Digital Equipment RW504-ZA, Service Manual

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2. Move the picker to the front of the storage element.
3. Get the cartridge from the storage element.
4. Do a flip.
5. Move the picker to the front of the disk insertion slot on the drive element.
6. Put the cartridge into the drive element.
The basic autochanger functions (macro-moves) are then divided into a series of
smaller movements called ‘‘micro-moves.’’ There are two types of micro-moves:
• Position move—move the driving motors a given distance at peak speed
• Saturation move—same as a position move except that a high force is
expected within a given distance; however, motion is halted if force exceeds a
specified threshold.
Position moves are used for high-speed, unobstructed movements of a known
distance. Saturation moves are used in low-speed, adaptive movements of
variable distance.
Macro-moves consists of one or more combinations of position or saturation type
micro-moves. Each macro-move has a tailored set of these submoves to insure
that the macro-move will be gentle. As a macro-move is executed, servo gains are
adjusted to allow for changes in load characteristics.
An example of the process for a flip is as follows.
1. Move picker finger assembly backwards a fixed distance to engage the flip
lock.
2. Change the gain to prepare for upcoming flip.
3. Move the picker finger assembly backwards a fixed distance to trip the
mechanism and start the flip.
4. Make sure the flip is completed by doing a saturate on the picker motor until
the force exceeds a fixed threshold.
5. Change the gain to prepare for picker finger assembly movement.
6. Move the picker finger assembly forward to relieve the force.
Each micro-move within a specific macro-move has a unique set of stability,
performance, error recovery, force, and reliability criteria. Therefore, each micro-
move is assigned a unique identification code (ID) which is used to determine how
the move should be performed. Before a micro-move is executed, its ID is used
to fetch acceleration, velocity and force limits to use. If the move fails, its ID
Theory of Operation 6–3