The “TaxiBot” was developed in a joint project by Siemens, the French TLD Group, Lufthansa LEOS and Isreal Aerospace Industries. Siemens developed the drive train based on the ELFA hybrid drive system for buses.
It is actually an electric tug, but there are also 2 diesel engines on board that generate the electricity.
The TaxiBot is driven by 4 wheel hub motors. The smaller model for aircraft with only one central aisle has an output of 500kW. The larger model for aircraft with 2 aisles even 1,000kW.
The 4 wheels can all be controlled individually. This is an advantage, especially in curves, since the forces that have to act to drive a wheel when pulling an aircraft are very high. Not only can different forces be applied to the wheels, but they can also move in opposite directions for a particularly small turning circle.
The remote-controlled tug automatically docks to the front wheel of the aircraft and pulls the aircraft over the runway to the take-off position. Only now does the aircraft start its turbines.
After intensive tests, Lufthansa has been using the TaxiBot at Frankfurt International Airport for several years. The kerosene savings have been 11,000 tonnes a year since regular operations began.