AZ: How to track absolute position from PLC

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AZ: How to track absolute position from PLC

Post by om_tech_support_JT » Thu Mar 31, 2016 7:48 pm

Q: I'm interested in using your new AZ series stepper motors with the ABZO sensing technology for sensorless absolute homing. I do have one question. From my PLC, what are the ways that I can acquire the motor's absolute position data from the motor driver? From my past experience with your products, I typically connect the ASG and BSG outputs from the motor driver to a high speed pulse counter on my PLC. However, I'm not sure how to do this on the AZ series. I also need to ensure that the position data on my master PLC and your AZ system are synchronized.

A: Thank you for your continued interest in OM's products. The AZ series stepper motors are packaged with either a pulse input type driver or a Flex type driver (with built-in pulse controller). The absolute position data can be acquired differently depending on the type of driver used.

On both of the drivers you can use ASG/BSG outputs for an external device to count and track motor position.

On the "Flex" driver, another way is to query the command or feedback position is from a Modbus RTU master via a RS-485 serial connection (similar to AR Flex drivers). You will need to have your Modbus RTU master or software send a query command to read the register address 00CDh (lower register).

If you are not using the AZ Flex driver in an RS-485 master/slave network, then another alternative is to use the I/O Position Output function as described below.

I/O position output function
The I/O position output function is a function to transmit position information or alarm information to the
master controller via clock synchronization type serial communication (SPI communication) according to
the monitor request inputs (MON-REQ0, MON-REQ1). When a pulse is input to the MON-CLK input, the
information output from MON-OUT is switched when the pulse is started. Communication is executed
from the least significant bit (LSB first). Data whose position information is 32 bit (*) and alarm information
8 bit (*) are transmitted, and checksum is transmitted finally. The checksum is the lower 8 bit obtained by
dividing the transmission data by 1 byte and adding each value.

In the case of an AZ pulse input type driver, then it would offer the ASG/BSG outputs. However, you'll have to use something called the Pulse Request function to acquire absolute position data. Please see below.

Pulse request function
The pulse request function is a function to transmit the present position (absolute position) to the master
controller by using the A-phase and B-phase outputs. When the A-phase and B-phase outputs of the
encoder counter of the master controller and driver are connected and the pulse request function is
executed, the present position of the driver can be output as A-phase and B-phase pulses. By setting the
encoder counter of the master controller to "0" in advance, the coordinate systems of the ABZO sensor
and master controller can be synchronized easily.

•Clear the encoder counter of the master controller to 0 after high-speed return-to-home operation, position preset, or return-to-home operation is complete.
•Match the values of the present position of the ABZO sensor and encoder counter of the master controller with the position coordinate information monitor function.

The full AZ functions manual is linked here for your reference. See PAGE 121 for Position coordinate information monitor functions. ... 60262E.pdf

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Joined: Wed Dec 14, 2016 4:58 am

Re: AZ: How to track absolute position from PLC

Post by artmuz62 » Wed Dec 14, 2016 10:55 am

I do not use the driver before. But the good reviews, you have to pay attention :)

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