tHe aSSEmBLIng

Four hours of wading through the knee deep dirty waters on the streets of Calcutta on a certain fateful rainy day and hundreds of electronics shops later I finally found the four potentiometers needed for our feedback master slave servomechanism.It was that very thing that had forced us to postpone our dates.
It was time to get back to durgapur and begin the design of the shafts,the joints and start construction as soon as possible.The parts were ready to be put together and the joints had to be manufactured.We made yet another mistake,underestimating the importance of the joints and its capability to withstand the weight of the links,the gearboxes,the end effector,the headers ,the screws.the potentiometers and everything put together.It was of prime importance that we minimise any sort of vibrational movement and bending of the plastic headers.The joints were bending after we had assembled it initially, the screws were unable to hold up the headers properly.It needed more clamping force.
Two days went by without much work.It was back to the drawing board job.
3 rd October the joint problem was solved.A shaft having gear tooth profiles at one end of it was machined from a brass shaft and inserted into the header hole of the headers by applying pressure(read hammering).It did its job well enough.
One headache was finally out of the way.The slave was ready and the potentiometers and the links and the headers and the gear boxes fitted in just fine and the joints were strong enough this time to hold the entire setup in an upright manner.Bending was minimised to the extent that was desirable and extra nuts were put at the ends of the links to make the movement of the links possible with minimum slipping.
The chassis was now a piece of cake to make as we had the materials and it had no such component that could cause much headache and it was completed without any fret.
5 th October----We were nearing completion and it seemed that it would take another two days to complete(yet another mistake).Having worked for 2 days on the trot on soldering the resistors,diodes,etc to the veroboard (and I had to "un"solder and "re"solder it a couple of times) it was finally ready for testing.Last moment checks were still to be made and we had to be sure that the components were soldered properly and the connections were made correctly.The transistors were particularly menacing in this respect and we had to download the data sheets of the transistors and check them out.
9 th October----The circuits were complete ,the connections were left to be made,the mounting was not complete and z-brackets(4) needed to be machined into place.Most of the work was done but it still was unfinished,it was still bits and pieces left to be put together.
10th October---Came back to Calcutta today.The autumn weather and the festive mood of the city was refreshing.Our little piece of creation could wait a few weeks i guess...................

pAtCHing uP

Servos did not come our way(they were available online though,but that did not seem to be a feasible solution).We decided to patch it up using chinese gear motors and high precision potentiometers as the input device and also for the feedback mechanism(ours will be an automatic servomechanism feedback control system).
The links are ready.They are made of 5 mm thick aluminium rods about 6 1/2 inches long .Currently work is going on the assembling of the gear boxes and the links on the platform.
After the assembly part is over we will start working on the circuit.we will be using OP-AMPS for amplifying the input voltage signals that will then be fed to the potentiometers attached to the gear boxes and the resultant signals will hopefully move them.
The construction part though is not going too well ,had to make numerous changes midway and it is taking up too much time .We would have liked it had it been completed in 2-3 days time as a chunk of the time will have to be spent on the simulation part and to check whether everything is falling in place.
For the time being we are engaged in drilling holes into plastic cases and aluminium rods(I hate to say it but the construction part has been up to late a comedy of errors).Trying hard to complete as efficiently as we can.Seems like we need a lot of luck to finish the entire thing by the 5th of next month.The hardest part was the conceptualisation and the designing part, we thought,and that everything after that would turn out to be a cakewalk .It seems now that our plan backfired .
moral:NEVER GO FOR MANUFACTURING WITHOUT THE COMPLETE PLAN LAID OUT IN FRONT OF YOU

