7334: digital signal processor for position tracking

Question

Hello!
I’m using the 7334 Motion Control, LabView 7.1, and Mdrive23 motors (stepping motor which comes with integrated encoders).
Making first tries with the MAX, the closed-loop-mode worked unsatisfying. E.g. the motor stopped at position 12 instead of target position 5000 after firstly running several times between 0 and 10000. Or it stopped at 4740 after starting and stopping several times around 5000.
Increasing the deadband to 50 didn’t help.
Reducing the velocity I could reach 5043 instead of 5000, but a velocity of 500 steps/s is very low and the result neither satisfying.
Therefore, I tried to control the position with LabView and it worked quite well, checking the current position and comparing it to the target position in a loop and accordingly stopping the motor.
But I’m a bit surprised why I have to do it manually? I thought the digital signal processor on the board would do it for me: stop the motor when the target position is (nearly) reached and set the “move complete” flag.
To do it with software intervention is quite time-critical for us. We need much higher velocities than 1000 steps/s and I imagine that a software deadband had to be rather large to work.
Where is the trick?
(Thank you!)

Answer 1

This type of error typically occurrs when the settings for encoder counts/rev and stepper steps/rev are wrong. Please refer to this document which explains how to find the correct settings for your hardware.
You may also find the information in this thread useful (especially the last post in this thread).
Jochen Klier
National Instruments Germany
Message Edited by Jochen on 09-21-2005 02:50 PM