No abstract

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.

No abstract

Soft pneumatic bending actuators generally produce a bending deformation through pressurization, but the force they produce diminishes significantly throughout the deformation for a given pressure level. This is useful to produce a controlled motion, but sensors are required to enable force control of the actuator throughout this motion. This paper introduces the use of an inflatable L-shaped prism as a soft actuator that has a constant equilibrium angle and produces a fairly constant force throughout most of its actuation range. This combination of characteristics makes the actuator ideal for applications where an easily controllable force without the use of sensors is required or preferable. However, it is unsuitable for applications where motion control is necessary due to its constant equilibrium angle. The effect of different geometric parameters and materials were tested, and it was found that this actuator could produce a blocked force of up to 13 N at 80 kPa and could maintain this force throughout most of this range of motion. This actuator concept was then used to build a threefingered soft exoglove capable of grasping a wide range of objects.