High motion performance, stiffness, and accuracy are crucial for
industrial robot applications, but these requirements are in practice
contradictory. Using a novel type of robot, the so called Gantry Tau,
new combinations of stiffness and accuracy are in principle possible,
except for the backlash in the drive-trains of each joint.

Existing techniques for backlash reduction are either mechanically
complex or limit the mechanical bandwidth. This paper presents an
approach based on dual motors connected in parallel to the load, such
that the entire robot structure can be made practically backlash free by
means of software and feedback control.

Different control strategies are presented and evaluated in
experiments ranging from a lab servo process via a table-sized robot
to a large industrial implementation with several meters of working
range. Special emphasis was on a dual motor test rig with a linear
high-resolution scale (not yet used for feedback) where the combined
motor torque was fully utilized for high acceleration, while reducing
backlash by over 96%.