Mechanical Engineering Seminar Abstract And Report 6
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Joined: Dec 2008
15-02-2009, 02:32 PM
Robot is a system with a mechanical body, using computer as its brain. Integrating the sensors and actuators built into the mechanical body, the motions are realised with the computer software to execute the desired task. Robots are more flexible in terms of ability to perform new tasks or to carry out complex sequence of motion than other categories of automated manufacturing equipment. Today there is lot of interest in this field and a separate branch of technology 'robotics' has emerged. It is concerned with all problems of robot design, development and applications. The technology to substitute or subsidise the manned activities in space is called space robotics. Various applications of space robots are the inspection of a defective satellite, its repair, or the construction of a space station and supply goods to this station and its retrieval etc. With the over lap of knowledge of kinematics, dynamics and control and progress in fundamental technologies it is about to become possible to design and develop the advanced robotics systems. And this will throw open the doors to explore and experience the universe and bring countless changes for the better in the ways we live.
Areas Of Application
The space robot applications can be classified into the following four categories
1 In-orbit positioning and assembly: For deployment of satellite and for assembly of modules to satellite/space station.
2 Operation: For conducting experiments in space lab.
3 Maintenance: For removal and replacement of faulty modules/packages.
4 Resupply: For supply of equipment, materials for experimentation in space lab and for the resupply of fuel.
The following examples give specific applications under the above categories
Conduct experimentation in space labs that may include
" Metallurgical experiments which may be hazardous.
" Astronomical observations.
" Biological experiments.
Assist crew in space station assembly
" Assist in deployment and assembly out side the station.
" Assist crew inside the space station: Routine crew functions inside the space station and maintaining life support system. Space servicing functions
" Replacement of faulty modules.
" Assist jammed mechanism say a solar panel, antenna etc.
Space craft enhancements
" Replace payloads by an upgraded module.
" Attach extra modules in space.
" Grab a satellite and effect orbital transfer.
" Efficient transfer of satellites from low earth orbit to geostationary orbit.
Space Shuttles and its Advancements
Space Shuttles and its Advancements
The successful explortion of space requires a system that will reliably transport payloads into space and return back to earth; without subjecting them an uncomfortable or hazardous environment. In other words, the space crafts and its pay loads have to be recovered safely into the earth. The space shuttle used at older times were not re-usable. So NASA invented re-usable space shuttle that could launch like a rocket but deliver and land like an aeroplane. Now NASA is planning to launch a series of air-breathing planes that would replace the space shuttle.
A Brief History Of The Space Shuttle
Near the end of the Apollo space program, NASA officials were looking at the future of the American space program. At that time, the rockets used to place astronauts and equipment in outer space was one-shot disposable rockets. What they needed was a reliable, but less expensive, rocket, perhaps one that was reusable. The idea of a reusable "space shuttle" that could launch like a rocket but deliver and land like an airplane was appealing and would be a great technical achievement.
NASA began design, cost and engineering studies on a space shuttle. Many aerospace companies also explored the concepts. In 1972 NASA announced that it would develop a reusable space shuttle or space transportation programme (STS).NASA decided that the shuttle would consist of an orbiter attached to solid rocket boosters and an external fuel tank because this design was considered safer and more cost effective.
At that time, spacecraft used ablative heat shields that would burn away as the spacecraft re-entered the Earth's atmosphere. However, to be reusable, a different strategy would have to be used. The designers of the space shuttle came up with an idea to cover the space shuttle with many insulating ceramic tiles that could absorb the heat of re-entry without harming the astronauts. Finally, after many years of construction and testing (i.e. orbiter, main engines, external fuel tank, solid rocket boosters), the shuttle was ready to fly. Four shuttles were made (Columbia, Discovery, Atlantis, Challenger). The first flight was in 1981 with the space shuttle Columbia, piloted by astronauts John Young and Robert Crippen. Columbia performed well and the other shuttles soon made several successful flights.
