Abbott VP 2000 Service Manual page 62

Technical Data
3-26
Positioning
The program constantly reads the position sensors on the
X-sensor board, Y-Table, and Rotation head during the
interrupt handler to determine where the X/Y Table is located.
The destination is also kept. During the polling loop, the
program checks to see if the position is equal to the
destination. If not, it then determines how to get to the
destination. This includes left/right, up/down, and back/front
motions. The motors are started, and then stopped during the
interrupt handler if position equals destination.
NOTE: For a complicated move, such as, going to the
other side and moving down, this is done in steps.
If a rotation is needed, the program checks to see that there is
room to rotate, and if not, it goes to a bath that allows room.
When the position seems to be the same as the required
destination, if the move was driven by a stepper motor, more
steps are given as required to center the carriage at the position
of an X sensor and to rotate the arm up against its stop for
rotational motion.
If the carriage is suddenly pulled out of a sensor, as when
someone physically abuses the slide holder, the program
cannot tell where the carriage is located. It knows when it is
lost, and then goes into a hunting sequence that allows it to
determine its position. Then it goes back to the correct
position.
All motion is guarded by timeouts that allow only enough
time for the carriage to complete the expected movements. If
the carriage seems to take too long to move, the Fault Light
will illuminate and the program will stop the motors. If the
Clear button is pressed, the program will try to recover and
continue the previous movement. If the Abort button is
pressed, the program will try to recover, but will then just stop.
Section 3
Abbott VP 2000™ Processor Service Manual
30-608308//R1—September 2008