The Procrastinator's Function

A conflict in the mind of a Robot

Author: Siva Sankar, CEG, Anna University

Contradictions between the three basic laws can make a robot go crazy. There will always be bugs in robot consciousness that might eventually result in their breakdowns. What is  so profound and interesting is their minds emerging from a series of commands that often contradict one another. Robot minds work differently from humans. What if there was a hitch in the assembly and a positronic brain of the robot is able to  read minds and understand feelings, then in such a case what if we ask the robot for an answer which might hurt our feeling. There’ll be irony falling into an elementary trap, won’t there be? But it won’t be Funny.  Well what trap are we talking about? Is something wrong with the robot? No nothing will be wrong with them— only with us. Surely you know the fundamental First Law of Robotics. Certainly, “a robot may not injure a human being or, through inaction, allow him to come to harm”

How nicely put but what kind of harm? Any kind! What about hurt feelings? What about deflation of one’s ego? What about the blasting of one’s hopes? Is that injury? But What would a robot know about feelings. You’ve caught on, haven’t you? What if this robot can read the mind? Do you suppose it doesn’t know everything about mental injury? Do you suppose that if asked a question, it wouldn’t give exactly that answer that one wants to hear? Wouldn’t any other answer hurt us, and wouldn’t that robot know that? Only that you didn’t want him to give you the solution. It would puncture your ego to have a machine do what you couldn’t. Why doesn’t it answer? It cannot. You will not want it to. You want the solution but not from the robot.

What’s the use of saying that it will not hurt u? Don’t you suppose that it can’t see past the superficial skin of your mind? Down below, you don’t want it to.  You can’t lose face to it without being hurt. That is deep in your mind and won’t be erased. It can’t give the solution.

But also the fact that it has the solution and won’t give it hurts us. 

And if the robot tells us the solution that will hurt us, too The robot can’t tell us because that would hurt and the robot mustn’t hurt. But if the robot doesn’t tell us, the robot hurts, so the robot must tell us. And if the robot do, the robot will hurt and the robot mustn’t, so the robot can’t tell us; but if the robot don’t, the robot hurts, so the robot must; but if the robot do, the robot hurt, so the robot mustn’t; but if the robot don’t, the robot hurt, so the robot must; but if the robot does, the robot–

 It will be confronted with the insoluble dilemma and it will eventually break down. We will have nothing left but to scrap him now because he’ll never be able to reach a decision.

Randomness and its constant uniformity

Random - How do you perceive it? Chaotic? Disorderly? Higgledy-piggledy? For most of us, these are the defining words for "Randomness". When you think about it, sometimes anything random seems to exhibit the most consistent behaviour. I thought of it and have come up with certain examples, the cases in which randomness is not really random!

1) A non-crystalline material

A crystal has the atoms arranged in an orderly manner. Hence, it is anisotropic - that is, it does not exhibit the same characteristics (Physical, optical, etc) in all the directions - irony. But a non crystalline material exhibits properties that uniform regardless of the direction. 

2) Concrete

My prof once asked me why they add small stones to cement and mix it thoroughly. Why? Its because they want the position of stones in the cement to be as random as possible. Again why? They want it to be "Isotropic" so that it does not have any planes or lines of weakness which will be there when the stones are arranged in an orderly way. It can be better explained with a potato and a wooden log. Try cutting a potato in different directions and you'll find it the same effort is required for all the directions. But thats not the case with a wooden log. Its easier to cut the log in the longitudinal direction than the transverse directions because the fibres are lined along the longitudinal direction (An orderly arrangement)

3) Sampling

For quality tests in industries to surveying people, always a "random sample" is taken. Why? It gives a  result that more or less describes the characteristics of the whole group of entities. No survey is accurate only when a particular closely related section of people are answering the questionnaires. 

4) Chemical reactions

Most of the chemical reactions take place when the reactants are "uniformly"  mixed. So, what is this uniform mixture?? Reactant A placed on top, B in the middle and C at the bottom? No, they call it uniform when the mixture is chaotic and random. For that matter, any uniform mixture is one that is random.

