Affiliations: [a] Institute of Fluid Science, Tohoku University,
Katahira 2-1-1, Aoba-ku, Sendai 980-857, Japan. Tel.: +81 22 217 5264; Fax:
+81 22 217 5264; E-mail: qiu@ifs.tohoku.ac.jp
| [b] Honda R&D Co., Ltd., Tochigi R&D Center, Haga-gun,
Tochigi 321-3393, Japan | [c] Platform Products, I/CD, Teradyne, Inc., 179 Lincoln
St., MS-L21, Boston, MA 02111, USA
Abstract: The main problem with Shape Memory Alloy (SMA) actuators is their
slow response speed. Current SMA actuators work in tens of seconds though they
can generate large force and displacement outputs. The objective of the
research in this paper is to improve the response speed of SMA actuators to 10
milliseconds or less. SMA actuators are driven by thermal energy and their slow
response is attributed to the inefficient heat transfer. To improve the
response, direct Ohmic heating was used in the experiments. The SMA actuators
used in this study are Ti-Ni-Cu columns of \phi 5\times 50
mm with residual strain produced upon unloading after 5.3% displacement
response of the SMA actuators without axial constraint and the transient force
response of the actuators under axial constraint were measured with direct
heating. The shortest response time achieved for unconstrained actuators is 4.6
ms and that for constrained actuators is 6.5 ms. The average value of maximum
recovery force is 10.8 kN, which corresponds to 550 MPa of recovery stress. It
was also found that constrained actuators need about 50% more energy for
heating than unconstrained actuators.
