servo control.


Thread Starter

ICM Automation

Hi all,
A friend of mine not on the list has a problem. He says,

i recently installed a new warner servo (rapidtrak) and noticed somthing interesting, the homing routine does not move off of the sensor to detect the "make / Break" window and make an offset adjustment. ????? is this somthing new. i have always used a make break in a homing sequence
and averaged the distance between sensors to get a "True" home position.just wondering if anyone else has run into this.

Any feedback on your experience would be helpful.
Email: [email protected]
Hi Mike (or was that the name of your friend?),

In the servo drives I've used (that had a dedicated homing command), you usually have the ability to choose which homing sequence to use. Check the parameter list to see if your drive has that ability (or possible a DIP switch setting?). The "factory default" setting may have been altered before shipment. I'm not sure what brand drive you're using.... I've used the RapidTrak positioners, but with Kollmorgen or GE drive packages.

Hope this helps,

- Eric Nelson
[email protected]
Packaging Associates Automation Inc. [email protected]
Rockaway, NJ, USA

Michael Griffin

I believe that this servo may be using the 'Z' marker on the encoder to home. The 'Z' marker is a one pulse per rev. signal which is in addition to the 'A' and 'B' quadrature signals.
The home switch is just used to provide an approximate location (within one encoder revolution). Once the controller sees the home switch, it begins to look for the 'Z' marker from the encoder and performs its final homing routine using that signal. The encoder signal should be more repeatable than an inductive prox or a limit switch.

Michael Griffin
London, Ont. Canada
[email protected]

David Lawton Mars

By "make break" I'm assuming you mean the motor moves until it gets the sensor input and then backs off until the sensor input goes off. You seemed to suggest using two sensors which I don't really understand? If you need a very accurate home position you can normally move the motor
until it sees the sensor input and then move it until it sees the next zero marker pulse from the encoder or resolver. I don't know how it's done with the motion system you mention but the above
is the "normal" method of homing.

Daniel Boudreault

Hello Mike,

The Warner RapidTrak Homing command looks for
a make OR break then stops (according to the decel rate!)

Here is what I've done in the past.

I use the Homing command, then jump to my subroutine to do a make then break move, then take the average of the two positions, then move to the center for my home position.

Dan Boudreault

ps. The decel rate had me debugging the homing sequence for day once...that is why I have it in ().

Cameron Anderson

Mike, I'm assuming your using the Superior (Warner) TDC servo drive on the Rapidtrak. I am very familar with this drive and have done many many different programs with it. Without setting one up on my desk, from what I remember, it does not have the capability when issuing the Move Home command to back off the home sensor. What I usually do is command a small move (ie. movei=.1) or use a:
This will jog the motor until input 1 (or Event 1, where the home input is wired to) is off and stop the motor. If your worried about hitting an EOT (End of Travel) switch, then use the pre-defined Error_Handler label and you can do some IF THEN statements and look at Limit +/- status.

If you need more help or are not using a TDC, let me know, I have used many different Servo/Stepper drives and controls.

Cameron Anderson
Senior Motion Control Specialist