Low-inertia vacuum-powered soft pneumatic actuator coil characterization and design methodology

Recently developed soft pneumatic actuators (SPAs) powered by negative pressure have demonstrated great potential in the future of soft robotics for their high strength, intrinsic safety, low weight, and often simple design. The majority of these limited examples have only provided linear force and motion profiles, however, despite the general prevalence of bending actuators common to positive pressure powered SPAs. The benefits of such bending type SPAs follow from the direct production of moment and angular motion that are highly desirable for diverse robotic applications and activities, which allows more simple design of soft robots with complex motion behavior. Following this motivation, a new vacuum powered bending actuator is developed here as an extension of a previously presented vacuum powered actuator, the V-SPA, which features simple, lightweight material construction and rapid fabrication. Leveraging these attributes, an empirical study of a new Coil V-SPA performance is conducted across a spectrum of eight actuator prototypes. The force, speed, and stiffness of the actuators are characterized, and a generalized design metric, the Geometric Compression Ratio (GCR), is defined to quantify the relationship between physical geometric parameters of Coil V-SPAs. Finally, the results of testing reveal the new low-inertia actuator is capable of high-speed, and high-bandwidth motion, up to 0.97 m/s and 1.59 Hz, respectively.