Nova Publishers
My Account Nova Publishers Shopping Cart
HomeBooksSeriesJournalsReference CollectionseBooksInformationSalesImprintsFor Authors
  Top » Catalog » Books » Materials Science » Shape Memory Alloys: Manufacture, Properties and Applications Chapters » My Account  |  Cart Contents  |  Checkout   
Quick Find
Use keywords to find the product you are looking for.
Advanced Search
What's New? more
A Crucible of Modern Sport: The Early Development of Football in Sheffield
Shopping Cart more
0 items
Shipping & Returns
Privacy Notice
Conditions of Use
Contact Us
Notifications more
NotificationsNotify me of updates to Shape Memory Alloys In Micropositioning Applications, pp. 441-485
Tell A Friend
Tell someone you know about this product.
Shape Memory Alloys In Micropositioning Applications, pp. 441-485 $100.00
Authors:  E. Asua, J. Feuchtwanger, V. Etxebarria and A. Garcia-Arribas
Shape memory alloys (SMA) are a special kind of smart materials whose dimensions
can be modified as the result of a temperature-dependent structural phase transition.
This property can be used to generate motion or force in electromechanical
devices and micromachines. The use of shape memory alloys in actuators offers the
opportunity to develop robust, simple and lightweight elements for application in a
multitude of different industries. Despite all these advantages, the accuracy of SMA
actuators is severely limited by their highly nonlinear stimulus-response characteristics.
Traditionally, they have been used as “on-off” electromechanical actuators due
to the non-linear and hysteretic nature of the martensite-austenite transformation. The
ideal solution to this problem is to model the hysteresis mathematically to compensate
for it in the control loop. However, useful models of phase transitions are difficult
to obtain. In this chapter, a Nickel-Titanium alloy (Nitinol) wire is considered as the
active element in micropositioning actuators. An electric current, applied through the
wire, heats it to induce the phase transition and the consequent contraction. The purpose
of this investigation is to finely control the wire contraction. The wire needs to
be able to contract and relax to an intermediate position within its range of movement
and the gradual contraction and relaxation needs to be controllable. An experimental
micropositioning device, based on a Ni-Ti wire, is controlled using several control
strategies. To account for the hysteresis effects, an inverse hysteresis model is obtained
using two different compensating methods. When used in a controller, the inverse
models nicely compensate the non-linear and hysteretic behavior of the wire, and
a proportional-integral with antiwindup control works adequately, obtaining position
accuracies around 3 micrometers. Once the real possibility of using these materials
as micrometric actuators is analyzed and tested, a SMA based actuator prototype grip
for a flexible robot is developed, so that it could be used in light applications. For this
purpose, the bulky LVDT (linear variable differential transformer) used in the previous
experiments to provide the position feedback to the controller must be replaced by
lighter alternatives. The first solution consists of deducing the strain of the SMA wire
from the readings of a set of strain gauges that are placed in the fingers of the grip.
Although the precision is limited by the strain gauge accuracy, position errors about
30 micrometers are achieved. The second one is the implementation of a sensorless
design, where the change in the resistivity of the SMA wire is used to determine the
strain of the active element. Position errors about 60 micrometers are achieved, with
the great advantage that the actuator is reduced to a single SMA element, specially
important if the goal is to reduce the overall size and weight of the actuator, like is the
trend in the miniaturization in mechatronics and robotics. The experiments presented
show that SMA wires as active elements are serious alternatives to be used as precision
actuators in micromachines. 

Available Options:
This Item Is Currently Unavailable.
Special Focus Titles
01.Chaliapin and the Jews: The Question of Chaliapin's Purported Antisemitism
02.The Humanities: Past, Present and Future
03.The Poles: Myths and Reality
04.Child-Rearing: Practices, Attitudes and Cultural Differences
05."A Home Away from Home": A Community of International and South African University Students
06.Palliative Care: Oncology Experience from Hong Kong
07.The Enigma of Autism: Genius, Disorder or Just Different?
08.The Collector Mentality: Modernization of the Hunter-Gatherer
09.Face Processing: Systems, Disorders and Cultural Differences
10.Occurrences, Structure, Biosynthesis, and Health Benefits Based on Their Evidences of Medicinal Phytochemicals in Vegetables and Fruits. Volume 8
11.Crystal Growth: Concepts, Mechanisms and Applications
12.The Economic, Social and Political Impact of Mining on Akyem Abuakwa from the Pre-Colonial Era up to 1943

Nova Science Publishers
© Copyright 2004 - 2017

Shape Memory Alloys In Micropositioning Applications, pp. 441-485