Stiffness analysis and experimental validation of modular-type hybrid antagonistic tendon-driven joint systems

Abstract

SUMMARYThis paper proposes a new antagonistic tendon-driven joint (TDJ) that exhibits higher stiffness and larger travel range than conventional types of TDJs. A detailed mathematical analysis of the stiffness of the proposed TDJ is conducted and compared to other TDJs. The effect of the tendon length is taken into consideration to establish a more precise and realistic stiffness model of the proposed TDJ. Thereafter, two hardware prototypes of the proposed TDJ design, developed in the form of a packaged modular structure that integrates two TDJs, are introduced. Using these prototypes, the stiffness characteristics of the proposed TDJs are verified through experimentation. Additionally, experimental results on the stiffness behavior during the mimicked needle insertion tasks are provided. Results show that the proposed TDJs present much higher stiffness than conventional ones and thus give a potential benefit to precision manipulation.

Modeling of a Cable-Based Revolute Joint Using Biphasic Media Variable Stiffness Actuation

“…Equation (5) was deducted considering u as spring's restoring force equal to F p and x * p as the desired position, where K E is the characteristic gain of the spring and u * is the desired control signal. The error of position is stated in (6) and its derivative with respect to time in (7), where γ is the tuning parameter to achieve minimal error.…”

“…This allows the designer to try different mechanism architectures to develop more complex devices, like cabledriven joints. Based on the work done in [3], [6], [7], a simple antagonistic revolute joint was modeled, like the one displayed on Fig. 3.…”

“…A cable-based active variable stiffness module is presented in [6]; its main characteristic is to have independent stiffness modulation with the desired tension due to controlled changes in structural parameters. A comparison of modulartype antagonistic tendon-driven joints (TDJ) is detailed in [7] in order to design a new joint with higher stiffness and larger travel range than conventional TDJs.…”

Positioning and stiffening of an articulated/continuum manipulator for implant delivery in minimally invasive surgery

“…As a matter of fact, controllable stiffness mechanisms are receiving growing attention, and different strategies were proposed based on the variation of the geometrical/material properties of the manipulator (involving, eg, material phase transition, or structural interactions between system components, such as for jamming) or on actuation‐related aspects (including, eg, pressurization and variable impedance mechanisms) . Cable tensioning, which falls within the latter class, may be regarded to as a popular strategy, yet it still poses issues especially for joint design . To the best of our knowledge, manipulator stiffening based on cable tensioning was quantitatively addressed by a limited number of studies.…”

“…11 Cable tensioning, which falls within the latter class, may be regarded to as a popular strategy, yet it still poses issues especially for joint design. 12 To the best of our knowledge, manipulator stiffening based on cable tensioning was quantitatively addressed by a limited number of studies. Among them, a model was introduced in Loschak et al 13 for the stiffening of a catheter composed by a series of bead-shaped vertebras connected by ball-socket joints and containing four pull wires.…”