I am currently working on a school project where I am developing a simulation model (MATLAB Simulink) for my designed tilt-rotor QuadPlane (all motors tilting) and run the simulation analysis before I pursue transition test flights. I have already implemented Arducopter’s attitude + throttle controllers and Arduplane’s attitude + TECS controllers in my Simulink model. However, I am running into some problems to implement the transition controller and I am hoping someone could please answer my questions.
From my understanding, ArduPilot’s transition strategy for transitioning to fix-wing is essentially switching from Arducopter’s controller to Arduplane’s controller at the tilt angle of Q_tilt_max and speed of ARSPD_FBW_MIN. It can separates into 3 stages:1 Transition_Airspeed_Wait, 2 Transition_Timmer, 3 Transition_Done. In stage 1, the tilt angle depends on throttle position and Q_tilt_max. The UAV will gain speed until it reaches ARSPD_FBW_MIN. In this stage, Arducopter’s controllers are used to stabilized the UAV. In stage 2, the rotors will tilt all the way forward at tilt_rate_dn. In this stage ArduPlane’s controllers are used to stabilized the UAV. The transition is completed once the rotor is fully tilted (stage 3).
Here are my questions:
1. As the rotors are tilting down, there is a tilt_compesation factor (1/cos(tilt_angle)) multiplied to the throttle to compensate lost in lift. However, this factor becomes really large (~32) as the tilt-angle reaching 90 degrees. Does that mean tilt-rotors are going to operate at full rpm during transitions? Will the factor disappeared after the transition is done?
2. How’s the pilot’s inputs going to effect the UAV during transitions Mainly, does the pilot’s inputs changes in Transition_Airspeed_Wait stage to Transition_Timmer stage?
3. Can you transition from QHover to FBWB? I know it is recommended to transition from QHover to FBWA but won’t FBWB ensure no change in altitude? Also, does that mean your throttle position need to be larger than 50% to tell the controller you want to increase speed?
4. When transitioning from plane to quad, is the UAV immediately stabilized by Copter controllers? or it also depends on Q_TILT_MAX.
Thank you in advance to answer my questions.