Analysis of joint and hand impedance during teleoperation and free-hand task execution

Teleoperated robotic surgery allows filtering andscaling the hand motion to achieve high precision during thesurgical interventions. Teleoperation represents a very complexsensory-motor task, mainly due to the kinematic and kineticredundancies that characterize the human motor control. Itrequires an intensive training phase to acquire sufficient famil-iarity with the master-slave architecture.We estimated the hand stiffness modulation during theexecution of a simulated suturing task in teleoperation, withtwo different master devices, and in free-hand. Kinematicdata of eight right-handed users were acquired, using elec-tromagnetic and optical tracking systems, and analysed usinga musculoskeletal model. Through inverse dynamics, muscularactivation was computed and used to obtain the joint torqueand stiffness, leading to end-point stiffness estimation. Themaximal stiffness value and its angular displacement withrespect to the trajectory tangent was computed. The resultsshow that there is a difference in how the main stiffness axiswas modulated by using the two master devices with respectto free-hand, with higher values and variability for the seriallink manipulator. Moreover, a directional modulation of thehand stiffness through the trajectory was found, showing thatthe users were aligning the direction of the main stiffness axisperpendicularly to the trajectory.