Indirect measurement of pinch and pull forces at the shaft of laparoscopic graspers

Abstract

The grasping instruments used in minimally invasive surgery reduce the ability of the surgeon to feel the forces applied on the tissue, thereby complicating the handling of the tissue and increasing the risk of tissue damage. Force sensors implemented in the forceps of the instruments enable accurate measurements of applied forces, but also complicate the design of the instrument. Alternatively, indirect estimations of tissue interaction forces from measurements of the forces applied on the handle are prone to errors due to friction in the linkages. Further, the force transmission from handle to forceps exhibits large nonlinearities, so that extensive calibration procedures are needed. The kinematic analysis of the grasping mechanism and experimental results presented in this paper show that an intermediate solution, force measurements at the shaft and rod of the grasper, enables accurate measurements of the pinch and pull forces on tissue with only a limited number of calibration measurements. We further show that the force propagation from the shaft and rod to the forceps can be approximated by a linear two-dimensional function of the opening angle of the grasper and the force on the rod.

LAPKaans: Tool-Motion Tracking and Gripping Force-Sensing Modular Smart Laparoscopic Training System

“…This finding is consistent with previous works related to medical training [11,23,60]. Furthermore, contrary to expected and reported in the literature [31,46], the novice group tends to exert less force than the expert group. This may be due to the location of the force sensing system, representing that the expert group has a more constant and better instrument handgrip, resulting in higher maximum and average force values.…”

“…Regarding force measurement, most previous implementations measure forces along the instrument´s shaft [46][47][48][49][50][51], since it transmits the mechanical energy exerted by the surgeon towards the instrument's tip. Other investigators place the sensor at the instrument´s tip [17,24,52], near the handle [36,53,54], or do not focus their sensing system on the instrument, but to another component, such as the trocar [55] or surgeon's gestures [56], keeping the original design of the laparoscopic instruments intact.…”

A grip force model for the da Vinci end-effector to predict a compensation force

“…The relationship between the motor connector angle (θ 1 , θ 2 , θ 3 , θ 4 ) and the Euler angle (α, β, γ) was empirically calculated using Eqs. (3)(4)(5). However, in this paper, because Euler angles were intuitive for surgeons, the roll (α), pitch (β), and yaw (γ) angles can be used instead of da Vinci EndoWrist's connector angle (θ 1 , θ 2 , θ 3 , θ 4 ).…”

“…During the robotic surgery, surgeons do not realize that varying forces are being applied to the endeffector, because the system is an image-guided system; therefore, excessive mechanical force could be applied to cause the breakage of end-effector string ( Fig. 1) or could cause serious tissue injury, such as cutting arteries or nerves [3,10,14,18].…”

Force sensing in robot-assisted keyhole endoscopy: A systematic survey

“…Although the size, sterilizability, biocompatibility, and insulation requirements are more relaxed for the sensors placed outside the body, these locations are more prone to the factors causing sensor inaccuracy. The sensors at the instrument interface, base, and proximal shaft can have the electronics isolated from the patient (Van Den Dobbelsteen et al, 2012). The sensors in the instrument shaft can gain high precision in the lateral direction, but experiments (Lv et al, 2020;Maeda et al, 2016) showed that they do not provide high resolution in the axial direction unless the structure is modified to amplify axial strains.…”