Entropy the term that measures the degree of randomness is something so important in this universe. Want to know why? Read this.

Gravitational Red Shift

So...the first thing you'll have to know in order to understand this concept would be Doppler effect and its extension into light waves...

For those who are new to Doppler effect...

Whenever there is a relative motion between the source of sound and the observer, there is a change in the frequency of sound observed by the observer. If the relative motion is such that the source and observer approach each other, there is an increase in frequency, and if the relative motion is such that they recede away from each other, there is a decrease in frequency as observed by the observer.

Consider a similar case with light waves...

If the source moves towards the observer, we have an increase in frequency of light waves which we term as blue shift. If the source moves away from the observer, we have a decrease in frequency which is what we call as red shift. Practically, we don't feel this effect because the speed of the relative motion between the source and the observer is usually negligible compared to the velocity of light waves.

This redshift doesn't necessarily take place because of the Doppler effect.

Consider a photon travelling away from the earth's surface, or, let's say a gravity well. Its path would be similar to that taken up by a projectile which slows down as it gains altitude by transfering its kinetic energy to potential energy. But in the case of a photon, it cannot lose energy by slowing down as they are always considered to travel at 'c' . So we have to comprehend the loss in energy as a lowering in frequency of the photon waves, in other words, reddening of photons. This is termed as gravitational redshifting.

Here too, u have the gravitational blueshifting, which occurs when a photon falls into a gravity well.

If you are one of those techy guys looking for a valid derivation to support this theory, get some book relating to quantum physics.

- Maheshwar

Okay, now that is an interesting article from Mahesh. This article poses some unanswered questions.

1) In doppler effect (Sound) there is an apparent increase in frequency when the observer and source move towards each other. Frequency increase implies increase in energy. Where is this energy coming from?

2) Mahesh says that a photon can't lose or gain its kinetic energy and that is why the energy change happens through alteration of frequency. But a photon is always considered mass-less. Kinetic energy?

3) What is the difference between a normal redshift and a gravitational redshift?

4) If an observer is moving towards a source of light, the relative velocity between the light waves(or photons) and the observer is greater than the velocity of light. It is possible?

Take these questions to the forum or comment here.

-Premkumar

Coanda effect

This post offers a simple description of "The Coanda Effect". My obsession with "effects" continues. It started with the Magnus Effect, then the Domino effect and now the Coanda effect. While the magnus and domino have a strong theory behind them, the Coanda effect is more of a physical phenomenon. I'll briefly write my understanding of this effect.

The Coanda effect is the tendency of a fluid jet to get attracted towards a surface that is close to it. The picture below (Source: Wikipedia) illustrates this phenomenon

The reason for this effect is not all that complicated according to my perception of it. When there is a fluid jet, the nearby fluid gets "entrained" around the jet (Courtesy: wikipedia). This can be best visualized when you blow air into an empty and open polythene bag. The bag gets filled with air immediately. This is because when air is blown into it from the outside, the surrounding air also joins the stream and enters the bag to fill it. This is what I referred to as "entrainment" previously. If a surface is preventing the ambient fluid to get entrained, the jet moves towards the surface and this is the Coanda effect. 

It is to be noted that the this effect is possible only when the jet fluid and the ambient fluid are the same. For the flow to get attracted and stick to the surface, the surface must be smooth and curved. This is why aero foils have a smooth curvature. Even when the angle of attack is increased, the coanda effect directs the fluid to flow along the surface of the foil thus ensuring lift. When the angle of attack is too high, the coanda effect will no longer be able to keep the flow sticking to the surface. The flow will separate and it stalls. (Image courtesy: discoverhover.org)

There was once an aircraft built to use only the coanda effect for producing lift. That effort did not succeed and aircraft never took off the ground. But this effect has been utilised in many modern day aircrafts to augment its aerodynamic abilities.

