Haptic Sensing in Teleoperated Surgery

Minimally Invasive Surgery (MIS) procedures, such as laparoscopy, have excited up-to-date surgery by decreasing incisions, minimizing patient recovery, time and cost. been encouraged and facilitated by teleoperated surgical robotic systems. But surgical processes using long surgical tool through small incisions on the patient abdomen lack surgeons of dexterity, sense of touch, and hand-eye coordination that they are familiar in open surgery. Robot-assisted surgery via teleoperation is favorable path to overcome these hurdles. Teleoperation refers to the remote manipulation of a slave machine by a master device over a certain distance. The teleoperation process extends the presence of the human operator and his/her ability to perform complex tasks in inaccessible environments for humans. It enables surgeons to perform a surgery on a patient located at a remote site. In teleoperation system, the transmission of sensory information from the environment to the surgeon requires availability of certain sensor in the system. For this reason, the surgeon to feel the force feedback from the remote environment demands a force sensor to be mounted as close as possible to the tip of the surgical tool to directly calculates the contact (interaction) forces between the surgical tool and environment. Then the system is said to be bilaterally teleoperated. In this thesis, we introduce a bilateral teleoperation system, which consists of a 7 degrees-of-freedom (DOF) haptic interface Sigma. 7 (Force Dimension, Switzerland) as master device and 7 DOF robotic arm lightweight robot LWR4+ (KUKA, Germany) as slave device. Furthermore, surgical tool is placed on the slave device and the 6-axis force sensor M8128C6 (SRI, China) to measure the direct interaction forces of the surgical tool with the tissue. These forces are felt by surgeon’s hand on the haptic manipulator. The force sensor must be calibrated in the system where it will be used in order to have accurate measured contact forces to achieve transparency in teleoperation system. The force sensor cannot be mounted on the tip of the surgical tool to prevent electronics from entering the patient and for reasons of size and sterility. Thus, it is place between surgical tool and flange. However, in this arrangement, the force sensor during a surgical operation does not acquire only the interaction forces of the surgical tool with the tissue, but also acquires gravity force related to weight of the surgical tool, which is exerting force on the force sensor. Thus, the overall forces conveyed to haptic interface are the contact forces and the weight of the surgical tool. The aim of this thesis is to identify (compensate) the weight of a generic surgical tool measured by force sensor during teleoperation process, to feel on the haptic interface only the contact forces of the surgical tool with the tissue. Two methods were adopted separately for estimation of tool’s weight based on: Curve Fitting (CF) and Artificial Neural Network (ANN). Afterwards, calibration of multi-axis force sensor based on Singular Value Decomposition (SVD) procedure to ensure transparency in teleoperated surgery. Experimental results demonstrated that calibration of force sensor after identifying tool gravity component by ANN enhanced robot tool identification and calibration for bilateral teleoperation. In addition, the transparency of the system was achieved by demonstrating force and position tracking of master and slave