The UkeBot is a self playing ukulele which utilizes servos in order to move aluminum arms across the strings. The arms act as slides along the ukulele strings allowing for the ukulele to play different chords when the servos change angles. A wooden board was clipped onto the ukulele in order to hold the servos, which were attached to the board with clamps. We cut and drilled aluminum arms and attached them to the servos with a screw. The aluminum arms were bent to create divots which rests on the strings, preventing the arms from falling off . Since, the aluminum was a bit too light, so we adding weights on top of the arms in order to get the ideal pressure which would allow for the aluminum to press down on the strings and change the sound, but not press the strings against the neck. We found that the servos zero point tended to wander over time so four potentiometers were used in order to tune the machine while it is operating. To strum the machine, we used a string with knot on the end and attached it to a DC motor which we put on the bottom of the ukulele. Some limitations we faced were the length of the aluminum arms. Since the servo motors were attached at an angle to the strings, if an arm was extended too far it would fall off the string and push another arm off too so we had to keep the arms short. In order to advance the system I would recommend utilizing better servo motors and finding a better spot to place them near/on the ukulele to expand the range of the ukulele and to make sure the zero point stays the same. Another limitation was that we were trying to preserve the ukulele and therefore couldn’t permanently place items on it by gluing or drilling and therefore some of the components moved during transport which made it harder to keep ukulele in tune and have it play properly.
Along with the UkeBot, one of our partners used similar concepts to make a self playing Guitar robot with a HP Printer which he describes below:
The Uke – guitar playing bot – is an adaptation of the ukulele bot created by Douglas, Fiona, and Rohan, this time instead of a ukulele, an electric guitar. Because of this, new opportunities arise. Instead of having to pluck the strings, with an electric guitar one can simply press in between the frets of the neck. Similarly, by moving the pressing down action to either up or down along the neck, different notes can be obtained.
For this guitar bot, an HP printer was taken apart and the printer slider carriage mechanism was extracted. This became the sliding mechanism of the guitar body. Once the carriage was broken down, a servo was added to achieve the pressing down motion.
Now is the hard part: How to move the carriage in a precise way. The motor to drive the carriage mechanism was a 12 V DC motor attached to a belt that was able to slide the carriage along the shaft. The only way with just the motor, to power it, was to simply turn it on for an amount of time.
This wasn’t precise enough as the carriage would wander away from the note each time it duplicated the rhythm. The momentum of the carriage was too high, and the belt would only glide when it stopped. To solve this, an ultrasonic sensor was used to measure the distance in real time that the carriage was moving. The data fed through an Arduino and the mechanism was mounted to a 2 x 4 which ran under the guitar to mount to the body without harming it.
This design can be expanded upon, as seen in the video, by that additional rails can be used. In the video on the opposite side of the striker mechanism, there is a drum stick attached to a servo. That rail is an additional slider mechanism, allowing for even more notes to be played on the opposite side.
I wanted to create a low budget, easily duplicated, and predictable machine that can play any full-size guitar without damaging it.
I would say I achieved my goal for this project.
By: Rohan Curran, Fiona McEvilly, Douglas Moore, Timothy Rinaldi
Making Music With Machines, MU 2801, A-2020
