An Electrogoniometer Controls a Servo Motor

I think that it is my final project(or called game) before my TOEFL test. The concept is very simple. The arduino reads the voltage of an electrogoniometer and sends the analog signals to servo. However, the voltage of the electrogoniometer is unstable, so you can see the servo motor is shaking. No wander when I used the electrogoniometer for my research, I needed to smooth the data.