Multidirectional Bending Soft Pneumatic Actuator With Fishbone-Like Strain-Limiting Layer for Dexterous Manipulation

Abstract

Soft pneumatic actuators (SPAs), due to their compliance and adaptiveness, are promising solutions for manipulation. However, most SPAs have only simple motion modes and cannot perform the compound motion required for complex manipulation. In this letter, we propose a parallel-chamber actuator capable of multidirectional compound bending, short for CBPCA, to provide compound motion. The key component of the actuator is the specially trimmed fishbone-like strain-limiting layer. By differentially limiting the strain on the CBPCA surface, the layer induces the main bending while allowing lateral bending to enable multidirectional compound bending of CBPCA. Further, the layer is designable to tune the motion and mechanical properties of CBPCA. We develop a kinematic model based on constant curvature assumptions to analyze and forecast the motion of CBPCA. Further, we characterize the manipulation-related indicators of CBPCA, including workspace, passive stiffness, and blocked force. The proposed CBPCA can achieve a wide-range kite-shaped spatial workspace with a motion range of 80.5<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> and 76.9<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> actuator length in main and lateral bending directions, respectively. To verify the manipulation capability of CBPCA, we developed two typical forms of manipulators: a four-finger gripper and a three-finger anthropomorphic hand to conduct experiments. The results show that CBPCA performs effectively in dexterous manipulation where basic motion primitives and complex manipulation in activities of daily living, such as setting workpieces and installing bulbs, are well-completed.