A New Power Law Linking the Speed to the Geometry of Tool-Tip Orientation in Teleoperation of a Robot-Assisted Surgical System

Abstract

Fine manipulation is important in dexterous tasks executed via teleoperation, including in robot-assisted surgery. Discovering fundamental laws of human movement can benefit the design and control of teleoperated systems, and the training of their users. These laws are formulated as motor invariants, such as the well-studied speed-curvature power law. However, while the majority of these laws characterize translational movements, fine manipulation requires controlling the orientation of objects as well. This subject has received little attention in human motor control studies. Here, we report a new power law linking the speed to the geometry in orientation control -humans rotate their hands with an angular speed that is exponentially related to the local change in the direction of rotation. We demonstrate this law in teleoperated tasks performed by surgeons using surgical robotics research platforms. Additionally, we show that the law's parameters change slowly with the surgeons' training, and are robust within participants across task segments and repetitions. The fact that this power law is a robust motor invariant suggests that it may be an outcome of sensorimotor control. It also opens questions about the nature of this control and how it can be harnessed for better control of human-teleoperated robotic systems.

Orientation control strategies and adaptation to a visuomotor perturbation in rotational hand movements

“…Taken together, these results imply that the orientation of the hand is under kinematic control, yet the control is imperfect. The optimization of kinematics is also supported by our additional study that found a new power law that links the angular speed of a remote controlled tool that rotates around its center of mass with the local curvature of its orientation path [ 50 ]. Such optimization was observed in translational hand movements and is known as the speed-curvature power law [ 51 ], which was also observed in manipulation of remote controlled rigid bodies [ 52 ].…”