VELMEX VXM-1 - Getting Motor Position When Moving

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Getting Motor Position When Moving

Appendix E

It is possible to read motor position directly while motor is in motion using the “X” and “Y”

commands. At high motor speeds it might not be timely or accurate enough to transfer

motor position over the serial port while the motor is in motion. Another approach is to

use an external trigger to tell the VXM to capture motor position(s) for later retrieval (after

motion has ended.)

The Automatic Deceleration Capture

Every time the motor starts to decelerate to a stop the motor position is saved for later

retrieval with the “D” command. One use of this feature would be to stop the motor with

the decelerate-to-a-stop command (”D”) when an event has occurred. Then after waiting

for the move to end, (wait for “^”) and reading the position where deceleration started.

D (Asterisk) Request motor position when the last deceleration occurred. This

position can be from a normal index decelerating to a stop, or an interrupted

index from a "D" (Decelerate to a stop) command or Stop input/button (User input

4.) Below is what the host would receive if the last motor indexing started it’s

deceleration at position negative 14901.

-0014901<cr>

The Triggered Position Capture

The VXM can capture motor 1 and motor 2 position(s) either by the host sending a “!” or

from a pulse on input 4 (see Appendix C.) Up to 4 positions will be recorded (one for each

trigger input.) Then after waiting for the move to end, (wait for “^”) the positions can be

requested with the “x” and “y” commands.

! Capture motor 1 and motor 2 positions into FIFO buffer (4 positions maximum.)

Use the “x” and “y” commands to retrieve buffer data after move(s) are complete.

NOTE: buffer data is automatically zeroed at the start of every run.

x Request captured motor 1 positions from FIFO buffer (all 4 positions.)

NOTE: buffer data is automatically zeroed at the start of every run.

+0000521

+0000919

+0001149

+0000000

Example:

This example shows the values the VXM returned when the “!” was sent at

positions 521,919, and 1149 while motor 1 was indexing.

y Request captured motor 2 positions from FIFO buffer (all 4 positions.)

NOTE: buffer data is automatically zeroed at the start of every run.

-0002004

+0000000

Example:

This example shows the values the VXM returned when the “!” was sent at

position negative 2004 while motor 2 was indexing.