The space shuttle consists of the following major components:
" Two solid rocket boosters (SRB) - critical for the launch
" External fuel tank (ET) - carries fuel for the launch
" Orbiter - carries astronauts and payload
The Space Shuttle Mission
A typical shuttle mission lasts seven to eight days, but can extend to as much as 14 days depending upon the objectives of the mission.
A typical shuttle mission is as follows:
1. Getting into orbit
1.1 Launch - the shuttle lifts off the launching pad.
1.3 Orbital maneuvering burn.
2. Orbit-life in space.
Continuously variable transmission (CVT)
TContinuously variable transmission (CVT)
After more than a century of research and development, the internal combustion (IC) engine is nearing both perfection and obsolescence: engineers continue to explore the outer limits of IC efficiency and performance, but advancements in fuel economy and emissions have effectively stalled. While many IC vehicles meet Low Emissions Vehicle standards, these will give way to new, stricter government regulations in the very near future. With limited room for improvement, automobile manufacturers have begun full-scale development of alternative power vehicles. Still, manufacturers are loath to scrap a century of development and billions or possibly even trillions of dollars in IC infrastructure, especially for technologies with no history of commercial success. Thus, the ideal interim solution is to further optimize the overall efficiency of IC vehicles.
One potential solution to this fuel economy dilemma is the continuously variable transmission (CVT), an old idea that has only recently become a bastion of hope to automakers. CVTs could potentially allow IC vehicles to meet the first wave of new fuel regulations while development of hybrid electric and fuel cell vehicles continues. Rather than selecting one of four or five gears, a CVT constantly changes its gear ratio to optimize engine efficiency with a perfectly smooth torque-speed curve. This improves both gas mileage and acceleration compared to traditional transmissions.
The fundamental theory behind CVTs has undeniable potential, but lax fuel regulations and booming sales in recent years have given manufacturers a sense of complacency: if consumers are buying millions of cars with conventional transmissions, why spend billions to develop and manufacture CVTs?
Although CVTs have been used in automobiles for decades, limited torque capabilities and questionable reliability have inhibited their growth. Today, however, ongoing CVT research has led to ever-more robust transmissions, and thus ever-more-diverse automotive applications. As CVT development continues, manufacturing costs will be further reduced and performance will continue to increase, which will in turn increase the demand for further development. This cycle of improvement will ultimately give CVTs a solid foundation in the world's automotive infrastructure.
CVT Theory & Design
Today's automobiles almost exclusively use either a conventional manual or automatic transmission with "multiple planetary gear sets that use integral clutches and bands to achieve discrete gear ratios" . A typical automatic uses four or five such gears, while a manual normally employs five or six. The continuously variable transmission replaces discrete gear ratios with infinitely adjustable gearing through one of several basic CVT designs.
The term "Cryogenics" originates from Greek word which means creation or production by means of cold. As prices for energy and raw materials rise and concern for the environment makes safe waste disposal difficult and Costly, resource recovery becomes a vital matter for today's business. Cryogenic grinding technology can efficiently grind most tough materials and can also facilitate Cryogenic recycling of tough composite materials and multi component scrap. The heart of this technology is the CRYO-GRIND SYSTEM. It employs a cryogenic process to embrittle and grind materials to achieve consistent particle size for a wide range of products. The cryogenic process also has a unique capability for recycling difficult to separate composite materials.
Cryogenic grinding is a method of powdering herbs at sub-zero temperatures ranging from 0 to minus 70Ã‚Â°F. The herbs are frozen with liquid nitrogen as they are being ground. This process does not damage or alter the chemical composition of the plant in any way. Normal grinding processes which do not use a cooling system can reach up to 200Ã‚Â°F. These high temperatures can reduce volatile components and heat-sensitive constituents in herbs. The cryogenic grinding process starts with air-dried herbs, rather than freeze-dried herbs.
