Hakan YORULMUŞ 030070111 WEEK 9

1)Non Contact Near Object Detection (Group: Sensors)

In order to meet the particulate contamination abjectives, physical contact with wafers should be kept to an absolute minimum, and for this reason non-contact sensing is preferable. Types of non-contact sensing:

1. Acustic sensing
2. Proximity sensors
3. Photo-electric sensors
4. Optical time-of-flight sensors
5. Vision sensors

(Gray, J. O., Caldwell, D. G., Advanced Robotics & Intelligent Machines, p. 239)

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Last time, we learned how leaf switches are used as a form of touch sensor to detect contact with objects. Contact detection provides an immediate signal that something looms directly in the way.

Non-contact detection senses objects without having to hit them first. Near-object detection does just what its name implies: It senses objects that are close by. from perhaps just a breath away to as much as eight or 10 feet. These are objects that a robot can consider to be in its immediate space; objects it may have to deal with, and soon. These objects may be people, animals, furniture, or other robots.

By detecting them, your robot can take appropriate action which is defined by the programming you give it. Your bot may be programmed to come up to people and ask for their name. Or. it might be programmed to run away whenever it sees movement. In either case, it won't be able to accomplish either behavior unless it can detect the objects in its neighborhood.

There are two common methods of achieving near-object detection: proximity and distance.

• Proximity sensors care only that some object is within a zone of relevance. Thatis. if an object is near enough to be considered important. Objects beyond the proximal range of a sensor are effectively ignored because they are not seen. Out of view, out of mind. • Distance measurement sensors determine the space between the sensor and whatever object is within detection range. Distance measurement techniques vary; almost all have notable minimum and maximum ranges. Few yield accurate data if an object is smack-dab next to the robot, or very far away.

Collectively, these sensor types are often referred to as rangefinders, though only a device that actually measures and reports the distance of the covered range is a true rangefinder.

Among the most common proximity and distance measurement detectors used in robotics are ultrasonic transducers, and specialty infrared sensors made by Sharp. Depending on the design of the specific sensor, either can be used for proximity or distance measurement. In practice however, the Sharp IR sensors are best suited for proximity, and ultrasound sensors are the ideal choice for measuring distance. That's how these two detectors are used in the ArdBot.

(Servo,03.2011,page 44-45;http://www.servomagazine.com/index.php?/magazine/article/march2011_McComb)

2)Polypropylene (Group: Material)

--Polypropylene is a thermoplastic material that is produced by polymerizing propylene moleculesi which are the monomer units, into very long polymer molecule or chains. There are number of different ways to link the monomers together but PP asa commercially used material in its most widely used form is made with catalyst that is a semi-crystalline solid with good pysical, mechanical and thermal properties. Another form of PP, produced in much lower volumes as a byproduct of semicrystalline PP production and having very poor mechanical and thermal properties, is a soft, tacky material used in adhesives, sealants, and caulk products. The above two products are often referred to "isostatic" (crystallizable) PP (i-PP) and "static" (non-crystallizable) PP (a-PP), respectively.

(By Karian, Marcel Dekker, Handbook of Polypropylene and Polypropylene Composites, page 10)

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Polypropylene (PP) was first produced by G. Natta, following the work of K. Ziegler, by the polymerisation of propylene monomer in 1954 . The macromoleculce of PP contains 10,000 to 20,000 monomer units. The steric arrangement of the methyl groups attached lo every  second carbon atom in the chain may vary (see Figure 2). If all the methyl groups are on the same side of the winding spiral chain molecule, the product is referred to as isotactic PP. A PP structure where pendant methylene groups are attached to the polymer backbone chain in an alternating manner is known as syndiotaclic PP. The structure where pendant groups arc located in a random manner on the polymer backbone is the atactic form.Only Istlactic PP has die requisite properties required lor a useful plastic material. Stereospeciflc or Ziegler-Natla catalysts are used to polymerise PP in this form. .The pendant methylene group in PP is replaced by a chlorine atom in polyvinyl chloride (PVO) by a benzene ring in polystyrene (PS) and by a hydrogen atom in polyethylene

(PE). The pendant group significantly affects the properties of the polymer, and consequently the properties of PP are very different from other commodity plastics such as PH. PVC and PS.).

