  This study is part of research aiming at increasing the range of dynamic
tasks for teleoperated field robotics in order to allow operators to use the
full range of human motions without being limited by the dynamics of the
robotic manipulator. A new variable impedance actuator (VIA) was designed,
capable of reproducing motions through teleoperation from precise positioning
tasks to highly dynamic tasks. The design requirements based on previous human
user studies were a stiffness changing time of 50 ms, a peak output velocity of
20 rad/s and variable damping allowing to suppress undesired oscillations. This
is a unique combination of features that was not met by other VIAs. The new
design has three motors in parallel configuration: two responsible for changing
the VIA's neutral position and effective stiffness through a sliding pivot
point lever mechanism, and the third acting as variable damper. A prototype was
built and its performance measured with an effective stiffness changing time of
50 to 120 ms for small to large stiffness steps, nominal output velocity of 16
rad/s and a variable damper with a damping torque from 0 to 3 Nm. Its effective
stiffness range is 0.2 to 313 Nm/rad. This concludes that the new actuator is
particularly suitable for highly dynamic tasks. At the same time, the new
actuator is also very versatile, making it especially interesting for
teleoperation and human-robot collaboration.
