| Summary: | Proportional � Integral � Derivative Controller (PID controller) is a
generic control loop feedback mechanism (controller) widely used in industrial
control systems. PID is the most commonly used feedback controller. A PID
Controller calculates an \"error\" value as the difference between a measured
process variable and a desired set point. The controller attempts to minimize the
error by adjusting the process control inputs.
System that has been made is an automatic guitar tuner that applied a
simple PID controller using sound sensor module as its input device. Sound
sensor will sense the guitar string�s sound vibration and convert it to a certain
voltage for a processing unit to read. Then, the processing unit will count the
sound�s frequency which represents the picked guitar string�s tone using the
counting zero-crossing method based on the voltage change that happened
earlier. The error value between measured frequency and setpoint will be used as
an input for the control system. Its outputs are speed and direction of a stepper
motor that coupled and spins the picked guitar peg until the error value reaches
zero.
System tests are done by testing the sensor placement effect on system
performance and testing the PID control characteristics. The best sensor
performance results are achieved by placing the sensor attached to guitar tube
with 99,74% accuracy of frequency counting. From the test result, it is known that
this system�s optimal gain values are: Kp = 3, Ki = 1,5, and Kd = 2,5. This
system is capable to tune a guitar in average time of 11,2 seconds each string.
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