     //우회전
     if( ch == 'd' )
     {
-      rc_pwm_L = constrain(rc_pwm_L++, 100, 2000);
-      rc_pwm_R = constrain(rc_pwm_R--, 100, 2000);
+      rc_pwm_L = constrain(rc_pwm_L++, 0, 2000);
+      rc_pwm_R = constrain(rc_pwm_R--, 0, 2000);
       RovServo[0].write(rc_pwm_L);   // 좌측모터 출력 증가
       RovServo[2].write(rc_pwm_R);    //우측모터 출력 감소
       Serial.println("Left=");

    //시동 
    if( ch == 'o' )
    {
      rc_pwm_L = 100, rc_pwm_R = 100, rc_pwm_T = 100;
      RovServo[0].write(rc_pwm_L);
      RovServo[1].write(rc_pwm_R);
      RovServo[2].write(rc_pwm_T);

    //정지 (시동끄기)
    if( ch == 'p' )
    {
      rc_pwm_L = 0, rc_pwm_R = 0, rc_pwm_T = 0;
      RovServo[0].write(rc_pwm_L);
      RovServo[1].write(rc_pwm_R);
      RovServo[2].write(rc_pwm_T);
