ARMSTRUM

Abstract

The goal of our project was to create a guitar accessory that includes single-hand amputees in the user-base of guitar players and shoppers. The accessory is meant to help the user learn to play using any guitar available to them, using a single hand.

Brainstorming

We started by outlining a few types of musical instruments, types of disabilities, and types of individuals for whom we could design. After debating it as a group we decided to go with: “Reimagining a tap-based musical instrument for Tara, a 15-year-old double hand-amputee, who comes from a lower-middle class household.” We then mapped out many ideas for the same.

Some of our more interesting ones were:

1. Game-object based instrument

These included instruments played by using touch-sensitive hoola-hoops, rolling a ball between her feet, skating/sliding around on a disc.

2. Body movement

Instrument played by dancing between mapped sensors, parts of instrument mapped to different parts of her body, etc.

3. Voice-enabled

An instrument that could react to her singing voice by weaving a complimentary melody around it, or an instrument that reacts to speech input

We narrowed down the scope and defined the diability for which we wanted to design and modify the instrument for.

4. Mouth-based

Played by chewing a gum sounds that could be stretched and manipulated using the shape of the gum. Another one was an instrument mapped to her teeth so that she might be able to play it by sliding her tongue over her teeth.

5. Breath-based

Blowing air through a pipe onto a mapped surface, or using the air pressure through a pipe to fuel the intensity of the sound created by an instrument

6. Others

Using prosthetics with mini fingers, using 50 synthetic fingers on each hand, using eye-tracking.

Problem statement

The final problem statement we chose was “Design an accessory for an electric guitar that enables Ram, a single-hand amputee who loves The Beatles to learn to play his favorite song ‘Hey Jude’”

Design Process

Discuss possible ideas > Secondary research > Finalize idea > Paper prototyping > Testing > Material prototyping

We decided to design a solution for the ‘strumming’ hand, assuming that the user would use his existing hand for playing the chords/notes.

The initial solutions included a digital interface in place of the frets (automatic/digital strumming), a responsive prosthetic arm (strumming using muscle contractions), a hexagonal guitar with concentric strings (easy to access all the frets without moving the arm too much) and a mechanical arm attached to the guitar which is played by using a pedal (strumming in real-time using the foot).

The idea that we chose was the pedal-controlled strumming since we wanted the user to have control over the rhythm of the strumming in real-time. Also, the idea was to help the user learn to play a guitar and this accessory was not meant for professional playing.

Paper prototyping

Material prototyping

After testing the paper prototype we laser cut an MDF sheet to build the electronic arm. The pedal was 3D modeled and 3D printed, and then assembled with a spring attached to the hinge.

Arm mechanism with microcontroller augmented on the guitar

Arduino Code

          #include <Servo.h>

          Servo myservo, plec;  // create servo object to control a servo for the arm and the plectrum

          int flag=0;
          int potpin = 0;  		// analog pin used to connect the potentiometer
          int val;   				 // variable to read the value from the potentiometer
          const int buttonPin = 2;    
          int buttonState = 0;



          void setup() {

            myservo.attach(5);
            pick.attach(9);				// attaches the servo on pin 9 to the servo object
            pinMode(buttonPin, INPUT);
            Serial.begin(9600);

          }

          void loop() {

             val = analogRead(potpin);  
             Serial.println(val);			// reads the value of the potentiometer (value between 0 and 1023)
             val = map(val, 0, 100, 30, 0);    //  maps the pedal movement to the arm movement
             flag = digitalRead(buttonPin);
           
             Serial.println(val);
             if(flag!=0)
             
              {   plec.write(0);		   //sets the plectrum on the strings for one way strumming
                  myservo.write(val);
                  delay(15);  

              }

              else

              {   pleck.write(40);         //sets the plectrum off the strings for one way strumming
                  myservo.write(val);
                  delay(15);  

              }

            
           }
                             



        
    

Design challenges

Ease of use

Strumming Vs Plucking Individual strings

One of the main points of discussion was, how does this pedal allow users not only to strum but also pluck individual strings? There were a number of solutions we discussed, some of them are:

• Attach a sliding pad (with buttons) to the neck of the guitar which the user can control using his thumb. Each button is linked to an individual string. The problem with this was that ergonomically it would be difficult for the hand to touch the guitar frets with the fingers and also select buttons with the thumb. It would also be cognitively difficult to perform both actions with one hand.
• A more complex idea was to allow the foot-pedal to rotate sideways and use a needle at the tip of the pedal to select strings. For example, if there were 7 buttons at the top of the pedal which could be pressed by the needle: “All strings”, “string 1”, “string 2”.. And so on. This would allow the user to pick individual strings using his foot. This mechanism required a lot of physical dexterity on the part of the user, and we were not sure about its learning curve.
• Use an engage or disengage button on the pedal (or on a different pedal). This will allow the arm to disengage and hover over the strings without touching them. The user can use this to ‘engage’ with different strings individually without strumming the others. This is the idea that we took forward for the final prototype.



What problem are we solving?

While doing secondary research on the topic, we found videos of single-hand amputees who had found a way to attach the plectrum to the elbow of their amputated arm and strum the guitar. There are videos of arm-amputees playing the guitar perfectly using just their feet and toes. With the current state of affordable prosthetics, there is some scope for a user to do basic strumming.

So is it really a problem that needs to be solved? While we were designing the accessory, we regularly found ourselves faced with this question. However, these existing solutions had some constraints, i.e. the plectrum on elbow required the user to have an elbow, while playing a guitar with the feet required the user to overcome a steep learning curve, and prosthetics did not account for the wrist movement required for strumming. We found that the design we came up with did not have too many constraints as it was designed specifically for a single-handed user. While this design is not as fine-tuned, it is one way to start thinking about access to guitar-playing for the differently-abled.

Final Prototype