Screw theory-based stiffness analysis for a fluidic-driven soft robotic manipulator

Abstract

Soft robotic manipulators have been created and investigated for a number of applications due to their advantages over rigid robots. In minimally invasive surgery, for instance, soft robots have successfully demonstrated a number of benefits due to the compliant and flexible nature of the material they are made of. However, these type of robots struggle with performing tasks that require on-demand stiffness i.e. exerting higher forces to the surrounding environment. A number of semi-active and active mechanisms have been investigated to change and control the stiffness of soft robotic manipulators. Embedding these mechanisms in soft manipulators for spacerestricted applications can be challenging though.To better understand the inherent passive stiffness properties of soft manipulators, we propose a screw theory-based stiffness analysis for fluidic-driven continuum soft robotic manipulators. First, we derive the forward kinematics based on a parameterbased piece-wise constant curvature model. It is worth noting, our stiffness analysis can be conducted based on any freespace forward kinematic model. Then our stiffness analysis and mapping methodology is conducted based on screw theory. Initial results of our approach demonstrate the feasibility comparing computational and experimental data.

Miniaturised Soft Manipulators with Reinforced Actuation Chambers on the Sub-Centimetre Scale

“…6 and 7 highlight that the lifting height ∆z could be less than zero, especially in the case that three chambers are actuated. This can be explained by the fact that the overall stiffness of soft robots decreases as their elongation ratio increases [34]. As such, it would be advisable to consider the number of actuated chambers when dealing with payloads, i.e, actuating just two chambers to generate better payload capability.…”

“…Payloads of 0g, 1g, 2g, 3g, 4g, and 5g, were applied at the tip of two robots while they generated in-plane and out-of-plane bending motions. Please note that the terms 'inplane' and 'out-of-plane' refer to that the backbone of a soft robot bends within a single plane as well as through different planes [34]. Throughout all tests, the actuation pressure was set at 1.2 bar.…”

Stiffness modelling and analysis of soft fluidic-driven robots using Lie theory

“…κ ( s ) i is the curvature, s ( s ) i is the curve length and ϕ ( s ) i is the angle of the arc that rotates from the x- z plane. Using the exponential mapping from Lie theory, the homogeneous transformation g i ( i+ 1) from ith arc to ( i + 1)th arc using screws (Webster and Jones 2010; Shi et al, 2021). The general form of g i ( i+ 1) is shown in (43) (see Appendix C).…”

“…In our previous work (Shi et al, 2021), we proposed a Cartesian stiffness modelling method based on the PCC model for a single fluidic-driven soft robot. The paper included preliminary validation data on the tip stiffness.…”

An Operating Stiffness Controller for the Medical Continuum Robot Based on Impedance Control

“…Unlike traditional rigid robots, the inherent flexibility of continuum robots enhances their safety during navigation access to the surgical sites [ 10 – 14 ]. However, in actual surgical scenarios, continuum manipulators not only need excellent accessibility to facilitate flexible and safe access to the instruments but also require sufficient effectiveness to contribute to stable and precise operations of the instrument, which demands greater stiffness [ 15 ], as shown in Fig. 1 .…”