  Variable impedance actuators (VIAs) as tool devices for teleoperation could
extend the range of tasks that humans can perform through a teleoperated robot
by mimicking the change of upper limb stiffness that humans perform for
different tasks, increasing the dynamic range of the robot. This requires
appropriate impedance control. Goal of this study is to show the effectiveness
of a controller that does not require additional sensors, reducing system
complexity and increasing ease of use. The controller should allow to perform
precise positioning tasks and dynamic tasks like hammering through
teleoperation with a VIA tool device automatically adapting the impedance
setting of the VIA. This is achieved by a control law according to the
principle "slow-stiff/fast-soft". The controller was tested in a human user
study with 24 participants comparing the human-machine performance with the
self-adapting controller in a bilateral telemanipulation experiment with two
tasks (precision/dynamic) using three impedance settings (high/low/adaptive
impedance). The results indicate that the proposed system performs equally well
as state of the art stiff teleoperation devices for precision tasks, while
having benefits in terms of increased safety and reduced wear for dynamic
tasks. This is a step towards teleoperation with a wide dynamic range.