Solid materials are ground or pulverized by way of hammer mills, attrition mills, granulators or other equipment. A smaller particle size is usually needed to enhance the further processing of the solid, as in mixing with other materials. A finer particle also helps in melting of rubber and plastics for molding. However, many materials are either very soft or very tough at room temperatures. By cooling to cryogenic temperatures with liquid nitrogen, these may be embrittled and easily fractured into small particles.
A scientifically controlled study using four herbs was conducted at Frontier Herbs in the Fall of 1996, comparing cryogenic grinding methods with normal grinding methods. The herbs tested included feverfew, goldenseal, valerian and echinacea. In all cases the cryogenically ground herb contained greater amounts of the constituents tested. Feverfew herb showed the greatest difference, with the cryogenically ground herb containing 21.8% higher levels of parthenolide, the primary active constituent. Valerian root showed an 18.7% increase in valerenic acid when cryogenically ground. Goldenseal root showed a 16.4% increase in berberine and 10.7% increase in hydrastine. Lastly, Echinacea purpurea root showed a 12.1% increase in total phenolic content in the cryogenically ground root. Test results were obtained by HPLC (high performance liquid chromatography) methods.
Cryogenic grinding was shown to significantly affect active constituent levels in herbs. Test results showed an average increase of 15.6% in constituents tested in four medicinal herbs when they were ground cryogenically. The range was 10.7% to 21.8%, indicating that some herbs are affected more than others by the temperatures at which they're ground.
CRYOGENIC GRINDING PROCESS
Since almost all materials embrittle when exposed to cold temperatures, cryogenic size reduction utilizes the cold energy available from liquid nitrogen to cool, embrittle and inert materials prior to and or during the grinding process. All materials which due to their specific properties at ambient temperatures are elastic, have low melting points, contain volatile or oily substances, have low combustion temperatures and are sensitive to oxygen, are ideal candidates for cryogenic size reduction.
Physical properties of liquid nitrogen is produced by the separation of air into its components in an air separation plant and is distributed in vacuum insulated transport vessels to the end user where it is stored in a vacuum insulated storage vessel till it is used. At atmospheric pressure liquid nitrogen is at a temperature of -320 deg F and possesses a latent energy content of 94 BTU/LB resulting in a total cooling energy content of 179.6 BTU/LB. Nitrogen is anon-flammable, non toxic and inert gas which makes up 78.09% of the air we breathe.
Design, Analysis, Fabrication And Testing Of A Composite Leaf Spring
Design, Analysis, Fabrication And Testing Of A Composite Leaf Spring
In order to conserve natural resources and economize energy, weight reduction has been the main focus of automobile manufacturers in the present scenario. Weight reduction can be achieved primarily by the introduction of better material, design optimization and better manufacturing processes. The suspension leaf spring is one of the potential items for weight reduction in automobiles as it accounts for 10% - 20% of the unsprung weight. This achieves the vehicle with more fuel efficiency and improved riding qualities. The introduction of composite materials was made it possible to reduce the weight of leaf spring without any reduction on load carrying capacity and stiffness. Since, the composite materials have more elastic strain energy storage capacity and high strength to weight ratio as compared with those of steel, multi-leaf steel springs are being replaced by mono-leaf composite springs. The composite material offer opportunities for substantial weight saving but not always be cost-effective over their steel counterparts.
Investigation of composite leaf spring in the early 60's failed to yield the production facility because of inconsistent fatigue performance and absence of strong need for mass reduction. Researches in the area of automobile components have been receiving considerable attention now. Particularly the automobile manufacturers and parts makers have been attempting to reduce the weight of the vehicles in recent years. Emphasis of vehicles weight reduction in 1978 justified taking a new look at composite springs. Studies are made to demonstrate viability and potential of FRP in automotive structural application.
