Servos were trembling, especially when reaching 100% PWM duty cycle

T

retrolefty:
You don't 'talk' to servos with analogWrite() commands. You include the servo library and use servo write commands as in the
following example.

#include <Servo.h> 

Servo myservo;

void setup()
{
  myservo.attach(9);
  myservo.write(90);  // set servo to mid-point
}

void loop() {}




More info can be found here: http://arduino.cc/en/Reference/Servo

Thank you retrolefty!
Yes I used <servo.h> to control servos. And analogWrite() is used for PWM fans control.
Do you think they could somehow influence each other?