  To achieve high fidelity haptic rendering of soft objects in a high mobility
virtual environment, we propose a novel haptic display DandelionTouch. The
tactile actuators are delivered to the fingertips of the user by a swarm of
drones. Users of DandelionTouch are capable of experiencing tactile feedback in
a large space that is not limited by the device's working area. Importantly,
they will not experience muscle fatigue during long interactions with virtual
objects. Hand tracking and swarm control algorithm allow guiding the swarm with
hand motions and avoid collisions inside the formation.
  Several topologies of the impedance connection between swarm units were
investigated in this research. The experiment, in which drones performed a
point following task on a square trajectory in real-time, revealed that drones
connected in a Star topology performed the trajectory with low mean positional
error (RMSE decreased by 20.6% in comparison with other impedance topologies
and by 40.9% in comparison with potential field-based swarm control). The
achieved velocities of the drones in all formations with impedance behavior
were 28% higher than for the swarm controlled with the potential field
algorithm.
  Additionally, the perception of several vibrotactile patterns was evaluated
in a user study with 7 participants. The study has shown that the proposed
combination of temporal delay and frequency modulation allows users to
successfully recognize the surface property and motion direction in VR
simultaneously (mean recognition rate of 70%, maximum of 93%). DandelionTouch
suggests a new type of haptic feedback in VR systems where no hand-held or
wearable interface is required.
