Design of a two degree of freedom shape memory alloy actuator for mirror positioning

Due to improvements in material properties through research, actuation mechanisms utilizing shape memory alloys (SMA) have been attracting more attention. Many actuation mechanisms have utilized the phase transformation of SMA's to generate motion. One new arena for the application of the alloys is the automotive industry, where they can reduce size and cost of the actuator in current models. The three major types of actuators employing SMA wires will be discussed. One such type, the antagonistic actuator, has begun to find applications where position can be controlled through the use of SMA wire. Based on this antagonistic actuator, a novel two degree of freedom SMA actuator is proposed which controls the position of an external rear view mirror. This design would replace the current DC motor design with a cheaper and more compact mechanism. The prototype concept is implemented using an antagonistic actuator based on an SMA wire, a joystick and a microcontroller.