The development of a liteflex suspension leaf spring is first achieved. Based on consideration of chipping resistance base part resistance and fatigue resistance, a carbon glass fiber hybrid laminated spring is constructed. A general discussion on analysis and design of constant width, variable thickness, composite leaf spring is presented. The fundamental characteristics of the double tapered FRP beam are evaluated for leaf spring application. Recent developments have been achieved in the field of materials improvement and quality assured for composite leaf springs based on microstructure mechanism. All these literature report that the cost of composite; leaf spring is higher than that of steel leaf spring. Hence an attempt has been made to fabricate the composite leaf spring with the same cost as that of steel leaf spring.
Material properties and design of composite structures are reported in many literatures. Very little information are available in connection with finite element analysis of leaf spring in the literature, than too in 2D analysis of leaf spring. At the same time, the literature available regarding experimental stress analysis more. The experimental procedures are described in national and international standards. Recent emphasis on mass reduction and developments in materials synthesis and processing technology has led to proven production -worthy vehicle equipment.
Materials constitute nearly 60%-70% of the vehicle cost and contribute to the quality and the performance of the vehicle. Even a small amount in weight reduction of the vehicle, may have a wider economic impact. Composite materials are proved as suitable substitutes for steel in connection with weight reduction of the vehicle. Hence, the composite material have been selected for leaf spring design.
Solar Power Satellites
Iontophoresis is an effective and painless method of delivering medication to a localized tissue area by applying electrical current to a solution of the medication. The delivered dose depends on the current flowing and its duration.
Iontophoresis is a recognized therapeutic method for delivering ionic compounds, i.e. drugs, into and through the skin by applying electrical current. It has proven to be a beneficial treatment for many localized skin disorders such as; nail diseases, Herpies lesions, psoriasis, eczematous, and cutaneous T-cell lymphoma. The method has also been reported useful for topical anesthesia to the skin prior to cut-down for artificial kidney dialysis, insertion of tracheotomy tubes and infiltration of lidocaine into the skin prior to venipuncture. Treatment of various musculoskeletal disorders with anti-inflammatory agents has been reported in the literature. Iontophoresis enhances the transdermal delivery of ionized drugs through the skin's outermost layer (stratum corneum) which is the main barrier to drug transport. The absorption rate of the drug is increased, however, once the drug passes through the skin barrier natural diffusion and circulation are required to shuttle the drug to its proper location. The mechanism by which iontophoresis works is based upon the knowledge that like electrical charges repel. Application of a positive current from an electrode to a solution applied to a skin surface will drive the positively charged drug ions away from the electrode and into the skin. Obviously, negatively charged ions will behave in the same manner.
The method of iontophoresis was described by Pivati in 1747.Galvani and Volta, two well-known scientists working in the 18th century, combined the knowledge that electricity can move different metal ions, and that movements of ions produce electricity. The method of administrating pharmacological drugs by iontophoresis became popular at the beginning of the 20th century due to the work of Leduc (1900) who introduce the word 'iontotherapy' and formulated the laws for this process. Iontophoresis is defined as the introduction by means of a direct electrical current, of ions of soluble salts into the tissues of the body for therapeutic purposes. It is a technique used to enhance the absorption of drugs across biological tissues, such as the skin. Another method for drug delivery through the skin, called phonophoresis, uses ultrasound instead of an electric current. Both these techniques are complicated because of other processes that occur simultaneously with the delivery of the drug. With the present knowledge about these processes, it is easier to select and prepare appropriate drugs and vehicles for iontophoresis than for phonophoresis.In clinical practice, iontophoresis devices are used primarily for the treatment of inflammatory conditions in skin, muscles, tendons and joints, such as in temperomandibular joint dysfunctions. More recently, iontophoresis has been used in combination with laser Doppler technology as a diagnostic tool in diseases comprising the vascular bed.
Principles of iontophoresis
AsBy definition, iontophoresis is the increased movement of ions in an applied electric field. Iontophoresis is based on the general principle that like charges repel each other and unlike charges attract each other.An external energy source can be used to increase the rate of penetration of drugs through the membrane. When a negatively charged drug is to be delivered across an epithelial barrier which is placed under the negatively charged delivery electrode (cathode) from which it is repelled, to be attracted to the positive electrode placed elsewhere on the body.
