1. change the security height in rotocraft_basic_YI_2013_7_16.xml to 2 meters.
2. make a copy of airframe configuration xml file and renamed as quadrotor_lisa_m_2_pwm_YI_Edward_F450.xml for 450 frame.
3. the quadrotor_lisa_m_2_pwm_YI_Edward_xbee_api.xml now stored PID values for F330 frame.
4. when the quadcopter received ack = 0xfe, it will now call autopilot_set_mode(AP_MODE_NAV) and set the nav_block and nav_stage to be 0.

TODO:
find a way to let the quadcopter goto the target position i have assigned for it