A general design of bias force shape memory alloy (BFSMA) actuators and an electrically controlled SMA knee and leg muscle exerciser for paraplegics and quadriplegics

This dissertation presents a general design methodology of bias force shape memory alloy actuators based on one-dimensional thermomechanical constitutive model for shape memory alloys, quasi-static analyses of shape memory alloy actuators and the concept of bias-stress-variation coefficient. The methodology is general in a sense that various configurations of shape memory alloy actuators and general load functions are covered. The bias-stress-variation coefficient serves as a central design parameter and a guidance for decision making in a design practice. This design methodology provides a systematic way for the design of bias force shape memory alloy actuators. It is especially effective in design for specifications of maximum load and maximum displacement of an actuator. Design formulas have been developed and are easy to use.