Control of nitinol wire actuator.
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
The Stewart Platform is well known parallel robotic mechanism often used for flight simulators. Less well known applications involve robotics and machine tools. This research deals with Stewart Platforms that use Nitinol wire, a shape memory alloy, as binary actuators that are switched on and off to control the position of the platform. Binary control of the six actuators on a platform yields sixty four possible platform positions, and four stacked platforms yield 256E12 possible positions. The design of a simple basic four stages model is described in this research. Experiments were conducted on the Nitinol wire to investigate the shape memory effects, hysteresis and the martensite/austenite phase transformations. These results were used in the design of a high power to weight ratio Stewart Platform, overcoming many of the drawbacks of previous models that are powered by heavy hydraulics or electric motors. Due to the complexity of some of the parts and small numbers required, rapid prototyping was used to manufacture over 90% of the structure. In this research, the control system proposed is expected to be useful for not only Shape Memory Alloy (SMA) actuators but also other actuators with hysteresis, for example, piezoceramic actuators, rubber actuators driven by air supply, bellows actuators, etc.