Shape Memory Alloy Actuator

My research involves a novel shape memory alloy (SMA) actuator that overcomes two of the main drawbacks of SMAs, those being limited strain and limited cycle lifetime. The abundant force available with SMA fibers is efficiently transformed to increase linear displacement by weaving the fibers in a double helix fashion around supporting disks. This can also provide increased lifetime as the fibers can now be operated at lower than absolute percent strain.

SMA Actuator in action!
An actuator prototype has been constructed with the following properties:

light weight - 6 grams,

compact - 17 mm cylinder, 25 mm long,

powerful - 3.5 newtons,

linear direct drive actuator,

requires no gears or lubrication,

elastic - smooth movements,

acoustically silent,

modular and

inexpensive with simple construction.

Some Publications:

Grant, D., Hayward, V. 1997a. Variable Structure Control of Shape Memory Alloy Actuators. IEEE Systems and Control Magazine. Vol. 17, No. 3, pp. 80--88.

Grant, D., Hayward, V. 1997b. Controller for a High Strain Shape Memory Alloy Actuator: Quenching of Limit Cycles Proc. IEEE Int. Conf. on Robotics and Automation. Vol. 1, pp. 254-259.

Lu, X., Grant, Danny, Hayward, V. 1997. Design and Comparison of High Strain Shape Memory Actuators. in the 1997 Proc. IEEE Int. Conf. on Robotics and Automation. Vol. 1, pp. 260-267.

Grant, D., Hayward, V. 1995. Design of high strain shape memory actuator under Variable Structure Control. Proc. Int. IEEE Conference on Robotics and Automation. pp. 2305--2312.

A compact pan, tilt, and torsion camera unit was also constructed implementing the SMA actuators to demonstrate their feasibility in a miniature application. The camera was designed for a foveated vision system also being developed here at Mcgill.

This first camera prototype has the following preliminary characteristics:

speed = 350 degrees/s

acceleration = 5800 degrees/s^2

size = 180 mm x 77 mm x 77 mm

Weight

camera = 50 grams

actuators = 24 grams

sensors = 25 grams

support structure = 250 grams

total weight = 349 grams

Publication:

Baron, T., Levine, M. L., Hayward, V., Bolduc, M., Grant, D. 1994. (November, Ottawa). A biologically-motivated robot eye system. Proc. 8th Canadian Astronautics and Space Institute (CASI) Annual Conference. pp. 231-240. (Best Paper Award).

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