Domino effect - Its more than just a fall

There is none who hasn't heard of the domino effect. Its the chain reaction triggered by one falling object on the other (dominoes) which in turn fall on the other and so on. Simple isn't it? But when I was surfing the net reading about the energy conversions involved in a domino effect, I was amazed to see how naive I have been in thinking that the effect is nothing but a successive fall of dominoes. Here are some of the interesting aspects of a domino effect that I came across

1) The speed

The speed of the domino effect depends on the distance between the successive dominoes. The farther they are placed apart, the slower is the progression because it takes a longer time for the falling domino to knock down the next one - common sense. 

2) An Infinite arrangement of dominoes

An infinite dominoes set poses some interesting questions. Will the system continuously lose energy continuously through heat and sound and eventually come to a halt? The answer is no. The energy of the system comes from the potential energy of each of the dominoes that was stored while setting them up in a metastable position. An initial trigger to the first domino will convert its potential energy into kinetic energy while falling and a fraction of this kinetic energy will push the next domino to an unstable position thereby making it fall and converting its potential energy into kinetic. Thus the system is self sustained and never comes to a stop. In fact, as the first domino pushes the next at a speed, the second one falls faster than the first. This in turn topples the next one even faster and thus the progression is actually accelerated.

So, if the progression is accelerated, will an infinite dominoes system reach the velocity of light at one point? the answer is no again. Consider this analogy - a ball falling towards the earth's surface from about a height of 1000 km should ideally reach a velocity of 42 km/sec when it reaches the surface. But that does not happen because the atmospheric air dampens its acceleration and makes it reach a "terminal velocity" which will be constant till it touches the ground. Here energy is lost by friction and buoyancy and an equilibrium is reached. In a similar way, in a domino-effect, the energy is lost during the impact through heat and sound. this energy loss is more when the speed of impact is more. Thus the system reaches a point in time when the acceleration and energy loss reach an equilibrium and the progression will be at a constant velocity from then on.

There may be still more to a domino-effect when you consider the size and geometry of the dominoes. May be I'll look for more on this topic and write about it sometime later. From now, when you witness a domino effect, remember, there is more to it than what meets the eye! ;)

References: Wikipedia, www.physicsforums.com

Project Euler

My friend has told me long ago about Project Euler. It took me almost half a year to check out what it is. Project euler hosts some 275+ problems which are mostly mathematical and analytical. Well, though they are mathematical, its impossible to solve them without the help of a computer program.

Some of the problems are as simple as find the sum of all multiples of 3 or 5 less than 1000. There is one problem which asks u to find the pythagorean triplet a,b,c such that a+b+c=1000. There are also freakin big probs like find the last five digits before the trailing zeroes of factorial(1,000,000,000,000).

I just started coding for few problems. You too check those probs @ projecteuler.net

Get a head start on simple robotics

I'm back to posting something almost after a month. Still I'm lazy enough to post the same thing which i've wriiten for CSAU's(Computer Society of Anna University) next edition of cursor magazine. Its about simple robotics and here it goes... 


check out this moving butterfly robot

‘Robotics’ is a very common word among the guys and girls of CEG. Many people misinterpret this term as something big and hi-fi. Yeah, even for me the first thing that comes to my mind when I hear the word ‘robot’ is ASIMO! In reality, the bots we actually make at college level are quite simple and fascinating. In fact, making robots will make a great hobby. I was fortunate enough to have seniors who helped me a lot in gaining some insight into this field. In this article, I’ll discuss some theoretical aspects for building a manual radio-controlled bot.

Invariably, all the bots that we make at college move on wheels (on belts or chains too) and DC motors drive them. As Wikipedia defines a robot as an Electro-Mechanical entity, we have to primarily design a robot on Electronic and Mechanical point of view.

The mechanical design includes the chassis design, drive system and the mechanism to complete its objective. The chassis design is simple. You just have to decide where to place the motors (2 or 4 according to the bot’s objective), battery and the circuit boards. Make sure that the centre of gravity of the robot is as low as possible for greater stability. For the drive system, there are two major types

· Steering drive

· Differential drive

The steering drive is the drive system used in cars. A rack and pinion arrangement is used to steer the front wheels. This type of drive can be used in building bots for which speed is of great importance as the bot can be driven forward as well as be steered to any one direction simultaneously. But the great disadvantage is that building a precise steering mechanism is highly complicated. So, we practically don’t use this system for most projects.

