Fabrication and Dynamic Modeling of Bidirectional Bending Soft Actuator Integrated with Optical Waveguide Curvature Sensor

Abstract

Soft robots exhibit many exciting properties due to their softness and body compliance. However, to interact with the environment safely and to perform a task effectively, a soft robot faces a series of challenges such as dexterous motion, proprioceptive sensing, and robust control of its deformable bodies. To address these issues, this article presents a method for fabrication and dynamic modeling of a novel bidirectional bending soft pneumatic actuator that embeds a curvature proprioceptive sensor. The bidirectional bending deformation was generated by two similar chambers with a sinusoidal shape for reducing the internal dampness during bending deformation. An optical waveguide made from flexible poly (methyl methacrylate) material that is immune to the inlet pressure was embedded into the actuator body to measure its bending angle. A dynamic modeling framework based on step response and parameter fitting was proposed to establish a simple differential equation that can describe the nonlinear behavior of the soft actuator. Hence, a sliding mode controller is designed based on this differential equation and the Taylor expansion. The proposed dynamical model and the sliding mode controller were validated by trajectory tracking experiments. The performance of the bidirectional bending soft actuator, such as the linear output of the curvature sensor in different inflating patterns, the proprioceptive sensitiveness to the external environment, the output force, and large bending range under relatively small pressure, was evaluated by relevant experimental paradigms. Prototypes from the novel design and fabrication process demonstrated the soft actuator's potential applications in industrial grasping and hand rehabilitation.

Soft Origami Optical-Sensing Actuator for Underwater Manipulation

“…A popular remedy to this problem is customizing soft strain sensors for the soft actuator to sense the motion. Examples are resistance strain sensors ( Russo et al, 2015 ; Morrow et al, 2016 ; Shen et al, 2016 ; Low et al, 2017 ; Yang et al, 2017 ), capacitance strain sensors ( Bilodeau et al, 2015 ; Farrow et al, 2017 ; Bilodeau et al, 2018 ; Yuen et al, 2018 ), and optical waveguide sensors ( Sareh et al, 2015 ; To et al, 2015 ; Zhao et al, 2016 ; Molnar et al, 2018 ; Chen et al, 2019 ), which hold great potential in this field, although they have suffered from limited reliability and repeatability due to soft materials (either the material itself or connections of soft and rigid components) and complicated fabrication methods. Among these soft sensors, optical waveguide sensors work with a different mechanism that could efficiently avoid soft-rigid connections on the sensing part, therefore largely improving the reliability.…”

Modeling of a Soft-Rigid Gripper Actuated by a Linear-Extension Soft Pneumatic Actuator

“…Compared to the soft actuators, such as those that are tendon driven using cables or shape memory alloy [ 13 , 14 ], electrically driven using electroactive polymers [ 15 , 16 ], or thermally driven using hydrogels [ 17 , 18 ], soft pneumatic actuators are widely used. These soft pneumatic actuators can achieve high bearing capacity and fast responses, such as a fiber-reinforced soft actuator [ 19 , 20 , 21 ] and a bellows-type soft actuator [ 22 , 23 , 24 ]. A variety of soft grippers actuated by soft pneumatic actuators have been developed, which can grip not only regular-shaped objects such as cubes and cylinders, but also irregular-shaped objects such as keys, mice, and scissors [ 25 , 26 , 27 ].…”

Improved Continuum Joint Configuration Estimation Using a Linear Combination of Length Measurements and Optimization of Sensor Placement

“…Many papers have focused on using optical methods that tend to revolve around novel combinations or topologies for Fiber Bragg Grating (FBG) sensors (see Wang et al, 2016 ; Zhuang et al, 2018 ; He et al, 2019 ; Sheng et al, 2019 ). However, other related methods focus on the basic idea of using optical fibers in general (see Yuan et al, 2011 ; Chen et al, 2019 ; Godaba et al, 2020 ). Using optical frequency domain reflectometry combined with added optical gratings the authors in Monet et al ( 2020 ) were able to show that they could improve configuration estimation when in contact or with non-constant curvature for medical applications.…”