A dynamically consistent hierarchical control architecture for robotic-assisted tele-echography

This paper discusses a new control approach for robotic-assisted tele-echography. A dynamically consistent hierarchical architecture is proposed, where an explicit Cartesian force control arises as the primary task while orientation control is designed in the null space. Cartesian force control, driven by position errors, establishes the interaction dynamics between probe and patient, implemented with computed torque control techniques in the task space. Probe orientation is controlled at joint level, where motion control is driven by task space orientation errors converted into joint velocity references. Control performance is boosted by Kalman active observers (AOBs). Experiments with a 7-DOF WAM™ validate the architecture, where an ultrasound probe is teleoperated in 6 Cartesian dimensions, executing typical echographic tasks.