Mathematical Models for Guiding Pneumatic Soft Actuator Design
Connolly, Fionnuala Patricia
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AbstractSoft actuators are the components responsible for producing motion in soft robots. Although soft actuators have facilitated a variety of innovative applications of soft robots, there is a need for design tools that can help to efficiently and systematically design actuators for particular functions. Mathematical modeling can provide quantitative insights into the response of soft actuators. These insights can be used to guide actuator design, thus accelerating the design process.
By performing finite element simulations of fiber-reinforced soft actuators, I quantify the relationship between the fiber angle of the actuators and their deformation as a function of inflation pressure. I then verify the simulation results by experimentally characterizing the actuators. By combining actuator segments in series, combinations of motions tailored to specific tasks can be achieved. I demonstrate this by using the results of simulations of separate actuators to design a segmented wormlike soft device, capable of propelling itself through a tube and performing an orientation-specific peg insertion task at the end of the tube.
Following on from this work, I then use nonlinear elasticity theory to develop analytical models of fiber-reinforced soft actuators. I present a design strategy that takes a kinematic trajectory as its input and uses the analytical models, together with optimization, to identify the optimal design parameters for an actuator that will follow this trajectory upon pressurization. I experimentally verify my modeling approach and demonstrate how the strategy works, by designing actuators that replicate the motion of the index finger and thumb.
Finally, I study a newer type of pneumatic soft actuator, made from textiles. Textiles are promising materials for soft actuators, as they are lightweight, conformable, stretchable, and intrinsically anisotropic. I perform mechanical characterization to identify textiles which have the properties necessary to produce a bending actuator. I then describe a layered lamination manufacturing approach, which allows us to quickly and easily coat textiles to make them air-impermeable, and seal them together to form an airtight pocket. I present a mathematical model of the actuators and use this model to design actuators for an assistive glove.
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