen when I have run the system for several hours?

Will I loose accuracy over time?

A: The motion operates in counts and all the values are stored as Integers.  (64 bit on the MC4/5/6 ranges)

UNITS is used to present engineering values to the user and to the programs.  Therefore when you set REP_DIST = 180, the value that is stored is INT(180 * UNITS).  When the axis parameters or program reads back REP_DIST it shows the internal repdist / UNITS.

UNITS is a float.  So your UNITS is 2^23 * 3/360 = 69,905.0666667.  The recurring decimal is a sign that you may get errors over a long time, but let’s check the REP_DIST;…

REP_DIST = 180 is stored as 180 * 69,905.0666667 = 12582912.  That is an exact integer.  However there is always a chance that the FP maths could have a small error that could make it 12582911.999999 and the integer would be 12582911

 The safest way is to set the REP_DIST with UNITS 1 using the exact counts.

REP_DIST = 12582912
UNITS = 2^23*3/360

    • Related Articles

    • How do I limit movement to one direction to stop reversal of the axis?

      If it is an axis with a REP_DIST and REP_OPTION set to 1, then when the end position is “behind” the current position, add the REP_DIST to the MOVEABS target position value. IF new_position - DPOS < 0 THEN     New_position = new_position + REP_DIST ...
    • MC_CONFIG vs Flash parameters

      All Motion Coordinators store the IP_ADDRESS, IP_NETMASK and IP_GATEWAY in Flash memory.  So there is usually no need to add them to the MC_CONFIG. There are some differences with other system parameters. MC4N-ECAT, MC4N-RTX, MC6N-ECAT, Flex-6 Nano ...
    • UNITs vs Arcs question

      In and XY motion system, if you make only linear lines, it does not matter if X and Y UNITS are not the same. But the MOVECIRC and MHELICAL must have the UNITS on X then same as UNITS on Y, otherwise they produce elipses and not circular arcs. The ...
    • AN-307 Move Embedded Parameters

      Move Embedded Parameters are a new feature within the Trio MC4XX Motion Coordinator system software. Each move can have up to 2 user parameters per axis pass through the motion buffers and become available during the motion for processing. The first ...
    • AN-386 FRAME 34 - 2 Rotational 3 axis robot User Guide

      The FRAME 34 transformation is specifically designed for dispensing on to a rotating product tilted with 2 axes under an XYZ machine. This document explains regarding FRAME 34 and example on how to use it