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					AutoGuitar

   Zachary Bier
 Joshua Kinnison
Andrew Richarson
 Michael Ristoski
Overview

   Introduction
   Meet the Competition
   High Level Design
   Design Considerations
   Pitch Detection
   Current Progress
   Some Remaining Tasks
   Conclusion
   Questions
Introduction

   Manual tuning of guitar becomes a hassle
   Market need
   Cheap
   User-friendly
   Capable of tuning six strings simultaneously
   Allows for “special tuning” outside the standard
    “E-A-g-d-b-e”
Meet the Competition


   Gibson's “Robot Guitar”
       Thousands of dollars in cost
       Only caters to experts

   “String Master Guitar Tuner”
       One string at a time
       Manually held over each machine head
High Level Design

   Broken down into Mechanical and Digital

   Mechanical
       Servos and linkages
       Physical connection to the machine heads
   Digital
       Pitch detection
       Control signal generation
       User interface
High Level Design (cont.)‫‏‬




          Figure 1: High level Design
High Level Design(cont.)‫‏‬




         Figure 2: Concept of Design
Design Considerations

   Mechanical
       Metal backplate installed on the guitar head to house
        tuning actuators
       'Hitec' HS-645 servo
       Hobby servo which includes control circuitry
       Provides adequate torque
Design Considerations (cont.)‫‏‬

   Mechanical (cont.)
       Servos controlled using Pulse Width Modulation
            Pulses sent with 20ms periodicity
            Duration between 600 and 2400 µs
            Neutral position at around 1500 µs
       Allows for bi-directional rotation
       Potentiometer replaced by resistor
Design Considerations (cont.)‫‏‬

   Digital
       Computations performed on TI C5510
       Spartan-3 for LED output and user input
       Pitch detection using Harmonic Product Spectrum
Pitch Detection

   Harmonics make things interesting
   HPS to the rescue
       Algorithm for detecting fundamental freq.
       Eliminates harmonics
       Downsample → Multiply → Rinse → Repeat
Harmonic Product Spectrum




        Figure 3: HPS Algorithm
current_state

   MATLAB used to read real guitar data
   Data processed for FFT and pitch detection
   Obstacles:
       Threshold determination
       Harmonics
   HS-645 servo tested for adequate torque
   Successful replacement of potentiometer in servo
    to allow for bi-directional rotation
next_state

   Conversion of MATLAB code to C
   VHDL code for Spartan-3 functionality
   Developing PI control programming
   Build working model
   Fine-tune
   Final Product
Conclusion

   AutoGuitar adds robust, cheap tool to musicians
    toolbox
   Currently in production stage
   Two versions: pre-installed and self-installations
   Tasks to be broken down
   Manageability of task will increase
Sources

Cuadra, Patricio de La, Aaron Master, and Craig Sapp. "Efficient Pitch Detection Techniques for
  Interactive Music." Stanford University. <http://ccrma-www.stanford.edu/~craig/papers/01
  /icmc01-pitch.pdf>
Questions
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posted:3/2/2011
language:English
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