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Author Topic: Getting started.. robot hand  (Read 2821 times)

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Offline j_lyfTopic starter

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Getting started.. robot hand
« on: January 02, 2011, 10:23:28 AM »
Hi all. I want to build a simple robot hand that is able to play the piano. so i guess the fingers need to be able to move up and down, but I'm not sure whether the middle joint of the finger needs freedom. I'm thinking of using Meccano to construct the robot. What do you think?

At this stage, I'm not sure where to get started. Funny because I'm a third year EE student who has done subjects on Control, microcontrollers (ARM) and embedded computing but I don't even know how to use a Servo.

Can anyone recommend any tutorials or books for me to start on this project?


Offline Kelpy

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Re: Getting started.. robot hand
« Reply #1 on: January 02, 2011, 03:18:56 PM »
j_lyf.

Have a look at this simple design ;)

http://letsmakerobots.com/node/22942

Offline photomark

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Re: Getting started.. robot hand
« Reply #2 on: January 02, 2011, 05:27:16 PM »
How well would you like it to be able to play the piano ?

The human hand is the most complex machine there is

Offline azy

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Re: Getting started.. robot hand
« Reply #3 on: January 02, 2011, 07:58:46 PM »
There's a good video on there

http://www.societyofrobots.com/robotforum/index.php?topic=12895.0

to play the piano you can either have a set of simple levers attached to a sliding rack (think of a printer head skipping back and forth)

or

you need a robot arm with many degrees of freedom and complex hands with fingers that can lock rigid as they press down hard on the keys


if you want to get the most out of velocity sensitive keys ,play notes loud or quiet you will need considerable strength and speed for accurate play. Mini servos wont be up for the task , you will need to play at least 4 if not 8 notes a second to make music. Fast passages approach 16 notes per second. Servos are not quick enough unless they have a long lever, which greatly reduces there strength.

 Finger servos strong and fast enough to play properly would need to be held in place with a 10 kilo weight....for every action their is an equal and opposite reaction...a 10 kilo weight would need to rest in the wrist if the hand was held near level with the keys. (humans sit over and lean into the keyboard when playing, the weight and muscles in their arms keeping the fingers on the money)

cheap solution is attach at least 1 solenoid to a sliding rack that zips up and down the keyboard, that would be impressive to watch at speed and perhaps importantly be a great demo for your talent and ability into the bargain....you might even go on a concert tour...and why not if its good enough ?


playing a keyboard is 3 dimensional.  

1 dimension is the frequency of the musical note
1 dimension is the time spacing between the notes
1 dimension is how loud you play note (the faster the key is depressed the louder the note sounds & is true of real pianos as well as midi)

holding down a key (midi) or pressing damping or sustain pedals (real piano) are other actions that can be consider to be additional dimensions

check on you tube for piano playing robots, i have seen half a dozen systems on there


If you are serious, i would strongly suggest writing a computer program that can play a virtual (software) midi keybaord. These virtual instruments can be dloaded for free. Once you have got your program playing music well , then you can start coding the hardware to do the job in the real world. Plunkety plunk wont be a particularly rewarding out come.



bet you are starting to wish you had never asked now  :o , that $50 robot is calling your name
« Last Edit: January 02, 2011, 08:36:50 PM by azy »

Offline j_lyfTopic starter

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Re: Getting started.. robot hand
« Reply #4 on: January 05, 2011, 04:48:17 AM »
I like the idea of levers on a sliding rack.. whats is the principle behind movement? Ive never used solenoids before..?

Offline azy

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Re: Getting started.. robot hand
« Reply #5 on: January 05, 2011, 11:18:46 AM »
solenoids push harder and faster if you apply more volts , just the same as an electric motor (solenoid = a metal that rod slides in and out of a coil of wire)

if the solenoids are suspended vertically over the keys they will have gravity on there side , tip add some weights to the plungers and a rubber stopper so the wont scratch the keys (the spring in the keys will help the solenoid retract )

for the sliding rack i would say go for a toothed belt , or possibly a light weight bicycle or motorcycle chain, if u= you use a motor with a position sensor you should be able to get it to stop the solenoid over the right key

 if money was no object id have a solenoid for each key , lol  and then you could do without the sliding rack


to simulate 2 humans hands you would need 10 sliding racks with 1 solenoid on each , no easy task



you could maybe hijack a BIG old printer , attach a lever to magnify the swing , just ask the printer to print and it will move the solenoid over the key (there are linkages which will allow left and right but maintain the distance (drawing a straight line not an arc)

just throwing some ideas up in the air

mechanical self playing pianos have been around for 100 years plus , take a look at how they work , you might be able to combine OLD tech with NEW tech , that would be cool

after thought , if you had a mini keyboard and a large printer the same width as the keyboard that would save you a lot of work

playing the flute or sax would be much simpler , only a few keys , fix the solenoids in place over each one
you will have 100% control and be able to make realy good quality music , maybe even play flight of the bumble bee.

Q you have to ask yourself , do you want to make quality music with your setup or just experiment and get your hands dirty with robotics kit ?








« Last Edit: January 05, 2011, 11:27:22 AM by azy »

Offline s-ter

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Re: Getting started.. robot hand
« Reply #6 on: May 08, 2011, 08:32:00 AM »
Hi, I am esther. I am doing the same project. I am trying to figure out which components are manage to control the robotic finger with best efficiency.

May I know how much each Solenoid cost?

 


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