Research Plan

Project Subject

Motion is mostly provided by using electric motors and many different methods. However these methods generally cause noise pollution and the parts that provide movement are big in volume and also heavy. Because of these reasons, it is researched, if it may be possible to develop smaller and lighter systems to provide movement especially in small applications.

Engineering Goals

It is aimed to produce a new and different alternative to motion methods used today. At the same time it is intended to contribute clean technology, which has a rising importance nowadays. In this project, Nickel-Titanium wire which is one of shape memory alloys is researched. By developing new movement methods with these wires, it was shown that Nickel-Titanium wires can be used in different kinds of motions. Moreover the purpose of the project is to bring a new perspective to the studies about robots.

Dates and Plans

1-15.06.2008 : Project starting date
2-15.06.2008 – 30.06.2008: Collection of useful ideas from the internet and making plans for the project period.
3-01.07.2008 – 15.07.2008: Making the first experiments with the example Nickel-Titanium wires in the hand and making decision which diameters of the wires should be obtained from Germany.
4-16.08.2008 – 16.09.2008: Making experiments with the Nickel-Titanium wires to see the behaviors of the material.
5-16.09.2008 – 30.09.2008: Creating designs for the applications which will provide movement using Nickel-Titanium wires.
6-01.10.2008 – 15.10.2008: Drawing the designs using a computer to be able to make applications easier and better.
7-16.10.2008 – 07.11.2008: Making the first application ( so-called “Six Leg Spider” )
8-08.11.2008 – 30.11.2008: Making the second application ( so-called “Wheeler” )
9-01.12.2008 – 30.12.2008: Making the last application ( so-called “Two Leg Robot” )
10-01.01.2009 – 30.01.2009: Improvement of the applications.
11-01.02.2009 – 28.02.2009: Writing of the project report

Procedure

Nickel-Titanium alloy will to be used in the project as main material. The wire form of Nickel-Titanium alloy will be used. According to the references, these wires can become 8% short of their length while changing phase from martensite to austenite. Nickel-Titanium is made of a metallic and crystal structure that can return to original shape determined by heat. These phases occur because of shape changes in crystal structure of Nickel-Titanium alloy.

Experiments will be done with Nickel-Titanium. The behaviors of Nickel-Titanium will be analyzed related to the mass, the stretching percentage, the current passed through and power. Charts will be made using datas from the experiments. The efficiency of Nickel-Titanium wires will be found with the help of the experiments.

Applications will be made using Nickel-Titanium wires. Different kinds of motions should be obtained using Nickel-Titanium wires. The applications will be designed taking advantages of Nickel-Titanium wires. It is aimed to make small applications, indeed.

Data Analysis

According to the experiments, Nickel-Titanium wire works most efficiently in 170mA. It starts to shorten in 120mA. It begins to change the phase from martensite to austenite in 120mA.

As the current passed increases, heating of wire increases too. So shortening percentage goes up. Related to this, after a certain flow a big difference is seen in wire’s shortening. The reason for this is the changes in crystal structure of the wire. The diameter of wire increases and the length decreases with changes in crystal structure. As seen in the experiments, there is a big increase in shortening percentage in 170mA. Because at 170mA wire completes its phase change in a big ratio. There is not a big difference in percentage of shortening at higher currents. But the current is fixed at 190mA when current is stabled in experiments and applications. The reason of why it is fixed at 190mA is that sudden resistance changes are seen below 190mA. This change complicates to stable the current.

The wire works most stable at 0,47 watt ( 190mA ) when 200 gr. is hung on Nickel-Titanium wire. In the applications when shortening was not enough, 0.69 watt (230mA) was given.

The experiments showed that Nickel-Titanium wire works most efficiently when 0.47 watt is given and 300 gr. is hung. The efficiency is 22.5 % with these values.

Three applications were made. As the applications were done completely with hands, there have been some difficulties in installation step. This caused the applications not to be as small as planned. Also no devices, as light as needed could be found. For this reason applications are in model stage at the moment. The ways to produce lighter and smaller models are being looked for. By this way, it is aimed to move the systems as planned.

Bibliography

1.Erfolgreich Experimenten mit Nitinol Mini-Robotern – Fied Wagenknecht. (2000), München, Germany
2.Muscle Wires Project Book – Roger G. Gilbertson (2000), ABD
3.Prof. Dr. Ayşegül Akdoğan – Şekil Hafızalı Alaşımlar (Shape Memory Alloys)
Images by IEL-TÜBİTAK Research Group