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Alan Case
June 5th, 2002, 08:29 AM
Hi all. Mine is a specific AB question. I am trying to move an item at 2 metres a second and stop it with about 3mm accuracy.
I am using an AB micrologix 1200 HSC, a bulletin 160 drive, a squirrel cage motor with brake and an encoder.
I have the system working but I am not sure if there is a better way.

Sequence of events.

Load a high preset into the HSC

Release the brake and on the output for 50 Hz to the drive

In the normal scan when the item is close to the position I on the slow speed command to the drive. 3 hz

When the HSC sees the high preset reached, the HSC program file is run.

In this file the outputs controlling the drive and the brake are unlatched. Then I use an immediate output to set the outputs to what the data table says they should be. I also set the binary bits that control these outputs elsewhere in the program to a state that will not turn them on again.

When the item has performed all the tasks at this position the process is repeated. I am getting the accuracy I require but is this the usual way to attack a job like this.

Regards Alan Case

iant
June 10th, 2002, 12:13 PM
A similar system is used by Colby Systems the speed is much faster 15m/s+.
but they use an Absolute encoder.
This allows them to ignore the precise value whilst in full speed motion.
and allows you to begin to slow down without the posibility of loosing Pulses.(assuming it is a rotary encoder)

Alternative measurement systems of Absolute detection are more reliable, and more expensive. What do you need. and What distance?

Toyota (Victoria) has a Panel handeling system which runs at 12m/s
its accuracy is .1mm.
the motor is a servo but the movement is still senced by a seperate absolute encoder. :)