The paper is available at https://lnkd.in/gfS5fGSw
The research is the result of a remarkable collaboration between Yang Yang from CUHK and ZJU, Sam, Jiewen Lai from CUHK, Chaochao Xu from NUS, Zhiguo He and Pengcheng Jiao from ZJU, and Hongliang Ren from CUHK and NUS.
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There has been a growing need for soft robots operating various force-sensitive tasks due to their environmental adaptability, satisfactory controllability, and nonlinear mobility unique from rigid robots. It is of desire to further study the system instability and strongly nonlinear interaction phenomenon that are the main influence factors to the actuations of lightweight soft actuators.
Here, we present a design principle on lightweight pneumatically elastic backbone structure (PEBS) with the modular construction for soft actuators, which contains a backbone printed as one piece and a common strip balloon. We build a prototype of a lightweight (<80 g) soft actuator, which can perform bending motions with satisfactory output forces (~ 20 times self-weight).
Experiments are conducted on the bending effects generated by interactions between the hyper-elastic inner balloon and the elastic backbone. We investigated the nonlinear interaction and system instability experimentally, numerically and parametrically. To overcome them, we further derived a theoretical nonlinear model and a numerical model. Satisfactory agreements are obtained between the numerical, theoretical and experimental results. The accuracy of the numerical model is fully validated. Parametric studies are conducted on the backbone geometry and stiffness, balloon stiffness, thickness, and diameter. The accurate controllability, operation safety, modularization ability, and collaborative ability of the PEBS are validated by designing PEBS into a soft laryngoscope, a modularized PEBS library for a robotic arm, and a PEBS system that can operate remote surgery. The reported work provides a further applicability potential of soft robotics studies.
FIG. 1. Illustrative demonstration of the PEBS: (a) the detailed structure and dimensions of the PEBS, (b) the design principle that can be divided into the separation stage and the interaction stage, and (c) the design principle that can be specifically divided into the separation stage, the insufficient interaction stage, the full interaction stage, and the excessive interaction stage, based on the interaction conditions.
FIG. 2. Nonlinear interaction phenomenon analyses: (a) the free oscillation phenomenon of the backbone structure generated by the structural asymmetric stress responses to gravity, (b) the interaction performances of the backbone structure and the density plot showing the relationship between the gap numbers, pressures, and bending angles, (c) the interaction performances of the balloon and the relationships between the pressures and expansion ratios regarding the radial and axial expansion ratios, respectively, (d) relationships between the pressures and stresses regarding the backbone structure and balloon, respectively.
FIG. 3. Applications of PEBS demonstrate unique advantages of accurate controllability, operation safety, modularization ability, and collaborative ability. (a) A PEBS soft laryngoscope that can operate laryngeal diagnosis. (b) Real-time images captured by the integrated image sensor. (c) Modularized PEBS library that can be installed onto a robot arm. (d) A PEBS grasper that can operate various grasping tasks. (e) The PEBS system can be potentially applied to operate a debridement.
