  This work focuses on the agile transportation of liquids with robotic
manipulators. In contrast to existing methods that are either computationally
heavy, system/container specific or dependant on a singularity-prone pendulum
model, we present a real-time slosh-free tracking technique. This method solely
requires the reference trajectory and the robot's kinematic constraints to
output kinematically feasible joint space commands. The crucial element
underlying this approach consists on mimicking the end-effector's motion
through a virtual quadrotor, which is inherently slosh-free and differentially
flat, thereby allowing us to calculate a slosh-free reference orientation.
Through the utilization of a cascaded proportional-derivative (PD) controller,
this slosh-free reference is transformed into task space acceleration commands,
which, following the resolution of a Quadratic Program (QP) based on Resolved
Acceleration Control (RAC), are translated into a feasible joint configuration.
The validity of the proposed approach is demonstrated by simulated and
real-world experiments on a 7 DoF Franka Emika Panda robot.
  Code: https://github.com/jonarriza96/gsft Video: https://youtu.be/4kitqYVS9n8