Differential drive is used in almost all simple robots. In this system, a left or right turn is achieved by the differential motion of the left and right wheels. The turns can be achieved in more than one way.

Left turn – 1) Right wheels rotating in forward direction while the left ones aren’t moving (Arc turn)

2) Right wheels rotating in forward direction and the left wheels in the reverse (Spot turn)

3) Right wheels rotating faster than the left wheels. (This type is not in practice)

The right turn can be achieved in a similar way. The great advantage of this system is that it is very easy to build the electronic control. However, the bot has to stop moving forward every time it needs to turn.

There is another type of drive – the pivoted drive. This method is used for making precise turns. This is fit for use only in autonomous robots and hence I am not discussing that now.

Additional mechanisms are based on the bot’s mission. It may be a hand to pick objects, a wedge in front for sumo bots or event rack and pinion arrangements to lift objects. These things can be designed according to your choices. Often simple ingenious designs work better than complex mechanisms as greater the complexity, greater the chances for failure.

Electrical design

For a radio controlled bot, we require a transmitter and receiver module. We need not design these components. The transmitter and receiver module can be hacked from a RC toy car. I’ve given a layout of the electrical design below

The Receiver module operates at 5V whereas the motors we usually use are rated at 12V. So, in simple words, the motor driver converts the 5V output signals from the receiver to 12V and gives them to the various motors used. This driver circuit is the only circuit that we make originally for a simple bot. A typical transmitter-receiver module handles 4 signals. I’ll write on how to hack a receiver module from a toy car and how to use those four signals to effectively operate the bot in the next post.

The power of Composites

Can a sheet of aluminium withstand an impact of a 2kg bird at 700 kmph? No! It can't. Can the same impact be withstood by a sheet of fibre glass? I'm not sure or may be not. But a sheet of Aluminium reinforced with glass fibres? Yeah, it can. And thats the material used for making the body of the Airbus A380.

Lets see how it works. There are two essential properties that most engineering materials are expected to possess. One is that it should not deform considerably and the other is that the material should not fail or fracture. Now, for the body of the aircraft, a strong material that isn't heavy is required. Naturally we go for aluminium based alloys for this purpose. But is that strong enough to survive a a bird's impact at a relative velocity of about 700 kmph? Obviously not! So, there is need for reinforcement of the alloy with some stronger material. Surprisingly, the engineers have chosen glass! Glass is a highly brittle material and the possible failure of this material is through a brittle fracture. The mechanism of brittle fracture is given by Griffith's theory.

According to this theory, there are microscopic flaws(cracks) which propagate to form bigger cracks on the application of excessive stress. A part of the energy from the load is used to create the new surfaces as the new cracks are formed. When these cracks propagate to the surface, fracture occurs and the material fails. This is the mechanism by which glass fractures. When glass is heated and drawn into a fibre, these microscopic cracks are eliminated. Thus, when glass is in the form of fibres, fracture is prevented to a greater extent. These glass fibres are used to reinforce the Aluminum alloys and this composite is used to build the body of the A380.

A typical fiberglass sheet.

I feel the need for some research!

Well, its been a habit of mine to write exactly what I understood. In my previous posts, I've just given some (vague) ideas of how certain things work and nothing more. Blogging for more than a couple of years now, I feel that its time for me to take my writing to the next level. Yeah, from now my posts would have not just simple understandings of various phenomena or gadgets, but also some theory supporting it!

And yeah, as I promised, my next post will be about the composite used in the construction of the Airbus A380.

Landing Gear of the Airbus A380

Before writing this article, I just want to say - "I'M BACK!"

