The thermal shape memory effect is based on a structural reorganization of a material’s crystal lattice when thermal energy is furnished. This reorganization allows Shape Memory Alloys (SMAs) to return from a deformed state into its initial shape performing mechanical work. SMA wires are known for their high energy density and allow for the construction of compact, lightweight as well as energy efficient systems. The “self-sensing” effect makes SMA actuators smart and thus suitable for various applications.
This work approaches the development of an SMA actuated positioning system using the example of a bicycle derailleur gear. Starting from the geometrical description of derailleur gears, a model of its kinematics is derived and extended by the dynamic behaviour. Based on the actuator properties of SMA wires, an actuation concept is developed. As part of this work, the concept has been implemented in the design of a prototype. An experimental setup is realized to test and measure the prototypes behaviour and validate the model prediction.