Abstract
Soft pneumatic actuators (SPAs) are found in mobile robots, assistive wearable devices, and rehabilitative technologies. While soft actuators have been one of the most crucial elements of technology leading the development of the soft robotics field, they fall short of force output and bandwidth requirements for many tasks. In addition, other general problems remain open, including robustness, controllability, and repeatability. The SPA-pack architecture presented here aims to satisfy these standards of reliability crucial to the field of soft robotics, while also improving the basic performance capabilities of SPAs by borrowing advantages leveraged ubiquitously in biology; namely, the structured parallel arrangement of lower power actuators to form the basis of a larger and more powerful actuator module. An SPA-pack module consisting of a number of smaller SPAs will be studied using an analytical model and physical prototype. Experimental measurements show an SPA pack to generate over 112 N linear force, while the model indicates the benefit of parallel actuator grouping over a geometrically equivalent single SPA scale as an increasing function of the number of individual actuators in the group. For a module of four actuators, a 23% increase in force production over a volumetrically equivalent single SPA is predicted and validated, while further gains appear possible up to 50%. These findings affirm the advantage of utilizing a fascicle structure for high-performance soft robotic applications over existing monolithic SPA designs. An example of high-performance soft robotic platform will be presented to demonstrate the capability of SPA-pack modules in a complete and functional system.
Highlights
Soft pneumatic actuators (SPAs), which are intrinsically compliant and readily manufacturable, are paving the way for a future of new robotic systems that benefit from inherent safety, adaptability, and customizability.[1,2,3,4] While the force output of a robotic actuator is an important performance metric for many applications, it does not always accurately reflect the requirements of a full robotic system in others
There may even be no decrease in functionality at all, as a unit actuator loss may be compensated by shifting work to the remaining units in the pack. This extends the utility of soft actuators in robotics even further to applications, where safety benefits from the use of compliant materials and from the improved controllability of devices powered by soft actuator packs
We proposed a design method to address one of the major challenges of current soft robotics: shortcomings of soft actuators
Summary
Soft pneumatic actuators (SPAs), which are intrinsically compliant and readily manufacturable, are paving the way for a future of new robotic systems that benefit from inherent safety, adaptability, and customizability.[1,2,3,4] While the force output of a robotic actuator is an important performance metric for many applications, it does not always accurately reflect the requirements of a full robotic system in others. A common method for improving the robustness of some engineered systems is the introduction of a fail-safe or a secondary mechanism that can be activated in the case of unexpected primary mechanism failure.[5] In some systems, this fail-safe operation may be an emergency shutoff or a similar irreversible action, while in others it may be accomplished by the addition of redundancy or parallel multiplicity. Certain insects are capable of maintaining mobility despite the loss of nearly any number of their legs,[6] and larger order animals’ muscular tissue, essential for maintaining most activities of daily living, is arranged with parallel cellular structures that serve the dual purpose of redundancy and the summation of parallel action to increase strength.[7] This latter example is as applicable to engineered systems, such as robots, as it is to biology
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