#include <Servo.h>

Servo myservo;
float pos;   
int angleInit;
int angleMax;
int angleMin;
int dif = 60;

void setup() 
{  
  Serial.begin(9600);
  myservo.attach(9);  // attaches the servo on pin 9 to the servo object   
  angleInit = 90;
  angleMax = angleInit+dif;
  angleMin = angleInit-dif;
  myservo.write(angleInit); 
} 

int angle = angleInit;
float inc = 1;
void loop() {
  inc = 1;
  for (pos = angleMin; pos <= angleMax -1; pos += inc) { // goes from 0 degrees to 180 degrees
    // in steps of 1 degree
    inc = 4*(angleMax- pos)/(angleMax- angleMin);
//    Serial.print("UP: ");
//    Serial.println(pos);
    myservo.write((int)pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
  inc = 1;
  for (pos = angleMax; pos >= angleMin + 1; pos -= inc) { // goes from 180 degrees to 0 degrees
    inc = 4*(pos - angleMin)/(angleMax- angleMin);
//    Serial.print("DOWN: ");
//    Serial.println(pos);
    myservo.write((int)pos);              // tell servo to go to position in variable 'pos'
    delay(15);                       // waits 15ms for the servo to reach the position
  }
}