I switched to the National Geographic channel at 10.30 AM and found that the program was to end at 11 AM. The program was about the making of the world's largest airliner- The Airbus A380. At that time of the program, the material used for making its body was being shown. It was actually a composite - Glass and Aluminium together. I'll post a separate article about this. For now I just want to write about what impressed me the most - the landing gear!

The landing gear is one of the most important components of an aircraft. For an aircraft like the A380, it should be strong enough to bear the immense weight ( The Airbus A380 weighs about 276.8 tonnes when empty) as well as absorb the shock off landing. For such a massive component, the people at Airbus came up with a very simple yet effective design for the shock absorber. Its the 'cycle pump' concept. The concept is simple- the shock absorber is a piston that moves inside a cylinder just similar to a cycle pump. As the air inside the cylinder is compressed, the shock is absorbed. In the A380's landing gear, instead of just air, oil is used As greater energy is required to compress the highly viscous oil into a chamber, greater shock is absorbed and the landing is smoother. In the NGC program, the engineer who designed the shock absorber demonstrated its capabilities using ordinary cycle pumps filled with water. It was amazing to see how those pumps absorbed the shock when a big piano was dropped(the array of pumps were fitted under the piano) and kept it intact!

And they even showed a footage of a Korean Airlines' Boeing plane landing safely in a crosswind with ONLY ONE wheel touching down first. That very well described how strong they ought to be! Hail engineering! :-)

Crunch time!

Well, I'm back to post about something after quite a long time! I can tell you what I want to tell using a simple equation.

" Practical examinations + End-Semester exams + IPL = No time for blogging "

With exams around, I dont think I'll find time to post anything in the coming fortnight. Hoping to get back with a bang from May 12th(Yeah, thats when the exams get over).

SAE Baja 2010

As soon as I saw a poster in my class's notice board inviting second year students for an open interview for recruiting second year members for CEG's SAE(Society of Automotive Engineers) Baja 2010 team, I remembered the baja vehicle that was displayed during Kurukshetra '08. Building an ATV(All Terrain Vehicle) during the second year of your Engineering course sounds great! I badly wanted to be a part of that team. I attended the interview with a strong resume backing me. After the 15-minute interview(quite long for this kind), I came out confident of getting selected. As I expected, my name was present in the selection list.

Now that the team is finalised and registered for Baja 2010, its time to wonder about what exactly we're gonna do - build an ATV from scratch? Probably yes! Baja tests every aspect of your vehicle - the design, stability, power, speed and aesthetics too! The venue for baja 2010 is the same as that of 2009 - Pithampur, Madhya Pradesh. As we'd be starting our work soon, I guess there are exciting times ahead!

This is the SAE baja's website... http://bajasaeindia.org/

AI Programming

From the time I entered college, I was fascinated about game programming. Once my senior told me, when the API of the game is already in you hands, the coding part can be as easy and fun as it can ever get. Yet it took me almost two years to get the determination to code for a game programming event. It was for Abacus '09, the National level symposium organised by the Department of computer science in our college. The game scenario was simple. Its similar to the snake game that everyone invariably must have played on a nokia mobile. The difference was there will be two snakes on the arena and food will be randomly generated at four points on the play area. Also, the snakes will have an energy associated with them which will decrease by a unit for every move and increase by some units for each food particle consumed. The organisers provided the API and all we had to do is to code a function that returns one of the four characters - U, D, R, L as output corresponding to the up, down, right and left movement of the snake. We are provided with the snake's position i.e., row and column number of each of the element of the snake's body, opponents position, our energy and opponents energy. Each coordinate of the play area is assigned a character where 'E' corresponds to empty, 'F'-food, 'X'-boundary, 'A'-snake A's body, 'B'-snake B's body. With so much information available at hand, the coding becomes really easy. but still, I'm a beginner! :)

I started coding and tested the game by using the same code for both the snakes(during the event, one snake will use your code and the other will use your opponent's code). After a couple of days, I thought I've done whatever I could do and submitted the code. As I'm not a great programmer, I didnt plan the algorithm at the beginning. I kept changing the structure as I kept testing the game. during submission, I could easily see that my code was divided into 4 parts.

