     //상단모터 감속
     if( ch == 'e' )
     {
-      rc_pwm_T = constrain(rc_pwm_T--, 100, 2000);
+      rc_pwm_T = constrain(rc_pwm_T--, 0, 2000);
       RovServo[1].write(rc_pwm_T);   
       Serial.println("Top=");
       Serial.println(rc_pwm_T);

    //우회전
    if( ch == 'd' )
    {
      rc_pwm_L = constrain(rc_pwm_L++, 100, 2000);
      rc_pwm_R = constrain(rc_pwm_R--, 100, 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 = 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);
