Shape memory alloy automotive power mirror system with microprocessor control

This thesis explores the possibility of applying shape memory alloy ( SMA ) actuators to an automotive power mirror system. The use of shape memory alloy materials is discussed in detail. This introduction of SMA materials focuses on the properties of SMA materials and illustrates the advantages, disadvantages and limitations of SMA usage. The design and development of an SMA-based, power-adjustable, automotive mirror system with potential memory settings is presented. This prototype design involves microprocessor control of the mirror system using a Motorola MC68HC11 microcontroller. The 68HC11 generates pulse width modulated ( PWM ) voltage signals to activate the SMA wires and interfaces with an optical encoder for digital, feedback control of the mirror mechanism. The prototype design is controlled by a variable, increasing PWM voltage signal that prevents overheating of the SMA wires. An input capture interrupt is used to interface with the optical encoder. Problems leading to poor motion control of the prototype are discussed and recommendations are made for improving the design.