The Twisted Future of Linear Actuators

By twisting common polymer fibers, like Nylon 6,6 into dense helix structures, a process known as super coiling, one can create a cheap, thermally driven, pliable, lightweight, compact, and long lived actuator. In PHASE I of the research at SFA, actuators were hand made by twisting fibers via stepper motor on a physics test stand. While multiple examples of TCPAs have been constructed using this technique, the process has proven to be difficult and inefficient. The constant breakage, ``birds nesting,'' and ``side coiling'' have proven that mass production or precision characterization of TCPAs will be impossible with the current fabrication techniques. The research team devised an automated muscle twister, employing a strain gauge, automatic PID twist control and micro-controller system, to untangle the problem of rapidly and precisely manufacturing TCPAs. The muscle twisting system was modeled in SolidWorks and its function simulated before manufacturing. The sub-assemblies, such as the right and left end plates, coiling carriage and motor mounts will be shown and a discussion of design and possible improvements will be provided. One of the major advantages of the system is the precise tuning of number of twists, tension, and final actuator length. As a result, rapid precision production of TCPAs to any desired specification can be performed at much greater speed.