PP is very popular as a high-volume commodity plastic. However, it is referred to as a low-tost engineering plastic. Higher stiffness at lower density and resistance to higher temperatures when not subjected to mechanical stress (particularly in comparison to high and low density PE (HDPE and LDPE)) are the key properties. In addition to this, PP offers good fatigue resistance, good chemical resistance, good environmental stress cracking resistance, good detergent resistance, good hardness  and contact transparency and ease of machining, together witli good processibilty 1 ity by injection moulding and extrusion. These advantages of PP are further elaborated in later sections.The properties of unmodified PP are compared] with olher competitive thermoplastics. It can be seen that PP offers advantages over most of its competitive materials OD the basis of specific modulus (modulus to density ratio), heal deflection temperature (HDT), maximum continuous use temperature or modulus to cost ratio. Environmental and food legislation may further lip the balance in favour of PP.

(Devesh Tripathi, Practical Guide To Polypropylene;2002;page 1-2)

3)Polysulfone(Group: Material)

Polysulfone is a family of sulfur-containing thermoplastics. It was first introduces as Bakelite Polysulfone (Udel-TM) by Union Carbide in 2965. The family of polysulfones also includepolyarylsulfones, polyethersulfones, polyphenylsulfones, and polyarylether sulfones. Polysulfones are prepered via two different methods of condensation polymerization. The first is polysulfonylation; the second is polyetherification. The principle characteristics of polysulfones include their outstanding heat resistance, exceptional resistance to creep, rigidity, transparency, and their resistance to greases, solvents and chemicals. Additionally, they are self-extinguishing. They are among the higher priced engineering thermoplastics and so are only used in situations where polycarbonates or other cheaper materials are not suitable. Polysulfones have the highest service temperature (170C) of all melt-processible thermoplastics.

(DIANE Publishing Company, New Materials Society, Challenges and Opportunities, Vol-2, pg.8-50, Kayra Ermutlu)

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Not less lhan 18 suppliers of polysulfone dialyzers are currently on the market underlining the great success of this membrane polymer. Polysulfone fits all demands of a modern polymer: It is sierilizablc with all methods (-v-ray, (J-ray, cthylcnc-oxidc, steam), biocompatible, has physical strength, and chemical resis­tance. The membrane material exhibits its good performance characteristics both in its low-flux as well as in its high-flux versions that remove considerable amounts of ^2*m by filtration. Moreover, polysulfone is suitable as an endotoxin adsorber and thus an active protection system for contaminated dialysis fluids (Table 1.2).

Because of all these advantages more and more membrane producers have developed their own polysulfone, although it is sometimes hidden among difficult nomenclature. Frescnius introduced the first high-flux polysulfone in 1983 ¡20), followed by the low-flux version in 1989. Table 1.2 provides an overview about the different manufacturers of polysulfones and some special features of the particular polymer. Due to patent protection, all polysulfones developed till date have to be different from the original Fresenius Polysulfone. They differ in their basic copo-lymer/polymer alloy, the addition of polyvinylpyrrolidone (PVP) (polysulfone alone is hydrophobic and has to be made more hydrophilic, which happens in most cases by blending the polymer with the hydrophilic PVP or not), and in their entire production processes, resulting in different morphologies.

In chemistry, 'be terminus "polysulfone" comprises simply a group of polymers containing sulfone groups and alkyi or aryl (e.g., arylelher) groups. However, according to chemical convention, all such polymers that additionally contain isopropyliden groups are termed as polysulfones (Fresenius Polysulfone, Asahi Polysulfone. Toraysulfone). Those dialysis membrane polysulfones that do not contain isopropyliden groups are termed as polyarylethersulCones or shortly aspolyethersulfones (D1APES, Arylane). This is a little bit confusing because, as mentioned above, all dialysis membrane polysulfones include an arylether. PEPA and PolyamideS contain another polymer in addition to polyarylethersulfone: PEPA polyarylaieand PolyamideS polyamide and PVP [66). The polyamide in PolyamideS is a matter of debate at the moment because some investigators could not find any polyamide in PolyamideS [65).

PEPA is the only polysulfone membrane thai does not contain PVP and therefore exhibits some special characteristics: it adsorbs larger quantities of p^-m, which is uncommon for all other membranes, but despite this adsorption removal rates for pVm are even lower than that of the other polysulfone membranes.

(Klaus-Viktor Peinemann,Suzana Pereira Nunes,Membranes for Life Sciences;2008;page 15-16)