In anodal iontophoresis (positively charged ions), the electrode orientation is reversed .The choice of drug is of importance depending on whether the compound is unionised or ionised. Non-ionised compounds are generally better absorbed through the skin than ionised substances. The penetration across the skin or other epithelial surfaces is usually slow due to their excellent barrier properties. Many drug candidates for local applications only exist in an ionised form, which makes effective membrane impossible.
Aerodynamics can be used to control the handling of a car in high-speed corners (greater than approximately 60 mph). Aerodynamic components push down on the car, or create downforce, which helps the tires maintain better traction. The two main aerodynamic upgrades are front bumpers and rear wings. While these two components can increase cornering speeds when installed on your car, they will also increase drag and limit your top speed.
Aerodynamic components should only be used to tune high speed cornering characteristics. They will have little or no effect on low-speed handling. Additionally, aerodynamics should be relied upon to increase the overall grip of your car. It should not be used to correct severe understeer or oversteer. Try to rely upon mechanical suspension tuning to control understeer/oversteer. Only turn to aerodynamics as a last resort. This is because aerodynamic grip cannot always be relied upon in a racing situation. For instance, if you are closely following another car, there will be less air flowing over your car because the car in front is breaking through the air for you. The reduced airflow (and therefore downforce) on your car will cause you to lose grip. If you rely heavily on aerodynamics to improve handling, your car will become difficult to drive when you are in close proximity with other cars.
Aerodynamic components work by deflecting air in a way to create a downward force on the car. Air hits the car at an angle, which pushes the car into the ground. At the same time, the air gets deflected up and over the car. Aggressively sloped front bumpers and large wings will generally create more downforce than small wings and mild front bumpers.
Usually, it is not possible to adjust the amount of front downforce without changing your front bumper. However, wings often have inserts and angle adjustments that can be used to change rear downforce. By increasing wing angle or adding wing inserts, you increase downforce on the rear of the car. This pushes the rear wheels more firmly into the ground and prevents them from slipping. Oversteer can be corrected in this way. If your car understeers in high-speed corners, you can reduce the angle of the wing or take out wing inserts to reduce rear downforce and correct the understeer. Keep in mind that adding downforce will help you increase your cornering speeds but will lower your top speed due to the extra drag. Still, you will usually want to maximize the downforce because the majority of road courses do not have very long straights. On a track with long straights, reducing downforce (and therefore drag) may improve your lap times.
Micro-electro Mechanical Systems
Micro-electro Mechanical Systems
Micro-electromechanical systems (MEMS) is a technology that combines computers with tiny mechanical devices such as sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips.
MEMS are already used as accelerometers in automobile air-bags. They've replaced a less reliable device at lower cost and show promise of being able to inflate a bag not only on the basis of sensed deceleration but also on the basis of the size of the person they are protecting. Basically, a MEMS device contains micro-circuitry on a tiny silicon chip into which some mechanical device such as a mirror or a sensor has been manufactured. Potentially, such chips can be built in large quantities at low cost, making them cost-effective for many uses.
Among the presently available uses of MEMS or those under study are:
Global position system sensors that can be included with courier parcels for constant tracking and that can also sense parcel treatment en route .
Sensors built into the fabric of an airplane wing so that it can sense and react to air flow by changing the wing surface resistance; effectively creating a myriad of tiny wing flaps .
Optical switching devices that can switch light signals over different paths at 20-nanosecond switching speeds Sensor-driven heating and cooling systems that dramatically improve energy savings . Building supports with imbedded sensors that can alter the flexibility properties of a material based on atmospheric stress sensing
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28-03-2009, 09:49 AM
(15-02-2009, 02:32 PM)remshad_m Wrote: Space Robotics