1) Locating all the 4 food particles
2) Locating the food particle that is nearest to the snake's position
3) An initial instruction for navigation towards the food(avoiding the boundary)
4) Checking whether the initial instruction is a valid move(bumping into yourself or the opponent means you are out of the game!) and giving a valid and safe instruction.

This code works efficiently until the randomly generated food makes you move in such a way that you make a trap for yourself!


In the above picture you can see the snakes moving towards the nearest food.

In this picture, snake a bumped onto itself and lost the game!

As, many of the participants(except one) coded in a similar way, it was obvious that the random generation of the food will be the factor determining the winner. The better your luck, the greater your chances of winning. My luck was so good that my code won the second position!! Only later I heard from the organisers that the guy's code which won the first place was far more superior than the rest. That code was such that the snake wont trap itself often and also it'll try to blog the opponent and trap it!! How about that?!?!

A rewarding blog, atlast!

This year's Kriya at PSG Tech introduced an online blogging event. I've been blogging for more than two years(though spent much less time on updating blogs). So I wanted to try my luck in the event. i named the blog "Techster" and started blogging. The Kriya team used MU-Wordpress on their server to host the blogs. i enjoyed working with wordpress after a long time. As usual, I wrote some technical articles and few general ones, altogether 7 of them. With just seven posts on the blog, I never expected to wi the event and was surprised and elated after the results were announced. When i was there at PSG Tech to collect my prize, the event coordinator told me that my blog was selected for the originality of posts. A reward for original work! :)

Swing of a Cricket ball

Its time to write about something which I love the most - Cricket! When we [members of CEG cricket team] were sitting at the sidelines while our batsmen were doing the job against IIT Madras 'B' Team, one of my team mates told me that my bowling is quite effective as I deliver the ball with an upright seam which eventually aids swing. But how does it swing???

The Physics

The fundamental elements involved in the physics of swing of a cricket ball are turbulent and laminar flow of air around the ball. The swing caused is NOT BECAUSE OF MAGNUS EFFECT as the movement is along the axis of rotation of the ball and not perpendicular to it.

Inswing and Outswing

For conventional swing, the ball will move towards the rougher side. When the seam is held such that it points towards the slip and the ball is held with the rougher side on the left side, the flow of air around the ball will be turbulent on the left side and laminar on the right side. This happens when the ball is bowled at about 120 kmph or less. As the pressure on the turbulent side is lesser, in accordance with Bernoulli’s principle, the ball swings towards the left(outswinger). Inswinger occurs in a similar way when the rougher side is on the right.

Reverse swing

When the ball becomes old and if the bowler is able to generate pace higher that 120 kmph, the swing characteristics differ. The ball begins to swing in the direction of the polished side and hence reverse swing. Incase of reverse swing, the magnitude of the ball’s movement is stronger than conventional swing. It also occurs late after the ball is delivered. At higher speeds of the ball, the flow is turbulent on both sides, but the separation of airflow from the ball occurs earlier on the rougher side. So the smoother side will have constant turbulent flow and hence have a low pressure. Thus the ball moves towards the shiny side. The raised seam aids separation of airflow(also for conventional swing).

Well, as we all know Zaheer and Ishant are capable of getting reverse swing consistently(remember Ishant’s 8 over spell against Ponting?). Hope India wins the series against New Zealand

Add an icon to the page title!

For long I wanted to change the "B" icon thats displayed alogside the title of every blogger blog and have a unique icon for this blog. As usual, i approached Google for help and found one too! Now let me write how I changed the usual icon and used this "T" (For Techster, ofcourse!) icon. The works involved in this are

(i) Create an icon
(ii) Uploaded it to any web server
(iii) Use that for your blogger blog

Instead of going for any web server, I preffered to use blogger for storing my image. Since blogger doesn't allow you to upload a ".ico" file, I used the 'KIconEdit(Using KDE 3.5.4-10.fc6 Fedora-Core)' application in our college's browsing centre to create a simple icon and saved it as a png file. Then I created a new post(not for publishing) and uploaded this png image there. I copied the location of this image. Finally I added the following code inside the head section of the html code (Goto Layout ---> Edit html) of my blog page.

