Soft Morphing Buttons Based on Actuator and Sensor Properties of Shape Memory Alloy Wires

Abstract

As a smart material thermal shape memory alloys (SMAs) feature actuator behavior combined with self-sensing capabilities. With their high energy density and design flexibility they are predestined to be used in soft robotics and the emerging field of morphing surfaces. Such shape changing surfaces can be used for novel human-machine interaction (HMI) elements based on mode-/situation-dependent interfaces that may be applied to all kind of machines, appliances and smart home devices as well as automotive interiors. Since many of those contain textile surfaces, it is of special interest to place SMA-based actuator-sensor-elements beneath a textile cover or integrated them in the textile itself. In this study, the unique features of SMAs are used to design a system which represents an active “morphing” button. It can lower into the surface it is integrated in, pops up to be used and shows a proportional signal output depending on the pushing stroke. The system is characterized concerning haptics and sensor technology. The button consists of a TPU structure, to which two NiTi wires are attached. When activated, the SMAs contract and the structure curves upwards. The user can now push on the device to use it as a button. In the future, the use of SMA wires and for example TPU fibers enables direct integration in the production process of a possible smart and functional textile.

Design of a lightweight SMA driven parallel gripper for collaborative robots

“…So that the stress level matches the geometric calculation in figure 3, a total number of 48 NiTi wires in parallel is required. To enable the installation of that many single wires, several wires are bundled with the help of a controlled resistance welding process [10], [15]. One such bundle consists of six parallel 76 µm NiTi wires with a length of 85 mm (martensite +, zero stress) which are welded to thin steel plates with dimensions of 5 mm x 6 mm x 0.4 mm.…”