Jumping Tensegrity Robot Based on Torsionally Prestrained SMA Springs

This paper introduces the addition of torsional prestrain into the manufacturing process of shape memory alloy (SMA) springs to form torsionally prestrained SMA springs. These springs have a better performance at the same power input for the same loads and same coil dimensions as regular SMA springs. A modified thermoconstitutive model was presented that can predict the behavior of the actuator based on the amount of torsional prestrain added into the manufacturing process, and a simple two-state model is used to predict its actuation stroke. These improved actuators were used in the development of a tensegrity robots capable of fast rolling motions and jumping both vertically and horizontally. This robot is capable of rolling at 0.14 BL/s (body length per second) and can jump up to nearly a full body length.