Save the edits and view your blog. You'l be getting your new icon for the title! :)

Note:
(i) You can directly use a jpeg picture. Just upload the pic, copy its lopcation and add the given line of code
(ii) I've used a picture of the code here since blogger will take it as a html tag if I type it directly.

Satellites collide!

I was bored to the core and wanted to read something interesting. It was then I found a truly interesting article on the home page of Wikipedia. It was something about the "collision of satellites" - something that I have never heard of before! On February 10 this year, two satellites in orbit - Iridium 33 and Kosmos-2251 collided with each other directly while orbiting the earth. This direct collision was so severe that both were completely destroyed and more than 500 pieces of debris were tracked by U.S. Space Surveillance Network.

The Iridium 33 was launched on September 14, 1997 and was operational till the collision. The Kosmos-2251 was launched on June 16, 1993 and was retired before several years.

Hope that the debris produced by this collision won't pose a threat to the other spacecrafts and upcoming launches.

An artist's depiction!

The K! Project

Well, I'm back to take care of my log after quite a long period! Yeah, its not easy even to have proper meals when you are a part of the Project team of K '09. So, now that I'm back, without much bla bla bla, I'll directly jump into what I wanted to do all these days - post about our Kurukshetra Mega project.

This year's Mega project for Kurukshetra was A Strategic All-Terrain Robotic Platform. I was a part of the Mechanical Team comprising two - myself and Arun seashatri for the project. Santhosh, Vijayakumar and Karthikeyan took care of the electronics and programming part.

The objective
Our objective was to build a small robust unit that could navigate in rugged terrain and tackle small obstacles and most importantly do a surveillance work.

The Construction
We had certain things to keep in mind before starting the construction..

1) The most important thing - ALL TERRAIN NAVIGATION
2) Effective suspension - For enhanced camera feed from the vehicle
3) Sturdiness - our imported 130 RPM, 24 V motors may very well disintegrate the unit if it has a weak frame. Moreover it should hold 2 12 V UPS batteries each weighing more than 2.5 Kg.
4) An effective arm to pick small objects

Now, for the first concern - all terrain navigation - we had to decide on the type of wheels. We had a look at the trainer wheels in kids' cycles and thought that it would work out for us. Then we worked on the suspension. We fell upon the springs used in the gear box of ambassador cars. With the essential parts in hand, the design of the body was done easily. All that we had to do then was - go to the workshop; cut the metal (we used Mild Steel) ; put the things in place and bolt them! Wait, I forgot to tell about the arm! Even before deciding on the wheels, we finished the construction of the arm using 6mm thick Aluminium plates. Seshatri came up with an effective idea of a pulley system that could make the maximum use of low torque motors. It was very simple yet effective considering the limited options we had.

Finally after some two months(semester exams slowed us down), we were done with the chassis. It was time for a test run! The first test run gave us a BIG BIG BLOW!! Yeah, we totally forgot the "Buckling and twisting" nature of springs during the construction. The very high torque motors that we used made the springs twisted in different directions and caused big variations in the alignment of wheels. We had to use unconventional methods like placing bolts and clamps at appropriate places to control the twisting. But we couldn't stop the buckling. Only during the next test run, we realised that buckling - which is considered to be a bad aspect in suspension, actually helped us save the bot from the juggernaut of the motor!! The initial acceleration was immense that it could have toppled the bot without the spring that absorbed the force. Finally we added the gripper to the arm and mounted the arm. Santhosh turned up with better wheels for the bot - those wheels used in trolleys seen at airports. That type of wheel impressed all and we used that finally. (I'm simply sayin "we mounted the arm".. this is an understatement! we had to work for days and experienced sleepless night in doing these works!)

