Design of a composite SMA actuator for a pressurized hyper-redundant manipulator

Hyper-redundant devices are characterized by repeating independently controlled structures connected in series, much like the architecture of a snake or worm. This thesis evaluates the performance of a pressurized hyper-redundant manipulator design driven by high strain shape memory alloy actuators. The proposed design is composed of four identical modules; each providing three degrees of freedom from three symmetrically positioned actuators. The modules have an outer diameter of 31mm and a length of 33mm at full extension. The actuator return force and manipulator stiffness are controlled by an air pump connected at the base. Although connection failures between the actuator tabs and vertebrae prevented the validation of the hyper-redundant manipulator prototype, the unit module element was successfully fabricated and evaluated. The unit module could achieve linear contractions of 40% and rotations of over 50° at a frequency of 0.05Hz. Several limitations remain to be addressed in order to build a reliable device; these include: (1) The high current requirement of the actuators, (2) The inefficient actuation system, and (3) The connectivity issues between the actuators and the modules.