Numerical and experimental methods for the assessment of a human finger-inspired soft pneumatic actuator for gripping applications

Abstract

The increasing demand for soft robotic systems in agricultural, biomedical and other applications has driven the development of actuators that can mimic the flexibility and adaptability of human muscles. Several studies have explored the design and implementation of soft actuators for robotic applications, however, there is a need for soft actuators demonstrating delicate gripping capabilities but also excel in specific biomedical applications, such as therapeutic massaging. The objective of this work is to develop a multi-finger soft pneumatic actuator mimicking human fingers for Ayurvedic therapeutic massaging and gripping applications. The actuator is geometrically modeled to mimic the dexterity and flexibility of a human finger and its mechanical behavior such as bending angle and gripping force under air pressure is studied through finite element analysis (FEA). The simulation results are experimentally validated. The finger-based actuator is fabricated using liquid silicone rubber, and its performance namely, bending deformation and gripping force generated at various pressure is determined and these results are compared with the simulated test cases. The study also provides a detailed analysis of the performance of the actuator, thus providing detailed insights into its applicability in therapeutic purposes.•Human finger inspired actuators are expected to demonstrate the dexterity and flexibility of human hands, which poses challenges in its modeling and analysis.•The load carrying capacity and bending movements of the actuator is assessed using numerical method of Finite Element Analysis.•Simulation results are validated through an experimental method using force sensors and image analysis of the bending movement of the soft actuator.

Keywords: Biomedical; Finite element method; Gripper; Numerical and experimental methods; Pneumatic; Soft actuator; Soft robotics.

Graphical abstract

Fig. 1

Geometric model of the proposed actuator.

Fig. 2

The soft actuator and human hand CAD models for massaging simulation.

Fig. 3

(a) The inner walls of the actuator subjected to fluid pressure and (b) outer walls highlighted with possible interaction (contacts).

Fig. 4

Meshed model of the actuator.

Fig. 5

Prescribed boundary conditions used for (a) contact force and (b) massing analysis: the blue colored portions are constrained in all directions.

Fig. 6

Fabricated soft actuator.

Fig. 7

(a) Experimental setup for force sensing resistor readings, (b) circuit for force sensing sensor readings.

Fig. 8

(a) Bending angle variations obtained in the FE simulations at different pressures with respect to time, bending profiles obtained at (b) 60 kPa and (c) 100 kPa.

Fig. 9

(a) The bending angle variation with inflation pressures, (b) absolute percentage error between numerical and experimental results at different pressure levels.

Fig. 10

(a) Bending angle variations obtained in experiments, (b) bending deformations observed at various pressures.

Fig. 11

Reaction force variations obtained in the FE simulations at different pressures with respect to time.

Fig. 12

Reaction force variations obtained in the experiments at different pressures with time.

Fig. 13

Total deformation (in m) observed in the human arm model.

Fig. 14

Linearized equivalent stress along the length of the actuator obtained in FE simulations.

Fig. 15

Average equivalent (a) stress and (b) strain variations obtained in the FE simulations at different pressures with respect to time.

Fig. 16

(a) Three-finger actuator, actuator (b) before and (c) after pressurization.