Large quantities are put into storage in a high-bay warehouse. There are many aisles but the material flow rate is low; the
storage and retrieval system therefore has to have cornering capability to travel along the 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
using 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
Cornering capability, electronic differential
Intelligent inverters are needed particularly for cornering capability. The machine control cannot manage this task.
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
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
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 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
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.