The Base Console
Atlast, after a lot of fine tuning and adjustments, the base console was ready. The base console was the most attractive part of the bot. The base being a computer, the console application displays
1) The camera feed
2) Parameters like system voltage, system current, motor supply voltage, remaining battery power etc..
3) The GPS module placed in the bot displays the coordinates of its current position and its velocity
4) Google map embedded in the application provides visuals of its location

Due to unexpected and shocking happenings like burning of TV tuner card in the computer, failure of the wireless transmitter of camera and so on just on the day before the date of display, we had to postpone the date of display by 2 days. After doing the necessary changes, we finally had a good show during the display. One thing which most people like about it was the unique suspension system ;-)..

Right now, I dont have the screenshots of the base console with me. So, I'll upload them later. as for now, I'll upload the only pic of the bot that I've got

Science in Sports - The Magnus Effect

My brother looks back at the cylindrical filter of a reverse osmosis unit substituted for a lone stump, toppled by the plastic ball I threw. He had played a perfect forward defense that would have made Rahul Dravid proud! Yet the ball, tracing a curved path in the shape of a banana had whizzed past the outside edge to hit the "stump". "Yeah, that's the Magnus Effect", I thought to myself. The same effect that helps Roberto Carlos score a goal as well as threaten the ball boy standing 10 yards away from the goal!

So, what is the Magnus Effect? When a cylindrical body or a spherical spins and moves in one direction through a fluid, experiences a force perpendicular to the direction of its velocity.



Consider there is no wind and the velocity of the ball is V. So, the relative velocity of air around the ball with respect to the ball is V. Now, due to the spin on the ball, the air in contact with its surface acquires some velocity. In the above picture (I got the picture from wikipedia) you can see that the flow of air is assisted by the spin. Therefore the relative velocity of air will be greater than V. On the other side, the flow is being opposed by the spin and hence lesser relative velocity of air with respect to the linear motion of the ball. This difference in velocity, in accordance with Bernoulli's theorem, will create a difference in pressure between the top and bottom side. With the bottom side having a lesser pressure due to high velocity of air, the ball experiences a net downward force.

This force is given by the relation,
Here F is the force, ρ is the density of air, V is the relative velocity of air over the ball with respect to the ball, A is the area of cross section of the ball and l is spin ratio.

l = rw/(2*linear velocity) where w is the angular velocity of the ball and r is its radius.

Now that you know what exactly is the magnus effect, lets see its influence in various sports. And yeah, in the order of my favourite ones! ;-)

Cricket
I guess most people know that the lateral movement of the cricket ball when a fast bowler bowls is due to the varied degree of smoothness on the two sides. So, this has got nothing to do with the magnus effect though bernoulli's theorem comes into play. In cricket the only scenario where I've observed this effect is when a spin bowler bowls.

When an off spinner bowls, he gets the ball to drift away from the batsman and when a leggie bowls, the ball drifts into the batsman. When the ball leaves the bowler's hand(in both cases), it spins around an axis that is slightly inclined to the horizontal. So, the angular velocity has a component in the horizontal plane and this accounts for the drift!(Hope you could visualise what I mean)

Tennis
In tennis the magnus effect is the reason behind the dip in the ball's trajectory after being hit. In tennis terminology this is called "topspin". When Roger Federer imparts heavy topspin on the ball with a forehand shot, the initial path traversed by it would apparently take it way outside the baseline, but the considerable force acting in the downward direction keeps it in play!

A similar action is observed in Table Tennis too. Without the help of the magnus effect there is no way to keep the ball within the limits of the table!

Football
Beckham does it, Gerrard does it, Roberto Carlos does it and almost every one of those skilled players does it!

Check this video http://www.youtube.com/watch?v=-wL5w_GxIoo
Its self explanatory!!!

But wait! A cricket ball is imparted with much more spin that that on a football and yet the football moves more! The reason is simple.

• *Magnus force is proportional to the area of cross section of the ball. A football is larger than a cricket ball.
• *F=m*a, when mass is less the acceleration is more for a constant force. Football is lighter than a cricket ball(i guess so :P)

The other sports like golf and volleyball are also influenced by Magnus effect.

Learnt some facts from wikipedia.