Fabrication and Testing of a Simple “Bionic Arm” Demonstrator

Artificial or “bionic” limbs have been the subject of considerable research, TV shows, and dreams by children. The “Six Million Dollar Man” show was about a man who received artificial limbs after his own were lost in an accident. To get students interested in practical engineering, the current work showcases a simple artificial arm that produces greater force than a typical man, demonstrates the capability of Rubber Muscle Actuators (RMA), and provides a portable “arm wrestling platform” for student recruitment efforts. The actuators for “Kingsville Arm One & Two” are McKibben-like actuators made from fiber-reinforced elastomeric composites. These actuators offer excellent strength-to-weight ratios and contract similar to a human muscle. RMAs produce greater force and have less “blow-outs” than typical McKibben actuators because of optimized braid angles and ends that transfer loads through the braid fibers. Kingsville Arm One (KA1) was developed in just two weeks. It consisted of carbon/fiberglass/epoxy composite tubular bones, a metal clevis “elbow” and four RMAs. With considerable effort, a very large student was able to overcome the force generated in an “arm wrestling” contest. KA1’s actuators had end attachments that transferred loads well and enabled flexibility, but easily tore and had air leaks. Kingsville Arm Two (KA2) had new “bones” and RMAs. Although slightly smaller diameters, the KA2 RMAs produced comparable forces to the KA1 RMAs and had molded end attachments. The rigid ends did not allow as much rotation as expected and necessitated using just 2 RMAs. With only two RMAs, KA2 produced approximately the same “arm strength” as KA1. Future work will focus on flexible but durable RMA molded ends, life-like skins and a realistic “hand.”