Operation
Theory of Operation
6
MagneMotion
Rockwell Automation Publication MMI-UM002E-EN-P - March 2016
Block Acquisition
The master controller for each motor takes ownership of vehicles (pucks) when they enter the
motor and maintains that ownership the entire time the vehicle is on the motor. Ownership
includes identification of the final destination, maximum acceleration, and maximum velocity
as defined in the current movement order and determination of the vehicle’s interim destina-
tion and current acceleration and velocity set points.
The master ensures that the vehicle has acquired sufficient empty blocks ahead of the vehicle
in the direction of movement to ensure brick-wall headway is maintained based on the current
motion profile. This is done by defining new interim destinations and communicating with the
motors ahead of the vehicle to ensure sufficient blocks can be acquired.
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The vehicle master uses the position of the most recently acquired block farthest from
the vehicle as an interim destination (target) to calculate the next profile set point
(Pset, Vset, Aset).
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A new interim destination (target) block is only granted if the block has not been allo-
cated to another vehicle (i.e., permission is granted for only one vehicle per motor
block).
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A new target is requested only immediately before the vehicle must start slowing
down for its current target to minimize the number of committed blocks and to ensure
brick-wall headway is maintained.
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Permission to enter a motor block is only granted after previous vehicles have com-
pletely exited the block.
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Each vehicle is controlled in such a manner that it is always able to stop in the last
motor block it was granted permission to enter.
Anti-Collision
The MagneMover LITE transport system allows only one vehicle per motor block; this is the
basic rule on which the anti-collision feature of the MM LITE transport system controls is
founded on. Since two vehicles are not allowed to be in the same motor block, they will not
collide. Note that this affects how many vehicles can fit on a motor or path.
Also, the magnet arrays on the vehicles have a slight repulsive force which causes them to
passively separate from each other a short distance when they are manually pushed together
and not being servoed (actively controlled). The distance they will passively separate will
vary based on vehicle (puck) and track conditions which are impacted by friction but it will
typically be about 30 mm. Therefore, the passively parked center-to-center spacing (or pitch)
is about 90 mm.
The vehicles can be servoed to a tighter spacing but they need to be forced to do so by con-
stantly driving the motor. They can be driven to a pitch where they are practically in contact
with each other but if this constant, close position condition is held for a period of time the