Soft Pneumatic Actuators Using Negative Pressure

Abstract

Soft robotics is a growing field where scientists and engineers collaborate to design machines that collaborate safely with humans (namely “collaborative robot”), and manipulate soft or delicate objects safely. Soft pneumatic actuators are excellent tools in building soft robots, since both the elastomer used in building the actuators and the air used to power them are naturally compliant. This compliance distributes the contact force over the area of contact, and limits the contact pressure. Soft pneumatic actuators changes shape with pressure, and use strain-limiting components imbedded in an elastomeric enclosure to generate various motions.

This dissertation explores design and fabrication of soft pneumatic actuators by combining vacuum with reversible buckling of elastomeric beams. Buckling is a classical mechanical instability often seen as a failure mode in hard materials. The reversible buckling of elastomeric beams, however, allows buckling to be harnessed as a method to generate a range of motion, and allows the fabrication of actuators that mimic the performance of actuators (i.e. muscles) found in nature.

Chapter 1 provides a short overview of the history of soft pneumatic actuators, and of the use of vacuum instead of pressure as a source of power. Chapter 2 and Appendix I describe rotary soft pneumatic actuators—the buckling actuator—based on vacuum and buckling of elastomeric beams. Chapter 3 and Appendix II describe the design of linear soft pneumatic actuators—vacuum-actuated muscle-inspired pneumatic structures (VAMPs)—based on the same technology, which mimics the mechanical performance and many useful features of human muscle. Chapter 4 and Appendix III describe a design of vacuum-actuated soft linear actuators (VASAs) that overcome the usual limit of one atmosphere in the output pressure by generating a mechanical advantage. Appendix IV demonstrates that the buckling of arrays of elastomeric beams can also be used in building soft metamaterials with useful functions, such as shape memory metamaterials. Beyond soft pneumatics actuators, novel methods of non-damaging manipulations, such as magnetic levitation, can prove useful in orientation and examination of objects (Appendix V, VI).