BitS AND pIEceS

So far our search for a suitable servo motor has proved futile.Getting the things that we require seems an uphill task as of now.Well without wasting any time i had to think about the programming part (although i would have liked to have dealt with it at a later stage).
Anyhow it seems now that a job done can be fruitful in the future,and keeping in mind just that here is an overview of what exxactly are we trying to achieve or rather intending to achieve
1.a method of manually feeding by using a robot control device by
(a)specifying a target co ordinate system for the manual feed
(b)selecting a reference co odinate system to manually feed the specified target co ordinate system
(c)inputting the content of the manual feed according to the given co ordinate system of the robot controller
(d)moving the given target co ordinate system accordingly and lastly
(e)to make the arm move accordingly and equivalently to the successive movements


For the programming aspect it seems that as of now G-code would be appropriate.First of all it is a programming language for contolling CNC machines.It is mainly used to command the machine what type of action to perform(it is mainly used in champhering,drilling etc by CNC machines;wikipedia has an overview of the G-code in case u have no idea on what it is)
It is a simple programming language that can be learnt in a few hours and definitely not too hard to grasp.Although when writing sophisticated programs it can be tedious as the script often exceed 1000s of pages and can be quite a pain to debug.Programming is not my forte,though our arm would not require any complicated coding as far as i can think ans some basic appliations of this simple machine tol language can prove to be useful.
We are only thinking of keeping the manufacturing and controlling as simple as we can.If our project turns out to be a success we can always change the coding and make it more functionable (we can use BASIC language on PIC microcontrollers to have better results)
But that I would consider another day.

[ .. ]

Regular updates will be provided in this blog site regarding the ongoing project.Those who are interested can post their comments.I will be more than happy to consider your opinions.

bOt wRiteR

I am currently working on a project involving manufacturing of an elecromechanical device ,a robotic arm capable of amplifying human arm action.
I have the design sketched out in my mind (i want to keep it as simple as possible).It will be a computer controlled manipulator consisting of aluminium links connected mostly by revolute joints,one end will bw attached to a supporting base while the other end would be free to perform a given task.
The design will have three parts:
1)the chassis or the supporting base(this will hold the circuitry and the arm )
2)the the shoulder or the hindarm.This will be in direct contact with the base capable of rotating in a two dimensional plane and the other end of it will be attached to the third part i.e the forearm
3)the forearm will be the final part of the design(again this should be able to rotate w.r.t the shoulder).
Now that the basic design is chalked out we must enable the arm to move and for that we would be requiring stepper motors , gears etc.
The frivolities being over this is the part that gets really confunding; that is how to make the arm write.I am not going to delve into the programming part as yet,but will try and keep you updated on the latest developments.
(Feel free to post your comments )

NoTHing tO WritE ABouT(what the heck)

The universe seems to be as unique as it appears,the stars seem to be in their places and the earth (i can't tell for sure) is surely on its rightful course,but still something seems different over the past three days.My semester exams and the two weeks of arduous training period are finally over and as it appears that I have loads of time to waste,but.... something has been stirring deep within for quite sometime now(and no it is not indigestion) and time to kill has been hard to get.Something is definitely brewing upstairs,i can smell it(a burnt one most of the times).
When i returned to Calcutta I had no intention whatsoever to try and learn what a microcontroller is or even attempt to fathom a run-time machine language module(see I told you I am growing weird and for the record my friends would testify to the fact that I am basically lazy).
It has been raining since i can rememeber.The entire city is flooded.The MET Dept. has registered 160mm of rain since yesterday.The mood in the city is depressing (and the mud and dirty water has'nt helped either).I have'nt seen sunshine since I came here,but nothing it seems can dampen my spirits.At first I thought this was just a passing fad but it has refused to budge even an inch and as if things could not get any more worse,I am currently contemplating getting my hands on a processor board to simulate C expressions and function calls.
Now that I am sitting infront of my comp with"coming back to life "(by pink floyd in case a few don't know)playinng in the background I could not help but plagiarise a portion of their lyrics.It goes somewhat like this:
"lost in thought and lost in time
while the seeds of life and the seeds of change were planted

Outside the rain fell dark and slow
While I pondered on this dangerous but irresistable past time
I took a heavenly ride through our silence
I knew the moment had arrived
For killing the past and coming back to life"

All postings will be done after 1st july