Comparison of Control Modes of a Hand-Held Robot for Laparoscopic Surgery

Teleoperated robots for minimally invasive surgery make surgeons loose direct contact with the patient. We are developing a handheld, dexterous surgical robot that can be controlled with one hand only, while standing at the operating table. The instrument is composed of a master part (the handle) and a slave part (the tip). This work compares the performance of different control modes, i.e. different ways to map the degrees of freedom of the handle to those of the tip. We ask users to drive the tip along complex trajectories in a virtual environment, using the real master to drive a simulated slave, and assess their performance. Results show that, concerning time, users with no training in laparoscopy prefer a direct mapping of position and orientation, like in free hand motion. However, users trained in laparoscopy perform equally fast with our hand-held robot and, concerning precision, make a smaller number of errors

Design of a novel bimanual robotic system for single-port laparoscopy

Abstract—This paper presents the design and fabrication of Single-Port lapaRoscopy bImaNual roboT (SPRINT), a novel tele-operated robotic system for minimally invasive surgery. SPRINT, specifically designed for single-port laparoscopy, is a high-dexterity miniature robot, able to reproduce the movement of the hands of the surgeon, who controls the system through a master interface. It comprises two arms with six degrees of freedom (DOFs) that can be individually inserted and removed in a 30-mm-diameter umbilical access port. The system is designed to leave a central lumen free during operations, thus allowing the insertion of other laparoscopic tools. The four distal DOFs of each arm are actuated by on-board brushless dc motors, while the two proximal DOFs of the shoulder are actuated by external motors. The constraints gen-erated by maximum size and power requirements led to the design of compact mechanisms for the actuation of the joints. The wrist is actuated by three motors hosted in the forearm, with a peculiar differential mechanism that allows us to have intersecting roll– pitch–roll axes. Preliminary tests and validations were performed ex vivo by surgeons on a first prototype of the system. Index Terms—Bimanual robot, miniature robotic arm, mini-mally invasive surgery, robotic surgery, single-port laparoscopy (SPL). I

Variable Stiffness Actuators for Fast and Safe Motion Control

In this paper we propose Variable Stiffness actuation as a viable mechanical/control co–design approach for guaranteeing control performance for robot arms that are inherently safe to humans in their environment. A new actuator under development in our Lab is then proposed, which incorporate the possibility to vary transmission stiffness during motion execution, thus allowing substantial motion speed-up while maintaining low injury risk levels

Hydrostatic lubrication with cryogenic fluids

The paper presents a computational procedure that can be useful in assessing the main performance parameters (load, flow rate, attitude angle) of hydrostatic journal bearings, without resorting to full numerical computing. The procedure is based on the “lumped resistance method”, which has been extended to take into account turbulence and inertia effects. Comparison with available experimental data shows a pretty reasonable agreement, in spite of the approximations that have been introduced. The procedure has been used to design a number of bearings that have been tested in order to study the possible replacement of rolling bearings in cryogenic turbopumps