A Planar Cable-Driven Under-Sensing Model to Measure Forces and Displacements

Abstract

This paper presents a planar cable-driven model of a simple mechanism that is able to measure forces and displacements. Recently, a preliminary study based on a cable-driven sensitive mechanism was presented to the research community, underlining the innovative characteristics of the model in under-actuation and under-sensing. The core of the research work was to conceive a compliant system able to measure forces and displacements from a point located in a different zone with respect to the one where the force is applied, and this is possible thanks to cable-driven systems. In this paper, a new simplified model with respect to our published work is presented, reducing the number of cables and including the calculation of friction in the developed test bench. The formulation to calculate the displacement of the point of the applied force and the formulation to calculate the force are presented and validated with a simulation and by using a real test bench for experimentation. A multi-body system is used for the simulation, and the results are compared and discussed. Four cases are analysed to test the formulation, including the friction in pulleys and in the joint connection between the mobile part and the fixed part of the mechanism. Future works will be oriented toward reducing the dimensions of the conceived mechanism in order to implement the model in minimally invasive robotic surgery instruments.

Cable-Driven Mechanism Models for Sensitive and Actuated Minimally Invasive Robotic Instruments

“…The two models were conceived to measure the forces and torques on part C connected to the forceps (by using cables) during the interaction with the environment. Another simplified sensitive cable-driven mechanism model (MM3), with motion in a plane, and validated algorithms to measure forces and displacements were presented in [12]. Figure 6 shows a section of the planar model MM3.…”

“…A revolute joint in O allows for the performance of the motion of the planar system with 1 degree of freedom and for the measurement of external loads and displacements by using only two cables. More details on this mechanism model can be shown in [12].…”

“…[5] and ref. [12], focused on this new research direction [13][14][15][16][17][18][19]. Some recent work measures the tension on cables, in which the fixed part has bigger dimensions than the mobile part [15,19].…”

“…The MIRI sterilization that limits the life of electronic components in the sensing system (e.g., Micro-Electro-Mechanical Systems sensors [12], which could be included in MIRIs to measure a tactile interaction with the tissues [4]); • Errors during the motion of forceps [3];…”

“…Recently, we published a paper in which we proposed and validated a mechanism model and general formulations, using two test benches for experimentation [5]. Another simplified mechanism model with a new formulation was validated in a virtual multi-body model and tested in a planar test bench for experimentation [12].…”