AZ: Finding the nearest absolute home position with WRAP

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AZ: Finding the nearest absolute home position with WRAP

Postby om_tech_support_JT » Tue Apr 05, 2016 5:42 pm

Q: I have a rotary application which involves indexing a sensor assembly repeatedly in the same direction for an extensive amount of rotations. Whenever I turn on the Z-HOME input after running the motor for a while, the motor seems to rotate in the other direction forever. How can I make my motor stop at the nearest home position instead? For example, if I start from a home position let's say 12 'o clock and index my motor 360 degrees 10 times, when I turn on the Z-HOME input, I would like the motor to home to the closest home, or 12 o' clock position, instead of rotating 10 revolutions backwards. Is this possible?

A: The AZ series stepper motor and driver package series features our very own ABZO absolute position sensor. This sensor keeps track of the motor's absolute position up to 1,800 revolutions at the motor. This means if you rotate in one direction for an extensive period of time, when the Z-HOME input is turned on, the motor is going to rotate continuously backwards until it stops at the Z-HOME position. The Z-HOME position can be set with an input, a push button on the driver, or with Modbus RTU network communication during installation. However, there is a setting you can change in order to do what you want with the Z-HOME input.

The AZ Series features a WRAP function. The wrap function is a function to automatically resets the position counter when the number of revolutions of the motor output shaft exceeds the set value. The wrap setting unit on the AZ series is in revolutions. This means that you can set a specific value of revolutions the motor takes before the counter is set back to zero. A graphical representation of this can be found in the AZ manual on page 108. A screenshot of this page is below:

AZ Z-Home Operation endlessly rotating - Wrap function from manual.jpg
AZ Z-Home Operation endlessly rotating - Wrap function from manual.jpg (191.8 KiB) Viewed 4123 times


EXAMPLE: I can set a WRAP of 3 revolutions. This means that when the motor has gone 3 revolutions, the position/step counter resets to zero. NOTE: When operating in the WRAP setting, when the Z-HOME input is turned on, the motor will rotate in the direction which is the shortest to the Home position. For example if I go 2 revolutions forward, then the motor will rotate 1 revolution forward to go to the home position.

In order to have this function operate as described above, you also need to change some parameters in the "Motor & Mechanism (Coordinates/JOG/Home Operation)" Section. In this section, you will need to change the "Initial Coordinate Generation & wrap setting range [rev]" to the value that you want (in the example I have changed this to 3.0 revolutions). Then you will need to change the "Initial coordinate generator & manual wrap setting" from "Auto setting (use encoder parameter (if any))" to "Manual setting (use driver parameter)." Depending on how you want the position value to show up on the software, you may have to adjust your "Initial coordinate generation & wrap range offset ratio" setting. A visual depiction of these changes is below and highlighted in yellow/tan:

AZ Z-Home Operation endlessly rotating - Wrap setting in MEXE02 SW.jpg
AZ Z-Home Operation endlessly rotating - Wrap setting in MEXE02 SW.jpg (193.09 KiB) Viewed 4123 times


Please see the AZ series functions manual for more detailed information, or discuss your application with our technical support group.

AZ series functions manual download: http://www.orientalmotor.com/products/p ... 60262E.pdf

To read more about the ABZO sensor on AZ series stepper motors, please download our technology paper:
http://www.orientalmotor.com/technology ... otors.html

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