servo motor home positioning

[bernie_carlton]

To Lucifer - The Parker/Compumotor Apex and Gemini have logic 'keep alive' power connections. The Emerson/Control Techniques Epsilon drives also have a 'keep alive' logic voltage input but it's rather a weird one supplied by their additional power supply.

 

[kamenges]

Mike-
You need to be a little careful with the 'stall in a known position' type of reference. I used to work for an OEM that used this method in several applications. Every once in a while something would get into the axis path or the powertrain would get a little dirty, etc. The axis would stall before it reached the rigid stop it was supposed to reference against. The next controlled move after that reference was usually something to behold. It sometimes ended in a god, solid, high velocity crash into some machine member.
I'm not saying this is a bad reference method. I still use it myself. Just be aware of the possible consequences.

Keith

 

[grovehaven]

Absolute positioning

Hello,
In machine tools, absolute positioning is very common.
The servo motor is fitted with a absolute encoder.
Some new encoders will hold position internally without external batteries.
Of course the absolute position from the encoder is no good if the control is not setup to use it properly.
When a machine is first commissioned, the encoders and control are both set at the machine home position.
They will stay in sync unless the match is broken.
This problem sounds like the servo knows where it is but the control does not.
Make sure the control comes up looking at the encoders absolute position and not something else.
See if the control and encoder agree at power on.
Good luck