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Storage and retrieval system
Storage and retrieval system with cornering capability
Drive application: Storage and retrieval system with
cornering capability
Large quantities are put into storage in a high-bay
warehouse. There are many aisles but the material flow rate
is low. In this case, the storage and retrieval system has
to have cornering capability because it must travel along
many aisles. Cornering capability means that there is a
differential between the front and rear drives, and that
high transverse force during cornering can be avoided by
means of active cornering control. When the front wheel
enters the corner, the rear wheel is still running on the
straight and is decelerated. Then, when the rear wheel
enters the corner, the front one is running on the straight
again. This results in a significant acceleration of the
rear wheel, which may be as much as a factor of 2 or more
depending on the radius and the distance between the axes.
This puts the following requirements on the drive system:
- Load distribution, both wheels are driven
- Slip control
- Cornering capability, electronic differential
Intelligent inverters are needed particularly for cornering
capability. The machine control cannot manage this task.
The solution with MOVIDRIVE®
Electronic differential with active cornering control
The basis for this is that the speed of both wheels is
known. Both wheels of the storage/retrieval system are
driven; the load is shared by both drives. The driving
motors are equipped with an incremental encoder and each one
is supplied by its own inverter.
Communication for success
Both wheels are driven and each one is supplied by its own
MOVIDRIVE® inverter. The inverters are connected
via the system bus (SBus) and via the RS-485 interface. Both
are standard.
- Electronic differential with system bus (SBus)
- Load distribution with the RS-485 interface
Movement control with IPOSplus®
A significant feature of MOVIDRIVE® drive
inverters, the IPOSplus® positioning and
sequence control system, now comes into play. An IPOSplus®
program in MOVIDRIVE® calculates the
setpoint speed of the master drive based on the speed
specification for cornering and the actual speed of both
drive wheels. The slave drive operates with torque control.
The advantages at a glance
- The MOVIDRIVE® units exchange the data for
speed control and load distribution via the system bus
and the RS-485 interface.
- All movement control is carried out by the IPOSplus®
program in MOVIDRIVE®.
- High overhung loads are avoided through the electronic
differential, which ensures safer operation of the
storage/retrieval system.
- Safe traction of the storage/retrieval system through
slip control
- With active cornering control it is possible to
negotiate corners 2.5 to 3 times as quickly
- Safe operation of asynchronous AC motors even in the
field weakening range
- Simple integration into higher-level machine control
systems is possible via fieldbus.
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